Java tutorial
/* * Copyright (C) 2013 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.givewaygames.transition; import android.animation.Animator; import android.animation.AnimatorListenerAdapter; import android.animation.TimeInterpolator; import android.support.v4.util.ArrayMap; import android.util.Log; import android.util.LongSparseArray; import android.util.SparseArray; import android.view.View; import android.view.ViewGroup; import android.widget.ListView; import com.givewaygames.transition.views.Transitionable; import java.util.ArrayList; import java.util.List; /** * A Transition holds information about animations that will be run on its * targets during a scene change. Subclasses of this abstract class may * choreograph several child transitions ({@link android.transition.TransitionSet} or they may * perform custom animations themselves. Any Transition has two main jobs: * (1) capture property values, and (2) play animations based on changes to * captured property values. A custom transition knows what property values * on View objects are of interest to it, and also knows how to animate * changes to those values. For example, the {@link android.transition.Fade} transition tracks * changes to visibility-related properties and is able to construct and run * animations that fade items in or out based on changes to those properties. * * <p>Note: Transitions may not work correctly with either {@link android.view.SurfaceView} * or {@link android.view.TextureView}, due to the way that these views are displayed * on the screen. For SurfaceView, the problem is that the view is updated from * a non-UI thread, so changes to the view due to transitions (such as moving * and resizing the view) may be out of sync with the display inside those bounds. * TextureView is more compatible with transitions in general, but some * specific transitions (such as {@link android.transition.Fade}) may not be compatible * with TextureView because they rely on {@link android.view.ViewOverlay} functionality, * which does not currently work with TextureView.</p> * * <p>Transitions can be declared in XML resource files inside the <code>res/transition</code> * directory. Transition resources consist of a tag name for one of the Transition * subclasses along with attributes to define some of the attributes of that transition. * For example, here is a minimal resource file that declares a {@link android.transition.ChangeBounds} transition:</p> * * {@sample development/samples/ApiDemos/res/transition/changebounds.xml ChangeBounds} * * <p>Note that attributes for the transition are not required, just as they are * optional when declared in code; Transitions created from XML resources will use * the same defaults as their code-created equivalents. Here is a slightly more * elaborate example which declares a {@link android.transition.TransitionSet} transition with * {@link android.transition.ChangeBounds} and {@link android.transition.Fade} child transitions:</p> * * {@sample * development/samples/ApiDemos/res/transition/changebounds_fadeout_sequential.xml TransitionSet} * * <p>In this example, the transitionOrdering attribute is used on the TransitionSet * object to change from the default {@link android.transition.TransitionSet#ORDERING_TOGETHER} behavior * to be {@link android.transition.TransitionSet#ORDERING_SEQUENTIAL} instead. Also, the {@link android.transition.Fade} * transition uses a fadingMode of {@link android.transition.Fade#OUT} instead of the default * out-in behavior. Finally, note the use of the <code>targets</code> sub-tag, which * takes a set of {@link R.styleable#TransitionTarget target} tags, each * of which lists a specific <code>targetId</code> which this transition acts upon. * Use of targets is optional, but can be used to either limit the time spent checking * attributes on unchanging views, or limiting the types of animations run on specific views. * In this case, we know that only the <code>grayscaleContainer</code> will be * disappearing, so we choose to limit the {@link android.transition.Fade} transition to only that view.</p> * * Further information on XML resource descriptions for transitions can be found for * {@link R.styleable#Transition}, {@link R.styleable#TransitionSet}, * {@link R.styleable#TransitionTarget}, and {@link R.styleable#Fade}. * */ public abstract class Transition implements Cloneable { private static final String LOG_TAG = "Transition"; static final boolean DBG = false; private String mName = getClass().getName(); long mStartDelay = -1; long mDuration = -1; TimeInterpolator mInterpolator = null; ArrayList<Integer> mTargetIds = new ArrayList<Integer>(); ArrayList<View> mTargets = new ArrayList<View>(); ArrayList<Integer> mTargetIdExcludes = null; ArrayList<View> mTargetExcludes = null; ArrayList<Class> mTargetTypeExcludes = null; ArrayList<Integer> mTargetIdChildExcludes = null; ArrayList<View> mTargetChildExcludes = null; ArrayList<Class> mTargetTypeChildExcludes = null; private TransitionValuesMaps mStartValues = new TransitionValuesMaps(); private TransitionValuesMaps mEndValues = new TransitionValuesMaps(); TransitionSet mParent = null; // Per-animator information used for later canceling when future transitions overlap private static ThreadLocal<ArrayMap<Animator, AnimationInfo>> sRunningAnimators = new ThreadLocal<ArrayMap<Animator, AnimationInfo>>(); // Scene Root is set at createAnimator() time in the cloned Transition ViewGroup mSceneRoot = null; // Whether removing views from their parent is possible. This is only for views // in the start scene, which are no longer in the view hierarchy. This property // is determined by whether the previous Scene was created from a layout // resource, and thus the views from the exited scene are going away anyway // and can be removed as necessary to achieve a particular effect, such as // removing them from parents to add them to overlays. boolean mCanRemoveViews = false; // Track all animators in use in case the transition gets canceled and needs to // cancel running animators private ArrayList<Animator> mCurrentAnimators = new ArrayList<Animator>(); // Number of per-target instances of this Transition currently running. This count is // determined by calls to start() and end() int mNumInstances = 0; // Whether this transition is currently paused, due to a call to pause() boolean mPaused = false; // Whether this transition has ended. Used to avoid pause/resume on transitions // that have completed private boolean mEnded = false; // The set of listeners to be sent transition lifecycle events. ArrayList<TransitionListener> mListeners = null; // The set of animators collected from calls to createAnimator(), // to be run in runAnimators() ArrayList<Animator> mAnimators = new ArrayList<Animator>(); /** * Constructs a Transition object with no target objects. A transition with * no targets defaults to running on all target objects in the scene hierarchy * (if the transition is not contained in a TransitionSet), or all target * objects passed down from its parent (if it is in a TransitionSet). */ public Transition() { } /** * Sets the duration of this transition. By default, there is no duration * (indicated by a negative number), which means that the Animator created by * the transition will have its own specified duration. If the duration of a * Transition is set, that duration will override the Animator duration. * * @param duration The length of the animation, in milliseconds. * @return This transition object. * @attr ref R.styleable#Transition_duration */ public Transition setDuration(long duration) { mDuration = duration; return this; } /** * Returns the duration set on this transition. If no duration has been set, * the returned value will be negative, indicating that resulting animators will * retain their own durations. * * @return The duration set on this transition, in milliseconds, if one has been * set, otherwise returns a negative number. */ public long getDuration() { return mDuration; } /** * Sets the startDelay of this transition. By default, there is no delay * (indicated by a negative number), which means that the Animator created by * the transition will have its own specified startDelay. If the delay of a * Transition is set, that delay will override the Animator delay. * * @param startDelay The length of the delay, in milliseconds. * @return This transition object. * @attr ref R.styleable#Transition_startDelay */ public Transition setStartDelay(long startDelay) { mStartDelay = startDelay; return this; } /** * Returns the startDelay set on this transition. If no startDelay has been set, * the returned value will be negative, indicating that resulting animators will * retain their own startDelays. * * @return The startDelay set on this transition, in milliseconds, if one has * been set, otherwise returns a negative number. */ public long getStartDelay() { return mStartDelay; } /** * Sets the interpolator of this transition. By default, the interpolator * is null, which means that the Animator created by the transition * will have its own specified interpolator. If the interpolator of a * Transition is set, that interpolator will override the Animator interpolator. * * @param interpolator The time interpolator used by the transition * @return This transition object. * @attr ref R.styleable#Transition_interpolator */ public Transition setInterpolator(TimeInterpolator interpolator) { mInterpolator = interpolator; return this; } /** * Returns the interpolator set on this transition. If no interpolator has been set, * the returned value will be null, indicating that resulting animators will * retain their own interpolators. * * @return The interpolator set on this transition, if one has been set, otherwise * returns null. */ public TimeInterpolator getInterpolator() { return mInterpolator; } /** * Returns the set of property names used stored in the {@link android.transition.TransitionValues} * object passed into {@link #captureStartValues(android.transition.TransitionValues)} that * this transition cares about for the purposes of canceling overlapping animations. * When any transition is started on a given scene root, all transitions * currently running on that same scene root are checked to see whether the * properties on which they based their animations agree with the end values of * the same properties in the new transition. If the end values are not equal, * then the old animation is canceled since the new transition will start a new * animation to these new values. If the values are equal, the old animation is * allowed to continue and no new animation is started for that transition. * * <p>A transition does not need to override this method. However, not doing so * will mean that the cancellation logic outlined in the previous paragraph * will be skipped for that transition, possibly leading to artifacts as * old transitions and new transitions on the same targets run in parallel, * animating views toward potentially different end values.</p> * * @return An array of property names as described in the class documentation for * {@link android.transition.TransitionValues}. The default implementation returns <code>null</code>. */ public String[] getTransitionProperties() { return null; } /** * This method creates an animation that will be run for this transition * given the information in the startValues and endValues structures captured * earlier for the start and end scenes. Subclasses of Transition should override * this method. The method should only be called by the transition system; it is * not intended to be called from external classes. * * <p>This method is called by the transition's parent (all the way up to the * topmost Transition in the hierarchy) with the sceneRoot and start/end * values that the transition may need to set up initial target values * and construct an appropriate animation. For example, if an overall * Transition is a {@link android.transition.TransitionSet} consisting of several * child transitions in sequence, then some of the child transitions may * want to set initial values on target views prior to the overall * Transition commencing, to put them in an appropriate state for the * delay between that start and the child Transition start time. For * example, a transition that fades an item in may wish to set the starting * alpha value to 0, to avoid it blinking in prior to the transition * actually starting the animation. This is necessary because the scene * change that triggers the Transition will automatically set the end-scene * on all target views, so a Transition that wants to animate from a * different value should set that value prior to returning from this method.</p> * * <p>Additionally, a Transition can perform logic to determine whether * the transition needs to run on the given target and start/end values. * For example, a transition that resizes objects on the screen may wish * to avoid running for views which are not present in either the start * or end scenes.</p> * * <p>If there is an animator created and returned from this method, the * transition mechanism will apply any applicable duration, startDelay, * and interpolator to that animation and start it. A return value of * <code>null</code> indicates that no animation should run. The default * implementation returns null.</p> * * <p>The method is called for every applicable target object, which is * stored in the {@link android.transition.TransitionValues#view} field.</p> * * * @param sceneRoot The root of the transition hierarchy. * @param startValues The values for a specific target in the start scene. * @param endValues The values for the target in the end scene. * @return A Animator to be started at the appropriate time in the * overall transition for this scene change. A null value means no animation * should be run. */ public Animator createAnimator(ViewGroup sceneRoot, TransitionValues startValues, TransitionValues endValues) { return null; } /** * This method, essentially a wrapper around all calls to createAnimator for all * possible target views, is called with the entire set of start/end * values. The implementation in Transition iterates through these lists * and calls {@link #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues)} * with each set of start/end values on this transition. The * TransitionSet subclass overrides this method and delegates it to * each of its children in succession. * * @hide */ protected void createAnimators(ViewGroup sceneRoot, TransitionValuesMaps startValues, TransitionValuesMaps endValues) { if (DBG) { Log.d(LOG_TAG, "createAnimators() for " + this); } ArrayMap<View, TransitionValues> endCopy = new ArrayMap<View, TransitionValues>(endValues.viewValues); SparseArray<TransitionValues> endIdCopy = new SparseArray<TransitionValues>(endValues.idValues.size()); for (int i = 0; i < endValues.idValues.size(); ++i) { int id = endValues.idValues.keyAt(i); endIdCopy.put(id, endValues.idValues.valueAt(i)); } LongSparseArray<TransitionValues> endItemIdCopy = new LongSparseArray<TransitionValues>( endValues.itemIdValues.size()); for (int i = 0; i < endValues.itemIdValues.size(); ++i) { long id = endValues.itemIdValues.keyAt(i); endItemIdCopy.put(id, endValues.itemIdValues.valueAt(i)); } // Walk through the start values, playing everything we find // Remove from the end set as we go ArrayList<TransitionValues> startValuesList = new ArrayList<TransitionValues>(); ArrayList<TransitionValues> endValuesList = new ArrayList<TransitionValues>(); for (View view : startValues.viewValues.keySet()) { TransitionValues start = null; TransitionValues end = null; boolean isInListView = false; if (view.getParent() instanceof ListView) { isInListView = true; } if (!isInListView) { int id = view.getId(); start = startValues.viewValues.get(view) != null ? startValues.viewValues.get(view) : startValues.idValues.get(id); if (endValues.viewValues.get(view) != null) { end = endValues.viewValues.get(view); endCopy.remove(view); } else if (id != View.NO_ID) { end = endValues.idValues.get(id); View removeView = null; for (View viewToRemove : endCopy.keySet()) { if (viewToRemove.getId() == id) { removeView = viewToRemove; } } if (removeView != null) { endCopy.remove(removeView); } } endIdCopy.remove(id); if (isValidTarget(view, id)) { startValuesList.add(start); endValuesList.add(end); } } else { ListView parent = (ListView) view.getParent(); if (parent.getAdapter().hasStableIds()) { int position = parent.getPositionForView(view); long itemId = parent.getItemIdAtPosition(position); start = startValues.itemIdValues.get(itemId); endItemIdCopy.remove(itemId); // TODO: deal with targetIDs for itemIDs for ListView items startValuesList.add(start); endValuesList.add(end); } } } int startItemIdCopySize = startValues.itemIdValues.size(); for (int i = 0; i < startItemIdCopySize; ++i) { long id = startValues.itemIdValues.keyAt(i); if (isValidTarget(null, id)) { TransitionValues start = startValues.itemIdValues.get(id); TransitionValues end = endValues.itemIdValues.get(id); endItemIdCopy.remove(id); startValuesList.add(start); endValuesList.add(end); } } // Now walk through the remains of the end set for (View view : endCopy.keySet()) { int id = view.getId(); if (isValidTarget(view, id)) { TransitionValues start = startValues.viewValues.get(view) != null ? startValues.viewValues.get(view) : startValues.idValues.get(id); TransitionValues end = endCopy.get(view); endIdCopy.remove(id); startValuesList.add(start); endValuesList.add(end); } } int endIdCopySize = endIdCopy.size(); for (int i = 0; i < endIdCopySize; ++i) { int id = endIdCopy.keyAt(i); if (isValidTarget(null, id)) { TransitionValues start = startValues.idValues.get(id); TransitionValues end = endIdCopy.get(id); startValuesList.add(start); endValuesList.add(end); } } int endItemIdCopySize = endItemIdCopy.size(); for (int i = 0; i < endItemIdCopySize; ++i) { long id = endItemIdCopy.keyAt(i); // TODO: Deal with targetIDs and itemIDs TransitionValues start = startValues.itemIdValues.get(id); TransitionValues end = endItemIdCopy.get(id); startValuesList.add(start); endValuesList.add(end); } ArrayMap<Animator, AnimationInfo> runningAnimators = getRunningAnimators(); for (int i = 0; i < startValuesList.size(); ++i) { TransitionValues start = startValuesList.get(i); TransitionValues end = endValuesList.get(i); // Only bother trying to animate with values that differ between start/end if (start != null || end != null) { if (start == null || !start.equals(end)) { if (DBG) { View view = (end != null) ? end.view : start.view; Log.d(LOG_TAG, " differing start/end values for view " + view); if (start == null || end == null) { Log.d(LOG_TAG, " " + ((start == null) ? "start null, end non-null" : "start non-null, end null")); } else { for (String key : start.values.keySet()) { Object startValue = start.values.get(key); Object endValue = end.values.get(key); if (startValue != endValue && !startValue.equals(endValue)) { Log.d(LOG_TAG, " " + key + ": start(" + startValue + "), end(" + endValue + ")"); } } } } // TODO: what to do about targetIds and itemIds? Animator animator = createAnimator(sceneRoot, start, end); if (animator != null) { // Save animation info for future cancellation purposes View view = null; TransitionValues infoValues = null; if (end != null) { view = end.view; String[] properties = getTransitionProperties(); if (view != null && properties != null && properties.length > 0) { infoValues = new TransitionValues(); infoValues.view = view; TransitionValues newValues = endValues.viewValues.get(view); if (newValues != null) { for (int j = 0; j < properties.length; ++j) { infoValues.values.put(properties[j], newValues.values.get(properties[j])); } } int numExistingAnims = runningAnimators.size(); for (int j = 0; j < numExistingAnims; ++j) { Animator anim = runningAnimators.keyAt(j); AnimationInfo info = runningAnimators.get(anim); if (info.values != null && info.view == view && ((info.name == null && getName() == null) || info.name.equals(getName()))) { if (info.values.equals(infoValues)) { // Favor the old animator animator = null; break; } } } } } else { view = (start != null) ? start.view : null; } if (animator != null) { AnimationInfo info = new AnimationInfo(view, getName(), infoValues); runningAnimators.put(animator, info); mAnimators.add(animator); } } } } } } /** * Internal utility method for checking whether a given view/id * is valid for this transition, where "valid" means that either * the Transition has no target/targetId list (the default, in which * cause the transition should act on all views in the hiearchy), or * the given view is in the target list or the view id is in the * targetId list. If the target parameter is null, then the target list * is not checked (this is in the case of ListView items, where the * views are ignored and only the ids are used). */ boolean isValidTarget(View target, long targetId) { if (mTargetIdExcludes != null && mTargetIdExcludes.contains(targetId)) { return false; } if (mTargetExcludes != null && mTargetExcludes.contains(target)) { return false; } if (mTargetTypeExcludes != null && target != null) { int numTypes = mTargetTypeExcludes.size(); for (int i = 0; i < numTypes; ++i) { Class type = mTargetTypeExcludes.get(i); if (type.isInstance(target)) { return false; } } } if (mTargetIds.size() == 0 && mTargets.size() == 0) { return true; } if (mTargetIds.size() > 0) { for (int i = 0; i < mTargetIds.size(); ++i) { if (mTargetIds.get(i) == targetId) { return true; } } } if (target != null && mTargets.size() > 0) { for (int i = 0; i < mTargets.size(); ++i) { if (mTargets.get(i) == target) { return true; } } } return false; } private static ArrayMap<Animator, AnimationInfo> getRunningAnimators() { ArrayMap<Animator, AnimationInfo> runningAnimators = sRunningAnimators.get(); if (runningAnimators == null) { runningAnimators = new ArrayMap<Animator, AnimationInfo>(); sRunningAnimators.set(runningAnimators); } return runningAnimators; } /** * This is called internally once all animations have been set up by the * transition hierarchy. \ * * @hide */ protected void runAnimators() { if (DBG) { Log.d(LOG_TAG, "runAnimators() on " + this); } start(); ArrayMap<Animator, AnimationInfo> runningAnimators = getRunningAnimators(); // Now start every Animator that was previously created for this transition for (Animator anim : mAnimators) { if (DBG) { Log.d(LOG_TAG, " anim: " + anim); } if (runningAnimators.containsKey(anim)) { start(); runAnimator(anim, runningAnimators); } } mAnimators.clear(); end(); } private void runAnimator(Animator animator, final ArrayMap<Animator, AnimationInfo> runningAnimators) { if (animator != null) { // TODO: could be a single listener instance for all of them since it uses the param animator.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationStart(Animator animation) { mCurrentAnimators.add(animation); } @Override public void onAnimationEnd(Animator animation) { runningAnimators.remove(animation); mCurrentAnimators.remove(animation); } }); animate(animator); } } /** * Captures the values in the start scene for the properties that this * transition monitors. These values are then passed as the startValues * structure in a later call to * {@link #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues)}. * The main concern for an implementation is what the * properties are that the transition cares about and what the values are * for all of those properties. The start and end values will be compared * later during the * {@link #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues)} * method to determine what, if any, animations, should be run. * * <p>Subclasses must implement this method. The method should only be called by the * transition system; it is not intended to be called from external classes.</p> * * @param transitionValues The holder for any values that the Transition * wishes to store. Values are stored in the <code>values</code> field * of this TransitionValues object and are keyed from * a String value. For example, to store a view's rotation value, * a transition might call * <code>transitionValues.values.put("appname:transitionname:rotation", * view.getRotation())</code>. The target view will already be stored in * the transitionValues structure when this method is called. * * @see #captureEndValues(android.transition.TransitionValues) * @see #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues) */ public abstract void captureStartValues(TransitionValues transitionValues); /** * Captures the values in the end scene for the properties that this * transition monitors. These values are then passed as the endValues * structure in a later call to * {@link #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues)}. * The main concern for an implementation is what the * properties are that the transition cares about and what the values are * for all of those properties. The start and end values will be compared * later during the * {@link #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues)} * method to determine what, if any, animations, should be run. * * <p>Subclasses must implement this method. The method should only be called by the * transition system; it is not intended to be called from external classes.</p> * * @param transitionValues The holder for any values that the Transition * wishes to store. Values are stored in the <code>values</code> field * of this TransitionValues object and are keyed from * a String value. For example, to store a view's rotation value, * a transition might call * <code>transitionValues.values.put("appname:transitionname:rotation", * view.getRotation())</code>. The target view will already be stored in * the transitionValues structure when this method is called. * * @see #captureStartValues(android.transition.TransitionValues) * @see #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues) */ public abstract void captureEndValues(TransitionValues transitionValues); /** * Adds the id of a target view that this Transition is interested in * animating. By default, there are no targetIds, and a Transition will * listen for changes on every view in the hierarchy below the sceneRoot * of the Scene being transitioned into. Setting targetIds constrains * the Transition to only listen for, and act on, views with these IDs. * Views with different IDs, or no IDs whatsoever, will be ignored. * * <p>Note that using ids to specify targets implies that ids should be unique * within the view hierarchy underneat the scene root.</p> * * @see android.view.View#getId() * @param targetId The id of a target view, must be a positive number. * @return The Transition to which the targetId is added. * Returning the same object makes it easier to chain calls during * construction, such as * <code>transitionSet.addTransitions(new Fade()).addTarget(someId);</code> */ public Transition addTarget(int targetId) { if (targetId > 0) { mTargetIds.add(targetId); } return this; } /** * Removes the given targetId from the list of ids that this Transition * is interested in animating. * * @param targetId The id of a target view, must be a positive number. * @return The Transition from which the targetId is removed. * Returning the same object makes it easier to chain calls during * construction, such as * <code>transitionSet.addTransitions(new Fade()).removeTargetId(someId);</code> */ public Transition removeTarget(int targetId) { if (targetId > 0) { mTargetIds.remove(targetId); } return this; } /** * Whether to add the given id to the list of target ids to exclude from this * transition. The <code>exclude</code> parameter specifies whether the target * should be added to or removed from the excluded list. * * <p>Excluding targets is a general mechanism for allowing transitions to run on * a view hierarchy while skipping target views that should not be part of * the transition. For example, you may want to avoid animating children * of a specific ListView or Spinner. Views can be excluded either by their * id, or by their instance reference, or by the Class of that view * (eg, {@link android.widget.Spinner}).</p> * * @see #excludeChildren(int, boolean) * @see #excludeTarget(android.view.View, boolean) * @see #excludeTarget(Class, boolean) * * @param targetId The id of a target to ignore when running this transition. * @param exclude Whether to add the target to or remove the target from the * current list of excluded targets. * @return This transition object. */ public Transition excludeTarget(int targetId, boolean exclude) { mTargetIdExcludes = excludeId(mTargetIdExcludes, targetId, exclude); return this; } /** * Whether to add the children of the given id to the list of targets to exclude * from this transition. The <code>exclude</code> parameter specifies whether * the children of the target should be added to or removed from the excluded list. * Excluding children in this way provides a simple mechanism for excluding all * children of specific targets, rather than individually excluding each * child individually. * * <p>Excluding targets is a general mechanism for allowing transitions to run on * a view hierarchy while skipping target views that should not be part of * the transition. For example, you may want to avoid animating children * of a specific ListView or Spinner. Views can be excluded either by their * id, or by their instance reference, or by the Class of that view * (eg, {@link android.widget.Spinner}).</p> * * @see #excludeTarget(int, boolean) * @see #excludeChildren(android.view.View, boolean) * @see #excludeChildren(Class, boolean) * * @param targetId The id of a target whose children should be ignored when running * this transition. * @param exclude Whether to add the target to or remove the target from the * current list of excluded-child targets. * @return This transition object. */ public Transition excludeChildren(int targetId, boolean exclude) { mTargetIdChildExcludes = excludeId(mTargetIdChildExcludes, targetId, exclude); return this; } /** * Utility method to manage the boilerplate code that is the same whether we * are excluding targets or their children. */ private ArrayList<Integer> excludeId(ArrayList<Integer> list, int targetId, boolean exclude) { if (targetId > 0) { if (exclude) { list = ArrayListManager.add(list, targetId); } else { list = ArrayListManager.remove(list, targetId); } } return list; } /** * Whether to add the given target to the list of targets to exclude from this * transition. The <code>exclude</code> parameter specifies whether the target * should be added to or removed from the excluded list. * * <p>Excluding targets is a general mechanism for allowing transitions to run on * a view hierarchy while skipping target views that should not be part of * the transition. For example, you may want to avoid animating children * of a specific ListView or Spinner. Views can be excluded either by their * id, or by their instance reference, or by the Class of that view * (eg, {@link android.widget.Spinner}).</p> * * @see #excludeChildren(android.view.View, boolean) * @see #excludeTarget(int, boolean) * @see #excludeTarget(Class, boolean) * * @param target The target to ignore when running this transition. * @param exclude Whether to add the target to or remove the target from the * current list of excluded targets. * @return This transition object. */ public Transition excludeTarget(View target, boolean exclude) { mTargetExcludes = excludeView(mTargetExcludes, target, exclude); return this; } /** * Whether to add the children of given target to the list of target children * to exclude from this transition. The <code>exclude</code> parameter specifies * whether the target should be added to or removed from the excluded list. * * <p>Excluding targets is a general mechanism for allowing transitions to run on * a view hierarchy while skipping target views that should not be part of * the transition. For example, you may want to avoid animating children * of a specific ListView or Spinner. Views can be excluded either by their * id, or by their instance reference, or by the Class of that view * (eg, {@link android.widget.Spinner}).</p> * * @see #excludeTarget(android.view.View, boolean) * @see #excludeChildren(int, boolean) * @see #excludeChildren(Class, boolean) * * @param target The target to ignore when running this transition. * @param exclude Whether to add the target to or remove the target from the * current list of excluded targets. * @return This transition object. */ public Transition excludeChildren(View target, boolean exclude) { mTargetChildExcludes = excludeView(mTargetChildExcludes, target, exclude); return this; } /** * Utility method to manage the boilerplate code that is the same whether we * are excluding targets or their children. */ private ArrayList<View> excludeView(ArrayList<View> list, View target, boolean exclude) { if (target != null) { if (exclude) { list = ArrayListManager.add(list, target); } else { list = ArrayListManager.remove(list, target); } } return list; } /** * Whether to add the given type to the list of types to exclude from this * transition. The <code>exclude</code> parameter specifies whether the target * type should be added to or removed from the excluded list. * * <p>Excluding targets is a general mechanism for allowing transitions to run on * a view hierarchy while skipping target views that should not be part of * the transition. For example, you may want to avoid animating children * of a specific ListView or Spinner. Views can be excluded either by their * id, or by their instance reference, or by the Class of that view * (eg, {@link android.widget.Spinner}).</p> * * @see #excludeChildren(Class, boolean) * @see #excludeTarget(int, boolean) * @see #excludeTarget(android.view.View, boolean) * * @param type The type to ignore when running this transition. * @param exclude Whether to add the target type to or remove it from the * current list of excluded target types. * @return This transition object. */ public Transition excludeTarget(Class type, boolean exclude) { mTargetTypeExcludes = excludeType(mTargetTypeExcludes, type, exclude); return this; } /** * Whether to add the given type to the list of types whose children should * be excluded from this transition. The <code>exclude</code> parameter * specifies whether the target type should be added to or removed from * the excluded list. * * <p>Excluding targets is a general mechanism for allowing transitions to run on * a view hierarchy while skipping target views that should not be part of * the transition. For example, you may want to avoid animating children * of a specific ListView or Spinner. Views can be excluded either by their * id, or by their instance reference, or by the Class of that view * (eg, {@link android.widget.Spinner}).</p> * * @see #excludeTarget(Class, boolean) * @see #excludeChildren(int, boolean) * @see #excludeChildren(android.view.View, boolean) * * @param type The type to ignore when running this transition. * @param exclude Whether to add the target type to or remove it from the * current list of excluded target types. * @return This transition object. */ public Transition excludeChildren(Class type, boolean exclude) { mTargetTypeChildExcludes = excludeType(mTargetTypeChildExcludes, type, exclude); return this; } /** * Utility method to manage the boilerplate code that is the same whether we * are excluding targets or their children. */ private ArrayList<Class> excludeType(ArrayList<Class> list, Class type, boolean exclude) { if (type != null) { if (exclude) { list = ArrayListManager.add(list, type); } else { list = ArrayListManager.remove(list, type); } } return list; } /** * Sets the target view instances that this Transition is interested in * animating. By default, there are no targets, and a Transition will * listen for changes on every view in the hierarchy below the sceneRoot * of the Scene being transitioned into. Setting targets constrains * the Transition to only listen for, and act on, these views. * All other views will be ignored. * * <p>The target list is like the {@link #addTarget(int) targetId} * list except this list specifies the actual View instances, not the ids * of the views. This is an important distinction when scene changes involve * view hierarchies which have been inflated separately; different views may * share the same id but not actually be the same instance. If the transition * should treat those views as the same, then {@link #addTarget(int)} should be used * instead of {@link #addTarget(android.view.View)}. If, on the other hand, scene changes involve * changes all within the same view hierarchy, among views which do not * necessarily have ids set on them, then the target list of views may be more * convenient.</p> * * @see #addTarget(int) * @param target A View on which the Transition will act, must be non-null. * @return The Transition to which the target is added. * Returning the same object makes it easier to chain calls during * construction, such as * <code>transitionSet.addTransitions(new Fade()).addTarget(someView);</code> */ public Transition addTarget(View target) { mTargets.add(target); return this; } /** * Removes the given target from the list of targets that this Transition * is interested in animating. * * @param target The target view, must be non-null. * @return Transition The Transition from which the target is removed. * Returning the same object makes it easier to chain calls during * construction, such as * <code>transitionSet.addTransitions(new Fade()).removeTarget(someView);</code> */ public Transition removeTarget(View target) { if (target != null) { mTargets.remove(target); } return this; } /** * Returns the array of target IDs that this transition limits itself to * tracking and animating. If the array is null for both this method and * {@link #getTargets()}, then this transition is * not limited to specific views, and will handle changes to any views * in the hierarchy of a scene change. * * @return the list of target IDs */ public List<Integer> getTargetIds() { return mTargetIds; } /** * Returns the array of target views that this transition limits itself to * tracking and animating. If the array is null for both this method and * {@link #getTargetIds()}, then this transition is * not limited to specific views, and will handle changes to any views * in the hierarchy of a scene change. * * @return the list of target views */ public List<View> getTargets() { return mTargets; } /** * Recursive method that captures values for the given view and the * hierarchy underneath it. * @param sceneRoot The root of the view hierarchy being captured * @param start true if this capture is happening before the scene change, * false otherwise */ void captureValues(ViewGroup sceneRoot, boolean start) { if (start) { mStartValues.viewValues.clear(); mStartValues.idValues.clear(); mStartValues.itemIdValues.clear(); } else { mEndValues.viewValues.clear(); mEndValues.idValues.clear(); mEndValues.itemIdValues.clear(); } if (mTargetIds.size() > 0 || mTargets.size() > 0) { if (mTargetIds.size() > 0) { for (int i = 0; i < mTargetIds.size(); ++i) { int id = mTargetIds.get(i); View view = sceneRoot.findViewById(id); if (view != null) { TransitionValues values = new TransitionValues(); values.view = view; if (start) { captureStartValues(values); } else { captureEndValues(values); } if (start) { mStartValues.viewValues.put(view, values); if (id >= 0) { mStartValues.idValues.put(id, values); } } else { mEndValues.viewValues.put(view, values); if (id >= 0) { mEndValues.idValues.put(id, values); } } } } } if (mTargets.size() > 0) { for (int i = 0; i < mTargets.size(); ++i) { View view = mTargets.get(i); if (view != null) { TransitionValues values = new TransitionValues(); values.view = view; if (start) { captureStartValues(values); } else { captureEndValues(values); } if (start) { mStartValues.viewValues.put(view, values); } else { mEndValues.viewValues.put(view, values); } } } } } else { captureHierarchy(sceneRoot, start); } } /** * Recursive method which captures values for an entire view hierarchy, * starting at some root view. Transitions without targetIDs will use this * method to capture values for all possible views. * * @param view The view for which to capture values. Children of this View * will also be captured, recursively down to the leaf nodes. * @param start true if values are being captured in the start scene, false * otherwise. */ private void captureHierarchy(View view, boolean start) { if (view == null) { return; } boolean isListViewItem = false; if (view.getParent() instanceof ListView) { isListViewItem = true; } if (isListViewItem && !((ListView) view.getParent()).getAdapter().hasStableIds()) { // ignore listview children unless we can track them with stable IDs return; } int id = View.NO_ID; long itemId = View.NO_ID; if (!isListViewItem) { id = view.getId(); } else { ListView listview = (ListView) view.getParent(); int position = listview.getPositionForView(view); itemId = listview.getItemIdAtPosition(position); view.setHasTransientState(true); } if (mTargetIdExcludes != null && mTargetIdExcludes.contains(id)) { return; } if (mTargetExcludes != null && mTargetExcludes.contains(view)) { return; } if (mTargetTypeExcludes != null && view != null) { int numTypes = mTargetTypeExcludes.size(); for (int i = 0; i < numTypes; ++i) { if (mTargetTypeExcludes.get(i).isInstance(view)) { return; } } } TransitionValues values = new TransitionValues(); values.view = view; if (start) { captureStartValues(values); } else { captureEndValues(values); } if (start) { if (!isListViewItem) { mStartValues.viewValues.put(view, values); if (id >= 0) { mStartValues.idValues.put((int) id, values); } } else { mStartValues.itemIdValues.put(itemId, values); } } else { if (!isListViewItem) { mEndValues.viewValues.put(view, values); if (id >= 0) { mEndValues.idValues.put((int) id, values); } } else { mEndValues.itemIdValues.put(itemId, values); } } if (view instanceof ViewGroup) { // Don't traverse child hierarchy if there are any child-excludes on this view if (mTargetIdChildExcludes != null && mTargetIdChildExcludes.contains(id)) { return; } if (mTargetChildExcludes != null && mTargetChildExcludes.contains(view)) { return; } if (mTargetTypeChildExcludes != null && view != null) { int numTypes = mTargetTypeChildExcludes.size(); for (int i = 0; i < numTypes; ++i) { if (mTargetTypeChildExcludes.get(i).isInstance(view)) { return; } } } ViewGroup parent = (ViewGroup) view; for (int i = 0; i < parent.getChildCount(); ++i) { captureHierarchy(parent.getChildAt(i), start); } } } /** * This method can be called by transitions to get the TransitionValues for * any particular view during the transition-playing process. This might be * necessary, for example, to query the before/after state of related views * for a given transition. */ public TransitionValues getTransitionValues(View view, boolean start) { if (mParent != null) { return mParent.getTransitionValues(view, start); } TransitionValuesMaps valuesMaps = start ? mStartValues : mEndValues; TransitionValues values = valuesMaps.viewValues.get(view); if (values == null) { int id = view.getId(); if (id >= 0) { values = valuesMaps.idValues.get(id); } if (values == null && view.getParent() instanceof ListView) { ListView listview = (ListView) view.getParent(); int position = listview.getPositionForView(view); long itemId = listview.getItemIdAtPosition(position); values = valuesMaps.itemIdValues.get(itemId); } // TODO: Doesn't handle the case where a view was parented to a // ListView (with an itemId), but no longer is } return values; } /** * Pauses this transition, sending out calls to {@link * com.hirevue.manager.tmp.transition.Transition.TransitionListener#onTransitionPause(com.hirevue.manager.tmp.transition.Transition)} to all listeners * and pausing all running animators started by this transition. * * @hide */ public void pause() { if (!mEnded) { ArrayMap<Animator, AnimationInfo> runningAnimators = getRunningAnimators(); int numOldAnims = runningAnimators.size(); for (int i = numOldAnims - 1; i >= 0; i--) { Animator anim = runningAnimators.keyAt(i); anim.pause(); } if (mListeners != null && mListeners.size() > 0) { ArrayList<TransitionListener> tmpListeners = (ArrayList<TransitionListener>) mListeners.clone(); int numListeners = tmpListeners.size(); for (int i = 0; i < numListeners; ++i) { tmpListeners.get(i).onTransitionPause(this); } } mPaused = true; } } /** * Resumes this transition, sending out calls to {@link * com.hirevue.manager.tmp.transition.Transition.TransitionListener#onTransitionPause(com.hirevue.manager.tmp.transition.Transition)} to all listeners * and pausing all running animators started by this transition. * * @hide */ public void resume() { if (mPaused) { if (!mEnded) { ArrayMap<Animator, AnimationInfo> runningAnimators = getRunningAnimators(); int numOldAnims = runningAnimators.size(); for (int i = numOldAnims - 1; i >= 0; i--) { Animator anim = runningAnimators.keyAt(i); anim.resume(); } if (mListeners != null && mListeners.size() > 0) { ArrayList<TransitionListener> tmpListeners = (ArrayList<TransitionListener>) mListeners.clone(); int numListeners = tmpListeners.size(); for (int i = 0; i < numListeners; ++i) { tmpListeners.get(i).onTransitionResume(this); } } } mPaused = false; } } /** * Called by TransitionManager to play the transition. This calls * createAnimators() to set things up and create all of the animations and then * runAnimations() to actually start the animations. */ void playTransition(ViewGroup sceneRoot) { ArrayMap<Animator, AnimationInfo> runningAnimators = getRunningAnimators(); int numOldAnims = runningAnimators.size(); for (int i = numOldAnims - 1; i >= 0; i--) { Animator anim = runningAnimators.keyAt(i); if (anim != null) { AnimationInfo oldInfo = runningAnimators.get(anim); if (oldInfo != null) { boolean cancel = false; TransitionValues oldValues = oldInfo.values; View oldView = oldInfo.view; TransitionValues newValues = mEndValues.viewValues != null ? mEndValues.viewValues.get(oldView) : null; if (newValues == null) { newValues = mEndValues.idValues.get(oldView.getId()); } if (oldValues != null) { // if oldValues null, then transition didn't care to stash values, // and won't get canceled if (newValues != null) { for (String key : oldValues.values.keySet()) { Object oldValue = oldValues.values.get(key); Object newValue = newValues.values.get(key); if (oldValue != null && newValue != null && !oldValue.equals(newValue)) { cancel = true; if (DBG) { Log.d(LOG_TAG, "Transition.playTransition: " + "oldValue != newValue for " + key + ": old, new = " + oldValue + ", " + newValue); } break; } } } } if (cancel) { if (anim.isRunning() || anim.isStarted()) { if (DBG) { Log.d(LOG_TAG, "Canceling anim " + anim); } anim.cancel(); } else { if (DBG) { Log.d(LOG_TAG, "removing anim from info list: " + anim); } runningAnimators.remove(anim); } } } } } createAnimators(sceneRoot, mStartValues, mEndValues); runAnimators(); } /** * This is a utility method used by subclasses to handle standard parts of * setting up and running an Animator: it sets the {@link #getDuration() * duration} and the {@link #getStartDelay() startDelay}, starts the * animation, and, when the animator ends, calls {@link #end()}. * * @param animator The Animator to be run during this transition. * * @hide */ protected void animate(Animator animator) { // TODO: maybe pass auto-end as a boolean parameter? if (animator == null) { end(); } else { if (getDuration() >= 0) { animator.setDuration(getDuration()); } if (getStartDelay() >= 0) { animator.setStartDelay(getStartDelay()); } if (getInterpolator() != null) { animator.setInterpolator(getInterpolator()); } animator.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { end(); animation.removeListener(this); } }); animator.start(); } } /** * This method is called automatically by the transition and * TransitionSet classes prior to a Transition subclass starting; * subclasses should not need to call it directly. * * @hide */ protected void start() { if (mNumInstances == 0) { if (mListeners != null && mListeners.size() > 0) { ArrayList<TransitionListener> tmpListeners = (ArrayList<TransitionListener>) mListeners.clone(); int numListeners = tmpListeners.size(); for (int i = 0; i < numListeners; ++i) { tmpListeners.get(i).onTransitionStart(this); } } mEnded = false; } mNumInstances++; } /** * This method is called automatically by the Transition and * TransitionSet classes when a transition finishes, either because * a transition did nothing (returned a null Animator from * {@link com.hirevue.manager.tmp.transition.Transition#createAnimator(android.view.ViewGroup, android.transition.TransitionValues, * android.transition.TransitionValues)}) or because the transition returned a valid * Animator and end() was called in the onAnimationEnd() * callback of the AnimatorListener. * * @hide */ protected void end() { --mNumInstances; if (mNumInstances == 0) { if (mListeners != null && mListeners.size() > 0) { ArrayList<TransitionListener> tmpListeners = (ArrayList<TransitionListener>) mListeners.clone(); int numListeners = tmpListeners.size(); for (int i = 0; i < numListeners; ++i) { tmpListeners.get(i).onTransitionEnd(this); } } for (int i = 0; i < mStartValues.itemIdValues.size(); ++i) { TransitionValues tv = mStartValues.itemIdValues.valueAt(i); View v = tv.view; if (v.hasTransientState()) { v.setHasTransientState(false); } } for (int i = 0; i < mEndValues.itemIdValues.size(); ++i) { TransitionValues tv = mEndValues.itemIdValues.valueAt(i); View v = tv.view; if (v.hasTransientState()) { v.setHasTransientState(false); } } mEnded = true; } } /** * This method cancels a transition that is currently running. * * @hide */ protected void cancel() { int numAnimators = mCurrentAnimators.size(); for (int i = numAnimators - 1; i >= 0; i--) { Animator animator = mCurrentAnimators.get(i); animator.cancel(); } if (mListeners != null && mListeners.size() > 0) { ArrayList<TransitionListener> tmpListeners = (ArrayList<TransitionListener>) mListeners.clone(); int numListeners = tmpListeners.size(); for (int i = 0; i < numListeners; ++i) { tmpListeners.get(i).onTransitionCancel(this); } } } /** * Adds a listener to the set of listeners that are sent events through the * life of an animation, such as start, repeat, and end. * * @param listener the listener to be added to the current set of listeners * for this animation. * @return This transition object. */ public Transition addListener(TransitionListener listener) { if (mListeners == null) { mListeners = new ArrayList<TransitionListener>(); } mListeners.add(listener); return this; } /** * Removes a listener from the set listening to this animation. * * @param listener the listener to be removed from the current set of * listeners for this transition. * @return This transition object. */ public Transition removeListener(TransitionListener listener) { if (mListeners == null) { return this; } mListeners.remove(listener); if (mListeners.size() == 0) { mListeners = null; } return this; } Transition setSceneRoot(ViewGroup sceneRoot) { mSceneRoot = sceneRoot; return this; } void setCanRemoveViews(boolean canRemoveViews) { mCanRemoveViews = canRemoveViews; } @Override public String toString() { return toString(""); } @Override public Transition clone() { Transition clone = null; try { clone = (Transition) super.clone(); clone.mAnimators = new ArrayList<Animator>(); clone.mStartValues = new TransitionValuesMaps(); clone.mEndValues = new TransitionValuesMaps(); } catch (CloneNotSupportedException e) { } return clone; } /** * Returns the name of this Transition. This name is used internally to distinguish * between different transitions to determine when interrupting transitions overlap. * For example, a ChangeBounds running on the same target view as another ChangeBounds * should determine whether the old transition is animating to different end values * and should be canceled in favor of the new transition. * * <p>By default, a Transition's name is simply the value of {@link Class#getName()}, * but subclasses are free to override and return something different.</p> * * @return The name of this transition. */ public String getName() { return mName; } String toString(String indent) { String result = indent + getClass().getSimpleName() + "@" + Integer.toHexString(hashCode()) + ": "; if (mDuration != -1) { result += "dur(" + mDuration + ") "; } if (mStartDelay != -1) { result += "dly(" + mStartDelay + ") "; } if (mInterpolator != null) { result += "interp(" + mInterpolator + ") "; } if (mTargetIds.size() > 0 || mTargets.size() > 0) { result += "tgts("; if (mTargetIds.size() > 0) { for (int i = 0; i < mTargetIds.size(); ++i) { if (i > 0) { result += ", "; } result += mTargetIds.get(i); } } if (mTargets.size() > 0) { for (int i = 0; i < mTargets.size(); ++i) { if (i > 0) { result += ", "; } result += mTargets.get(i); } } result += ")"; } return result; } /** * A transition listener receives notifications from a transition. * Notifications indicate transition lifecycle events. */ public static interface TransitionListener { /** * Notification about the start of the transition. * * @param transition The started transition. */ void onTransitionStart(Transition transition); /** * Notification about the end of the transition. Canceled transitions * will always notify listeners of both the cancellation and end * events. That is, {@link #onTransitionEnd(com.hirevue.manager.tmp.transition.Transition)} is always called, * regardless of whether the transition was canceled or played * through to completion. * * @param transition The transition which reached its end. */ void onTransitionEnd(Transition transition); /** * Notification about the cancellation of the transition. * Note that cancel may be called by a parent {@link android.transition.TransitionSet} on * a child transition which has not yet started. This allows the child * transition to restore state on target objects which was set at * {@link #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues) * createAnimator()} time. * * @param transition The transition which was canceled. */ void onTransitionCancel(Transition transition); /** * Notification when a transition is paused. * Note that createAnimator() may be called by a parent {@link android.transition.TransitionSet} on * a child transition which has not yet started. This allows the child * transition to restore state on target objects which was set at * {@link #createAnimator(android.view.ViewGroup, android.transition.TransitionValues, android.transition.TransitionValues) * createAnimator()} time. * * @param transition The transition which was paused. */ void onTransitionPause(Transition transition); /** * Notification when a transition is resumed. * Note that resume() may be called by a parent {@link android.transition.TransitionSet} on * a child transition which has not yet started. This allows the child * transition to restore state which may have changed in an earlier call * to {@link #onTransitionPause(com.hirevue.manager.tmp.transition.Transition)}. * * @param transition The transition which was resumed. */ void onTransitionResume(Transition transition); } /** * Utility adapter class to avoid having to override all three methods * whenever someone just wants to listen for a single event. * * @hide * */ public static class TransitionListenerAdapter implements TransitionListener { @Override public void onTransitionStart(Transition transition) { } @Override public void onTransitionEnd(Transition transition) { } @Override public void onTransitionCancel(Transition transition) { } @Override public void onTransitionPause(Transition transition) { } @Override public void onTransitionResume(Transition transition) { } } /** * Holds information about each animator used when a new transition starts * while other transitions are still running to determine whether a running * animation should be canceled or a new animation noop'd. The structure holds * information about the state that an animation is going to, to be compared to * end state of a new animation. */ private static class AnimationInfo { View view; String name; TransitionValues values; AnimationInfo(View view, String name, TransitionValues values) { this.view = view; this.name = name; this.values = values; } } /** * Utility class for managing typed ArrayLists efficiently. In particular, this * can be useful for lists that we don't expect to be used often (eg, the exclude * lists), so we'd like to keep them nulled out by default. This causes the code to * become tedious, with constant null checks, code to allocate when necessary, * and code to null out the reference when the list is empty. This class encapsulates * all of that functionality into simple add()/remove() methods which perform the * necessary checks, allocation/null-out as appropriate, and return the * resulting list. */ private static class ArrayListManager { /** * Add the specified item to the list, returning the resulting list. * The returned list can either the be same list passed in or, if that * list was null, the new list that was created. * * Note that the list holds unique items; if the item already exists in the * list, the list is not modified. */ static <T> ArrayList<T> add(ArrayList<T> list, T item) { if (list == null) { list = new ArrayList<T>(); } if (!list.contains(item)) { list.add(item); } return list; } /** * Remove the specified item from the list, returning the resulting list. * The returned list can either the be same list passed in or, if that * list becomes empty as a result of the remove(), the new list was created. */ static <T> ArrayList<T> remove(ArrayList<T> list, T item) { if (list != null) { list.remove(item); if (list.isEmpty()) { list = null; } } return list; } } }