Revert "Implement delayed event synthesis key event handling for Android (#19024)" (#19956)

This reverts commit 8825f91 because it breaks flutter_gallery__back_button_memory and a customer test.

Author: gspencergoog

shell/platform/android/BUILD.gn

@@ -430,7 +430,6 @@ action("robolectric_tests") {
   sources = [
     "test/io/flutter/FlutterTestSuite.java",
     "test/io/flutter/SmokeTest.java",
-    "test/io/flutter/embedding/android/AndroidKeyProcessorTest.java",
     "test/io/flutter/embedding/android/FlutterActivityAndFragmentDelegateTest.java",
     "test/io/flutter/embedding/android/FlutterActivityTest.java",
     "test/io/flutter/embedding/android/FlutterAndroidComponentTest.java",
@@ -448,7 +447,6 @@ action("robolectric_tests") {
     "test/io/flutter/embedding/engine/dart/DartExecutorTest.java",
     "test/io/flutter/embedding/engine/plugins/shim/ShimPluginRegistryTest.java",
     "test/io/flutter/embedding/engine/renderer/FlutterRendererTest.java",
-    "test/io/flutter/embedding/engine/systemchannels/KeyEventChannelTest.java",
     "test/io/flutter/embedding/engine/systemchannels/RestorationChannelTest.java",
     "test/io/flutter/external/FlutterLaunchTests.java",
     "test/io/flutter/plugin/common/StandardMessageCodecTest.java",

shell/platform/android/io/flutter/embedding/android/AndroidKeyProcessor.java

@@ -4,122 +4,37 @@
 
 package io.flutter.embedding.android;
 
-import android.util.Log;
 import android.view.KeyCharacterMap;
 import android.view.KeyEvent;
-import android.view.View;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import io.flutter.embedding.engine.systemchannels.KeyEventChannel;
 import io.flutter.plugin.editing.TextInputPlugin;
-import java.util.AbstractMap.SimpleImmutableEntry;
-import java.util.ArrayDeque;
-import java.util.Deque;
-import java.util.Map.Entry;
 
-/**
- * A class to process key events from Android, passing them to the framework as messages using
- * {@link KeyEventChannel}.
- *
- * <p>A class that sends Android key events to the framework, and re-dispatches those not handled by
- * the framework.
- *
- * <p>Flutter uses asynchronous event handling to avoid blocking the UI thread, but Android requires
- * that events are handled synchronously. So, when a key event is received by Flutter, it tells
- * Android synchronously that the key has been handled so that it won't propagate to other
- * components. Flutter then uses "delayed event synthesis", where it sends the event to the
- * framework, and if the framework responds that it has not handled the event, then this class
- * synthesizes a new event to send to Android, without handling it this time.
- */
 public class AndroidKeyProcessor {
-  private static final String TAG = "AndroidKeyProcessor";
-  private static long eventIdSerial = 0;
-
   @NonNull private final KeyEventChannel keyEventChannel;
   @NonNull private final TextInputPlugin textInputPlugin;
   private int combiningCharacter;
-  @NonNull private EventResponder eventResponder;
 
-  /**
-   * Constructor for AndroidKeyProcessor.
-   *
-   * <p>The view is used as the destination to send the synthesized key to. This means that the the
-   * next thing in the focus chain will get the event when the framework returns false from
-   * onKeyDown/onKeyUp
-   *
-   * <p>It is possible that that in the middle of the async round trip, the focus chain could
-   * change, and instead of the native widget that was "next" when the event was fired getting the
-   * event, it may be the next widget when the event is synthesized that gets it. In practice, this
-   * shouldn't be a huge problem, as this is an unlikely occurance to happen without user input, and
-   * it may actually be desired behavior, but it is possible.
-   *
-   * @param view takes the activity to use for re-dispatching of events that were not handled by the
-   *     framework.
-   * @param keyEventChannel the event channel to listen to for new key events.
-   * @param textInputPlugin a plugin, which, if set, is given key events before the framework is,
-   *     and if it has a valid input connection and is accepting text, then it will handle the event
-   *     and the framework will not receive it.
-   */
   public AndroidKeyProcessor(
-      @NonNull View view,
-      @NonNull KeyEventChannel keyEventChannel,
-      @NonNull TextInputPlugin textInputPlugin) {
+      @NonNull KeyEventChannel keyEventChannel, @NonNull TextInputPlugin textInputPlugin) {
     this.keyEventChannel = keyEventChannel;
     this.textInputPlugin = textInputPlugin;
-    this.eventResponder = new EventResponder(view);
-    this.keyEventChannel.setEventResponseHandler(eventResponder);
   }
 
-  /**
-   * Called when a key up event is received by the {@link FlutterView}.
-   *
-   * @param keyEvent the Android key event to respond to.
-   * @return true if the key event should not be propagated to other Android components. Delayed
-   *     synthesis events will return false, so that other components may handle them.
-   */
-  public boolean onKeyUp(@NonNull KeyEvent keyEvent) {
-    if (eventResponder.dispatchingKeyEvent) {
-      // Don't handle it if it is from our own delayed event synthesis.
-      return false;
-    }
-
+  public void onKeyUp(@NonNull KeyEvent keyEvent) {
     Character complexCharacter = applyCombiningCharacterToBaseCharacter(keyEvent.getUnicodeChar());
-    KeyEventChannel.FlutterKeyEvent flutterEvent =
-        new KeyEventChannel.FlutterKeyEvent(keyEvent, complexCharacter, eventIdSerial++);
-    keyEventChannel.keyUp(flutterEvent);
-    eventResponder.addEvent(flutterEvent.eventId, keyEvent);
-    return true;
+    keyEventChannel.keyUp(new KeyEventChannel.FlutterKeyEvent(keyEvent, complexCharacter));
   }
 
-  /**
-   * Called when a key down event is received by the {@link FlutterView}.
-   *
-   * @param keyEvent the Android key event to respond to.
-   * @return true if the key event should not be propagated to other Android components. Delayed
-   *     synthesis events will return false, so that other components may handle them.
-   */
-  public boolean onKeyDown(@NonNull KeyEvent keyEvent) {
-    if (eventResponder.dispatchingKeyEvent) {
-      // Don't handle it if it is from our own delayed event synthesis.
-      return false;
-    }
-
-    // If the textInputPlugin is still valid and accepting text, then we'll try
-    // and send the key event to it, assuming that if the event can be sent,
-    // that it has been handled.
+  public void onKeyDown(@NonNull KeyEvent keyEvent) {
     if (textInputPlugin.getLastInputConnection() != null
         && textInputPlugin.getInputMethodManager().isAcceptingText()) {
-      if (textInputPlugin.getLastInputConnection().sendKeyEvent(keyEvent)) {
-        return true;
-      }
+      textInputPlugin.getLastInputConnection().sendKeyEvent(keyEvent);
     }
 
     Character complexCharacter = applyCombiningCharacterToBaseCharacter(keyEvent.getUnicodeChar());
-    KeyEventChannel.FlutterKeyEvent flutterEvent =
-        new KeyEventChannel.FlutterKeyEvent(keyEvent, complexCharacter, eventIdSerial++);
-    keyEventChannel.keyDown(flutterEvent);
-    eventResponder.addEvent(flutterEvent.eventId, keyEvent);
-    return true;
+    keyEventChannel.keyDown(new KeyEventChannel.FlutterKeyEvent(keyEvent, complexCharacter));
   }
 
   /**
@@ -155,7 +70,7 @@ private Character applyCombiningCharacterToBaseCharacter(int newCharacterCodePoi
       return null;
     }
 
-    char complexCharacter = (char) newCharacterCodePoint;
+    Character complexCharacter = (char) newCharacterCodePoint;
     boolean isNewCodePointACombiningCharacter =
         (newCharacterCodePoint & KeyCharacterMap.COMBINING_ACCENT) != 0;
     if (isNewCodePointACombiningCharacter) {
@@ -167,8 +82,7 @@ private Character applyCombiningCharacterToBaseCharacter(int newCharacterCodePoi
         combiningCharacter = plainCodePoint;
       }
     } else {
-      // The new character is a regular character. Apply combiningCharacter to it, if
-      // it exists.
+      // The new character is a regular character. Apply combiningCharacter to it, if it exists.
       if (combiningCharacter != 0) {
         int combinedChar = KeyCharacterMap.getDeadChar(combiningCharacter, newCharacterCodePoint);
         if (combinedChar > 0) {
@@ -180,92 +94,4 @@ private Character applyCombiningCharacterToBaseCharacter(int newCharacterCodePoi
 
     return complexCharacter;
   }
-
-  private static class EventResponder implements KeyEventChannel.EventResponseHandler {
-    // The maximum number of pending events that are held before starting to
-    // complain.
-    private static final long MAX_PENDING_EVENTS = 1000;
-    final Deque<Entry<Long, KeyEvent>> pendingEvents = new ArrayDeque<Entry<Long, KeyEvent>>();
-    @NonNull private final View view;
-    boolean dispatchingKeyEvent = false;
-
-    public EventResponder(@NonNull View view) {
-      this.view = view;
-    }
-
-    /**
-     * Removes the pending event with the given id from the cache of pending events.
-     *
-     * @param id the id of the event to be removed.
-     */
-    private KeyEvent removePendingEvent(long id) {
-      if (pendingEvents.getFirst().getKey() != id) {
-        throw new AssertionError(
-            "Event response received out of order. Should have seen event "
-                + pendingEvents.getFirst().getKey()
-                + " first. Instead, received "
-                + id);
-      }
-      return pendingEvents.removeFirst().getValue();
-    }
-
-    /**
-     * Called whenever the framework responds that a given key event was handled by the framework.
-     *
-     * @param id the event id of the event to be marked as being handled by the framework. Must not
-     *     be null.
-     */
-    @Override
-    public void onKeyEventHandled(long id) {
-      removePendingEvent(id);
-    }
-
-    /**
-     * Called whenever the framework responds that a given key event wasn't handled by the
-     * framework.
-     *
-     * @param id the event id of the event to be marked as not being handled by the framework. Must
-     *     not be null.
-     */
-    @Override
-    public void onKeyEventNotHandled(long id) {
-      dispatchKeyEvent(removePendingEvent(id));
-    }
-
-    /** Adds an Android key event with an id to the event responder to wait for a response. */
-    public void addEvent(long id, @NonNull KeyEvent event) {
-      if (pendingEvents.size() > 0 && pendingEvents.getFirst().getKey() >= id) {
-        throw new AssertionError(
-            "New events must have ids greater than the most recent pending event. New id "
-                + id
-                + " is less than or equal to the last event id of "
-                + pendingEvents.getFirst().getKey());
-      }
-      pendingEvents.addLast(new SimpleImmutableEntry<Long, KeyEvent>(id, event));
-      if (pendingEvents.size() > MAX_PENDING_EVENTS) {
-        Log.e(
-            TAG,
-            "There are "
-                + pendingEvents.size()
-                + " keyboard events "
-                + "that have not yet received a response. Are responses being sent?");
-      }
-    }
-
-    /**
-     * Dispatches the event to the activity associated with the context.
-     *
-     * @param event the event to be dispatched to the activity.
-     */
-    public void dispatchKeyEvent(KeyEvent event) {
-      // Since the framework didn't handle it, dispatch the key again.
-      if (view != null) {
-        // Turn on dispatchingKeyEvent so that we don't dispatch to ourselves and
-        // send it to the framework again.
-        dispatchingKeyEvent = true;
-        view.dispatchKeyEvent(event);
-        dispatchingKeyEvent = false;
-      }
-    }
-  }
 }

shell/platform/android/io/flutter/embedding/android/FlutterView.java

@@ -679,7 +679,8 @@ public boolean onKeyUp(int keyCode, @NonNull KeyEvent event) {
       return super.onKeyUp(keyCode, event);
     }
 
-    return androidKeyProcessor.onKeyUp(event) || super.onKeyUp(keyCode, event);
+    androidKeyProcessor.onKeyUp(event);
+    return super.onKeyUp(keyCode, event);
   }
 
   /**
@@ -699,7 +700,8 @@ public boolean onKeyDown(int keyCode, @NonNull KeyEvent event) {
       return super.onKeyDown(keyCode, event);
     }
 
-    return androidKeyProcessor.onKeyDown(event) || super.onKeyDown(keyCode, event);
+    androidKeyProcessor.onKeyDown(event);
+    return super.onKeyDown(keyCode, event);
   }
 
   /**
@@ -849,7 +851,7 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
             this.flutterEngine.getPlatformViewsController());
     localizationPlugin = this.flutterEngine.getLocalizationPlugin();
     androidKeyProcessor =
-        new AndroidKeyProcessor(this, this.flutterEngine.getKeyEventChannel(), textInputPlugin);
+        new AndroidKeyProcessor(this.flutterEngine.getKeyEventChannel(), textInputPlugin);
     androidTouchProcessor =
         new AndroidTouchProcessor(this.flutterEngine.getRenderer(), /*trackMotionEvents=*/ false);
     accessibilityBridge =

shell/platform/android/io/flutter/embedding/engine/systemchannels/AccessibilityChannel.java

@@ -73,7 +73,6 @@ public void onMessage(
                 break;
               }
           }
-          reply.reply(null);
         }
       };