Java tutorial
/* * Copyright (C) 2015 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.support.design.widget; import android.annotation.TargetApi; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Rect; import android.os.Build; import android.os.Parcel; import android.os.Parcelable; import android.support.annotation.IntDef; import android.support.annotation.NonNull; import android.support.annotation.Nullable; import android.support.annotation.RequiresApi; import android.support.annotation.RestrictTo; import android.support.annotation.VisibleForTesting; import android.support.design.R; import android.support.v4.os.ParcelableCompat; import android.support.v4.os.ParcelableCompatCreatorCallbacks; import android.support.v4.view.AbsSavedState; import android.support.v4.view.ViewCompat; import android.support.v4.view.WindowInsetsCompat; import android.util.AttributeSet; import android.view.View; import android.view.ViewGroup; import android.view.animation.Interpolator; import android.widget.LinearLayout; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.ref.WeakReference; import java.util.ArrayList; import java.util.List; import static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP; import static android.support.design.widget.ViewUtils.objectEquals; /** * AppBarLayout is a vertical {@link LinearLayout} which implements many of the features of * material designs app bar concept, namely scrolling gestures. * <p> * Children should provide their desired scrolling behavior through * {@link LayoutParams#setScrollFlags(int)} and the associated layout xml attribute: * {@code app:layout_scrollFlags}. * * <p> * This view depends heavily on being used as a direct child within a {@link CoordinatorLayout}. * If you use AppBarLayout within a different {@link ViewGroup}, most of it's functionality will * not work. * <p> * AppBarLayout also requires a separate scrolling sibling in order to know when to scroll. * The binding is done through the {@link ScrollingViewBehavior} behavior class, meaning that you * should set your scrolling view's behavior to be an instance of {@link ScrollingViewBehavior}. * A string resource containing the full class name is available. * * <pre> * <android.support.design.widget.CoordinatorLayout * xmlns:android="http://schemas.android.com/apk/res/android" * xmlns:app="http://schemas.android.com/apk/res-auto" * android:layout_width="match_parent" * android:layout_height="match_parent"> * * <android.support.v4.widget.NestedScrollView * android:layout_width="match_parent" * android:layout_height="match_parent" * app:layout_behavior="@string/appbar_scrolling_view_behavior"> * * <!-- Your scrolling content --> * * </android.support.v4.widget.NestedScrollView> * * <android.support.design.widget.AppBarLayout * android:layout_height="wrap_content" * android:layout_width="match_parent"> * * <android.support.v7.widget.Toolbar * ... * app:layout_scrollFlags="scroll|enterAlways"/> * * <android.support.design.widget.TabLayout * ... * app:layout_scrollFlags="scroll|enterAlways"/> * * </android.support.design.widget.AppBarLayout> * * </android.support.design.widget.CoordinatorLayout> * </pre> * * @see <a href="http://www.google.com/design/spec/layout/structure.html#structure-app-bar"> * http://www.google.com/design/spec/layout/structure.html#structure-app-bar</a> */ @CoordinatorLayout.DefaultBehavior(AppBarLayout.Behavior.class) public class AppBarLayout extends LinearLayout { static final int PENDING_ACTION_NONE = 0x0; static final int PENDING_ACTION_EXPANDED = 0x1; static final int PENDING_ACTION_COLLAPSED = 0x2; static final int PENDING_ACTION_ANIMATE_ENABLED = 0x4; static final int PENDING_ACTION_FORCE = 0x8; /** * Interface definition for a callback to be invoked when an {@link AppBarLayout}'s vertical * offset changes. */ public interface OnOffsetChangedListener { /** * Called when the {@link AppBarLayout}'s layout offset has been changed. This allows * child views to implement custom behavior based on the offset (for instance pinning a * view at a certain y value). * * @param appBarLayout the {@link AppBarLayout} which offset has changed * @param verticalOffset the vertical offset for the parent {@link AppBarLayout}, in px */ void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset); } private static final int INVALID_SCROLL_RANGE = -1; private int mTotalScrollRange = INVALID_SCROLL_RANGE; private int mDownPreScrollRange = INVALID_SCROLL_RANGE; private int mDownScrollRange = INVALID_SCROLL_RANGE; private boolean mHaveChildWithInterpolator; private int mPendingAction = PENDING_ACTION_NONE; private WindowInsetsCompat mLastInsets; private List<OnOffsetChangedListener> mListeners; private boolean mCollapsible; private boolean mCollapsed; private final int[] mTmpStatesArray = new int[2]; public AppBarLayout(Context context) { this(context, null); } public AppBarLayout(Context context, AttributeSet attrs) { super(context, attrs); setOrientation(VERTICAL); ThemeUtils.checkAppCompatTheme(context); if (Build.VERSION.SDK_INT >= 21) { // Use the bounds view outline provider so that we cast a shadow, even without a // background ViewUtilsLollipop.setBoundsViewOutlineProvider(this); // If we're running on API 21+, we should reset any state list animator from our // default style ViewUtilsLollipop.setStateListAnimatorFromAttrs(this, attrs, 0, R.style.Widget_Design_AppBarLayout); } final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.AppBarLayout, 0, R.style.Widget_Design_AppBarLayout); ViewCompat.setBackground(this, a.getDrawable(R.styleable.AppBarLayout_android_background)); if (a.hasValue(R.styleable.AppBarLayout_expanded)) { setExpanded(a.getBoolean(R.styleable.AppBarLayout_expanded, false), false, false); } if (Build.VERSION.SDK_INT >= 21 && a.hasValue(R.styleable.AppBarLayout_elevation)) { ViewUtilsLollipop.setDefaultAppBarLayoutStateListAnimator(this, a.getDimensionPixelSize(R.styleable.AppBarLayout_elevation, 0)); } a.recycle(); ViewCompat.setOnApplyWindowInsetsListener(this, new android.support.v4.view.OnApplyWindowInsetsListener() { @Override public WindowInsetsCompat onApplyWindowInsets(View v, WindowInsetsCompat insets) { return onWindowInsetChanged(insets); } }); } /** * Add a listener that will be called when the offset of this {@link AppBarLayout} changes. * * @param listener The listener that will be called when the offset changes.] * * @see #removeOnOffsetChangedListener(OnOffsetChangedListener) */ public void addOnOffsetChangedListener(OnOffsetChangedListener listener) { if (mListeners == null) { mListeners = new ArrayList<>(); } if (listener != null && !mListeners.contains(listener)) { mListeners.add(listener); } } /** * Remove the previously added {@link OnOffsetChangedListener}. * * @param listener the listener to remove. */ public void removeOnOffsetChangedListener(OnOffsetChangedListener listener) { if (mListeners != null && listener != null) { mListeners.remove(listener); } } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); invalidateScrollRanges(); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { super.onLayout(changed, l, t, r, b); invalidateScrollRanges(); mHaveChildWithInterpolator = false; for (int i = 0, z = getChildCount(); i < z; i++) { final View child = getChildAt(i); final LayoutParams childLp = (LayoutParams) child.getLayoutParams(); final Interpolator interpolator = childLp.getScrollInterpolator(); if (interpolator != null) { mHaveChildWithInterpolator = true; break; } } updateCollapsible(); } private void updateCollapsible() { boolean haveCollapsibleChild = false; for (int i = 0, z = getChildCount(); i < z; i++) { if (((LayoutParams) getChildAt(i).getLayoutParams()).isCollapsible()) { haveCollapsibleChild = true; break; } } setCollapsibleState(haveCollapsibleChild); } private void invalidateScrollRanges() { // Invalidate the scroll ranges mTotalScrollRange = INVALID_SCROLL_RANGE; mDownPreScrollRange = INVALID_SCROLL_RANGE; mDownScrollRange = INVALID_SCROLL_RANGE; } @Override public void setOrientation(int orientation) { if (orientation != VERTICAL) { throw new IllegalArgumentException( "AppBarLayout is always vertical and does" + " not support horizontal orientation"); } super.setOrientation(orientation); } /** * Sets whether this {@link AppBarLayout} is expanded or not, animating if it has already * been laid out. * * <p>As with {@link AppBarLayout}'s scrolling, this method relies on this layout being a * direct child of a {@link CoordinatorLayout}.</p> * * @param expanded true if the layout should be fully expanded, false if it should * be fully collapsed * * @attr ref android.support.design.R.styleable#AppBarLayout_expanded */ public void setExpanded(boolean expanded) { setExpanded(expanded, ViewCompat.isLaidOut(this)); } /** * Sets whether this {@link AppBarLayout} is expanded or not. * * <p>As with {@link AppBarLayout}'s scrolling, this method relies on this layout being a * direct child of a {@link CoordinatorLayout}.</p> * * @param expanded true if the layout should be fully expanded, false if it should * be fully collapsed * @param animate Whether to animate to the new state * * @attr ref android.support.design.R.styleable#AppBarLayout_expanded */ public void setExpanded(boolean expanded, boolean animate) { setExpanded(expanded, animate, true); } private void setExpanded(boolean expanded, boolean animate, boolean force) { mPendingAction = (expanded ? PENDING_ACTION_EXPANDED : PENDING_ACTION_COLLAPSED) | (animate ? PENDING_ACTION_ANIMATE_ENABLED : 0) | (force ? PENDING_ACTION_FORCE : 0); requestLayout(); } @Override protected boolean checkLayoutParams(ViewGroup.LayoutParams p) { return p instanceof LayoutParams; } @Override protected LayoutParams generateDefaultLayoutParams() { return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT); } @Override public LayoutParams generateLayoutParams(AttributeSet attrs) { return new LayoutParams(getContext(), attrs); } @Override protected LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) { if (Build.VERSION.SDK_INT >= 19 && p instanceof LinearLayout.LayoutParams) { return new LayoutParams((LinearLayout.LayoutParams) p); } else if (p instanceof MarginLayoutParams) { return new LayoutParams((MarginLayoutParams) p); } return new LayoutParams(p); } boolean hasChildWithInterpolator() { return mHaveChildWithInterpolator; } /** * Returns the scroll range of all children. * * @return the scroll range in px */ public final int getTotalScrollRange() { if (mTotalScrollRange != INVALID_SCROLL_RANGE) { return mTotalScrollRange; } int range = 0; for (int i = 0, z = getChildCount(); i < z; i++) { final View child = getChildAt(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); final int childHeight = child.getMeasuredHeight(); final int flags = lp.mScrollFlags; if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) { // We're set to scroll so add the child's height range += childHeight + lp.topMargin + lp.bottomMargin; if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) { // For a collapsing scroll, we to take the collapsed height into account. // We also break straight away since later views can't scroll beneath // us range -= ViewCompat.getMinimumHeight(child); break; } } else { // As soon as a view doesn't have the scroll flag, we end the range calculation. // This is because views below can not scroll under a fixed view. break; } } return mTotalScrollRange = Math.max(0, range - getTopInset()); } boolean hasScrollableChildren() { return getTotalScrollRange() != 0; } /** * Return the scroll range when scrolling up from a nested pre-scroll. */ int getUpNestedPreScrollRange() { return getTotalScrollRange(); } /** * Return the scroll range when scrolling down from a nested pre-scroll. */ int getDownNestedPreScrollRange() { if (mDownPreScrollRange != INVALID_SCROLL_RANGE) { // If we already have a valid value, return it return mDownPreScrollRange; } int range = 0; for (int i = getChildCount() - 1; i >= 0; i--) { final View child = getChildAt(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); final int childHeight = child.getMeasuredHeight(); final int flags = lp.mScrollFlags; if ((flags & LayoutParams.FLAG_QUICK_RETURN) == LayoutParams.FLAG_QUICK_RETURN) { // First take the margin into account range += lp.topMargin + lp.bottomMargin; // The view has the quick return flag combination... if ((flags & LayoutParams.SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED) != 0) { // If they're set to enter collapsed, use the minimum height range += ViewCompat.getMinimumHeight(child); } else if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) { // Only enter by the amount of the collapsed height range += childHeight - ViewCompat.getMinimumHeight(child); } else { // Else use the full height (minus the top inset) range += childHeight - getTopInset(); } } else if (range > 0) { // If we've hit an non-quick return scrollable view, and we've already hit a // quick return view, return now break; } } return mDownPreScrollRange = Math.max(0, range); } /** * Return the scroll range when scrolling down from a nested scroll. */ int getDownNestedScrollRange() { if (mDownScrollRange != INVALID_SCROLL_RANGE) { // If we already have a valid value, return it return mDownScrollRange; } int range = 0; for (int i = 0, z = getChildCount(); i < z; i++) { final View child = getChildAt(i); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); int childHeight = child.getMeasuredHeight(); childHeight += lp.topMargin + lp.bottomMargin; final int flags = lp.mScrollFlags; if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) { // We're set to scroll so add the child's height range += childHeight; if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) { // For a collapsing exit scroll, we to take the collapsed height into account. // We also break the range straight away since later views can't scroll // beneath us range -= ViewCompat.getMinimumHeight(child) + getTopInset(); break; } } else { // As soon as a view doesn't have the scroll flag, we end the range calculation. // This is because views below can not scroll under a fixed view. break; } } return mDownScrollRange = Math.max(0, range); } void dispatchOffsetUpdates(int offset) { // Iterate backwards through the list so that most recently added listeners // get the first chance to decide if (mListeners != null) { for (int i = 0, z = mListeners.size(); i < z; i++) { final OnOffsetChangedListener listener = mListeners.get(i); if (listener != null) { listener.onOffsetChanged(this, offset); } } } } final int getMinimumHeightForVisibleOverlappingContent() { final int topInset = getTopInset(); final int minHeight = ViewCompat.getMinimumHeight(this); if (minHeight != 0) { // If this layout has a min height, use it (doubled) return (minHeight * 2) + topInset; } // Otherwise, we'll use twice the min height of our last child final int childCount = getChildCount(); final int lastChildMinHeight = childCount >= 1 ? ViewCompat.getMinimumHeight(getChildAt(childCount - 1)) : 0; if (lastChildMinHeight != 0) { return (lastChildMinHeight * 2) + topInset; } // If we reach here then we don't have a min height explicitly set. Instead we'll take a // guess at 1/3 of our height being visible return getHeight() / 3; } @Override protected int[] onCreateDrawableState(int extraSpace) { final int[] extraStates = mTmpStatesArray; final int[] states = super.onCreateDrawableState(extraSpace + extraStates.length); extraStates[0] = mCollapsible ? R.attr.state_collapsible : -R.attr.state_collapsible; extraStates[1] = mCollapsible && mCollapsed ? R.attr.state_collapsed : -R.attr.state_collapsed; return mergeDrawableStates(states, extraStates); } /** * Sets whether the AppBarLayout has collapsible children or not. * * @return true if the collapsible state changed */ private boolean setCollapsibleState(boolean collapsible) { if (mCollapsible != collapsible) { mCollapsible = collapsible; refreshDrawableState(); return true; } return false; } /** * Sets whether the AppBarLayout is in a collapsed state or not. * * @return true if the collapsed state changed */ boolean setCollapsedState(boolean collapsed) { if (mCollapsed != collapsed) { mCollapsed = collapsed; refreshDrawableState(); return true; } return false; } /** * @deprecated target elevation is now deprecated. AppBarLayout's elevation is now * controlled via a {@link android.animation.StateListAnimator}. If a target * elevation is set, either by this method or the {@code app:elevation} attribute, * a new state list animator is created which uses the given {@code elevation} value. * * @attr ref android.support.design.R.styleable#AppBarLayout_elevation */ @Deprecated public void setTargetElevation(float elevation) { if (Build.VERSION.SDK_INT >= 21) { ViewUtilsLollipop.setDefaultAppBarLayoutStateListAnimator(this, elevation); } } /** * @deprecated target elevation is now deprecated. AppBarLayout's elevation is now * controlled via a {@link android.animation.StateListAnimator}. This method now * always returns 0. */ @Deprecated public float getTargetElevation() { return 0; } int getPendingAction() { return mPendingAction; } void resetPendingAction() { mPendingAction = PENDING_ACTION_NONE; } @VisibleForTesting final int getTopInset() { return mLastInsets != null ? mLastInsets.getSystemWindowInsetTop() : 0; } WindowInsetsCompat onWindowInsetChanged(final WindowInsetsCompat insets) { WindowInsetsCompat newInsets = null; if (ViewCompat.getFitsSystemWindows(this)) { // If we're set to fit system windows, keep the insets newInsets = insets; } // If our insets have changed, keep them and invalidate the scroll ranges... if (!objectEquals(mLastInsets, newInsets)) { mLastInsets = newInsets; invalidateScrollRanges(); } return insets; } public static class LayoutParams extends LinearLayout.LayoutParams { /** @hide */ @RestrictTo(LIBRARY_GROUP) @IntDef(flag = true, value = { SCROLL_FLAG_SCROLL, SCROLL_FLAG_EXIT_UNTIL_COLLAPSED, SCROLL_FLAG_ENTER_ALWAYS, SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED, SCROLL_FLAG_SNAP }) @Retention(RetentionPolicy.SOURCE) public @interface ScrollFlags { } /** * The view will be scroll in direct relation to scroll events. This flag needs to be * set for any of the other flags to take effect. If any sibling views * before this one do not have this flag, then this value has no effect. */ public static final int SCROLL_FLAG_SCROLL = 0x1; /** * When exiting (scrolling off screen) the view will be scrolled until it is * 'collapsed'. The collapsed height is defined by the view's minimum height. * * @see ViewCompat#getMinimumHeight(View) * @see View#setMinimumHeight(int) */ public static final int SCROLL_FLAG_EXIT_UNTIL_COLLAPSED = 0x2; /** * When entering (scrolling on screen) the view will scroll on any downwards * scroll event, regardless of whether the scrolling view is also scrolling. This * is commonly referred to as the 'quick return' pattern. */ public static final int SCROLL_FLAG_ENTER_ALWAYS = 0x4; /** * An additional flag for 'enterAlways' which modifies the returning view to * only initially scroll back to it's collapsed height. Once the scrolling view has * reached the end of it's scroll range, the remainder of this view will be scrolled * into view. The collapsed height is defined by the view's minimum height. * * @see ViewCompat#getMinimumHeight(View) * @see View#setMinimumHeight(int) */ public static final int SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED = 0x8; /** * Upon a scroll ending, if the view is only partially visible then it will be snapped * and scrolled to it's closest edge. For example, if the view only has it's bottom 25% * displayed, it will be scrolled off screen completely. Conversely, if it's bottom 75% * is visible then it will be scrolled fully into view. */ public static final int SCROLL_FLAG_SNAP = 0x10; /** * Internal flags which allows quick checking features */ static final int FLAG_QUICK_RETURN = SCROLL_FLAG_SCROLL | SCROLL_FLAG_ENTER_ALWAYS; static final int FLAG_SNAP = SCROLL_FLAG_SCROLL | SCROLL_FLAG_SNAP; static final int COLLAPSIBLE_FLAGS = SCROLL_FLAG_EXIT_UNTIL_COLLAPSED | SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED; int mScrollFlags = SCROLL_FLAG_SCROLL; Interpolator mScrollInterpolator; public LayoutParams(Context c, AttributeSet attrs) { super(c, attrs); TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.AppBarLayout_Layout); mScrollFlags = a.getInt(R.styleable.AppBarLayout_Layout_layout_scrollFlags, 0); if (a.hasValue(R.styleable.AppBarLayout_Layout_layout_scrollInterpolator)) { int resId = a.getResourceId(R.styleable.AppBarLayout_Layout_layout_scrollInterpolator, 0); mScrollInterpolator = android.view.animation.AnimationUtils.loadInterpolator(c, resId); } a.recycle(); } public LayoutParams(int width, int height) { super(width, height); } public LayoutParams(int width, int height, float weight) { super(width, height, weight); } public LayoutParams(ViewGroup.LayoutParams p) { super(p); } public LayoutParams(MarginLayoutParams source) { super(source); } @RequiresApi(19) @TargetApi(19) public LayoutParams(LinearLayout.LayoutParams source) { // The copy constructor called here only exists on API 19+. super(source); } @RequiresApi(19) @TargetApi(19) public LayoutParams(LayoutParams source) { // The copy constructor called here only exists on API 19+. super(source); mScrollFlags = source.mScrollFlags; mScrollInterpolator = source.mScrollInterpolator; } /** * Set the scrolling flags. * * @param flags bitwise int of {@link #SCROLL_FLAG_SCROLL}, * {@link #SCROLL_FLAG_EXIT_UNTIL_COLLAPSED}, {@link #SCROLL_FLAG_ENTER_ALWAYS}, * {@link #SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED} and {@link #SCROLL_FLAG_SNAP }. * * @see #getScrollFlags() * * @attr ref android.support.design.R.styleable#AppBarLayout_Layout_layout_scrollFlags */ public void setScrollFlags(@ScrollFlags int flags) { mScrollFlags = flags; } /** * Returns the scrolling flags. * * @see #setScrollFlags(int) * * @attr ref android.support.design.R.styleable#AppBarLayout_Layout_layout_scrollFlags */ @ScrollFlags public int getScrollFlags() { return mScrollFlags; } /** * Set the interpolator to when scrolling the view associated with this * {@link LayoutParams}. * * @param interpolator the interpolator to use, or null to use normal 1-to-1 scrolling. * * @attr ref android.support.design.R.styleable#AppBarLayout_Layout_layout_scrollInterpolator * @see #getScrollInterpolator() */ public void setScrollInterpolator(Interpolator interpolator) { mScrollInterpolator = interpolator; } /** * Returns the {@link Interpolator} being used for scrolling the view associated with this * {@link LayoutParams}. Null indicates 'normal' 1-to-1 scrolling. * * @attr ref android.support.design.R.styleable#AppBarLayout_Layout_layout_scrollInterpolator * @see #setScrollInterpolator(Interpolator) */ public Interpolator getScrollInterpolator() { return mScrollInterpolator; } /** * Returns true if the scroll flags are compatible for 'collapsing' */ boolean isCollapsible() { return (mScrollFlags & SCROLL_FLAG_SCROLL) == SCROLL_FLAG_SCROLL && (mScrollFlags & COLLAPSIBLE_FLAGS) != 0; } } /** * The default {@link Behavior} for {@link AppBarLayout}. Implements the necessary nested * scroll handling with offsetting. */ public static class Behavior extends HeaderBehavior<AppBarLayout> { private static final int MAX_OFFSET_ANIMATION_DURATION = 600; // ms private static final int INVALID_POSITION = -1; /** * Callback to allow control over any {@link AppBarLayout} dragging. */ public static abstract class DragCallback { /** * Allows control over whether the given {@link AppBarLayout} can be dragged or not. * * <p>Dragging is defined as a direct touch on the AppBarLayout with movement. This * call does not affect any nested scrolling.</p> * * @return true if we are in a position to scroll the AppBarLayout via a drag, false * if not. */ public abstract boolean canDrag(@NonNull AppBarLayout appBarLayout); } private int mOffsetDelta; private boolean mSkipNestedPreScroll; private boolean mWasNestedFlung; private ValueAnimatorCompat mOffsetAnimator; private int mOffsetToChildIndexOnLayout = INVALID_POSITION; private boolean mOffsetToChildIndexOnLayoutIsMinHeight; private float mOffsetToChildIndexOnLayoutPerc; private WeakReference<View> mLastNestedScrollingChildRef; private DragCallback mOnDragCallback; public Behavior() { } public Behavior(Context context, AttributeSet attrs) { super(context, attrs); } @Override public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes) { // Return true if we're nested scrolling vertically, and we have scrollable children // and the scrolling view is big enough to scroll final boolean started = (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0 && child.hasScrollableChildren() && parent.getHeight() - directTargetChild.getHeight() <= child.getHeight(); if (started && mOffsetAnimator != null) { // Cancel any offset animation mOffsetAnimator.cancel(); } // A new nested scroll has started so clear out the previous ref mLastNestedScrollingChildRef = null; return started; } @Override public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) { if (dy != 0 && !mSkipNestedPreScroll) { int min, max; if (dy < 0) { // We're scrolling down min = -child.getTotalScrollRange(); max = min + child.getDownNestedPreScrollRange(); } else { // We're scrolling up min = -child.getUpNestedPreScrollRange(); max = 0; } consumed[1] = scroll(coordinatorLayout, child, dy, min, max); } } @Override public void onNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) { if (dyUnconsumed < 0) { // If the scrolling view is scrolling down but not consuming, it's probably be at // the top of it's content scroll(coordinatorLayout, child, dyUnconsumed, -child.getDownNestedScrollRange(), 0); // Set the expanding flag so that onNestedPreScroll doesn't handle any events mSkipNestedPreScroll = true; } else { // As we're no longer handling nested scrolls, reset the skip flag mSkipNestedPreScroll = false; } } @Override public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout abl, View target) { if (!mWasNestedFlung) { // If we haven't been flung then let's see if the current view has been set to snap snapToChildIfNeeded(coordinatorLayout, abl); } // Reset the flags mSkipNestedPreScroll = false; mWasNestedFlung = false; // Keep a reference to the previous nested scrolling child mLastNestedScrollingChildRef = new WeakReference<>(target); } @Override public boolean onNestedFling(final CoordinatorLayout coordinatorLayout, final AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) { boolean flung = false; if (!consumed) { // It has been consumed so let's fling ourselves flung = fling(coordinatorLayout, child, -child.getTotalScrollRange(), 0, -velocityY); } else { // If we're scrolling up and the child also consumed the fling. We'll fake scroll // up to our 'collapsed' offset if (velocityY < 0) { // We're scrolling down final int targetScroll = -child.getTotalScrollRange() + child.getDownNestedPreScrollRange(); if (getTopBottomOffsetForScrollingSibling() < targetScroll) { // If we're currently not expanded more than the target scroll, we'll // animate a fling animateOffsetTo(coordinatorLayout, child, targetScroll, velocityY); flung = true; } } else { // We're scrolling up final int targetScroll = -child.getUpNestedPreScrollRange(); if (getTopBottomOffsetForScrollingSibling() > targetScroll) { // If we're currently not expanded less than the target scroll, we'll // animate a fling animateOffsetTo(coordinatorLayout, child, targetScroll, velocityY); flung = true; } } } mWasNestedFlung = flung; return flung; } /** * Set a callback to control any {@link AppBarLayout} dragging. * * @param callback the callback to use, or {@code null} to use the default behavior. */ public void setDragCallback(@Nullable DragCallback callback) { mOnDragCallback = callback; } private void animateOffsetTo(final CoordinatorLayout coordinatorLayout, final AppBarLayout child, final int offset, float velocity) { final int distance = Math.abs(getTopBottomOffsetForScrollingSibling() - offset); final int duration; velocity = Math.abs(velocity); if (velocity > 0) { duration = 3 * Math.round(1000 * (distance / velocity)); } else { final float distanceRatio = (float) distance / child.getHeight(); duration = (int) ((distanceRatio + 1) * 150); } animateOffsetWithDuration(coordinatorLayout, child, offset, duration); } private void animateOffsetWithDuration(final CoordinatorLayout coordinatorLayout, final AppBarLayout child, final int offset, final int duration) { final int currentOffset = getTopBottomOffsetForScrollingSibling(); if (currentOffset == offset) { if (mOffsetAnimator != null && mOffsetAnimator.isRunning()) { mOffsetAnimator.cancel(); } return; } if (mOffsetAnimator == null) { mOffsetAnimator = ViewUtils.createAnimator(); mOffsetAnimator.setInterpolator(AnimationUtils.DECELERATE_INTERPOLATOR); mOffsetAnimator.addUpdateListener(new ValueAnimatorCompat.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimatorCompat animator) { setHeaderTopBottomOffset(coordinatorLayout, child, animator.getAnimatedIntValue()); } }); } else { mOffsetAnimator.cancel(); } mOffsetAnimator.setDuration(Math.min(duration, MAX_OFFSET_ANIMATION_DURATION)); mOffsetAnimator.setIntValues(currentOffset, offset); mOffsetAnimator.start(); } private int getChildIndexOnOffset(AppBarLayout abl, final int offset) { for (int i = 0, count = abl.getChildCount(); i < count; i++) { View child = abl.getChildAt(i); if (child.getTop() <= -offset && child.getBottom() >= -offset) { return i; } } return -1; } private void snapToChildIfNeeded(CoordinatorLayout coordinatorLayout, AppBarLayout abl) { final int offset = getTopBottomOffsetForScrollingSibling(); final int offsetChildIndex = getChildIndexOnOffset(abl, offset); if (offsetChildIndex >= 0) { final View offsetChild = abl.getChildAt(offsetChildIndex); final LayoutParams lp = (LayoutParams) offsetChild.getLayoutParams(); final int flags = lp.getScrollFlags(); if ((flags & LayoutParams.FLAG_SNAP) == LayoutParams.FLAG_SNAP) { // We're set the snap, so animate the offset to the nearest edge int snapTop = -offsetChild.getTop(); int snapBottom = -offsetChild.getBottom(); if (offsetChildIndex == abl.getChildCount() - 1) { // If this is the last child, we need to take the top inset into account snapBottom += abl.getTopInset(); } if (checkFlag(flags, LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED)) { // If the view is set only exit until it is collapsed, we'll abide by that snapBottom += ViewCompat.getMinimumHeight(offsetChild); } else if (checkFlag(flags, LayoutParams.FLAG_QUICK_RETURN | LayoutParams.SCROLL_FLAG_ENTER_ALWAYS)) { // If it's set to always enter collapsed, it actually has two states. We // select the state and then snap within the state final int seam = snapBottom + ViewCompat.getMinimumHeight(offsetChild); if (offset < seam) { snapTop = seam; } else { snapBottom = seam; } } final int newOffset = offset < (snapBottom + snapTop) / 2 ? snapBottom : snapTop; animateOffsetTo(coordinatorLayout, abl, MathUtils.constrain(newOffset, -abl.getTotalScrollRange(), 0), 0); } } } private static boolean checkFlag(final int flags, final int check) { return (flags & check) == check; } @Override public boolean onMeasureChild(CoordinatorLayout parent, AppBarLayout child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) { final CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) child.getLayoutParams(); if (lp.height == CoordinatorLayout.LayoutParams.WRAP_CONTENT) { // If the view is set to wrap on it's height, CoordinatorLayout by default will // cap the view at the CoL's height. Since the AppBarLayout can scroll, this isn't // what we actually want, so we measure it ourselves with an unspecified spec to // allow the child to be larger than it's parent parent.onMeasureChild(child, parentWidthMeasureSpec, widthUsed, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), heightUsed); return true; } // Let the parent handle it as normal return super.onMeasureChild(parent, child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed); } @Override public boolean onLayoutChild(CoordinatorLayout parent, AppBarLayout abl, int layoutDirection) { boolean handled = super.onLayoutChild(parent, abl, layoutDirection); // The priority for for actions here is (first which is true wins): // 1. forced pending actions // 2. offsets for restorations // 3. non-forced pending actions final int pendingAction = abl.getPendingAction(); if (mOffsetToChildIndexOnLayout >= 0 && (pendingAction & PENDING_ACTION_FORCE) == 0) { View child = abl.getChildAt(mOffsetToChildIndexOnLayout); int offset = -child.getBottom(); if (mOffsetToChildIndexOnLayoutIsMinHeight) { offset += ViewCompat.getMinimumHeight(child) + abl.getTopInset(); } else { offset += Math.round(child.getHeight() * mOffsetToChildIndexOnLayoutPerc); } setHeaderTopBottomOffset(parent, abl, offset); } else if (pendingAction != PENDING_ACTION_NONE) { final boolean animate = (pendingAction & PENDING_ACTION_ANIMATE_ENABLED) != 0; if ((pendingAction & PENDING_ACTION_COLLAPSED) != 0) { final int offset = -abl.getUpNestedPreScrollRange(); if (animate) { animateOffsetTo(parent, abl, offset, 0); } else { setHeaderTopBottomOffset(parent, abl, offset); } } else if ((pendingAction & PENDING_ACTION_EXPANDED) != 0) { if (animate) { animateOffsetTo(parent, abl, 0, 0); } else { setHeaderTopBottomOffset(parent, abl, 0); } } } // Finally reset any pending states abl.resetPendingAction(); mOffsetToChildIndexOnLayout = INVALID_POSITION; // We may have changed size, so let's constrain the top and bottom offset correctly, // just in case we're out of the bounds setTopAndBottomOffset(MathUtils.constrain(getTopAndBottomOffset(), -abl.getTotalScrollRange(), 0)); // Update the AppBarLayout's drawable state for any elevation changes. // This is needed so that the elevation is set in the first layout, so that // we don't get a visual elevation jump pre-N (due to the draw dispatch skip) updateAppBarLayoutDrawableState(parent, abl, getTopAndBottomOffset(), 0, true); // Make sure we dispatch the offset update abl.dispatchOffsetUpdates(getTopAndBottomOffset()); return handled; } @Override boolean canDragView(AppBarLayout view) { if (mOnDragCallback != null) { // If there is a drag callback set, it's in control return mOnDragCallback.canDrag(view); } // Else we'll use the default behaviour of seeing if it can scroll down if (mLastNestedScrollingChildRef != null) { // If we have a reference to a scrolling view, check it final View scrollingView = mLastNestedScrollingChildRef.get(); return scrollingView != null && scrollingView.isShown() && !ViewCompat.canScrollVertically(scrollingView, -1); } else { // Otherwise we assume that the scrolling view hasn't been scrolled and can drag. return true; } } @Override void onFlingFinished(CoordinatorLayout parent, AppBarLayout layout) { // At the end of a manual fling, check to see if we need to snap to the edge-child snapToChildIfNeeded(parent, layout); } @Override int getMaxDragOffset(AppBarLayout view) { return -view.getDownNestedScrollRange(); } @Override int getScrollRangeForDragFling(AppBarLayout view) { return view.getTotalScrollRange(); } @Override int setHeaderTopBottomOffset(CoordinatorLayout coordinatorLayout, AppBarLayout appBarLayout, int newOffset, int minOffset, int maxOffset) { final int curOffset = getTopBottomOffsetForScrollingSibling(); int consumed = 0; if (minOffset != 0 && curOffset >= minOffset && curOffset <= maxOffset) { // If we have some scrolling range, and we're currently within the min and max // offsets, calculate a new offset newOffset = MathUtils.constrain(newOffset, minOffset, maxOffset); if (curOffset != newOffset) { final int interpolatedOffset = appBarLayout.hasChildWithInterpolator() ? interpolateOffset(appBarLayout, newOffset) : newOffset; final boolean offsetChanged = setTopAndBottomOffset(interpolatedOffset); // Update how much dy we have consumed consumed = curOffset - newOffset; // Update the stored sibling offset mOffsetDelta = newOffset - interpolatedOffset; if (!offsetChanged && appBarLayout.hasChildWithInterpolator()) { // If the offset hasn't changed and we're using an interpolated scroll // then we need to keep any dependent views updated. CoL will do this for // us when we move, but we need to do it manually when we don't (as an // interpolated scroll may finish early). coordinatorLayout.dispatchDependentViewsChanged(appBarLayout); } // Dispatch the updates to any listeners appBarLayout.dispatchOffsetUpdates(getTopAndBottomOffset()); // Update the AppBarLayout's drawable state (for any elevation changes) updateAppBarLayoutDrawableState(coordinatorLayout, appBarLayout, newOffset, newOffset < curOffset ? -1 : 1, false); } } else { // Reset the offset delta mOffsetDelta = 0; } return consumed; } @VisibleForTesting boolean isOffsetAnimatorRunning() { return mOffsetAnimator != null && mOffsetAnimator.isRunning(); } private int interpolateOffset(AppBarLayout layout, final int offset) { final int absOffset = Math.abs(offset); for (int i = 0, z = layout.getChildCount(); i < z; i++) { final View child = layout.getChildAt(i); final LayoutParams childLp = (LayoutParams) child.getLayoutParams(); final Interpolator interpolator = childLp.getScrollInterpolator(); if (absOffset >= child.getTop() && absOffset <= child.getBottom()) { if (interpolator != null) { int childScrollableHeight = 0; final int flags = childLp.getScrollFlags(); if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) { // We're set to scroll so add the child's height plus margin childScrollableHeight += child.getHeight() + childLp.topMargin + childLp.bottomMargin; if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) { // For a collapsing scroll, we to take the collapsed height // into account. childScrollableHeight -= ViewCompat.getMinimumHeight(child); } } if (ViewCompat.getFitsSystemWindows(child)) { childScrollableHeight -= layout.getTopInset(); } if (childScrollableHeight > 0) { final int offsetForView = absOffset - child.getTop(); final int interpolatedDiff = Math.round(childScrollableHeight * interpolator.getInterpolation(offsetForView / (float) childScrollableHeight)); return Integer.signum(offset) * (child.getTop() + interpolatedDiff); } } // If we get to here then the view on the offset isn't suitable for interpolated // scrolling. So break out of the loop break; } } return offset; } private void updateAppBarLayoutDrawableState(final CoordinatorLayout parent, final AppBarLayout layout, final int offset, final int direction, final boolean forceJump) { final View child = getAppBarChildOnOffset(layout, offset); if (child != null) { final LayoutParams childLp = (LayoutParams) child.getLayoutParams(); final int flags = childLp.getScrollFlags(); boolean collapsed = false; if ((flags & LayoutParams.SCROLL_FLAG_SCROLL) != 0) { final int minHeight = ViewCompat.getMinimumHeight(child); if (direction > 0 && (flags & (LayoutParams.SCROLL_FLAG_ENTER_ALWAYS | LayoutParams.SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED)) != 0) { // We're set to enter always collapsed so we are only collapsed when // being scrolled down, and in a collapsed offset collapsed = -offset >= child.getBottom() - minHeight - layout.getTopInset(); } else if ((flags & LayoutParams.SCROLL_FLAG_EXIT_UNTIL_COLLAPSED) != 0) { // We're set to exit until collapsed, so any offset which results in // the minimum height (or less) being shown is collapsed collapsed = -offset >= child.getBottom() - minHeight - layout.getTopInset(); } } final boolean changed = layout.setCollapsedState(collapsed); if (Build.VERSION.SDK_INT >= 11 && (forceJump || (changed && shouldJumpElevationState(parent, layout)))) { // If the collapsed state changed, we may need to // jump to the current state if we have an overlapping view layout.jumpDrawablesToCurrentState(); } } } private boolean shouldJumpElevationState(CoordinatorLayout parent, AppBarLayout layout) { // We should jump the elevated state if we have a dependent scrolling view which has // an overlapping top (i.e. overlaps us) final List<View> dependencies = parent.getDependents(layout); for (int i = 0, size = dependencies.size(); i < size; i++) { final View dependency = dependencies.get(i); final CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) dependency .getLayoutParams(); final CoordinatorLayout.Behavior behavior = lp.getBehavior(); if (behavior instanceof ScrollingViewBehavior) { return ((ScrollingViewBehavior) behavior).getOverlayTop() != 0; } } return false; } private static View getAppBarChildOnOffset(final AppBarLayout layout, final int offset) { final int absOffset = Math.abs(offset); for (int i = 0, z = layout.getChildCount(); i < z; i++) { final View child = layout.getChildAt(i); if (absOffset >= child.getTop() && absOffset <= child.getBottom()) { return child; } } return null; } @Override int getTopBottomOffsetForScrollingSibling() { return getTopAndBottomOffset() + mOffsetDelta; } @Override public Parcelable onSaveInstanceState(CoordinatorLayout parent, AppBarLayout abl) { final Parcelable superState = super.onSaveInstanceState(parent, abl); final int offset = getTopAndBottomOffset(); // Try and find the first visible child... for (int i = 0, count = abl.getChildCount(); i < count; i++) { View child = abl.getChildAt(i); final int visBottom = child.getBottom() + offset; if (child.getTop() + offset <= 0 && visBottom >= 0) { final SavedState ss = new SavedState(superState); ss.firstVisibleChildIndex = i; ss.firstVisibleChildAtMinimumHeight = visBottom == (ViewCompat.getMinimumHeight(child) + abl.getTopInset()); ss.firstVisibleChildPercentageShown = visBottom / (float) child.getHeight(); return ss; } } // Else we'll just return the super state return superState; } @Override public void onRestoreInstanceState(CoordinatorLayout parent, AppBarLayout appBarLayout, Parcelable state) { if (state instanceof SavedState) { final SavedState ss = (SavedState) state; super.onRestoreInstanceState(parent, appBarLayout, ss.getSuperState()); mOffsetToChildIndexOnLayout = ss.firstVisibleChildIndex; mOffsetToChildIndexOnLayoutPerc = ss.firstVisibleChildPercentageShown; mOffsetToChildIndexOnLayoutIsMinHeight = ss.firstVisibleChildAtMinimumHeight; } else { super.onRestoreInstanceState(parent, appBarLayout, state); mOffsetToChildIndexOnLayout = INVALID_POSITION; } } protected static class SavedState extends AbsSavedState { int firstVisibleChildIndex; float firstVisibleChildPercentageShown; boolean firstVisibleChildAtMinimumHeight; public SavedState(Parcel source, ClassLoader loader) { super(source, loader); firstVisibleChildIndex = source.readInt(); firstVisibleChildPercentageShown = source.readFloat(); firstVisibleChildAtMinimumHeight = source.readByte() != 0; } public SavedState(Parcelable superState) { super(superState); } @Override public void writeToParcel(Parcel dest, int flags) { super.writeToParcel(dest, flags); dest.writeInt(firstVisibleChildIndex); dest.writeFloat(firstVisibleChildPercentageShown); dest.writeByte((byte) (firstVisibleChildAtMinimumHeight ? 1 : 0)); } public static final Creator<SavedState> CREATOR = ParcelableCompat .newCreator(new ParcelableCompatCreatorCallbacks<SavedState>() { @Override public SavedState createFromParcel(Parcel source, ClassLoader loader) { return new SavedState(source, loader); } @Override public SavedState[] newArray(int size) { return new SavedState[size]; } }); } } /** * Behavior which should be used by {@link View}s which can scroll vertically and support * nested scrolling to automatically scroll any {@link AppBarLayout} siblings. */ public static class ScrollingViewBehavior extends HeaderScrollingViewBehavior { public ScrollingViewBehavior() { } public ScrollingViewBehavior(Context context, AttributeSet attrs) { super(context, attrs); final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ScrollingViewBehavior_Layout); setOverlayTop(a.getDimensionPixelSize(R.styleable.ScrollingViewBehavior_Layout_behavior_overlapTop, 0)); a.recycle(); } @Override public boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency) { // We depend on any AppBarLayouts return dependency instanceof AppBarLayout; } @Override public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) { offsetChildAsNeeded(parent, child, dependency); return false; } @Override public boolean onRequestChildRectangleOnScreen(CoordinatorLayout parent, View child, Rect rectangle, boolean immediate) { final AppBarLayout header = findFirstDependency(parent.getDependencies(child)); if (header != null) { // Offset the rect by the child's left/top rectangle.offset(child.getLeft(), child.getTop()); final Rect parentRect = mTempRect1; parentRect.set(0, 0, parent.getWidth(), parent.getHeight()); if (!parentRect.contains(rectangle)) { // If the rectangle can not be fully seen the visible bounds, collapse // the AppBarLayout header.setExpanded(false, !immediate); return true; } } return false; } private void offsetChildAsNeeded(CoordinatorLayout parent, View child, View dependency) { final CoordinatorLayout.Behavior behavior = ((CoordinatorLayout.LayoutParams) dependency .getLayoutParams()).getBehavior(); if (behavior instanceof Behavior) { // Offset the child, pinning it to the bottom the header-dependency, maintaining // any vertical gap and overlap final Behavior ablBehavior = (Behavior) behavior; ViewCompat.offsetTopAndBottom(child, (dependency.getBottom() - child.getTop()) + ablBehavior.mOffsetDelta + getVerticalLayoutGap() - getOverlapPixelsForOffset(dependency)); } } @Override float getOverlapRatioForOffset(final View header) { if (header instanceof AppBarLayout) { final AppBarLayout abl = (AppBarLayout) header; final int totalScrollRange = abl.getTotalScrollRange(); final int preScrollDown = abl.getDownNestedPreScrollRange(); final int offset = getAppBarLayoutOffset(abl); if (preScrollDown != 0 && (totalScrollRange + offset) <= preScrollDown) { // If we're in a pre-scroll down. Don't use the offset at all. return 0; } else { final int availScrollRange = totalScrollRange - preScrollDown; if (availScrollRange != 0) { // Else we'll use a interpolated ratio of the overlap, depending on offset return 1f + (offset / (float) availScrollRange); } } } return 0f; } private static int getAppBarLayoutOffset(AppBarLayout abl) { final CoordinatorLayout.Behavior behavior = ((CoordinatorLayout.LayoutParams) abl.getLayoutParams()) .getBehavior(); if (behavior instanceof Behavior) { return ((Behavior) behavior).getTopBottomOffsetForScrollingSibling(); } return 0; } @Override AppBarLayout findFirstDependency(List<View> views) { for (int i = 0, z = views.size(); i < z; i++) { View view = views.get(i); if (view instanceof AppBarLayout) { return (AppBarLayout) view; } } return null; } @Override int getScrollRange(View v) { if (v instanceof AppBarLayout) { return ((AppBarLayout) v).getTotalScrollRange(); } else { return super.getScrollRange(v); } } } }