[Android] Return keyboard pressed state (flutter#41695)

## Description

This PR updates the Android engine in order to answer to keyboard pressed state queries from the framework (as implemented in flutter#122885).

## Related Issue

Fixes flutter#122441
Android engine implementation for flutter#87391

## Tests

Adds 2 tests.

Author: bleroux

ci/licenses_golden/licenses_flutter

@@ -2338,6 +2338,7 @@ ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/rend
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/renderer/SurfaceTextureWrapper.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/DeferredComponentChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/KeyEventChannel.java + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/KeyboardChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/LifecycleChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/LocalizationChannel.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/MouseCursorChannel.java + ../../../flutter/LICENSE
@@ -2371,6 +2372,7 @@ ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/Listen
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/SpellCheckPlugin.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextEditingDelta.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextInputPlugin.java + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/keyboard/KeyboardPlugin.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/localization/LocalizationPlugin.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/mouse/MouseCursorPlugin.java + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/android/io/flutter/plugin/platform/AccessibilityEventsDelegate.java + ../../../flutter/LICENSE
@@ -4963,6 +4965,7 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/render
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/AccessibilityChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/DeferredComponentChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/KeyEventChannel.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/KeyboardChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/LifecycleChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/LocalizationChannel.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/MouseCursorChannel.java
@@ -4999,6 +5002,7 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/Listenab
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/SpellCheckPlugin.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextEditingDelta.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/editing/TextInputPlugin.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/keyboard/KeyboardPlugin.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/localization/LocalizationPlugin.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/mouse/MouseCursorPlugin.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/plugin/platform/AccessibilityEventsDelegate.java

shell/platform/android/BUILD.gn

@@ -249,6 +249,7 @@ android_java_sources = [
   "io/flutter/embedding/engine/systemchannels/AccessibilityChannel.java",
   "io/flutter/embedding/engine/systemchannels/DeferredComponentChannel.java",
   "io/flutter/embedding/engine/systemchannels/KeyEventChannel.java",
+  "io/flutter/embedding/engine/systemchannels/KeyboardChannel.java",
   "io/flutter/embedding/engine/systemchannels/LifecycleChannel.java",
   "io/flutter/embedding/engine/systemchannels/LocalizationChannel.java",
   "io/flutter/embedding/engine/systemchannels/MouseCursorChannel.java",
@@ -285,6 +286,7 @@ android_java_sources = [
   "io/flutter/plugin/editing/SpellCheckPlugin.java",
   "io/flutter/plugin/editing/TextEditingDelta.java",
   "io/flutter/plugin/editing/TextInputPlugin.java",
+  "io/flutter/plugin/keyboard/KeyboardPlugin.java",
   "io/flutter/plugin/localization/LocalizationPlugin.java",
   "io/flutter/plugin/mouse/MouseCursorPlugin.java",
   "io/flutter/plugin/platform/AccessibilityEventsDelegate.java",

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

@@ -62,6 +62,7 @@
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.editing.SpellCheckPlugin;
 import io.flutter.plugin.editing.TextInputPlugin;
+import io.flutter.plugin.keyboard.KeyboardPlugin;
 import io.flutter.plugin.localization.LocalizationPlugin;
 import io.flutter.plugin.mouse.MouseCursorPlugin;
 import io.flutter.plugin.platform.PlatformViewsController;
@@ -130,6 +131,7 @@ public class FlutterView extends FrameLayout
   @Nullable private MouseCursorPlugin mouseCursorPlugin;
   @Nullable private TextInputPlugin textInputPlugin;
   @Nullable private SpellCheckPlugin spellCheckPlugin;
+  @Nullable private KeyboardPlugin keyboardPlugin;
   @Nullable private LocalizationPlugin localizationPlugin;
   @Nullable private KeyboardManager keyboardManager;
   @Nullable private AndroidTouchProcessor androidTouchProcessor;
@@ -1177,6 +1179,8 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
     localizationPlugin = this.flutterEngine.getLocalizationPlugin();
 
     keyboardManager = new KeyboardManager(this);
+    keyboardPlugin = new KeyboardPlugin(keyboardManager, this.flutterEngine.getKeyboardChannel());
+
     androidTouchProcessor =
         new AndroidTouchProcessor(this.flutterEngine.getRenderer(), /*trackMotionEvents=*/ false);
     accessibilityBridge =
@@ -1273,10 +1277,12 @@ public void detachFromFlutterEngine() {
     if (spellCheckPlugin != null) {
       spellCheckPlugin.destroy();
     }
-
     if (mouseCursorPlugin != null) {
       mouseCursorPlugin.destroy();
     }
+    if (keyboardPlugin != null) {
+      keyboardPlugin.destroy();
+    }
 
     // Instruct our FlutterRenderer that we are no longer interested in being its RenderSurface.
     FlutterRenderer flutterRenderer = flutterEngine.getRenderer();

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

@@ -11,7 +11,9 @@
 import io.flutter.embedding.android.KeyboardMap.TogglingGoal;
 import io.flutter.plugin.common.BinaryMessenger;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.Map;
 
 /**
  * A {@link KeyboardManager.Responder} of {@link KeyboardManager} that handles events by sending
@@ -405,4 +407,14 @@ public void handleEvent(
       onKeyEventHandledCallback.onKeyEventHandled(true);
     }
   }
+
+  /**
+   * Returns an unmodifiable view of the pressed state.
+   *
+   * @return A map whose keys are physical keyboard key IDs and values are the corresponding logical
+   *     keyboard key IDs.
+   */
+  public Map<Long, Long> getPressedState() {
+    return Collections.unmodifiableMap(pressingRecords);
+  }
 }

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

@@ -13,6 +13,7 @@
 import io.flutter.plugin.editing.InputConnectionAdaptor;
 import io.flutter.plugin.editing.TextInputPlugin;
 import java.util.HashSet;
+import java.util.Map;
 
 /**
  * Processes keyboard events and cooperate with {@link TextInputPlugin}.
@@ -252,4 +253,15 @@ private void onUnhandled(@NonNull KeyEvent keyEvent) {
       Log.w(TAG, "A redispatched key event was consumed before reaching KeyboardManager");
     }
   }
+
+  /**
+   * Returns an unmodifiable view of the pressed state.
+   *
+   * @return A map whose keys are physical keyboard key IDs and values are the corresponding logical
+   *     keyboard key IDs.
+   */
+  public Map<Long, Long> getPressedState() {
+    KeyEmbedderResponder embedderResponder = (KeyEmbedderResponder) responders[0];
+    return embedderResponder.getPressedState();
+  }
 }

shell/platform/android/io/flutter/embedding/engine/FlutterEngine.java

@@ -26,6 +26,7 @@
 import io.flutter.embedding.engine.renderer.RenderSurface;
 import io.flutter.embedding.engine.systemchannels.AccessibilityChannel;
 import io.flutter.embedding.engine.systemchannels.DeferredComponentChannel;
+import io.flutter.embedding.engine.systemchannels.KeyboardChannel;
 import io.flutter.embedding.engine.systemchannels.LifecycleChannel;
 import io.flutter.embedding.engine.systemchannels.LocalizationChannel;
 import io.flutter.embedding.engine.systemchannels.MouseCursorChannel;
@@ -89,6 +90,7 @@ public class FlutterEngine implements ViewUtils.DisplayUpdater {
   // System channels.
   @NonNull private final AccessibilityChannel accessibilityChannel;
   @NonNull private final DeferredComponentChannel deferredComponentChannel;
+  @NonNull private final KeyboardChannel keyboardChannel;
   @NonNull private final LifecycleChannel lifecycleChannel;
   @NonNull private final LocalizationChannel localizationChannel;
   @NonNull private final MouseCursorChannel mouseCursorChannel;
@@ -324,6 +326,7 @@ public FlutterEngine(
 
     accessibilityChannel = new AccessibilityChannel(dartExecutor, flutterJNI);
     deferredComponentChannel = new DeferredComponentChannel(dartExecutor);
+    keyboardChannel = new KeyboardChannel(dartExecutor);
     lifecycleChannel = new LifecycleChannel(dartExecutor);
     localizationChannel = new LocalizationChannel(dartExecutor);
     mouseCursorChannel = new MouseCursorChannel(dartExecutor);
@@ -516,6 +519,12 @@ public AccessibilityChannel getAccessibilityChannel() {
     return accessibilityChannel;
   }
 
+  /** System channel that allows querying the keyboard pressed state. */
+  @NonNull
+  public KeyboardChannel getKeyboardChannel() {
+    return keyboardChannel;
+  }
+
   /** System channel that sends Android lifecycle events to Flutter. */
   @NonNull
   public LifecycleChannel getLifecycleChannel() {

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

@@ -0,0 +1,73 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.embedding.engine.systemchannels;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import io.flutter.embedding.engine.dart.DartExecutor;
+import io.flutter.plugin.common.MethodCall;
+import io.flutter.plugin.common.MethodChannel;
+import io.flutter.plugin.common.StandardMethodCodec;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Event message channel for keyboard events to/from the Flutter framework.
+ *
+ * <p>Receives asynchronous messages from the framework to query the engine known pressed state.
+ */
+public class KeyboardChannel {
+  private static final String TAG = "KeyboardChannel";
+
+  public final MethodChannel channel;
+  private KeyboardMethodHandler keyboardMethodHandler;
+
+  @NonNull
+  public final MethodChannel.MethodCallHandler parsingMethodHandler =
+      new MethodChannel.MethodCallHandler() {
+        @Override
+        public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
+          if (keyboardMethodHandler == null) {
+            return;
+          }
+          switch (call.method) {
+            case "getKeyboardState":
+              Map<Long, Long> pressedState = new HashMap<>();
+              try {
+                pressedState = keyboardMethodHandler.getKeyboardState();
+              } catch (IllegalStateException exception) {
+                result.error("error", exception.getMessage(), null);
+              }
+              result.success(pressedState);
+              break;
+            default:
+              result.notImplemented();
+              break;
+          }
+        }
+      };
+
+  public KeyboardChannel(@NonNull DartExecutor dartExecutor) {
+    channel = new MethodChannel(dartExecutor, "flutter/keyboard", StandardMethodCodec.INSTANCE);
+    channel.setMethodCallHandler(parsingMethodHandler);
+  }
+
+  /**
+   * Sets the {@link KeyboardMethodHandler} which receives all requests to query the keyboard state.
+   */
+  public void setKeyboardMethodHandler(@Nullable KeyboardMethodHandler keyboardMethodHandler) {
+    this.keyboardMethodHandler = keyboardMethodHandler;
+  }
+
+  public interface KeyboardMethodHandler {
+    /**
+     * Returns the keyboard pressed states.
+     *
+     * @return A map whose keys are physical keyboard key IDs and values are the corresponding
+     *     logical keyboard key IDs.
+     */
+    Map<Long, Long> getKeyboardState();
+  }
+}

shell/platform/android/io/flutter/plugin/keyboard/KeyboardPlugin.java

@@ -0,0 +1,57 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugin.keyboard;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.VisibleForTesting;
+import io.flutter.embedding.android.KeyboardManager;
+import io.flutter.embedding.engine.systemchannels.KeyboardChannel;
+import io.flutter.plugin.common.MethodChannel;
+import java.util.Map;
+
+/**
+ * {@link KeyboardPlugin} is the implementation of all functionalities needed for querying keyboard
+ * pressed state.
+ *
+ * <p>The plugin handles requests for querying keyboard pressed states by the {@link
+ * io.flutter.embedding.engine.systemchannels.KeyboardChannel} via returning the {@link
+ * io.flutter.embedding.android.KeyEmbedderResponder} pressed keys.
+ */
+public class KeyboardPlugin implements KeyboardChannel.KeyboardMethodHandler {
+
+  private final KeyboardChannel mKeyboardChannel;
+  private final KeyboardManager mKeyboardManager;
+
+  @VisibleForTesting MethodChannel.Result pendingResult;
+
+  public KeyboardPlugin(
+      @NonNull KeyboardManager keyboardManager, @NonNull KeyboardChannel keyboardChannel) {
+    mKeyboardManager = keyboardManager;
+    mKeyboardChannel = keyboardChannel;
+
+    mKeyboardChannel.setKeyboardMethodHandler(this);
+  }
+
+  /**
+   * Unregisters this {@code KeyboardPlugin} as the {@code KeyboardChannel.KeyboardMethodHandler},
+   * for the {@link io.flutter.embedding.engine.systemchannels.KeyboardChannel}.
+   *
+   * <p>Do not invoke any methods on a {@code KeyboardPlugin} after invoking this method.
+   */
+  public void destroy() {
+    mKeyboardChannel.setKeyboardMethodHandler(null);
+  }
+
+  /**
+   * Returns the keyboard pressed state.
+   *
+   * @return A map whose keys are physical keyboard key IDs and values are the corresponding logical
+   *     keyboard key IDs.
+   */
+  @Override
+  public Map<Long, Long> getKeyboardState() {
+    return mKeyboardManager.getPressedState();
+  }
+}

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

@@ -48,6 +48,7 @@
 import io.flutter.embedding.engine.renderer.FlutterRenderer;
 import io.flutter.embedding.engine.renderer.SurfaceTextureWrapper;
 import io.flutter.embedding.engine.systemchannels.AccessibilityChannel;
+import io.flutter.embedding.engine.systemchannels.KeyboardChannel;
 import io.flutter.embedding.engine.systemchannels.LifecycleChannel;
 import io.flutter.embedding.engine.systemchannels.LocalizationChannel;
 import io.flutter.embedding.engine.systemchannels.MouseCursorChannel;
@@ -59,6 +60,7 @@
 import io.flutter.plugin.common.ActivityLifecycleListener;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.editing.TextInputPlugin;
+import io.flutter.plugin.keyboard.KeyboardPlugin;
 import io.flutter.plugin.localization.LocalizationPlugin;
 import io.flutter.plugin.mouse.MouseCursorPlugin;
 import io.flutter.plugin.platform.PlatformPlugin;
@@ -124,12 +126,14 @@ static final class ViewportMetrics {
   private final FlutterRenderer flutterRenderer;
   private final NavigationChannel navigationChannel;
   private final LifecycleChannel lifecycleChannel;
+  private final KeyboardChannel keyboardChannel;
   private final LocalizationChannel localizationChannel;
   private final PlatformChannel platformChannel;
   private final SettingsChannel settingsChannel;
   private final SystemChannel systemChannel;
   private final InputMethodManager mImm;
   private final TextInputPlugin mTextInputPlugin;
+  private final KeyboardPlugin mKeyboardPlugin;
   private final LocalizationPlugin mLocalizationPlugin;
   private final MouseCursorPlugin mMouseCursorPlugin;
   private final KeyboardManager mKeyboardManager;
@@ -213,6 +217,7 @@ public void surfaceDestroyed(SurfaceHolder holder) {
 
     // Create all platform channels
     navigationChannel = new NavigationChannel(dartExecutor);
+    keyboardChannel = new KeyboardChannel(dartExecutor);
     lifecycleChannel = new LifecycleChannel(dartExecutor);
     localizationChannel = new LocalizationChannel(dartExecutor);
     platformChannel = new PlatformChannel(dartExecutor);
@@ -233,7 +238,9 @@ public void onPostResume() {
         mNativeView.getPluginRegistry().getPlatformViewsController();
     mTextInputPlugin =
         new TextInputPlugin(this, new TextInputChannel(dartExecutor), platformViewsController);
+
     mKeyboardManager = new KeyboardManager(this);
+    mKeyboardPlugin = new KeyboardPlugin(mKeyboardManager, keyboardChannel);
 
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
       mMouseCursorPlugin = new MouseCursorPlugin(this, new MouseCursorChannel(dartExecutor));

shell/platform/android/test/io/flutter/embedding/android/FlutterActivityAndFragmentDelegateTest.java

@@ -39,6 +39,7 @@
 import io.flutter.embedding.engine.renderer.FlutterRenderer;
 import io.flutter.embedding.engine.renderer.FlutterUiDisplayListener;
 import io.flutter.embedding.engine.systemchannels.AccessibilityChannel;
+import io.flutter.embedding.engine.systemchannels.KeyboardChannel;
 import io.flutter.embedding.engine.systemchannels.LifecycleChannel;
 import io.flutter.embedding.engine.systemchannels.LocalizationChannel;
 import io.flutter.embedding.engine.systemchannels.MouseCursorChannel;
@@ -1293,6 +1294,7 @@ private FlutterEngine mockFlutterEngine() {
     when(engine.getAccessibilityChannel()).thenReturn(mock(AccessibilityChannel.class));
     when(engine.getActivityControlSurface()).thenReturn(mock(ActivityControlSurface.class));
     when(engine.getDartExecutor()).thenReturn(mock(DartExecutor.class));
+    when(engine.getKeyboardChannel()).thenReturn(mock(KeyboardChannel.class));
     when(engine.getLifecycleChannel()).thenReturn(mock(LifecycleChannel.class));
     when(engine.getLocalizationChannel()).thenReturn(mock(LocalizationChannel.class));
     when(engine.getLocalizationPlugin()).thenReturn(mock(LocalizationPlugin.class));