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Diffstat (limited to 'core/java/android/view/ScrollCaptureTargetResolver.java')
| -rw-r--r-- | core/java/android/view/ScrollCaptureTargetResolver.java | 337 |
1 files changed, 0 insertions, 337 deletions
diff --git a/core/java/android/view/ScrollCaptureTargetResolver.java b/core/java/android/view/ScrollCaptureTargetResolver.java deleted file mode 100644 index e4316bbc9397..000000000000 --- a/core/java/android/view/ScrollCaptureTargetResolver.java +++ /dev/null @@ -1,337 +0,0 @@ -/* - * Copyright (C) 2020 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.view; - -import android.annotation.AnyThread; -import android.annotation.NonNull; -import android.annotation.Nullable; -import android.annotation.UiThread; -import android.graphics.Rect; -import android.os.Handler; -import android.os.Looper; -import android.os.SystemClock; -import android.util.Log; - -import com.android.internal.annotations.VisibleForTesting; - - -import java.util.Queue; -import java.util.concurrent.atomic.AtomicReference; -import java.util.function.Consumer; - -/** - * Queries additional state from a list of {@link ScrollCaptureTarget targets} via asynchronous - * callbacks, then aggregates and reduces the target list to a single target, or null if no target - * is suitable. - * <p> - * The rules for selection are (in order): - * <ul> - * <li>prefer getScrollBounds(): non-empty - * <li>prefer View.getScrollCaptureHint == SCROLL_CAPTURE_HINT_INCLUDE - * <li>prefer descendants before parents - * <li>prefer larger area for getScrollBounds() (clipped to view bounds) - * </ul> - * - * <p> - * All calls to {@link ScrollCaptureCallback#onScrollCaptureSearch} are made on the main thread, - * with results are queued and consumed to the main thread as well. - * - * @see #start(Handler, long, Consumer) - * - * @hide - */ -@UiThread -public class ScrollCaptureTargetResolver { - private static final String TAG = "ScrollCaptureTargetRes"; - - private final Object mLock = new Object(); - - private final Queue<ScrollCaptureTarget> mTargets; - private Handler mHandler; - private long mTimeLimitMillis; - - private Consumer<ScrollCaptureTarget> mWhenComplete; - private int mPendingBoundsRequests; - private long mDeadlineMillis; - - private ScrollCaptureTarget mResult; - private boolean mFinished; - - private boolean mStarted; - - private static int area(Rect r) { - return r.width() * r.height(); - } - - private static boolean nullOrEmpty(Rect r) { - return r == null || r.isEmpty(); - } - - /** - * Binary operator which selects the best {@link ScrollCaptureTarget}. - */ - private static ScrollCaptureTarget chooseTarget(ScrollCaptureTarget a, ScrollCaptureTarget b) { - if (a == null && b == null) { - return null; - } else if (a == null || b == null) { - ScrollCaptureTarget c = (a == null) ? b : a; - return c; - } - - boolean emptyScrollBoundsA = nullOrEmpty(a.getScrollBounds()); - boolean emptyScrollBoundsB = nullOrEmpty(b.getScrollBounds()); - if (emptyScrollBoundsA || emptyScrollBoundsB) { - if (emptyScrollBoundsA && emptyScrollBoundsB) { - // Both have an empty or null scrollBounds - Log.d(TAG, "chooseTarget: (both have empty or null bounds) return " + null); - return null; - } - // Prefer the one with a non-empty scroll bounds - if (emptyScrollBoundsA) { - Log.d(TAG, "chooseTarget: (a has empty or null bounds) return " + b); - return b; - } - Log.d(TAG, "chooseTarget: (b has empty or null bounds) return " + a); - return a; - } - - final View viewA = a.getContainingView(); - final View viewB = b.getContainingView(); - - // Prefer any view with scrollCaptureHint="INCLUDE", over one without - // This is an escape hatch for the next rule (descendants first) - boolean hintIncludeA = hasIncludeHint(viewA); - boolean hintIncludeB = hasIncludeHint(viewB); - if (hintIncludeA != hintIncludeB) { - ScrollCaptureTarget c = (hintIncludeA) ? a : b; - Log.d(TAG, "chooseTarget: (has hint=INCLUDE) return " + c); - return c; - } - - // If the views are relatives, prefer the descendant. This allows implementations to - // leverage nested scrolling APIs by interacting with the innermost scrollable view (as - // would happen with touch input). - if (isDescendant(viewA, viewB)) { - Log.d(TAG, "chooseTarget: (b is descendant of a) return " + b); - return b; - } - if (isDescendant(viewB, viewA)) { - Log.d(TAG, "chooseTarget: (a is descendant of b) return " + a); - return a; - } - - // finally, prefer one with larger scroll bounds - int scrollAreaA = area(a.getScrollBounds()); - int scrollAreaB = area(b.getScrollBounds()); - ScrollCaptureTarget c = (scrollAreaA >= scrollAreaB) ? a : b; - Log.d(TAG, "chooseTarget: return " + c); - return c; - } - - /** - * Creates an instance to query and filter {@code target}. - * - * @param targets a list of {@link ScrollCaptureTarget} as collected by {@link - * View#dispatchScrollCaptureSearch}. - * @see #start(Handler, long, Consumer) - */ - public ScrollCaptureTargetResolver(Queue<ScrollCaptureTarget> targets) { - mTargets = targets; - } - - void checkThread() { - if (mHandler.getLooper() != Looper.myLooper()) { - throw new IllegalStateException("Called from wrong thread! (" - + Thread.currentThread().getName() + ")"); - } - } - - /** - * Blocks until a result is returned (after completion or timeout). - * <p> - * For testing only. Normal usage should receive a callback after calling {@link #start}. - */ - @VisibleForTesting - public ScrollCaptureTarget waitForResult() throws InterruptedException { - synchronized (mLock) { - while (!mFinished) { - mLock.wait(); - } - } - return mResult; - } - - private void supplyResult(ScrollCaptureTarget target) { - checkThread(); - if (mFinished) { - return; - } - mResult = chooseTarget(mResult, target); - boolean finish = mPendingBoundsRequests == 0 - || SystemClock.uptimeMillis() >= mDeadlineMillis; - if (finish) { - mPendingBoundsRequests = 0; - mWhenComplete.accept(mResult); - synchronized (mLock) { - mFinished = true; - mLock.notify(); - } - mWhenComplete = null; - } - } - - /** - * Asks all targets for {@link ScrollCaptureCallback#onScrollCaptureSearch(Consumer) - * scrollBounds}, and selects the primary target according to the {@link - * #chooseTarget} function. - * - * @param timeLimitMillis the amount of time to wait for all responses before delivering the top - * result - * @param resultConsumer the consumer to receive the primary target - */ - @AnyThread - public void start(Handler uiHandler, long timeLimitMillis, - Consumer<ScrollCaptureTarget> resultConsumer) { - synchronized (mLock) { - if (mStarted) { - throw new IllegalStateException("already started!"); - } - if (timeLimitMillis < 0) { - throw new IllegalArgumentException("Time limit must be positive"); - } - mHandler = uiHandler; - mTimeLimitMillis = timeLimitMillis; - mWhenComplete = resultConsumer; - if (mTargets.isEmpty()) { - mHandler.post(() -> supplyResult(null)); - return; - } - mStarted = true; - uiHandler.post(this::run); - } - } - - private void run() { - checkThread(); - - mPendingBoundsRequests = mTargets.size(); - for (ScrollCaptureTarget target : mTargets) { - queryTarget(target); - } - mDeadlineMillis = SystemClock.uptimeMillis() + mTimeLimitMillis; - mHandler.postAtTime(mTimeoutRunnable, mDeadlineMillis); - } - - private final Runnable mTimeoutRunnable = () -> { - checkThread(); - supplyResult(null); - }; - - /** - * Adds a target to the list and requests {@link ScrollCaptureCallback#onScrollCaptureSearch} - * scrollBounds} from it. Results are returned by a call to {@link #onScrollBoundsProvided}. - * - * @param target the target to add - */ - @UiThread - private void queryTarget(@NonNull ScrollCaptureTarget target) { - checkThread(); - final ScrollCaptureCallback callback = target.getCallback(); - // from the UI thread, request scroll bounds - callback.onScrollCaptureSearch( - // allow only one callback to onReady.accept(): - new SingletonConsumer<Rect>( - // Queue and consume on the UI thread - ((scrollBounds) -> mHandler.post( - () -> onScrollBoundsProvided(target, scrollBounds))))); - } - - @UiThread - private void onScrollBoundsProvided(ScrollCaptureTarget target, @Nullable Rect scrollBounds) { - checkThread(); - if (mFinished) { - return; - } - - // Record progress. - mPendingBoundsRequests--; - - // Remove the timeout. - mHandler.removeCallbacks(mTimeoutRunnable); - - boolean doneOrTimedOut = mPendingBoundsRequests == 0 - || SystemClock.uptimeMillis() >= mDeadlineMillis; - - final View containingView = target.getContainingView(); - if (!nullOrEmpty(scrollBounds) && containingView.isAggregatedVisible()) { - target.updatePositionInWindow(); - target.setScrollBounds(scrollBounds); - supplyResult(target); - } - - if (!mFinished) { - // Reschedule the timeout. - mHandler.postAtTime(mTimeoutRunnable, mDeadlineMillis); - } - } - - private static boolean hasIncludeHint(View view) { - return (view.getScrollCaptureHint() & View.SCROLL_CAPTURE_HINT_INCLUDE) != 0; - } - - /** - * Determines if {@code otherView} is a descendant of {@code view}. - * - * @param view a view - * @param otherView another view - * @return true if {@code view} is an ancestor of {@code otherView} - */ - private static boolean isDescendant(@NonNull View view, @NonNull View otherView) { - if (view == otherView) { - return false; - } - ViewParent otherParent = otherView.getParent(); - while (otherParent != view && otherParent != null) { - otherParent = otherParent.getParent(); - } - return otherParent == view; - } - - /** - * A safe wrapper for a consumer callbacks intended to accept a single value. It ensures - * that the receiver of the consumer does not retain a reference to {@code target} after use nor - * cause race conditions by invoking {@link Consumer#accept accept} more than once. - */ - static class SingletonConsumer<T> implements Consumer<T> { - final AtomicReference<Consumer<T>> mAtomicRef; - - /** - * @param target the target consumer - **/ - SingletonConsumer(Consumer<T> target) { - mAtomicRef = new AtomicReference<>(target); - } - - @Override - public void accept(T t) { - final Consumer<T> consumer = mAtomicRef.getAndSet(null); - if (consumer != null) { - consumer.accept(t); - } - } - } -} |