Set Flutter View ID to the view ID instead of of the splash screen (#27262)

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

@@ -47,6 +47,7 @@ import io.flutter.embedding.engine.FlutterShellArgs;
 import io.flutter.embedding.engine.plugins.activity.ActivityControlSurface;
 import io.flutter.embedding.engine.plugins.util.GeneratedPluginRegister;
 import io.flutter.plugin.platform.PlatformPlugin;
+import io.flutter.util.ViewUtils;
 
 /**
  * {@code Activity} which displays a fullscreen Flutter UI.
@@ -215,7 +216,7 @@ public class FlutterActivity extends Activity
    * <p>This ID can be used to lookup {@code FlutterView} in the Android view hierarchy. For more,
    * see {@link android.view.View#findViewById}.
    */
-  public static final int FLUTTER_VIEW_ID = 0xF1F2;
+  public static final int FLUTTER_VIEW_ID = ViewUtils.generateViewId(0xF1F2);
 
   /**
    * Creates an {@link Intent} that launches a {@code FlutterActivity}, which creates a {@link
@@ -433,9 +434,7 @@ public class FlutterActivity extends Activity
 
     configureWindowForTransparency();
 
-    View flutterView = createFlutterView();
-    flutterView.setId(FLUTTER_VIEW_ID);
-    setContentView(flutterView);
+    setContentView(createFlutterView());
 
     configureStatusBarForFullscreenFlutterExperience();
   }
@@ -540,7 +539,10 @@ public class FlutterActivity extends Activity
   @NonNull
   private View createFlutterView() {
     return delegate.onCreateView(
-        null /* inflater */, null /* container */, null /* savedInstanceState */);
+        /* inflater=*/ null,
+        /* container=*/ null,
+        /* savedInstanceState=*/ null,
+        /*flutterViewId=*/ FLUTTER_VIEW_ID);
   }
 
   private void configureStatusBarForFullscreenFlutterExperience() {

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

@@ -11,7 +11,6 @@ import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
-import android.os.Build;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -28,6 +27,7 @@ import io.flutter.embedding.engine.FlutterShellArgs;
 import io.flutter.embedding.engine.dart.DartExecutor;
 import io.flutter.embedding.engine.renderer.FlutterUiDisplayListener;
 import io.flutter.plugin.platform.PlatformPlugin;
+import io.flutter.util.ViewUtils;
 import java.util.Arrays;
 
 /**
@@ -266,7 +266,10 @@ import java.util.Arrays;
    */
   @NonNull
   View onCreateView(
-      LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
+      LayoutInflater inflater,
+      @Nullable ViewGroup container,
+      @Nullable Bundle savedInstanceState,
+      int flutterViewId) {
     Log.v(TAG, "Creating FlutterView.");
     ensureAlive();
 
@@ -296,18 +299,12 @@ import java.util.Arrays;
     flutterView.addOnFirstFrameRenderedListener(flutterUiDisplayListener);
 
     flutterSplashView = new FlutterSplashView(host.getContext());
-    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
-      flutterSplashView.setId(View.generateViewId());
-    } else {
-      // TODO(mattcarroll): Find a better solution to this ID. This is a random, static ID.
-      // It might conflict with other Views, and it means that only a single FlutterSplashView
-      // can exist in a View hierarchy at one time.
-      flutterSplashView.setId(486947586);
-    }
+    flutterSplashView.setId(ViewUtils.generateViewId(486947586));
     flutterSplashView.displayFlutterViewWithSplash(flutterView, host.provideSplashScreen());
 
     Log.v(TAG, "Attaching FlutterEngine to FlutterView.");
     flutterView.attachToFlutterEngine(flutterEngine);
+    flutterView.setId(flutterViewId);
 
     return flutterSplashView;
   }

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

@@ -24,6 +24,7 @@ import io.flutter.embedding.engine.FlutterEngine;
 import io.flutter.embedding.engine.FlutterShellArgs;
 import io.flutter.embedding.engine.renderer.FlutterUiDisplayListener;
 import io.flutter.plugin.platform.PlatformPlugin;
+import io.flutter.util.ViewUtils;
 
 /**
  * {@code Fragment} which displays a Flutter UI that takes up all available {@code Fragment} space.
@@ -88,11 +89,20 @@ import io.flutter.plugin.platform.PlatformPlugin;
  * }</pre>
  *
  * <p>If Flutter is needed in a location that can only use a {@code View}, consider using a {@link
- * FlutterView}. Using a {@link FlutterView} requires forwarding some calls from an {@code
+ * io.flutter.embedding.android.FlutterView}. Using a {@link
+ * io.flutter.embedding.android.FlutterView} requires forwarding some calls from an {@code
  * Activity}, as well as forwarding lifecycle calls from an {@code Activity} or a {@code Fragment}.
  */
 public class FlutterFragment extends Fragment
     implements FlutterActivityAndFragmentDelegate.Host, ComponentCallbacks2 {
+  /**
+   * The ID of the {@code FlutterView} created by this activity.
+   *
+   * <p>This ID can be used to lookup {@code FlutterView} in the Android view hierarchy. For more,
+   * see {@link android.view.View#findViewById}.
+   */
+  public static final int FLUTTER_VIEW_ID = ViewUtils.generateViewId(0xF1F2);
+
   private static final String TAG = "FlutterFragment";
 
   /** The Dart entrypoint method name that is executed upon initialization. */
@@ -105,10 +115,14 @@ public class FlutterFragment extends Fragment
   protected static final String ARG_APP_BUNDLE_PATH = "app_bundle_path";
   /** Flutter shell arguments. */
   protected static final String ARG_FLUTTER_INITIALIZATION_ARGS = "initialization_args";
-  /** {@link RenderMode} to be used for the {@link FlutterView} in this {@code FlutterFragment} */
+  /**
+   * {@link RenderMode} to be used for the {@link io.flutter.embedding.android.FlutterView} in this
+   * {@code FlutterFragment}
+   */
   protected static final String ARG_FLUTTERVIEW_RENDER_MODE = "flutterview_render_mode";
   /**
-   * {@link TransparencyMode} to be used for the {@link FlutterView} in this {@code FlutterFragment}
+   * {@link TransparencyMode} to be used for the {@link io.flutter.embedding.android.FlutterView} in
+   * this {@code FlutterFragment}
    */
   protected static final String ARG_FLUTTERVIEW_TRANSPARENCY_MODE = "flutterview_transparency_mode";
   /** See {@link #shouldAttachEngineToActivity()}. */
@@ -290,8 +304,9 @@ public class FlutterFragment extends Fragment
     }
 
     /**
-     * Support a {@link TransparencyMode#transparent} background within {@link FlutterView}, or
-     * force an {@link TransparencyMode#opaque} background.
+     * Support a {@link TransparencyMode#transparent} background within {@link
+     * io.flutter.embedding.android.FlutterView}, or force an {@link TransparencyMode#opaque}
+     * background.
      *
      * <p>See {@link TransparencyMode} for implications of this selection.
      */
@@ -517,8 +532,9 @@ public class FlutterFragment extends Fragment
     }
 
     /**
-     * Support a {@link TransparencyMode#transparent} background within {@link FlutterView}, or
-     * force an {@link TransparencyMode#opaque} background.
+     * Support a {@link TransparencyMode#transparent} background within {@link
+     * io.flutter.embedding.android.FlutterView}, or force an {@link TransparencyMode#opaque}
+     * background.
      *
      * <p>See {@link TransparencyMode} for implications of this selection.
      */
@@ -710,7 +726,8 @@ public class FlutterFragment extends Fragment
   @Override
   public View onCreateView(
       LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
-    return delegate.onCreateView(inflater, container, savedInstanceState);
+    return delegate.onCreateView(
+        inflater, container, savedInstanceState, /*flutterViewId=*/ FLUTTER_VIEW_ID);
   }
 
   @Override
@@ -1002,8 +1019,8 @@ public class FlutterFragment extends Fragment
   }
 
   /**
-   * Returns the desired {@link RenderMode} for the {@link FlutterView} displayed in this {@code
-   * FlutterFragment}.
+   * Returns the desired {@link RenderMode} for the {@link io.flutter.embedding.android.FlutterView}
+   * displayed in this {@code FlutterFragment}.
    *
    * <p>Defaults to {@link RenderMode#surface}.
    *
@@ -1018,8 +1035,8 @@ public class FlutterFragment extends Fragment
   }
 
   /**
-   * Returns the desired {@link TransparencyMode} for the {@link FlutterView} displayed in this
-   * {@code FlutterFragment}.
+   * Returns the desired {@link TransparencyMode} for the {@link
+   * io.flutter.embedding.android.FlutterView} displayed in this {@code FlutterFragment}.
    *
    * <p>Defaults to {@link TransparencyMode#transparent}.
    *
@@ -1176,8 +1193,8 @@ public class FlutterFragment extends Fragment
   }
 
   /**
-   * Invoked after the {@link FlutterView} within this {@code FlutterFragment} starts rendering
-   * pixels to the screen.
+   * Invoked after the {@link io.flutter.embedding.android.FlutterView} within this {@code
+   * FlutterFragment} starts rendering pixels to the screen.
    *
    * <p>This method forwards {@code onFlutterUiDisplayed()} to its attached {@code Activity}, if the
    * attached {@code Activity} implements {@link FlutterUiDisplayListener}.
@@ -1195,8 +1212,8 @@ public class FlutterFragment extends Fragment
   }
 
   /**
-   * Invoked after the {@link FlutterView} within this {@code FlutterFragment} stops rendering
-   * pixels to the screen.
+   * Invoked after the {@link io.flutter.embedding.android.FlutterView} within this {@code
+   * FlutterFragment} stops rendering pixels to the screen.
    *
    * <p>This method forwards {@code onFlutterUiNoLongerDisplayed()} to its attached {@code
    * Activity}, if the attached {@code Activity} implements {@link FlutterUiDisplayListener}.

shell/platform/android/io/flutter/util/ViewUtils.java

@@ -7,6 +7,8 @@ package io.flutter.util;
 import android.app.Activity;
 import android.content.Context;
 import android.content.ContextWrapper;
+import android.os.Build;
+import android.view.View;
 
 public final class ViewUtils {
   /**
@@ -28,4 +30,19 @@ public final class ViewUtils {
     }
     return null;
   }
+
+  /**
+   * Generates a view id.
+   *
+   * <p>In API level 17 and above, this ID is unique. Below 17, the fallback id is used instead.
+   *
+   * @param fallbackId the fallback id.
+   * @return the view id.
+   */
+  public static int generateViewId(int fallbackId) {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
+      return View.generateViewId();
+    }
+    return fallbackId;
+  }
 }

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

@@ -86,7 +86,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // We're testing lifecycle behaviors, which require/expect that certain methods have already
     // been executed by the time they run. Therefore, we run those expected methods first.
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
 
     // --- Execute the behavior under test ---
     // By the time an Activity/Fragment is started, we don't expect any lifecycle messages
@@ -164,7 +164,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // The FlutterEngine is obtained in onAttach().
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
 
@@ -220,7 +220,7 @@ public class FlutterActivityAndFragmentDelegateTest {
 
     // --- Execute the behavior under test ---
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
 
     // Verify that the host was asked to configure a FlutterSurfaceView.
     verify(mockHost, times(1)).onFlutterSurfaceViewCreated(notNull(FlutterSurfaceView.class));
@@ -249,7 +249,7 @@ public class FlutterActivityAndFragmentDelegateTest {
 
     // --- Execute the behavior under test ---
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
 
     // Verify that the host was asked to configure a FlutterTextureView.
     verify(customMockHost, times(1)).onFlutterTextureViewCreated(notNull(FlutterTextureView.class));
@@ -282,7 +282,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // The initial route is sent in onStart().
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
 
     // Verify that the navigation channel was given our initial route.
@@ -306,7 +306,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // Dart is executed in onStart().
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
 
     // Verify that the host's Dart entrypoint was used.
@@ -335,7 +335,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // Dart is executed in onStart().
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
 
     // Verify that the host's Dart entrypoint was used.
@@ -647,7 +647,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // Push the delegate through all lifecycle methods all the way to destruction.
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
     delegate.onPause();
@@ -671,7 +671,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // Push the delegate through all lifecycle methods all the way to destruction.
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
     delegate.onPause();
@@ -702,7 +702,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // Push the delegate through all lifecycle methods all the way to destruction.
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
     delegate.onPause();
@@ -734,7 +734,7 @@ public class FlutterActivityAndFragmentDelegateTest {
     // --- Execute the behavior under test ---
     // Push the delegate through all lifecycle methods all the way to destruction.
     delegate.onAttach(RuntimeEnvironment.application);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
     delegate.onPause();

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

@@ -77,6 +77,7 @@ public class FlutterActivityTest {
 
     activity.onCreate(null);
     assertNotNull(activity.findViewById(FlutterActivity.FLUTTER_VIEW_ID));
+    assertTrue(activity.findViewById(FlutterActivity.FLUTTER_VIEW_ID) instanceof FlutterView);
   }
 
   @Test

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

@@ -82,7 +82,7 @@ public class FlutterAndroidComponentTest {
     assertNotNull(binding.getPlatformViewRegistry());
 
     delegate.onRestoreInstanceState(null);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
     delegate.onPause();
@@ -156,7 +156,7 @@ public class FlutterAndroidComponentTest {
     // Verify that after Activity creation, the plugin was allowed to restore state.
     verify(mockSaveStateListener, times(1)).onRestoreInstanceState(any(Bundle.class));
 
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
     delegate.onPause();
@@ -195,7 +195,7 @@ public class FlutterAndroidComponentTest {
     // Push the delegate through all lifecycle methods all the way to destruction.
     delegate.onAttach(RuntimeEnvironment.application);
     delegate.onRestoreInstanceState(null);
-    delegate.onCreateView(null, null, null);
+    delegate.onCreateView(null, null, null, 0);
     delegate.onStart();
     delegate.onResume();
     delegate.onPause();