support customize platformView theme

[SupSaiYaJin]

This is necessary when need a translucent AndroidView to make the Flutter UI visible below an AndroidView.

[matthew-carroll]

I'm going to leave this review for @amirh because I'm not familiar with the current architecture or possible implications of this change.

[SupSaiYaJin]

@amirh any updates?

[zhugogogo]

@xster pls check this pr?

[xster]

I don't really know how this works.

Though it seems a bit unfortunate to create this parallel mechanism to side-load this. Can it not be passed via args from the Flutter side and then use context.setTheme or something instead?

[matthew-carroll]

@SupSaiYaJin can you provide a screenshot or a mockup of what you're trying to achieve?

[SupSaiYaJin]

@matthew-carroll
There is a fullscreen AndroidView covering on other widgets.
Here is the screenshot of use default theme, the AndroidView is opaque. Widgets below it are covered and invisible.

Here is the screenshot of using android.R.style.Theme_Translucent_NoTitleBar_Fullscreen for presentation theme, The AndroidView becomes transparent. Widgets below it can be shown.

[matthew-carroll]

@SupSaiYaJin I'm not sure what your screenshots are trying to show. Are those screenshots of what you currently have? or are they mockups of what you're trying to achieve? Are part of them Flutter and part of them Android?

[SupSaiYaJin]

@SupSaiYaJin I'm not sure what your screenshots are trying to show. Are those screenshots of what you currently have? or are they mockups of what you're trying to achieve? Are part of them Flutter and part of them Android?

@matthew-carroll
Here is a simple example:
Dart:

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text("TestAndroidView"),
        ),
        body: Stack(
          children: <Widget>[
            Container(color: Colors.red,),
            Center(
              child: SizedBox(
                height: 100,
                child: AndroidView(
                  viewType: "test",
                ),
              ),
            )
          ],
        ),
      ),
    );
  }
}

Java:

  static class TestTextView implements PlatformView {

      TextView mTextView;

      TestTextView(Context context) {
          mTextView = new TextView(context);
          mTextView.setText("AndroidView Test Text");
          mTextView.setTextSize(32);
      }

      @Override
      public View getView() {
          return mTextView;
      }

      @Override
      public void dispose() {

      }
  }

Use default theme:

Use transparent theme:

        @Override
        public int getPresentationTheme() {
            return android.R.style.Theme_Translucent_NoTitleBar_Fullscreen;
        }

[SupSaiYaJin]

@matthew-carroll Any suggestions? Did I describe it clearly?😁

[matthew-carroll]

Thanks @SupSaiYaJin that helps.

Does the transparent background really require a custom theme? Can't you just setBackground() on the View to get the same effect?

[SupSaiYaJin]

Thanks @SupSaiYaJin that helps.

Does the transparent background really require a custom theme? Can't you just setBackground() on the View to get the same effect?

No, it didn't work, cause the Window of Presentation is opaque.

[SupSaiYaJin]

Thanks @SupSaiYaJin that helps.

Does the transparent background really require a custom theme? Can't you just setBackground() on the View to get the same effect?

The View is already transparent. But the Window isn't.

[matthew-carroll]

@amirh what do you think is the right approach here? Should platform views support theming, or is there some other way that transparency should be supported?

[cbracken]

@amirh have you had time to have a look at this? If so, any feedback?

[AndreaMiotto]

@SupSaiYaJin how can I bring your code to my flutter project? I can't find where the flutter engine is stored

[dfavaro]

@amirh issue still present. Any temporary workaround? Thanks

[bi-a]

@amirh can you please review this code for accept the merge request?

[AndreaMiotto]

@amirh when do you think this could be fixed? I have a sprint review with the client next week and I have to bring an answer for this problem.

cc @matthew-carroll

[amirh]

I apologize for the long delay on this.

It seems to me like it would make sense to just always have the VD's window be translucent. Normally in Android you'd only do it when needed in order to save a composition step between windows, but since the VD has just one window there should be no cost for always keeping that window translucent(which has a side effect of preserving alpha which is what we really want here).

I sent #9828 which is a simplified version of this PR to do that.

Thank you again for bringing this up and finding the solution!

[SupSaiYaJin]

@amirh I found that touch events would be misaligned the height of the status bar in some devices with notch screen such as Xiaomi 8. Use android.R.style.Theme_Panel will resolve this.

[amirh]

@SupSaiYaJin thanks for the quick report!
I sent #9849 as a speculative fix.

[amirh]

Closing this PR as the issue was addressed by #9849