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Commit 224c1343 authored by Johannes Gallmann's avatar Johannes Gallmann
Browse files

Remove restriction that only one callback with... 

...PRIORITY_SYSTEM_NAVIGATION_OBSERVER can be registered.

This CL removes the API restriction that only one back callback with
PRIORITY_SYSTEM_NAVIGATION_OBSERVER can be registered at a time.
Starting with SDK 37, an unrestricted number of observer callbacks can
be registered. All registered observer callbacks will receive back
events when a system back navigation happens.

Bug: 424146227
Test: WindowOnBackInvokedDispatcherTest
Flag: com.android.window.flags.multiple_system_navigation_observer_callbacks
Change-Id: Ibed2eb513e7a3c80cab128f4f884d359a06c01f4
parent ee7cfd43

core/java/android/view/ViewRootImpl.java

+2 −2
Original line number Diff line number Diff line
@@ -7734,7 +7734,7 @@ public final class ViewRootImpl implements ViewParent, 
                        if (keyEvent.isCanceled()) {

                            animationCallback.onBackCancelled();

                        } else {

                            dispatcher.tryInvokeSystemNavigationObserverCallback();

                            dispatcher.tryInvokeSystemNavigationObserverCallbacks();

                            topCallback.onBackInvoked();

                        }

                        break;
@@ -7742,7 +7742,7 @@ public final class ViewRootImpl implements ViewParent, 
            } else if (topCallback != null) {

                if (keyEvent.getAction() == KeyEvent.ACTION_UP) {

                    if (!keyEvent.isCanceled()) {

                        dispatcher.tryInvokeSystemNavigationObserverCallback();

                        dispatcher.tryInvokeSystemNavigationObserverCallbacks();

                        topCallback.onBackInvoked();

                    } else {

                        Log.d(mTag, "Skip onBackInvoked(), reason: keyEvent.isCanceled=true");

core/java/android/window/OnBackInvokedDispatcher.java

+15 −5
Original line number Diff line number Diff line
@@ -74,12 +74,22 @@ public interface OnBackInvokedDispatcher { 
     * Priority level of {@link OnBackInvokedCallback}s designed to observe system-level back

     * handling.

     *

     * <p>Callbacks registered with this priority do not consume back events. They receive back

     * events whenever the system handles a back navigation and have no impact on the normal back

     * navigation flow. Useful for logging or analytics.

     * <p>Callbacks registered with this priority are invoked only when a back event is not

     * consumed by any other registered {@link OnBackInvokedCallback} with a priority of

     * {@link #PRIORITY_DEFAULT} or higher. This means they are called when the system is about

     * to perform its default back navigation action, such as finishing the current activity or

     * executing a back-to-home animation.

     *

     * <p>Only one callback with {@link #PRIORITY_SYSTEM_NAVIGATION_OBSERVER} can be registered at a

     * time.

     * <p>These callbacks are purely observational. They do not consume the back event and

     * cannot intercept it. Their invocation has no impact on the normal back navigation flow,

     * making them suitable for logging, analytics, or triggering actions that should not

     * prevent the system's own back handling.

     *

     * <p>The invocation order for multiple callbacks registered with this priority is undefined.

     *

     * <p>On API level 36 only, there is a restriction that only one callback with

     * {@link #PRIORITY_SYSTEM_NAVIGATION_OBSERVER} can be registered at a time. On API level 37 and

     * higher, the number of registered observer callbacks is unrestricted.

     */

    @FlaggedApi(Flags.FLAG_PREDICTIVE_BACK_PRIORITY_SYSTEM_NAVIGATION_OBSERVER)

    int PRIORITY_SYSTEM_NAVIGATION_OBSERVER = -2;

core/java/android/window/WindowOnBackInvokedDispatcher.java

+51 −14
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ package android.window; 


import static android.window.SystemOverrideOnBackInvokedCallback.OVERRIDE_UNDEFINED;



import static com.android.window.flags.Flags.multipleSystemNavigationObserverCallbacks;

import static com.android.window.flags.Flags.predictiveBackSystemOverrideCallback;

import static com.android.window.flags.Flags.predictiveBackPrioritySystemNavigationObserver;

import static com.android.window.flags.Flags.predictiveBackTimestampApi;
@@ -54,7 +55,9 @@ import java.io.PrintWriter; 
import java.lang.ref.WeakReference;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.HashSet;

import java.util.Objects;

import java.util.Set;

import java.util.TreeMap;

import java.util.function.BooleanSupplier;

import java.util.function.Supplier;
@@ -111,6 +114,8 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 


    @VisibleForTesting

    public OnBackInvokedCallback mSystemNavigationObserverCallback = null;

    @VisibleForTesting

    public Set<OnBackInvokedCallback> mSystemNavigationObserverCallbacks = new HashSet<>();



    private Checker mChecker;

    private final Object mLock = new Object();
@@ -189,9 +194,13 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 
                }

                removeCallbackInternal(callback);

            }

            if (multipleSystemNavigationObserverCallbacks()) {

                mSystemNavigationObserverCallbacks.add(callback);

            } else {

                mSystemNavigationObserverCallback = callback;

            }

        }

    }



    /**

     * Register a callback bypassing platform checks. This is used to register compatibility
@@ -240,6 +249,15 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 
                Integer prevPriority = mAllCallbacks.get(callback);

                mOnBackInvokedCallbacks.get(prevPriority).remove(callback);

            }

            if (multipleSystemNavigationObserverCallbacks()) {

                if (mSystemNavigationObserverCallbacks.contains(callback)) {

                    mSystemNavigationObserverCallbacks.remove(callback);

                    if (DEBUG) {

                        Log.i(TAG, "Callback already registered (as system-navigation-observer "

                                + "callback). Removing and re-adding it.");

                    }

                }

            } else {

                if (mSystemNavigationObserverCallback == callback) {

                    mSystemNavigationObserverCallback = null;

                    if (DEBUG) {
@@ -247,6 +265,7 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 
                                + "callback). Removing and re-adding it.");

                    }

                }

            }



            OnBackInvokedCallback previousTopCallback = getTopCallback();

            callbacks.add(callback);
@@ -266,10 +285,17 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 
                mImeDispatcher.unregisterOnBackInvokedCallback(callback);

                return;

            }

            if (multipleSystemNavigationObserverCallbacks()) {

                if (mSystemNavigationObserverCallbacks.contains(callback)) {

                    mSystemNavigationObserverCallbacks.remove(callback);

                    return;

                }

            } else {

                if (mSystemNavigationObserverCallback == callback) {

                    mSystemNavigationObserverCallback = null;

                    return;

                }

            }

            if (callback instanceof ImeOnBackInvokedDispatcher.DefaultImeOnBackAnimationCallback) {

                callback = mImeBackAnimationController;

            }
@@ -373,6 +399,7 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 
            mAllCallbacks.clear();

            mOnBackInvokedCallbacks.clear();

            mSystemNavigationObserverCallback = null;

            mSystemNavigationObserverCallbacks.clear();

        }

    }
@@ -385,11 +412,11 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 
    }



    /**

     * Tries to call {@link OnBackInvokedCallback#onBackInvoked} on the system navigation observer

     * callback (if one is set and if the top-most regular callback has

     * Tries to call {@link OnBackInvokedCallback#onBackInvoked} on all system navigation observer

     * callback (if any are registered and if the top-most regular callback has

     * {@link OnBackInvokedDispatcher#PRIORITY_SYSTEM})

     */

    public void tryInvokeSystemNavigationObserverCallback() {

    public void tryInvokeSystemNavigationObserverCallbacks() {

        OnBackInvokedCallback topCallback = getTopCallback();

        Integer callbackPriority = mAllCallbacks.getOrDefault(topCallback, null);

        final boolean isSystemOverride = topCallback instanceof SystemOverrideOnBackInvokedCallback;
@@ -399,10 +426,20 @@ public class WindowOnBackInvokedDispatcher implements OnBackInvokedDispatcher { 
    }



    private void invokeSystemNavigationObserverCallback() {

        if (multipleSystemNavigationObserverCallbacks()) {

            Set<OnBackInvokedCallback> observerCallbacks;

            synchronized (mLock) {

                observerCallbacks = new HashSet<>(mSystemNavigationObserverCallbacks);

            }

            for (OnBackInvokedCallback callback : observerCallbacks) {

                callback.onBackInvoked();

            }

        } else {

            if (mSystemNavigationObserverCallback != null) {

                mSystemNavigationObserverCallback.onBackInvoked();

            }

        }

    }



    private void setTopOnBackInvokedCallback(@Nullable OnBackInvokedCallback callback) {

        if (mWindowSession == null || mWindow == null) {

core/java/android/window/flags/windowing_frontend.aconfig

+7 −0
Original line number Diff line number Diff line
@@ -522,3 +522,10 @@ flag { 
        purpose: PURPOSE_BUGFIX

    }

}



flag {

    name: "multiple_system_navigation_observer_callbacks"

    namespace: "windowing_frontend"

    description: "Removes restriction that only one back callback with PRIORITY_SYSTEM_NAVIGATION_OBSERVER can be registered"

    bug: "424146227"

}

core/tests/coretests/src/android/window/WindowOnBackInvokedDispatcherTest.java

+37 −1
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ import static android.window.OnBackInvokedDispatcher.PRIORITY_DEFAULT; 
import static android.window.OnBackInvokedDispatcher.PRIORITY_OVERLAY;

import static android.window.OnBackInvokedDispatcher.PRIORITY_SYSTEM_NAVIGATION_OBSERVER;



import static com.android.window.flags.Flags.FLAG_MULTIPLE_SYSTEM_NAVIGATION_OBSERVER_CALLBACKS;

import static com.android.window.flags.Flags.FLAG_PREDICTIVE_BACK_PRIORITY_SYSTEM_NAVIGATION_OBSERVER;

import static com.android.window.flags.Flags.FLAG_PREDICTIVE_BACK_TIMESTAMP_API;
@@ -167,7 +168,8 @@ public class WindowOnBackInvokedDispatcherTest { 
        int actualSizeOverlay = callbacksOverlay != null ? callbacksOverlay.size() : 0;

        assertEquals("mOnBackInvokedCallbacks OVERLAY size", expectedOverlay, actualSizeOverlay);



        int actualSizeObserver = mDispatcher.mSystemNavigationObserverCallback == null ? 0 : 1;

        int actualSizeObserver = mDispatcher.mSystemNavigationObserverCallback == null

                ? mDispatcher.mSystemNavigationObserverCallbacks.size() : 1;

        assertEquals("mOnBackInvokedCallbacks SYSTEM_NAVIGATION_OBSERVER size", expectedObserver,

                actualSizeObserver);

    }
@@ -666,6 +668,7 @@ public class WindowOnBackInvokedDispatcherTest { 


    @Test

    @RequiresFlagsEnabled(FLAG_PREDICTIVE_BACK_PRIORITY_SYSTEM_NAVIGATION_OBSERVER)

    @RequiresFlagsDisabled(FLAG_MULTIPLE_SYSTEM_NAVIGATION_OBSERVER_CALLBACKS)

    public void testObserverCallback_reregistrations() {

        mDispatcher.registerOnBackInvokedCallback(PRIORITY_SYSTEM_NAVIGATION_OBSERVER, mCallback1);

        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 1);
@@ -688,6 +691,39 @@ public class WindowOnBackInvokedDispatcherTest { 
        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 0);

    }



    @Test

    @RequiresFlagsEnabled({FLAG_PREDICTIVE_BACK_PRIORITY_SYSTEM_NAVIGATION_OBSERVER,

            FLAG_MULTIPLE_SYSTEM_NAVIGATION_OBSERVER_CALLBACKS})

    public void testObserverCallback_multiple_registrations() {

        mDispatcher.registerOnBackInvokedCallback(PRIORITY_SYSTEM_NAVIGATION_OBSERVER, mCallback1);

        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 1);

        assertTrue(mDispatcher.mSystemNavigationObserverCallbacks.contains(mCallback1));



        // test registration of another observer-callback

        mDispatcher.registerOnBackInvokedCallback(PRIORITY_SYSTEM_NAVIGATION_OBSERVER, mCallback2);

        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 2);

        assertTrue(mDispatcher.mSystemNavigationObserverCallbacks.contains(mCallback1));

        assertTrue(mDispatcher.mSystemNavigationObserverCallbacks.contains(mCallback2));



        // test reregistration of first observer-callback

        mDispatcher.registerOnBackInvokedCallback(PRIORITY_SYSTEM_NAVIGATION_OBSERVER, mCallback1);

        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 2);



        // test reregistration of observer-callback with default priority

        mDispatcher.registerOnBackInvokedCallback(PRIORITY_DEFAULT, mCallback1);

        assertCallbacksSize(/* default */ 1, /* overlay */ 0, /* observer */ 1);



        // test reregistration of regular callback as observer-callback

        mDispatcher.registerOnBackInvokedCallback(PRIORITY_SYSTEM_NAVIGATION_OBSERVER, mCallback1);

        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 2);



        mDispatcher.unregisterOnBackInvokedCallback(mCallback2);

        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 1);



        mDispatcher.unregisterOnBackInvokedCallback(mCallback1);

        assertCallbacksSize(/* default */ 0, /* overlay */ 0, /* observer */ 0);

    }



    private BackMotionEvent backMotionEventFrom(float progress) {

        return new BackMotionEvent(

                /* touchX = */ 0,