Add nested pre-fling for nested scrolling (b72be59a) · Commits · e / os / android_frameworks_base

api/current.txt

+3 −0

Original line number	Diff line number	Diff line
		@@ -33524,6 +33524,7 @@ package android.view {
		method public boolean dispatchKeyEventPreIme(android.view.KeyEvent);
		method public boolean dispatchKeyShortcutEvent(android.view.KeyEvent);
		method public boolean dispatchNestedFling(float, float, boolean);
		method public boolean dispatchNestedPreFling(float, float);
		method public boolean dispatchNestedPreScroll(int, int, int[], int[]);
		method public boolean dispatchNestedScroll(int, int, int, int, int[]);
		method public boolean dispatchPopulateAccessibilityEvent(android.view.accessibility.AccessibilityEvent);
		@@ -34334,6 +34335,7 @@ package android.view {
		method public boolean onInterceptTouchEvent(android.view.MotionEvent);
		method protected abstract void onLayout(boolean, int, int, int, int);
		method public boolean onNestedFling(android.view.View, float, float, boolean);
		method public boolean onNestedPreFling(android.view.View, float, float);
		method public void onNestedPreScroll(android.view.View, int, int, int[]);
		method public void onNestedScroll(android.view.View, int, int, int, int);
		method public void onNestedScrollAccepted(android.view.View, android.view.View, int);
		@@ -34479,6 +34481,7 @@ package android.view {
		method public abstract boolean isTextDirectionResolved();
		method public abstract void notifySubtreeAccessibilityStateChanged(android.view.View, android.view.View, int);
		method public abstract boolean onNestedFling(android.view.View, float, float, boolean);
		method public abstract boolean onNestedPreFling(android.view.View, float, float);
		method public abstract void onNestedPreScroll(android.view.View, int, int, int[]);
		method public abstract void onNestedScroll(android.view.View, int, int, int, int);
		method public abstract void onNestedScrollAccepted(android.view.View, android.view.View, int);

core/java/android/view/View.java

+37 −0

Original line number	Diff line number	Diff line
		@@ -18444,6 +18444,43 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
		return false;
		}

		/**
		* Dispatch a fling to a nested scrolling parent before it is processed by this view.
		*
		* <p>Nested pre-fling events are to nested fling events what touch intercept is to touch
		* and what nested pre-scroll is to nested scroll. <code>dispatchNestedPreFling</code>
		* offsets an opportunity for the parent view in a nested fling to fully consume the fling
		* before the child view consumes it. If this method returns <code>true</code>, a nested
		* parent view consumed the fling and this view should not scroll as a result.</p>
		*
		* <p>For a better user experience, only one view in a nested scrolling chain should consume
		* the fling at a time. If a parent view consumed the fling this method will return false.
		* Custom view implementations should account for this in two ways:</p>
		*
		* <ul>
		* <li>If a custom view is paged and needs to settle to a fixed page-point, do not
		* call <code>dispatchNestedPreFling</code>; consume the fling and settle to a valid
		* position regardless.</li>
		* <li>If a nested parent does consume the fling, this view should not scroll at all,
		* even to settle back to a valid idle position.</li>
		* </ul>
		*
		* <p>Views should also not offer fling velocities to nested parent views along an axis
		* where scrolling is not currently supported; a {@link android.widget.ScrollView ScrollView}
		* should not offer a horizontal fling velocity to its parents since scrolling along that
		* axis is not permitted and carrying velocity along that motion does not make sense.</p>
		*
		* @param velocityX Horizontal fling velocity in pixels per second
		* @param velocityY Vertical fling velocity in pixels per second
		* @return true if a nested scrolling parent consumed the fling
		*/
		public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
		if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
		return mNestedScrollingParent.onNestedPreFling(this, velocityX, velocityY);
		}
		return false;
		}

		/**
		* Gets a scale factor that determines the distance the view should scroll
		* vertically in response to {@link MotionEvent#ACTION_SCROLL}.

core/java/android/view/ViewGroup.java

+8 −0

Original line number	Diff line number	Diff line
		@@ -6065,6 +6065,14 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
		return false;
		}

		/**
		* @inheritDoc
		*/
		@Override
		public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
		return false;
		}

		/**
		* Return the current axes of nested scrolling for this ViewGroup.
		*

core/java/android/view/ViewParent.java

+23 −1

Original line number	Diff line number	Diff line
		@@ -523,10 +523,32 @@ public interface ViewParent {
		* parent instead. The parent may optionally consume the fling or observe a child fling.</p>
		*
		* @param target View that initiated the nested scroll
		* @param velocityX Horizontal velocity in pixels per second.
		* @param velocityX Horizontal velocity in pixels per second
		* @param velocityY Vertical velocity in pixels per second
		* @param consumed true if the child consumed the fling, false otherwise
		* @return true if this parent consumed or otherwise reacted to the fling
		*/
		public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed);

		/**
		* React to a nested fling before the target view consumes it.
		*
		* <p>This method siginfies that a nested scrolling child has detected a fling with the given
		* velocity along each axis. Generally this means that a touch scroll has ended with a
		* {@link VelocityTracker velocity} in the direction of scrolling that meets or exceeds
		* the {@link ViewConfiguration#getScaledMinimumFlingVelocity() minimum fling velocity}
		* along a scrollable axis.</p>
		*
		* <p>If a nested scrolling parent is consuming motion as part of a
		* {@link #onNestedPreScroll(View, int, int, int[]) pre-scroll}, it may be appropriate for
		* it to also consume the pre-fling to complete that same motion. By returning
		* <code>true</code> from this method, the parent indicates that the child should not
		* fling its own internal content as well.</p>
		*
		* @param target View that initiated the nested scroll
		* @param velocityX Horizontal velocity in pixels per second
		* @param velocityY Vertical velocity in pixels per second
		* @return true if this parent consumed the fling ahead of the target view
		*/
		public boolean onNestedPreFling(View target, float velocityX, float velocityY);
		}

core/java/android/view/ViewRootImpl.java

+5 −0

Original line number	Diff line number	Diff line
		@@ -6291,6 +6291,11 @@ public final class ViewRootImpl implements ViewParent,
		return false;
		}

		@Override
		public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
		return false;
		}

		void changeCanvasOpacity(boolean opaque) {
		Log.d(TAG, "changeCanvasOpacity: opaque=" + opaque);
		if (mAttachInfo.mHardwareRenderer != null) {