Transparent Activity

Activity.java

public class MainActivity extends AppCompatActivity {

  @Override 
  protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
        WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL);
  }
}

manifest.xml

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:name=".App"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true">

        <activity android:name=".MainActivity"
            android:theme="@style/Theme.Transparent.Activity">
            <intent-filter>
                <category android:name="android.intent.category.LAUNCHER" />
                <action android:name="android.intent.action.MAIN" />
            </intent-filter>
        </activity>
    </application>

</manifest>

style.xml

<resources>
    <style name="Theme.Transparent.Activity" parent="Theme.MaterialComponents.NoActionBar">
        <item name="android:windowIsTranslucent">true</item>
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:windowContentOverlay">@null</item>
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowIsFloating">true</item>
        <item name="android:backgroundDimEnabled">false</item>
    </style>
</resources>