BottomSheetDialog background blinking

Question

BottomSheetDialog's background is blinking when switching between apps. What am I doing wrong ?

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        findViewById(R.id.btn1).setOnClickListener(v -> {
            BottomSheetDialog bottomSheetDialog = new BottomSheetDialog(MainActivity.this);
            bottomSheetDialog.setContentView(R.layout.content);
            bottomSheetDialog.show();
        });
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">

    <Button
        android:id="@+id/btn1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

content.xml

<?xml version="1.0" encoding="utf-8"?>
<View xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="300dp"
    android:background="#F00" />

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.holtaf.testandroidapplication">

    <application
        android:allowBackup="true"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/Theme.AppCompat.Light.DarkActionBar">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

My appcompat version is 27.1.1.

Answer 1

The main reason for the flickering is due to the default styling of the BottomSheetDialog which defines a default animation and the dim behavior.

We can resolve the above issue by defining a custom theme using bottomSheetDialogTheme which in turn:

1. Disables the default window animation for the BottomSheet by setting windowAnimationStyle to @null.
2. Sets the backgroundDimEnabled attribute to false.

Example:

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>

    <item name="bottomSheetDialogTheme">@style/AppTheme.BottomSheetDialog</item>
</style>

<style name="AppTheme.BottomSheetDialog" parent="Theme.Design.BottomSheetDialog">
    <item name="android:windowAnimationStyle">@null</item>
    <item name="android:backgroundDimEnabled">false</item>

    <!-- optional -->
    <item name="android:windowBackground">#99323232</item> 
</style>