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FlutterFragment predictive back #44865

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FlutterFragment predictive back #44865

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89629fb
Seems to work whether Flutter is the first acitivty or not
justinmc Aug 18, 2023
bf4e1ec
Work with original onBackPressed mechanics
justinmc Aug 18, 2023
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13 changes: 13 additions & 0 deletions shell/platform/android/io/flutter/embedding/android/FlutterFragment.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1062,6 +1062,11 @@ public void onAttach(@NonNull Context context) {
delegate.onAttach(context);
if (getArguments().getBoolean(ARG_SHOULD_AUTOMATICALLY_HANDLE_ON_BACK_PRESSED, false)) {
requireActivity().getOnBackPressedDispatcher().addCallback(this, onBackPressedCallback);
// By default, Android handles backs, and predictive back is enabled. This
// can be changed by calling setFrameworkHandlesBack. For example, the
// framework will call this automatically in a typical app when it has
// routes to pop.
onBackPressedCallback.setEnabled(false);
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This is a potentially dangerous change. Does the framework guarantee that the callback will always be enabled when applicable via setFrameworkHandlesBack, regardless of API version?

}
context.registerComponentCallbacks(this);
}
Expand Down Expand Up @@ -1684,6 +1689,14 @@ public boolean popSystemNavigator() {
return false;
}

@Override
public void setFrameworkHandlesBack(boolean frameworkHandlesBack) {
if (getArguments().getBoolean(ARG_SHOULD_AUTOMATICALLY_HANDLE_ON_BACK_PRESSED, false)) {
return;
}
onBackPressedCallback.setEnabled(frameworkHandlesBack);
}

@VisibleForTesting
@NonNull
boolean shouldDelayFirstAndroidViewDraw() {
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4 changes: 4 additions & 0 deletions shell/platform/android/io/flutter/embedding/android/FlutterFragmentActivity.java
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Expand Up @@ -521,6 +521,7 @@ protected FlutterFragment createFlutterFragment() {
? TransparencyMode.opaque
: TransparencyMode.transparent;
final boolean shouldDelayFirstAndroidViewDraw = renderMode == RenderMode.surface;
final boolean shouldAutomaticallyHandleOnBackPressed = Build.VERSION.SDK_INT >= 33;
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With this change, you'll need to update the implementation of onBackPressed() below. On Android 33, the onBackPressed() method is still relevant, but it won't behave correctly without a call to super.onBackPressed().

Alternatively, you could make this condition always true and fully remove the onBackPressed() override below. That way you have less conditional behavior.

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I suppose removing the onBackPressed() override could impact behavior for any clients that subclass FlutterFragmentActivity and themselves override the method, but given that Android now formally discourages that anyways, that seems like a reasonable breaking change.


if (getCachedEngineId() != null) {
Log.v(
Expand All @@ -545,6 +546,7 @@ protected FlutterFragment createFlutterFragment() {
.shouldAttachEngineToActivity(shouldAttachEngineToActivity())
.destroyEngineWithFragment(shouldDestroyEngineWithHost())
.shouldDelayFirstAndroidViewDraw(shouldDelayFirstAndroidViewDraw)
.shouldAutomaticallyHandleOnBackPressed(shouldAutomaticallyHandleOnBackPressed)
.build();
} else {
Log.v(
Expand Down Expand Up @@ -581,6 +583,7 @@ protected FlutterFragment createFlutterFragment() {
.transparencyMode(transparencyMode)
.shouldAttachEngineToActivity(shouldAttachEngineToActivity())
.shouldDelayFirstAndroidViewDraw(shouldDelayFirstAndroidViewDraw)
.shouldAutomaticallyHandleOnBackPressed(shouldAutomaticallyHandleOnBackPressed)
.build();
}

Expand All @@ -596,6 +599,7 @@ protected FlutterFragment createFlutterFragment() {
.transparencyMode(transparencyMode)
.shouldAttachEngineToActivity(shouldAttachEngineToActivity())
.shouldDelayFirstAndroidViewDraw(shouldDelayFirstAndroidViewDraw)
.shouldAutomaticallyHandleOnBackPressed(shouldAutomaticallyHandleOnBackPressed)
.build();
}
}
Expand Down