Android实现三段式滑动效果

实现的效果：

我们实现的效果和高德差距不是很大，也很顺滑。具体实现其实就是集成CoordinatorLayout.Behavior

/** * 高德首页滑动效果 */public class GaoDeBottomSheetBehavior<V extends View> extends CoordinatorLayout.Behavior<V> { public static final int STATE_DRAGGING = 1; public static final int STATE_SETTLING = 2; public static final int STATE_EXPANDED = 3; public static final int STATE_COLLAPSED = 4; public static final int STATE_HIDDEN = 5; public static final int STATE_HALF_EXPANDED = 6; public static final int PEEK_HEIGHT_AUTO = -1; private static final float HIDE_THRESHOLD = 0.5F; private static final float HIDE_FRICTION = 0.1F; public static final int MIDDLE_HEIGHT_AUTO = -1; private boolean fitToContents = true; private float maximumVelocity; private int peekHeight; private boolean peekHeightAuto; private int peekHeightMin; private int lastPeekHeight; int fitToContentsOffset; int halfExpandedOffset; int collapsedOffset; boolean hideable; private boolean skipCollapsed; int state = STATE_COLLAPSED; ViewDragHelper viewDragHelper; private boolean ignoreEvents; private int lastNestedScrollDy; private boolean nestedScrolled; int parentHeight; WeakReference<V> viewRef; WeakReference<View> nestedScrollingChildRef; private GaoDeBottomSheetBehavior.BottomSheetCallback callback; private VelocityTracker velocityTracker; int activePointerId; private int initialY; boolean touchingScrollingChild; private Map<View, Integer> importantForAccessibilityMap; private final Callback dragCallback; private int mMiddleHeight; private boolean mMiddleHeightAuto; public GaoDeBottomSheetBehavior() {this.dragCallback = new NamelessClass_1(); } public GaoDeBottomSheetBehavior(Context context, AttributeSet attrs) {super(context, attrs);this.dragCallback = new NamelessClass_1();TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.BottomSheetBehavior_Layout);TypedValue value = a.peekValue(R.styleable.BottomSheetBehavior_Layout_behavior_peekHeight);if (value != null && value.data == -1) { this.setPeekHeight(value.data);} else { this.setPeekHeight(a.getDimensionPixelSize(R.styleable.BottomSheetBehavior_Layout_behavior_peekHeight, -1));}this.setHideable(a.getBoolean(R.styleable.BottomSheetBehavior_Layout_behavior_hideAble, false));this.setFitToContents(a.getBoolean(R.styleable.BottomSheetBehavior_Layout_behavior_fitToContents, true));this.setSkipCollapsed(a.getBoolean(R.styleable.BottomSheetBehavior_Layout_behavior_skipCollapse, false));setMiddleHeight(a.getDimensionPixelSize(R.styleable.BottomSheetBehavior_Layout_behavior_middleHeight, MIDDLE_HEIGHT_AUTO));a.recycle();ViewConfiguration configuration = ViewConfiguration.get(context);this.maximumVelocity = (float) configuration.getScaledMaximumFlingVelocity(); } class NamelessClass_1 extends Callback {NamelessClass_1() {}@Overridepublic boolean tryCaptureView(@NonNull View child, int pointerId) { if (GaoDeBottomSheetBehavior.this.state == STATE_DRAGGING) {return false; } else if (GaoDeBottomSheetBehavior.this.touchingScrollingChild) {return false; } else {if (GaoDeBottomSheetBehavior.this.state == 3 && GaoDeBottomSheetBehavior.this.activePointerId == pointerId) { View scroll = (View) GaoDeBottomSheetBehavior.this.nestedScrollingChildRef.get(); if (scroll != null && scroll.canScrollVertically(-1)) {return false; }}return GaoDeBottomSheetBehavior.this.viewRef != null && GaoDeBottomSheetBehavior.this.viewRef.get() == child; }}@Overridepublic void onViewPositionChanged(@NonNull View changedView, int left, int top, int dx, int dy) { GaoDeBottomSheetBehavior.this.dispatchOnSlide(top);}@Overridepublic void onViewDragStateChanged(int state) { if (state == 1) {GaoDeBottomSheetBehavior.this.setStateInternal(STATE_DRAGGING); }}@Overridepublic void onViewReleased(@NonNull View releasedChild, float xvel, float yvel) { int top; byte targetState; int currentTop; if (yvel < 0.0F) {if (GaoDeBottomSheetBehavior.this.fitToContents) { currentTop = releasedChild.getTop(); if (currentTop < (collapsedOffset + HIDE_THRESHOLD) && currentTop >= halfExpandedOffset) {top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;targetState = STATE_HALF_EXPANDED; } else {top = GaoDeBottomSheetBehavior.this.fitToContentsOffset;targetState = STATE_EXPANDED; }} else { currentTop = releasedChild.getTop(); if (currentTop > GaoDeBottomSheetBehavior.this.halfExpandedOffset) {top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;targetState = STATE_HALF_EXPANDED; } else {top = 0;targetState = STATE_EXPANDED; }} } else if (!GaoDeBottomSheetBehavior.this.hideable || !GaoDeBottomSheetBehavior.this.shouldHide(releasedChild, yvel) || releasedChild.getTop() <= GaoDeBottomSheetBehavior.this.collapsedOffset && Math.abs(xvel) >= Math.abs(yvel)) {if (yvel != 0.0F && Math.abs(xvel) <= Math.abs(yvel)) { currentTop = releasedChild.getTop(); if (currentTop < halfExpandedOffset) {top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;targetState = STATE_HALF_EXPANDED; } else {top = GaoDeBottomSheetBehavior.this.collapsedOffset;targetState = STATE_COLLAPSED; }} else { currentTop = releasedChild.getTop(); if (GaoDeBottomSheetBehavior.this.fitToContents) {if (Math.abs(currentTop - GaoDeBottomSheetBehavior.this.fitToContentsOffset) < Math.abs(currentTop - GaoDeBottomSheetBehavior.this.collapsedOffset)) { top = GaoDeBottomSheetBehavior.this.fitToContentsOffset; targetState = STATE_EXPANDED;} else { top = GaoDeBottomSheetBehavior.this.collapsedOffset; targetState = STATE_COLLAPSED;} } else if (currentTop < GaoDeBottomSheetBehavior.this.halfExpandedOffset) {if (currentTop < Math.abs(currentTop - GaoDeBottomSheetBehavior.this.collapsedOffset)) { top = 0; targetState = STATE_EXPANDED;} else { top = GaoDeBottomSheetBehavior.this.halfExpandedOffset; targetState = STATE_HALF_EXPANDED;} } else if (Math.abs(currentTop - GaoDeBottomSheetBehavior.this.halfExpandedOffset) < Math.abs(currentTop - GaoDeBottomSheetBehavior.this.collapsedOffset)) {top = GaoDeBottomSheetBehavior.this.halfExpandedOffset;targetState = STATE_HALF_EXPANDED; } else {top = GaoDeBottomSheetBehavior.this.collapsedOffset;targetState = STATE_COLLAPSED; }} } else {top = GaoDeBottomSheetBehavior.this.parentHeight;targetState = STATE_HIDDEN; } if (GaoDeBottomSheetBehavior.this.viewDragHelper.settleCapturedViewAt(releasedChild.getLeft(), top)) {GaoDeBottomSheetBehavior.this.setStateInternal(STATE_SETTLING);ViewCompat.postOnAnimation(releasedChild, GaoDeBottomSheetBehavior.this.new SettleRunnable(releasedChild, targetState)); } else {GaoDeBottomSheetBehavior.this.setStateInternal(targetState); }}@Overridepublic int clampViewPositionVertical(@NonNull View child, int top, int dy) { return MathUtils.clamp(top, GaoDeBottomSheetBehavior.this.getExpandedOffset(), GaoDeBottomSheetBehavior.this.hideable ? GaoDeBottomSheetBehavior.this.parentHeight : GaoDeBottomSheetBehavior.this.collapsedOffset);}@Overridepublic int clampViewPositionHorizontal(@NonNull View child, int left, int dx) { return child.getLeft();}@Overridepublic int getViewVerticalDragRange(@NonNull View child) { return GaoDeBottomSheetBehavior.this.hideable ? GaoDeBottomSheetBehavior.this.parentHeight : GaoDeBottomSheetBehavior.this.collapsedOffset;} } @Override public Parcelable onSaveInstanceState(CoordinatorLayout parent, V child) {return new GaoDeBottomSheetBehavior.SavedState(super.onSaveInstanceState(parent, child), this.state); } @Override public void onRestoreInstanceState(CoordinatorLayout parent, V child, Parcelable state) {GaoDeBottomSheetBehavior.SavedState ss = (GaoDeBottomSheetBehavior.SavedState) state;super.onRestoreInstanceState(parent, child, ss.getSuperState());if (ss.state != STATE_DRAGGING && ss.state != STATE_SETTLING) { this.state = ss.state;} else { this.state = STATE_COLLAPSED;} } @Override public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {if (ViewCompat.getFitsSystemWindows(parent) && !ViewCompat.getFitsSystemWindows(child)) { child.setFitsSystemWindows(true);}int savedTop = child.getTop();parent.onLayoutChild(child, layoutDirection);this.parentHeight = parent.getHeight();if (this.peekHeightAuto) { if (this.peekHeightMin == 0) {this.peekHeightMin = parent.getResources().getDimensionPixelSize(R.dimen.design_bottom_sheet_peek_height_min); } this.lastPeekHeight = Math.max(this.peekHeightMin, this.parentHeight - parent.getWidth() * 9 / 16);} else { this.lastPeekHeight = this.peekHeight;}if (mMiddleHeightAuto) { mMiddleHeight = this.parentHeight;}this.fitToContentsOffset = Math.max(0, this.parentHeight - child.getHeight());this.halfExpandedOffset = this.parentHeight - mMiddleHeight;this.calculateCollapsedOffset();if (this.state == STATE_EXPANDED) { ViewCompat.offsetTopAndBottom(child, this.getExpandedOffset());} else if (this.state == STATE_HALF_EXPANDED) { ViewCompat.offsetTopAndBottom(child, this.halfExpandedOffset);} else if (this.hideable && this.state == STATE_HIDDEN) { ViewCompat.offsetTopAndBottom(child, this.parentHeight);} else if (this.state == STATE_COLLAPSED) { ViewCompat.offsetTopAndBottom(child, this.collapsedOffset);} else if (this.state == STATE_DRAGGING || this.state == STATE_SETTLING) { ViewCompat.offsetTopAndBottom(child, savedTop - child.getTop());}if (this.viewDragHelper == null) { this.viewDragHelper = ViewDragHelper.create(parent, this.dragCallback);}this.viewRef = new WeakReference(child);this.nestedScrollingChildRef = new WeakReference(this.findScrollingChild(child));return true; } @Override public boolean onInterceptTouchEvent(CoordinatorLayout parent, V child, MotionEvent event) {if (!child.isShown()) { this.ignoreEvents = true; return false;} else { int action = event.getActionMasked(); if (action == 0) {this.reset(); } if (this.velocityTracker == null) {this.velocityTracker = VelocityTracker.obtain(); } this.velocityTracker.addMovement(event); switch (action) {case 0: int initialX = (int) event.getX(); this.initialY = (int) event.getY(); View scroll = this.nestedScrollingChildRef != null ? (View) this.nestedScrollingChildRef.get() : null; if (scroll != null && parent.isPointInChildBounds(scroll, initialX, this.initialY)) {this.activePointerId = event.getPointerId(event.getActionIndex());this.touchingScrollingChild = true; } this.ignoreEvents = this.activePointerId == -1 && !parent.isPointInChildBounds(child, initialX, this.initialY); break;case 1:case 3: this.touchingScrollingChild = false; this.activePointerId = -1; if (this.ignoreEvents) {this.ignoreEvents = false;return false; }case 2: } if (!this.ignoreEvents && this.viewDragHelper != null && this.viewDragHelper.shouldInterceptTouchEvent(event)) {return true; } else {View scroll = this.nestedScrollingChildRef != null ? (View) this.nestedScrollingChildRef.get() : null;return action == 2 && scroll != null && !this.ignoreEvents && this.state != 1 && !parent.isPointInChildBounds(scroll, (int) event.getX(), (int) event.getY()) && this.viewDragHelper != null && Math.abs((float) this.initialY - event.getY()) > (float) this.viewDragHelper.getTouchSlop(); }} } @Override public boolean onTouchEvent(CoordinatorLayout parent, V child, MotionEvent event) {if (!child.isShown()) { return false;} else { int action = event.getActionMasked(); if (this.state == STATE_DRAGGING && action == 0) {return true; } else {if (this.viewDragHelper != null) { this.viewDragHelper.processTouchEvent(event);}if (action == 0) { this.reset();}if (this.velocityTracker == null) { this.velocityTracker = VelocityTracker.obtain();}this.velocityTracker.addMovement(event);if (action == 2 && !this.ignoreEvents && Math.abs((float) this.initialY - event.getY()) > (float) this.viewDragHelper.getTouchSlop()) { this.viewDragHelper.captureChildView(child, event.getPointerId(event.getActionIndex()));}return !this.ignoreEvents; }} } @Override public boolean onStartNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View directTargetChild, @NonNull View target, int axes, int type) {this.lastNestedScrollDy = 0;this.nestedScrolled = false;return (axes & 2) != 0; } @Override public void onNestedPreScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, int dx, int dy, @NonNull int[] consumed, int type) {if (type != 1) { View scrollingChild = (View) this.nestedScrollingChildRef.get(); if (target == scrollingChild) {int currentTop = child.getTop();int newTop = currentTop - dy;if (dy > 0) { if (newTop < this.getExpandedOffset()) {consumed[1] = currentTop - this.getExpandedOffset();ViewCompat.offsetTopAndBottom(child, -consumed[1]);this.setStateInternal(STATE_EXPANDED); } else {consumed[1] = dy;ViewCompat.offsetTopAndBottom(child, -dy);this.setStateInternal(STATE_DRAGGING); }} else if (dy < 0 && !target.canScrollVertically(-1)) { if (newTop > this.collapsedOffset && !this.hideable) {consumed[1] = currentTop - this.collapsedOffset;ViewCompat.offsetTopAndBottom(child, -consumed[1]);this.setStateInternal(STATE_COLLAPSED); } else {consumed[1] = dy;ViewCompat.offsetTopAndBottom(child, -dy);this.setStateInternal(STATE_DRAGGING); }}this.dispatchOnSlide(child.getTop());this.lastNestedScrollDy = dy;this.nestedScrolled = true; }} } @Override public void onStopNestedScroll(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, int type) {if (child.getTop() == this.getExpandedOffset()) { this.setStateInternal(STATE_EXPANDED);} else if (target == this.nestedScrollingChildRef.get() && this.nestedScrolled) { int top; byte targetState; if (this.lastNestedScrollDy > 0) {int currentTop = child.getTop();if (currentTop <= collapsedOffset - HIDE_THRESHOLD && currentTop >= halfExpandedOffset) { top = this.halfExpandedOffset; targetState = STATE_HALF_EXPANDED;} else { top = this.getExpandedOffset(); targetState = STATE_EXPANDED;} } else if (this.hideable && this.shouldHide(child, this.getYVelocity())) {top = this.parentHeight;targetState = STATE_HIDDEN; } else if (this.lastNestedScrollDy == 0) {int currentTop = child.getTop();if (this.fitToContents) { if (Math.abs(currentTop - this.fitToContentsOffset) < Math.abs(currentTop - this.collapsedOffset)) {top = this.fitToContentsOffset;targetState = STATE_EXPANDED; } else {top = this.collapsedOffset;targetState = STATE_COLLAPSED; }} else if (currentTop < this.halfExpandedOffset) { if (currentTop < Math.abs(currentTop - this.collapsedOffset)) {top = 0;targetState = STATE_EXPANDED; } else {top = this.halfExpandedOffset;targetState = STATE_HALF_EXPANDED; }} else if (Math.abs(currentTop - this.halfExpandedOffset) < Math.abs(currentTop - this.collapsedOffset)) { top = this.halfExpandedOffset; targetState = STATE_HALF_EXPANDED;} else { top = this.collapsedOffset; targetState = STATE_COLLAPSED;} } else {int currentTop = child.getTop();if (currentTop <= halfExpandedOffset + HIDE_THRESHOLD && currentTop > HIDE_THRESHOLD) { top = this.halfExpandedOffset; targetState = STATE_HALF_EXPANDED;} else { top = this.collapsedOffset; targetState = STATE_COLLAPSED;} } if (this.viewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) {this.setStateInternal(STATE_SETTLING);ViewCompat.postOnAnimation(child, new GaoDeBottomSheetBehavior.SettleRunnable(child, targetState)); } else {this.setStateInternal(targetState); } this.nestedScrolled = false;} } @Override public boolean onNestedPreFling(@NonNull CoordinatorLayout coordinatorLayout, @NonNull V child, @NonNull View target, float velocityX, float velocityY) {return target == this.nestedScrollingChildRef.get() && (this.state != STATE_EXPANDED || super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY)); } public boolean isFitToContents() {return this.fitToContents; } public void setFitToContents(boolean fitToContents) {if (this.fitToContents != fitToContents) { this.fitToContents = fitToContents; if (this.viewRef != null) {this.calculateCollapsedOffset(); } this.setStateInternal(this.fitToContents && this.state == STATE_HALF_EXPANDED ? STATE_HALF_EXPANDED : this.state);} } public final void setPeekHeight(int peekHeight) {boolean layout = false;if (peekHeight == -1) { if (!this.peekHeightAuto) {this.peekHeightAuto = true;layout = true; }} else if (this.peekHeightAuto || this.peekHeight != peekHeight) { this.peekHeightAuto = false; this.peekHeight = Math.max(0, peekHeight); this.collapsedOffset = this.parentHeight - peekHeight; layout = true;}if (layout && this.state == STATE_COLLAPSED && this.viewRef != null) { V view = (V) this.viewRef.get(); if (view != null) {view.requestLayout(); }} } public final void setMiddleHeight(int middleHeight) {boolean layout = false;if (middleHeight == PEEK_HEIGHT_AUTO) { if (!mMiddleHeightAuto) {mMiddleHeightAuto = true;layout = true; }} else if (mMiddleHeightAuto || mMiddleHeight != middleHeight) { mMiddleHeightAuto = false; mMiddleHeight = Math.max(0, middleHeight); layout = true;}if (layout && this.state == STATE_COLLAPSED && viewRef != null) { V view = viewRef.get(); if (view != null) {view.requestLayout(); }} } public final int getPeekHeight() {return this.peekHeightAuto ? -1 : this.peekHeight; } public final int getMiddleHeight() {return this.mMiddleHeightAuto ? -1 : this.mMiddleHeight; } public final int getParentHeight() {return this.parentHeight; } public void setHideable(boolean hideable) {this.hideable = hideable; } public boolean isHideable() {return this.hideable; } public void setSkipCollapsed(boolean skipCollapsed) {this.skipCollapsed = skipCollapsed; } public boolean getSkipCollapsed() {return this.skipCollapsed; } public void setBottomSheetCallback(GaoDeBottomSheetBehavior.BottomSheetCallback callback) {this.callback = callback; } public final void setState(final int state) {if (state != this.state) { if (this.viewRef == null) {if (state == STATE_COLLAPSED || state == STATE_EXPANDED || state == STATE_HALF_EXPANDED || this.hideable && state == STATE_HIDDEN) { this.state = state;} } else {final V child = (V) this.viewRef.get();if (child != null) { ViewParent parent = child.getParent(); if (parent != null && parent.isLayoutRequested() && ViewCompat.isAttachedToWindow(child)) {child.post(new Runnable() { @Override public void run() {GaoDeBottomSheetBehavior.this.startSettlingAnimation(child, state); }}); } else {this.startSettlingAnimation(child, state); }} }} } public final int getState() {return this.state; } void setStateInternal(int state) {if (this.state != state) { this.state = state; if (state != STATE_HALF_EXPANDED && state != STATE_EXPANDED) {if (state == STATE_HIDDEN || state == STATE_COLLAPSED) { this.updateImportantForAccessibility(false);} } else {this.updateImportantForAccessibility(true); } View bottomSheet = (View) this.viewRef.get(); if (bottomSheet != null && this.callback != null) {this.callback.onStateChanged(bottomSheet, state); }} } private void calculateCollapsedOffset() {if (this.fitToContents) { this.collapsedOffset = Math.max(this.parentHeight - this.lastPeekHeight, this.fitToContentsOffset);} else { this.collapsedOffset = this.parentHeight - this.lastPeekHeight;} } private void reset() {this.activePointerId = -1;if (this.velocityTracker != null) { this.velocityTracker.recycle(); this.velocityTracker = null;} } boolean shouldHide(View child, float yvel) {if (this.skipCollapsed) { return true;} else if (child.getTop() < this.collapsedOffset) { return false;} else { float newTop = (float) child.getTop() + yvel * HIDE_FRICTION; return Math.abs(newTop - (float) this.collapsedOffset) / (float) this.peekHeight > HIDE_THRESHOLD;} } @VisibleForTesting View findScrollingChild(View view) {if (ViewCompat.isNestedScrollingEnabled(view)) { return view;} else { if (view instanceof ViewGroup) {ViewGroup group = (ViewGroup) view;int i = 0;for (int count = group.getChildCount(); i < count; ++i) { View scrollingChild = this.findScrollingChild(group.getChildAt(i)); if (scrollingChild != null) {return scrollingChild; }} } return null;} } private float getYVelocity() {if (this.velocityTracker == null) { return 0.0F;} else { this.velocityTracker.computeCurrentVelocity(1000, this.maximumVelocity); return this.velocityTracker.getYVelocity(this.activePointerId);} } private int getExpandedOffset() {return this.fitToContents ? this.fitToContentsOffset : 0; } void startSettlingAnimation(View child, int state) {int top;if (state == STATE_COLLAPSED) { top = this.collapsedOffset;} else if (state == STATE_HALF_EXPANDED) { top = this.halfExpandedOffset;} else if (state == STATE_EXPANDED) { top = this.getExpandedOffset();} else { if (!this.hideable || state != STATE_HIDDEN) {throw new IllegalArgumentException('Illegal state argument: ' + state); } top = this.parentHeight;}if (this.viewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) { this.setStateInternal(STATE_SETTLING); ViewCompat.postOnAnimation(child, new GaoDeBottomSheetBehavior.SettleRunnable(child, state));} else { this.setStateInternal(state);} } void dispatchOnSlide(int top) {View bottomSheet = (View) this.viewRef.get();if (bottomSheet != null && this.callback != null) { if (top > this.collapsedOffset) {this.callback.onSlide(bottomSheet, (float) (this.collapsedOffset - top) / (float) (this.parentHeight - this.collapsedOffset)); } else {this.callback.onSlide(bottomSheet, (float) (this.collapsedOffset - top) / (float) (this.collapsedOffset - this.getExpandedOffset())); }} } @VisibleForTesting int getPeekHeightMin() {return this.peekHeightMin; } public static <V extends View> GaoDeBottomSheetBehavior<V> from(V view) {LayoutParams params = view.getLayoutParams();if (!(params instanceof CoordinatorLayout.LayoutParams)) { throw new IllegalArgumentException('The view is not a child of CoordinatorLayout');} else { Behavior behavior = ((CoordinatorLayout.LayoutParams) params).getBehavior(); if (!(behavior instanceof GaoDeBottomSheetBehavior)) {throw new IllegalArgumentException('The view is not associated with BottomSheetBehavior'); } else {return (GaoDeBottomSheetBehavior) behavior; }} } @SuppressLint('WrongConstant') private void updateImportantForAccessibility(boolean expanded) {if (this.viewRef != null) { ViewParent viewParent = ((View) this.viewRef.get()).getParent(); if (viewParent instanceof CoordinatorLayout) {CoordinatorLayout parent = (CoordinatorLayout) viewParent;int childCount = parent.getChildCount();if (VERSION.SDK_INT >= 16 && expanded) { if (this.importantForAccessibilityMap != null) {return; } this.importantForAccessibilityMap = new HashMap(childCount);}for (int i = 0; i < childCount; ++i) { View child = parent.getChildAt(i); if (child != this.viewRef.get()) {if (!expanded) { if (this.importantForAccessibilityMap != null && this.importantForAccessibilityMap.containsKey(child)) {ViewCompat.setImportantForAccessibility(child, (Integer) this.importantForAccessibilityMap.get(child)); }} else { if (VERSION.SDK_INT >= 16) {this.importantForAccessibilityMap.put(child, child.getImportantForAccessibility()); } ViewCompat.setImportantForAccessibility(child, 4);} }}if (!expanded) { this.importantForAccessibilityMap = null;} }} } protected static class SavedState extends AbsSavedState {final int state;public static final Creator<GaoDeBottomSheetBehavior.SavedState> CREATOR = new ClassLoaderCreator<GaoDeBottomSheetBehavior.SavedState>() { @Override public GaoDeBottomSheetBehavior.SavedState createFromParcel(Parcel in, ClassLoader loader) {return new GaoDeBottomSheetBehavior.SavedState(in, loader); } @Override public GaoDeBottomSheetBehavior.SavedState createFromParcel(Parcel in) {return new GaoDeBottomSheetBehavior.SavedState(in, (ClassLoader) null); } @Override public GaoDeBottomSheetBehavior.SavedState[] newArray(int size) {return new GaoDeBottomSheetBehavior.SavedState[size]; }};public SavedState(Parcel source) { this(source, (ClassLoader) null);}public SavedState(Parcel source, ClassLoader loader) { super(source, loader); this.state = source.readInt();}public SavedState(Parcelable superState, int state) { super(superState); this.state = state;}@Overridepublic void writeToParcel(Parcel out, int flags) { super.writeToParcel(out, flags); out.writeInt(this.state);} } private class SettleRunnable implements Runnable {private final View view;private final int targetState;SettleRunnable(View view, int targetState) { this.view = view; this.targetState = targetState;}@Overridepublic void run() { if (GaoDeBottomSheetBehavior.this.viewDragHelper != null && GaoDeBottomSheetBehavior.this.viewDragHelper.continueSettling(true)) {ViewCompat.postOnAnimation(this.view, this); } else {GaoDeBottomSheetBehavior.this.setStateInternal(this.targetState); }} } @Retention(RetentionPolicy.SOURCE) @RestrictTo({Scope.LIBRARY_GROUP}) public @interface State { } public abstract static class BottomSheetCallback {public BottomSheetCallback() {}public abstract void onStateChanged(@NonNull View var1, int var2);public abstract void onSlide(@NonNull View var1, float var2); }}

使用的时候直接设置：

<androidx.appcompat.widget.LinearLayoutCompat android: android:layout_width='match_parent' android:layout_height='match_parent' android:background='@android:color/white' android:orientation='vertical' android:visibility='visible' app:behavior_hideable='false' app:behavior_middleHeight='200dp' app:behavior_peekHeight='80dp' app:layout_behavior='.gaode.GaoDeBottomSheetBehavior' tools:ignore='MissingPrefix'> //.... </androidx.appcompat.widget.LinearLayoutCompat>

对于按钮滑动及通明度渐变隐藏显示也是通过实现behavior，因为比较的简单直接上代码：

/** * 高德首页按钮处理 */public class GaoDeBtnBehavior extends CoordinatorLayout.Behavior { private View rightActions; private View topActions; public GaoDeBtnBehavior() { } public GaoDeBtnBehavior(Context context, AttributeSet attrs) {super(context, attrs); } @Override public boolean onLayoutChild(@NonNull CoordinatorLayout parent, @NonNull View child, int layoutDirection) {if (ViewCompat.getFitsSystemWindows(parent) && !ViewCompat.getFitsSystemWindows(child)) { child.setFitsSystemWindows(true);}if (rightActions == null) { rightActions = parent.findViewById(R.id.rightActions);}if (topActions == null) { topActions = parent.findViewById(R.id.topActions);}return super.onLayoutChild(parent, child, layoutDirection); } @Override public boolean layoutDependsOn(@NonNull CoordinatorLayout parent, @NonNull View child, @NonNull View dependency) {return dependency instanceof LinearLayoutCompat || super.layoutDependsOn(parent, child, dependency); } @Override public boolean onDependentViewChanged(@NonNull CoordinatorLayout parent, @NonNull View child, @NonNull View dependency) {//判断当前dependency 是内容布局if (dependency instanceof LinearLayoutCompat && dependency.getId() == R.id.bottom_sheet) { if (rightActions != null) {GaoDeBottomSheetBehavior behavior = GaoDeBottomSheetBehavior.from(dependency);int middleHeight = behavior.getParentHeight() - behavior.getMiddleHeight() - rightActions.getMeasuredHeight();CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) rightActions.getLayoutParams();int newY = dependency.getTop() - rightActions.getHeight() - layoutParams.bottomMargin;if (newY >= middleHeight) { rightActions.setTranslationY(newY - layoutParams.bottomMargin);} else { rightActions.setTranslationY(middleHeight);}int offset = behavior.getParentHeight() - behavior.getMiddleHeight() - layoutParams.bottomMargin - dependency.getTop();float alpha = 1f - offset * 1.0f / rightActions.getHeight();rightActions.setAlpha(alpha);if (topActions != null) { topActions.setAlpha(alpha);} }}return super.onDependentViewChanged(parent, child, dependency); }}

源码地址：

https://github.com/yixiaolunhui/FGaoDeIndexDemo

到这里就结束啦。

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