Reland "Keyboard support for embedded Android views. (flutter#9203) (f…

…lutter#9257)

flutter#9203 broke the keyboard_resize integration test(see more details in flutter/flutter#34085 (comment)).

This re-lands @9203 and fixes the issue the integration test uncovered by always allowing to hide the keyboard.

The difference from the original change is 07d2598

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

@@ -477,7 +477,8 @@ public void attachToFlutterEngine(@NonNull FlutterEngine flutterEngine) {
     // in a way that Flutter understands.
     textInputPlugin = new TextInputPlugin(
         this,
-        this.flutterEngine.getDartExecutor()
+        this.flutterEngine.getDartExecutor(),
+        null
     );
     androidKeyProcessor = new AndroidKeyProcessor(
         this.flutterEngine.getKeyEventChannel(),

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

@@ -26,6 +26,13 @@ public class PlatformViewsChannel {
   private final MethodChannel channel;
   private PlatformViewsHandler handler;
 
+  public void invokeViewFocused(int viewId) {
+    if (channel == null) {
+      return;
+    }
+    channel.invokeMethod("viewFocused", viewId);
+  }
+
   private final MethodChannel.MethodCallHandler parsingHandler = new MethodChannel.MethodCallHandler() {
     @Override
     public void onMethodCall(MethodCall call, MethodChannel.Result result) {
@@ -51,6 +58,9 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
         case "setDirection":
           setDirection(call, result);
           break;
+        case "clearFocus":
+          clearFocus(call, result);
+          break;
         default:
           result.notImplemented();
       }
@@ -172,6 +182,20 @@ private void setDirection(@NonNull MethodCall call, @NonNull MethodChannel.Resul
         );
       }
     }
+
+    private void clearFocus(MethodCall call, MethodChannel.Result result) {
+      int viewId = call.arguments();
+      try {
+        handler.clearFocus(viewId);
+        result.success(null);
+      } catch (IllegalStateException exception) {
+        result.error(
+                "error",
+                exception.getMessage(),
+                null
+        );
+      }
+    }
   };
 
   /**
@@ -241,6 +265,11 @@ void resizePlatformView(
      */
     // TODO(mattcarroll): Introduce an annotation for @TextureId
     void setDirection(int viewId, int direction);
+
+    /**
+     * Clears the focus from the platform view with a give id if it is currently focused.
+     */
+    void clearFocus(int viewId);
   }
 
   /**

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

@@ -70,6 +70,10 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
             result.error("error", exception.getMessage(), null);
           }
           break;
+        case "TextInput.setPlatformViewClient":
+          final int id = (int) args;
+          textInputMethodHandler.setPlatformViewClient(id);
+          break;
         case "TextInput.setEditingState":
           try {
             final JSONObject editingState = (JSONObject) args;
@@ -218,6 +222,16 @@ public interface TextInputMethodHandler {
     // TODO(mattcarroll): javadoc
     void setClient(int textInputClientId, @NonNull Configuration configuration);
 
+    /**
+     * Sets a platform view as the text input client.
+     *
+     * Subsequent calls to createInputConnection will be delegated to the platform view until a
+     * different client is set.
+     *
+     * @param id the ID of the platform view to be set as a text input client.
+     */
+    void setPlatformViewClient(int id);
+
     // TODO(mattcarroll): javadoc
     void setEditingState(@NonNull TextEditState editingState);
 

shell/platform/android/io/flutter/plugin/editing/TextInputPlugin.java

@@ -18,7 +18,7 @@
 
 import io.flutter.embedding.engine.dart.DartExecutor;
 import io.flutter.embedding.engine.systemchannels.TextInputChannel;
-import io.flutter.view.FlutterView;
+import io.flutter.plugin.platform.PlatformViewsController;
 
 /**
  * Android implementation of the text input plugin.
@@ -30,7 +30,8 @@ public class TextInputPlugin {
     private final InputMethodManager mImm;
     @NonNull
     private final TextInputChannel textInputChannel;
-    private int mClient = 0;
+    @NonNull
+    private InputTarget inputTarget = new InputTarget(InputTarget.Type.NO_TARGET, 0);
     @Nullable
     private TextInputChannel.Configuration configuration;
     @Nullable
@@ -39,7 +40,13 @@ public class TextInputPlugin {
     @Nullable
     private InputConnection lastInputConnection;
 
-    public TextInputPlugin(View view, @NonNull DartExecutor dartExecutor) {
+    private PlatformViewsController platformViewsController;
+
+    // When true following calls to createInputConnection will return the cached lastInputConnection if the input
+    // target is a platform view. See the comments on lockPlatformViewInputConnection for more details.
+    private boolean isInputConnectionLocked;
+
+    public TextInputPlugin(View view, @NonNull DartExecutor dartExecutor, PlatformViewsController platformViewsController) {
         mView = view;
         mImm = (InputMethodManager) view.getContext().getSystemService(
                 Context.INPUT_METHOD_SERVICE);
@@ -61,6 +68,11 @@ public void setClient(int textInputClientId, TextInputChannel.Configuration conf
                 setTextInputClient(textInputClientId, configuration);
             }
 
+            @Override
+            public void setPlatformViewClient(int platformViewId) {
+                setPlatformViewTextInputClient(platformViewId);
+            }
+
             @Override
             public void setEditingState(TextInputChannel.TextEditState editingState) {
                 setTextInputEditingState(mView, editingState);
@@ -71,13 +83,49 @@ public void clearClient() {
                 clearTextInputClient();
             }
         });
+        this.platformViewsController = platformViewsController;
+        platformViewsController.attachTextInputPlugin(this);
     }
 
     @NonNull
     public InputMethodManager getInputMethodManager() {
         return mImm;
     }
 
+    /***
+     * Use the current platform view input connection until unlockPlatformViewInputConnection is called.
+     *
+     * The current input connection instance is cached and any following call to @{link createInputConnection} returns
+     * the cached connection until unlockPlatformViewInputConnection is called.
+     *
+     * This is a no-op if the current input target isn't a platform view.
+     *
+     * This is used to preserve an input connection when moving a platform view from one virtual display to another.
+     */
+    public void lockPlatformViewInputConnection() {
+        if (inputTarget.type == InputTarget.Type.PLATFORM_VIEW) {
+            isInputConnectionLocked = true;
+        }
+    }
+
+    /**
+     * Unlocks the input connection.
+     *
+     * See also: @{link lockPlatformViewInputConnection}.
+     */
+    public void unlockPlatformViewInputConnection() {
+        isInputConnectionLocked = false;
+    }
+
+    /**
+     * Detaches the text input plugin from the platform views controller.
+     *
+     * The TextInputPlugin instance should not be used after calling this.
+     */
+    public void destroy() {
+        platformViewsController.detachTextInputPlugin();
+    }
+
     private static int inputTypeFromTextInputType(
         TextInputChannel.InputType type,
         boolean obscureText,
@@ -128,8 +176,16 @@ private static int inputTypeFromTextInputType(
     }
 
     public InputConnection createInputConnection(View view, EditorInfo outAttrs) {
-        if (mClient == 0) {
+        if (inputTarget.type == InputTarget.Type.NO_TARGET) {
             lastInputConnection = null;
+            return null;
+        }
+
+        if (inputTarget.type == InputTarget.Type.PLATFORM_VIEW) {
+            if (isInputConnectionLocked) {
+                return lastInputConnection;
+            }
+            lastInputConnection = platformViewsController.getPlatformViewById(inputTarget.id).onCreateInputConnection(outAttrs);
             return lastInputConnection;
         }
 
@@ -158,7 +214,7 @@ public InputConnection createInputConnection(View view, EditorInfo outAttrs) {
 
         InputConnectionAdaptor connection = new InputConnectionAdaptor(
             view,
-            mClient,
+            inputTarget.id,
             textInputChannel,
             mEditable
         );
@@ -180,17 +236,28 @@ private void showTextInput(View view) {
     }
 
     private void hideTextInput(View view) {
+        // Note: a race condition may lead to us hiding the keyboard here just after a platform view has shown it.
+        // This can only potentially happen when switching focus from a Flutter text field to a platform view's text
+        // field(by text field here I mean anything that keeps the keyboard open).
+        // See: https://github.com/flutter/flutter/issues/34169
         mImm.hideSoftInputFromWindow(view.getApplicationWindowToken(), 0);
     }
 
     private void setTextInputClient(int client, TextInputChannel.Configuration configuration) {
-        mClient = client;
+        inputTarget = new InputTarget(InputTarget.Type.FRAMEWORK_CLIENT, client);
         this.configuration = configuration;
         mEditable = Editable.Factory.getInstance().newEditable("");
 
         // setTextInputClient will be followed by a call to setTextInputEditingState.
         // Do a restartInput at that time.
         mRestartInputPending = true;
+        unlockPlatformViewInputConnection();
+    }
+
+    private void setPlatformViewTextInputClient(int platformViewId) {
+        inputTarget = new InputTarget(InputTarget.Type.PLATFORM_VIEW, platformViewId);
+        mImm.restartInput(mView);
+        mRestartInputPending = false;
     }
 
     private void applyStateToSelection(TextInputChannel.TextEditState state) {
@@ -220,6 +287,45 @@ private void setTextInputEditingState(View view, TextInputChannel.TextEditState
     }
 
     private void clearTextInputClient() {
-        mClient = 0;
+        if (inputTarget.type == InputTarget.Type.PLATFORM_VIEW) {
+            // Focus changes in the framework tree have no guarantees on the order focus nodes are notified. A node
+            // that lost focus may be notified before or after a node that gained focus.
+            // When moving the focus from a Flutter text field to an AndroidView, it is possible that the Flutter text
+            // field's focus node will be notified that it lost focus after the AndroidView was notified that it gained
+            // focus. When this happens the text field will send a clearTextInput command which we ignore.
+            // By doing this we prevent the framework from clearing a platform view input client(the only way to do so
+            // is to set a new framework text client). I don't see an obvious use case for "clearing" a platform views
+            // text input client, and it may be error prone as we don't know how the platform view manages the input
+            // connection and we probably shouldn't interfere.
+            // If we ever want to allow the framework to clear a platform view text client we should probably consider
+            // changing the focus manager such that focus nodes that lost focus are notified before focus nodes that
+            // gained focus as part of the same focus event.
+            return;
+        }
+        inputTarget = new InputTarget(InputTarget.Type.NO_TARGET, 0);
+        unlockPlatformViewInputConnection();
+    }
+
+    static private class InputTarget {
+        enum Type {
+            NO_TARGET,
+            // InputConnection is managed by the TextInputPlugin, and events are forwarded to the Flutter framework.
+            FRAMEWORK_CLIENT,
+            // InputConnection is managed by an embedded platform view.
+            PLATFORM_VIEW
+        }
+
+        public InputTarget(@NonNull Type type, int id) {
+            this.type = type;
+            this.id = id;
+        }
+
+        @NonNull
+        Type type;
+        // The ID of the input target.
+        //
+        // For framework clients this is the framework input connection client ID.
+        // For platform views this is the platform view's ID.
+        int id;
     }
 }

shell/platform/android/io/flutter/plugin/platform/PlatformViewsAccessibilityDelegate.java

@@ -11,7 +11,6 @@
  * Facilitates interaction between the accessibility bridge and embedded platform views.
  */
 public interface PlatformViewsAccessibilityDelegate {
-
     /**
      * Returns the root of the view hierarchy for the platform view with the requested id, or null if there is no
      * corresponding view.