Reapply "Stop ViewCapture functionality if memory is low, Delete data"

import static com.android.app.viewcapture.data.ExportedData.MagicNumber.MAGIC_NUMBER_H;

import static com.android.app.viewcapture.data.ExportedData.MagicNumber.MAGIC_NUMBER_L;

import android.content.ComponentCallbacks2;

import android.content.Context;

import android.content.res.Configuration;

import android.content.res.Resources;

import android.media.permission.SafeCloseable;

import android.os.HandlerThread;

        WindowListener listener = new WindowListener(view, name);

        if (mIsEnabled) MAIN_EXECUTOR.execute(listener::attachToRoot);

        mListeners.add(listener);

        Context context = view.getContext();

        context.registerComponentCallbacks(listener);

        return () -> {

            context.unregisterComponentCallbacks(listener);

            mListeners.remove(listener);

            listener.detachFromRoot();

        };

     * view tree on the main thread every time onDraw is called. It then saves the state of the view

     * tree traversed in a local list of nodes, so that this list of nodes can be processed on a

     * background thread, and prepared for being dumped into a bugreport.

     *

     * <p>

     * Since some of the work needs to be done on the main thread after every draw, this piece of

     * code needs to be hyper optimized. That is why we are recycling ViewRef and ViewPropertyRef

     * objects and storing the list of nodes as a flat LinkedList, rather than as a tree. This data

     * structure allows recycling to happen in O(1) time via pointer assignment. Without this

     * optimization, a lot of time is wasted creating ViewRef objects, or finding ViewRef objects to

     * recycle.

     *

     * <p>

     * Another optimization is to only traverse view nodes on the main thread that have potentially

     * changed since the last frame was drawn. This can be determined via a combination of private

     * flags inside the View class.

     *

     * <p>

     * Another optimization is to not store or manipulate any string objects on the main thread.

     * While this might seem trivial, using Strings in any form causes the ViewCapture to hog the

     * main thread for up to an additional 6-7ms. It must be avoided at all costs.

     *

     * <p>

     * Another optimization is to only store the class names of the Views in the view hierarchy one

     * time. They are then referenced via a classNameIndex value stored in each ViewPropertyRef.

     *

     * <p>

     * TODO: b/262585897: If further memory optimization is required, an effective one would be to

     * only store the changes between frames, rather than the entire node tree for each frame.

     * The go/web-hv UX already does this, and has reaped significant memory improves because of it.

     *

     * <p>

     * TODO: b/262585897: Another memory optimization could be to store all integer, float, and

     * boolean information via single integer values via the Chinese remainder theorem, or a similar

     * algorithm, which enables multiple numerical values to be stored inside 1 number. Doing this

     * would allow each ViewProperty / ViewRef to slim down its memory footprint significantly.

     *

     * <p>

     * One important thing to remember is that bugs related to recycling will usually only appear

     * after at least 2000 frames have been rendered. If that code is changed, the tester can

     * use hard-coded logs to verify that recycling is happening, and test view capturing at least

     * ~8000 frames or so to verify the recycling functionality is working properly.

     * <p>

     * Each WindowListener is memory aware and will both stop collecting view capture information,

     * as well as delete their current stash of information upon a signal from the system that

     * memory resources are scarce. The user will need to restart the app process before

     * more ViewCapture information is captured.

     */

    private class WindowListener implements ViewTreeObserver.OnDrawListener {

    private class WindowListener implements ViewTreeObserver.OnDrawListener, ComponentCallbacks2 {

        @Nullable // Nullable in tests only

        @Nullable

        public View mRoot;

        public final String name;

        private int mFrameIndexBg = -1;

        private boolean mIsFirstFrame = true;

        private final long[] mFrameTimesNanosBg = new long[mMemorySize];

        private final ViewPropertyRef[] mNodesBg = new ViewPropertyRef[mMemorySize];

        private long[] mFrameTimesNanosBg = new long[mMemorySize];

        private ViewPropertyRef[] mNodesBg = new ViewPropertyRef[mMemorySize];

        private boolean mIsActive = true;

        private final Consumer<ViewRef> mCaptureCallback = this::captureViewPropertiesBg;

        }

        private void safelyEnableOnDrawListener() {

            if (mRoot != null) {

                mRoot.getViewTreeObserver().removeOnDrawListener(this);

                mRoot.getViewTreeObserver().addOnDrawListener(this);

            }

        }

        @WorkerThread

        private WindowData dumpToProto(ViewIdProvider idProvider, ArrayList<Class> classList) {

                return ref;

            }

        }

        @Override

        public void onTrimMemory(int level) {

            if (ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL == level

                    || ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW == level) {

                mNodesBg = new ViewPropertyRef[0];

                mFrameTimesNanosBg = new long[0];

                if (mRoot != null && mRoot.getContext() != null) {

                    mRoot.getContext().unregisterComponentCallbacks(this);

                }

                detachFromRoot();

                mRoot = null;

            }

        }

        @Override

        public void onConfigurationChanged(Configuration configuration) {

            // No Operation

        }

        @Override

        public void onLowMemory() {

            onTrimMemory(ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW);

        }

    }

    private static class ViewPropertyRef {

    private static class ViewRef implements Runnable {

        public View view;

        public int childCount = 0;

        @Nullable

        public ViewRef next;

        public Consumer<ViewRef> callback = null;