From Picture-in-Picture activity to Back-Stack activity not working in android?

Question

I have two activity A & B, A activity have list of videos. After click the video it goes to B(Player) activity to play video.

Issue faced

A(Video List) --> B(Player Activity)

1. When i click the back button B activity goes to PIP mode. Now A is visible & B activity in PIP mode(Video Playing). Again i click the back button it closed the A activity, but B still in PIP Mode. Now B activity leave PIP mode to Full activity.

   Now again click the back button, i want to show the A as back stack B activity to PIP mode. But B activity goes to PIP mode but Back screen as homes screen.

2. When i clicked the Home button while in B activity, B activity goes to PIP mode. B activity in PIP now can access the home screens. Now click the PIP mode screen to full activity.

   Now again click the back button, i want to show the A as back stack B activity to PIP mode. But B activity goes to PIP mode but Back screen as homes screen.

Manifest

<activity
   android:name=".MainActivity"
   android:screenOrientation="portrait"/>

<activity
   android:name=".PlayerActivity"
   android:allowTaskReparenting="true"
   android:autoRemoveFromRecents="true"
   android:configChanges="screenSize|smallestScreenSize|screenLayout|orientation|layoutDirection"
   android:excludeFromRecents="true"
   android:launchMode="singleTask"
   android:resizeableActivity="true"
   android:screenOrientation="sensor"
   android:supportsPictureInPicture="true" />

Picuture-in-Picture code

private void pictureInPictureMode() {

    if (supportsPiPMode() && getPackageManager().hasSystemFeature(PackageManager.FEATURE_PICTURE_IN_PICTURE)) {

        Rational aspectRatio = new Rational(playerView.getWidth(), playerView.getHeight());
        pictureInPictureParamsBuilder.setAspectRatio(aspectRatio).build();
        if (canEnterPiPMode()) enterPictureInPictureMode(pictureInPictureParamsBuilder.build());

    }

}

@Override
public void onPictureInPictureModeChanged(boolean isInPictureInPictureMode, Configuration newConfig) {
    inPIP = isInPictureInPictureMode;
    if (isInPictureInPictureMode) {
        landscapeViews();
        bottomAdv.setVisibility(View.GONE);
    } else {
        portraitViews();
    }
}

@Override
protected void onUserLeaveHint() {
     pictureInPictureMode();
}

private boolean canEnterPiPMode() {

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
        AppOpsManager appOpsManager = (AppOpsManager) getSystemService(Context.APP_OPS_SERVICE);
        return (AppOpsManager.MODE_ALLOWED == appOpsManager.checkOpNoThrow(AppOpsManager.OPSTR_PICTURE_IN_PICTURE, Process.myUid(), getPackageName()));
    }

    return false;
 }

public boolean supportsPiPMode() {
    return Build.VERSION.SDK_INT >= Build.VERSION_CODES.O;
}

In B activity whenever click the back button need A activity as back stack B to PIP mode. Guide me to solve this issue.