test onBackInvokedCallback for different SDK

Author: maRci002

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

@@ -659,7 +659,7 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
    */
   @VisibleForTesting
   public void registerOnBackInvokedCallback() {
-    if (Build.VERSION.SDK_INT >= 33 && onBackInvokedCallback != null) {
+    if (Build.VERSION.SDK_INT >= 33) {
       getOnBackInvokedDispatcher()
           .registerOnBackInvokedCallback(
               OnBackInvokedDispatcher.PRIORITY_DEFAULT, onBackInvokedCallback);
@@ -675,18 +675,20 @@ public void registerOnBackInvokedCallback() {
    */
   @VisibleForTesting
   public void unregisterOnBackInvokedCallback() {
-    if (Build.VERSION.SDK_INT >= 33 && onBackInvokedCallback != null) {
+    if (Build.VERSION.SDK_INT >= 33) {
       getOnBackInvokedDispatcher().unregisterOnBackInvokedCallback(onBackInvokedCallback);
       hasRegisteredBackCallback = false;
     }
   }
 
-  final OnBackInvokedCallback onBackInvokedCallback = createOnBackInvokedCallback();
+  final OnBackInvokedCallback onBackInvokedCallback =
+      Build.VERSION.SDK_INT < 33 ? null : createOnBackInvokedCallback();
 
+  @NonNull
+  @TargetApi(33)
+  @RequiresApi(33)
   private OnBackInvokedCallback createOnBackInvokedCallback() {
-    if (Build.VERSION.SDK_INT == 33) {
-      return this::onBackPressed;
-    } else if (Build.VERSION.SDK_INT >= 34) {
+    if (Build.VERSION.SDK_INT >= 34) {
       return new OnBackAnimationCallback() {
         @Override
         public void onBackInvoked() {
@@ -710,7 +712,7 @@ public void onBackStarted(@NonNull BackEvent backEvent) {
       };
     }
 
-    return null;
+    return this::onBackPressed;
   }
 
   @Override

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

@@ -24,6 +24,7 @@
 import android.os.Bundle;
 import android.window.BackEvent;
 import android.window.OnBackAnimationCallback;
+import android.window.OnBackInvokedCallback;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.lifecycle.DefaultLifecycleObserver;
@@ -125,8 +126,44 @@ public void itUnregistersOnBackInvokedCallbackOnRelease() {
   }
 
   @Test
-  @TargetApi(34)
-  public void itHandlesOnBackAnimationCallbackAsExpected() {
+  @Config(maxSdk = Build.VERSION_CODES.S_V2)
+  public void onBackInvokedCallbackIsNullForSdk32OrLower() {
+    Intent intent = FlutterActivity.createDefaultIntent(ctx);
+    ActivityController<FlutterActivity> activityController =
+        Robolectric.buildActivity(FlutterActivity.class, intent);
+    FlutterActivity flutterActivity = activityController.get();
+
+    flutterActivity.onCreate(null);
+
+    assertNull(
+        "onBackInvokedCallback should be null for SDK 32 or lower",
+        flutterActivity.onBackInvokedCallback);
+  }
+
+  @Test
+  @Config(sdk = Build.VERSION_CODES.TIRAMISU)
+  @TargetApi(Build.VERSION_CODES.TIRAMISU)
+  public void onBackInvokedCallbackCallsOnBackPressedForSdk33() {
+    Intent intent = FlutterActivityWithReportFullyDrawn.createDefaultIntent(ctx);
+    ActivityController<FlutterActivityWithReportFullyDrawn> activityController =
+        Robolectric.buildActivity(FlutterActivityWithReportFullyDrawn.class, intent);
+    FlutterActivityWithReportFullyDrawn activity = spy(activityController.get());
+
+    activity.onCreate(null);
+
+    assertNotNull(
+        "onBackInvokedCallback should not be null for SDK 33", activity.onBackInvokedCallback);
+
+    OnBackInvokedCallback callback = activity.onBackInvokedCallback;
+
+    callback.onBackInvoked();
+    verify(activity, times(1)).onBackPressed();
+  }
+
+  @Test
+  @Config(sdk = Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
+  @TargetApi(Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
+  public void itHandlesOnBackAnimationCallbackAsExpectedForSdk34OrHigher() {
     Intent intent = FlutterActivityWithReportFullyDrawn.createDefaultIntent(ctx);
     ActivityController<FlutterActivityWithReportFullyDrawn> activityController =
         Robolectric.buildActivity(FlutterActivityWithReportFullyDrawn.class, intent);
@@ -135,7 +172,7 @@ public void itHandlesOnBackAnimationCallbackAsExpected() {
     activity.onCreate(null);
 
     assertTrue(
-        "onBackInvokedCallback should be an instance of OnBackAnimationCallback",
+        "onBackInvokedCallback should be an instance of OnBackAnimationCallback for SDK 34 or higher",
         activity.onBackInvokedCallback instanceof OnBackAnimationCallback);
 
     OnBackAnimationCallback callback = (OnBackAnimationCallback) activity.onBackInvokedCallback;