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 android.transition; import android.annotation.UnsupportedAppUsage; import android.content.Context; import android.util.SparseArray; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; /** * A scene represents the collection of values that various properties in the * View hierarchy will have when the scene is applied. A Scene can be * configured to automatically run a Transition when it is applied, which will * animate the various property changes that take place during the * scene change. */ public final class Scene { private Context mContext; private int mLayoutId = -1; private ViewGroup mSceneRoot; private View mLayout; // alternative to layoutId @UnsupportedAppUsage Runnable mEnterAction; @UnsupportedAppUsage Runnable mExitAction; /** * Returns a Scene described by the resource file associated with the given * <code>layoutId</code> parameter. If such a Scene has already been created for * the given <code>sceneRoot</code>, that same Scene will be returned. * This caching of layoutId-based scenes enables sharing of common scenes * between those created in code and those referenced by {@link TransitionManager} * XML resource files. * * @param sceneRoot The root of the hierarchy in which scene changes * and transitions will take place. * @param layoutId The id of a standard layout resource file. * @param context The context used in the process of inflating * the layout resource. * @return The scene for the given root and layout id */ public static Scene getSceneForLayout(ViewGroup sceneRoot, int layoutId, Context context) { SparseArray<Scene> scenes = (SparseArray<Scene>) sceneRoot .getTag(com.android.internal.R.id.scene_layoutid_cache); if (scenes == null) { scenes = new SparseArray<Scene>(); sceneRoot.setTagInternal(com.android.internal.R.id.scene_layoutid_cache, scenes); } Scene scene = scenes.get(layoutId); if (scene != null) { return scene; } else { scene = new Scene(sceneRoot, layoutId, context); scenes.put(layoutId, scene); return scene; } } /** * Constructs a Scene with no information about how values will change * when this scene is applied. This constructor might be used when * a Scene is created with the intention of being dynamically configured, * through setting {@link #setEnterAction(Runnable)} and possibly * {@link #setExitAction(Runnable)}. * * @param sceneRoot The root of the hierarchy in which scene changes * and transitions will take place. */ public Scene(ViewGroup sceneRoot) { mSceneRoot = sceneRoot; } /** * Constructs a Scene which, when entered, will remove any * children from the sceneRoot container and will inflate and add * the hierarchy specified by the layoutId resource file. * * <p>This method is hidden because layoutId-based scenes should be * created by the caching factory method {@link Scene#getCurrentScene(View)}.</p> * * @param sceneRoot The root of the hierarchy in which scene changes * and transitions will take place. * @param layoutId The id of a resource file that defines the view * hierarchy of this scene. * @param context The context used in the process of inflating * the layout resource. */ private Scene(ViewGroup sceneRoot, int layoutId, Context context) { mContext = context; mSceneRoot = sceneRoot; mLayoutId = layoutId; } /** * Constructs a Scene which, when entered, will remove any * children from the sceneRoot container and add the layout * object as a new child of that container. * * @param sceneRoot The root of the hierarchy in which scene changes * and transitions will take place. * @param layout The view hierarchy of this scene, added as a child * of sceneRoot when this scene is entered. */ public Scene(ViewGroup sceneRoot, View layout) { mSceneRoot = sceneRoot; mLayout = layout; } /** * @deprecated use {@link #Scene(ViewGroup, View)}. */ @Deprecated public Scene(ViewGroup sceneRoot, ViewGroup layout) { mSceneRoot = sceneRoot; mLayout = layout; } /** * Gets the root of the scene, which is the root of the view hierarchy * affected by changes due to this scene, and which will be animated * when this scene is entered. * * @return The root of the view hierarchy affected by this scene. */ public ViewGroup getSceneRoot() { return mSceneRoot; } /** * Exits this scene, if it is the current scene * on the scene's {@link #getSceneRoot() scene root}. The current scene is * set when {@link #enter() entering} a scene. * Exiting a scene runs the {@link #setExitAction(Runnable) exit action} * if there is one. */ public void exit() { if (getCurrentScene(mSceneRoot) == this) { if (mExitAction != null) { mExitAction.run(); } } } /** * Enters this scene, which entails changing all values that * are specified by this scene. These may be values associated * with a layout view group or layout resource file which will * now be added to the scene root, or it may be values changed by * an {@link #setEnterAction(Runnable)} enter action}, or a * combination of the these. No transition will be run when the * scene is entered. To get transition behavior in scene changes, * use one of the methods in {@link TransitionManager} instead. */ public void enter() { // Apply layout change, if any if (mLayoutId > 0 || mLayout != null) { // empty out parent container before adding to it getSceneRoot().removeAllViews(); if (mLayoutId > 0) { LayoutInflater.from(mContext).inflate(mLayoutId, mSceneRoot); } else { mSceneRoot.addView(mLayout); } } // Notify next scene that it is entering. Subclasses may override to configure scene. if (mEnterAction != null) { mEnterAction.run(); } setCurrentScene(mSceneRoot, this); } /** * Set the scene that the given view is in. The current scene is set only * on the root view of a scene, not for every view in that hierarchy. This * information is used by Scene to determine whether there is a previous * scene which should be exited before the new scene is entered. * * @param view The view on which the current scene is being set */ @UnsupportedAppUsage static void setCurrentScene(View view, Scene scene) { view.setTagInternal(com.android.internal.R.id.current_scene, scene); } /** * Gets the current {@link Scene} set on the given view. A scene is set on a view * only if that view is the scene root. * * @return The current Scene set on this view. A value of null indicates that * no Scene is currently set. */ static Scene getCurrentScene(View view) { return (Scene) view.getTag(com.android.internal.R.id.current_scene); } /** * Scenes that are not defined with layout resources or * hierarchies, or which need to perform additional steps * after those hierarchies are changed to, should set an enter * action, and possibly an exit action as well. An enter action * will cause Scene to call back into application code to do * anything else the application needs after transitions have * captured pre-change values and after any other scene changes * have been applied, such as the layout (if any) being added to * the view hierarchy. After this method is called, Transitions will * be played. * * @param action The runnable whose {@link Runnable#run() run()} method will * be called when this scene is entered * @see #setExitAction(Runnable) * @see Scene#Scene(ViewGroup, int, Context) * @see Scene#Scene(ViewGroup, ViewGroup) */ public void setEnterAction(Runnable action) { mEnterAction = action; } /** * Scenes that are not defined with layout resources or * hierarchies, or which need to perform additional steps * after those hierarchies are changed to, should set an enter * action, and possibly an exit action as well. An exit action * will cause Scene to call back into application code to do * anything the application needs to do after applicable transitions have * captured pre-change values, but before any other scene changes * have been applied, such as the new layout (if any) being added to * the view hierarchy. After this method is called, the next scene * will be entered, including a call to {@link #setEnterAction(Runnable)} * if an enter action is set. * * @see #setEnterAction(Runnable) * @see Scene#Scene(ViewGroup, int, Context) * @see Scene#Scene(ViewGroup, ViewGroup) */ public void setExitAction(Runnable action) { mExitAction = action; } /** * Returns whether this Scene was created by a layout resource file, determined * by the layoutId passed into * {@link #getSceneForLayout(android.view.ViewGroup, int, android.content.Context)}. * This is called by TransitionManager to determine whether it is safe for views from * this scene to be removed from their parents when the scene is exited, which is * used by {@link Fade} to fade these views out (the views must be removed from * their parent in order to add them to the overlay for fading purposes). If a * Scene is not based on a resource file, then the impact of removing views * arbitrarily is unknown and should be avoided. */ boolean isCreatedFromLayoutResource() { return (mLayoutId > 0); } }