[remake] Restore old back handling for FlutterFragmentActivity (#161545)
Remake of https://github.com/flutter/engine/pull/56565. Quoting from an
old comment, slightly edited:
------------
https://github.com/flutter/engine/pull/52302 seems to have
unintentionally had the effect of not allowing people to "opt out" of
predictive back. This is actually aligned with what the android docs say
should happen:
https://developer.android.com/guide/navigation/custom-back/predictive-back-gesture
> Note: OnBackPressedCallback is always called regardless of the value
of android:enableOnBackInvokedCallback. In other words, disabling the
system animation doesn't affect your app's back handling logic if it
uses OnBackPressedCallback.
But this wasn't actually true for flutter apps before
https://github.com/flutter/engine/pull/52302, because we were not
calling `super`, and `FlutterFragmentActivity` extends a
`FragmentActivity` which in turn extends a `ComponentActivity`, which
uses the old `onBackPressed` to [invoke the new back
handling](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:activity/activity/src/main/java/androidx/activity/ComponentActivity.kt;l=587?q=ComponentActivity):
```kotlin
override fun onBackPressed() {
onBackPressedDispatcher.onBackPressed()
}
```
So while the docs imply that removing the `onBackPressed` in
`FlutterFragmentActivity` shouldn't have had an effect, that wasn't true
because in our case we were consuming the back event and ignoring the
warning
```java
@Override
@SuppressWarnings("MissingSuperCall")
public void onBackPressed() {
flutterFragment.onBackPressed();
}
```
What all this means is that apps that _aren't_ opting in to predictive
back had their back handling migrated to the new code path
automatically. FlutterFragmentActivity was uniquely is forced into the
new back handling codepath by
https://github.com/flutter/engine/pull/52302, which this PR fixes.
------------
## Pre-launch Checklist
- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [ ] All existing and new tests are passing.
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on [Discord].
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---------
Co-authored-by: Gray Mackall <mackall@google.com>diff --git a/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterFragmentActivity.java b/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterFragmentActivity.java
index d0562be..033ea57 100644
--- a/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterFragmentActivity.java
+++ b/engine/src/flutter/shell/platform/android/io/flutter/embedding/android/FlutterFragmentActivity.java
@@ -620,6 +620,15 @@
super.onNewIntent(intent);
}
+ // Intentionally missing super call to align FlutterFragmentActivity predictive back behavior
+ // with FlutterActivity, with respect to how it responds to the
+ // android:enableOnBackInvokedCallback manifest property.
+ @Override
+ @SuppressWarnings("MissingSuperCall")
+ public void onBackPressed() {
+ flutterFragment.onBackPressed();
+ }
+
@Override
public void onRequestPermissionsResult(
int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
diff --git a/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterFragmentActivityTest.java b/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterFragmentActivityTest.java
index 73274cb..f25b134 100644
--- a/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterFragmentActivityTest.java
+++ b/engine/src/flutter/shell/platform/android/test/io/flutter/embedding/android/FlutterFragmentActivityTest.java
@@ -13,6 +13,7 @@
import static org.junit.Assert.assertTrue;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import android.annotation.TargetApi;
@@ -302,6 +303,23 @@
@Test
@Config(minSdk = Build.API_LEVELS.API_34)
@TargetApi(Build.API_LEVELS.API_34)
+ public void onBackPressedCallsGetForwardedToFragment() {
+ FlutterFragmentActivityWithProvidedEngine activity =
+ spy(Robolectric.buildActivity(FlutterFragmentActivityWithProvidedEngine.class).get());
+
+ FlutterFragment fragment = mock(FlutterFragment.class);
+ when(activity.retrieveExistingFlutterFragmentIfPossible()).thenReturn(null, fragment);
+ FlutterEngine engine = mock(FlutterEngine.class);
+ when(fragment.getFlutterEngine()).thenReturn(engine);
+ activity.onCreate(null);
+
+ activity.onBackPressed();
+ verify(fragment).onBackPressed();
+ }
+
+ @Test
+ @Config(minSdk = Build.API_LEVELS.API_34)
+ @TargetApi(Build.API_LEVELS.API_34)
public void whenNotUsingCachedEngine_predictiveBackStateIsNotSaved() {
ActivityScenario<FlutterActivity> flutterActivityScenario =
ActivityScenario.launch(FlutterActivity.class);
