Predictive back breakage fix (#42789)

Fixes breakages related to setFrameworkHandlesBack, for the Predictive Back feature for Android.

Author: justinmc

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

@@ -701,10 +701,10 @@ public void onBackInvoked() {
           : null;
 
   @Override
-  public void setFrameworkHandlesBack(boolean frameworkHandlesBacks) {
-    if (frameworkHandlesBacks && !hasRegisteredBackCallback) {
+  public void setFrameworkHandlesBack(boolean frameworkHandlesBack) {
+    if (frameworkHandlesBack && !hasRegisteredBackCallback) {
       registerOnBackInvokedCallback();
-    } else if (!frameworkHandlesBacks && hasRegisteredBackCallback) {
+    } else if (!frameworkHandlesBack && hasRegisteredBackCallback) {
       unregisterOnBackInvokedCallback();
     }
   }

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

@@ -1689,11 +1689,6 @@ boolean shouldDelayFirstAndroidViewDraw() {
     return getArguments().getBoolean(ARG_SHOULD_DELAY_FIRST_ANDROID_VIEW_DRAW);
   }
 
-  @Override
-  public void setFrameworkHandlesBack(boolean frameworkHandlesBacks) {
-    // Irrelevant to FlutterFragment.
-  }
-
   private boolean stillAttachedForEvent(String event) {
     if (delegate == null) {
       Log.w(TAG, "FlutterFragment " + hashCode() + " " + event + " called after release.");

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

@@ -138,8 +138,8 @@ public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result
                 break;
               case "SystemNavigator.setFrameworkHandlesBack":
                 {
-                  boolean frameworkHandlesBacks = (boolean) arguments;
-                  platformMessageHandler.setFrameworkHandlesBack(frameworkHandlesBacks);
+                  boolean frameworkHandlesBack = (boolean) arguments;
+                  platformMessageHandler.setFrameworkHandlesBack(frameworkHandlesBack);
                   result.success(null);
                   break;
                 }
@@ -516,8 +516,14 @@ public interface PlatformMessageHandler {
      */
     void setSystemUiOverlayStyle(@NonNull SystemChromeStyle systemUiOverlayStyle);
 
-    /** The Flutter application would or would not like to handle navigation pop events itself. */
-    void setFrameworkHandlesBack(boolean frameworkHandlesBack);
+    /**
+     * The Flutter application would or would not like to handle navigation pop events itself.
+     *
+     * <p>Relevant for registering and unregistering the app's OnBackInvokedCallback for the
+     * Predictive Back feature, for example as in {@link
+     * io.flutter.embedding.android.FlutterActivity}.
+     */
+    default void setFrameworkHandlesBack(boolean frameworkHandlesBack) {}
 
     /**
      * The Flutter application would like to pop the top item off of the Android app's navigation

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

@@ -57,7 +57,14 @@ public interface PlatformPluginDelegate {
      */
     boolean popSystemNavigator();
 
-    void setFrameworkHandlesBack(boolean frameworkHandlesBacks);
+    /**
+     * The Flutter application would or would not like to handle navigation pop events itself.
+     *
+     * <p>Relevant for registering and unregistering the app's OnBackInvokedCallback for the
+     * Predictive Back feature, for example as in {@link
+     * io.flutter.embedding.android.FlutterActivity}.
+     */
+    default void setFrameworkHandlesBack(boolean frameworkHandlesBack) {}
   }
 
   @VisibleForTesting
@@ -112,8 +119,8 @@ public void setSystemUiOverlayStyle(
         }
 
         @Override
-        public void setFrameworkHandlesBack(boolean frameworkHandlesBacks) {
-          PlatformPlugin.this.setFrameworkHandlesBack(frameworkHandlesBacks);
+        public void setFrameworkHandlesBack(boolean frameworkHandlesBack) {
+          PlatformPlugin.this.setFrameworkHandlesBack(frameworkHandlesBack);
         }
 
         @Override
@@ -482,8 +489,8 @@ private void setSystemChromeSystemUIOverlayStyle(
     currentTheme = systemChromeStyle;
   }
 
-  private void setFrameworkHandlesBack(boolean frameworkHandlesBacks) {
-    platformPluginDelegate.setFrameworkHandlesBack(frameworkHandlesBacks);
+  private void setFrameworkHandlesBack(boolean frameworkHandlesBack) {
+    platformPluginDelegate.setFrameworkHandlesBack(frameworkHandlesBack);
   }
 
   private void popSystemNavigator() {

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

@@ -419,6 +419,6 @@ public boolean popSystemNavigator() {
     }
 
     @Override
-    public void setFrameworkHandlesBack(boolean frameworkHandlesBacks) {}
+    public void setFrameworkHandlesBack(boolean frameworkHandlesBack) {}
   }
 }