Question

I’m very new to Android. I want to pop up a transparent screen when the user receives a call. I have this code to open up the MyActivity screen, but it’s white instead of transparent.

public class CallReceiver extends BroadcastReceiver {

  @Override
  public void onReceive(Context context, Intent intent) {
    String state = intent.getStringExtra(TelephonyManager.EXTRA_STATE);
    if (TelephonyManager.EXTRA_STATE_RINGING.equals(state)) {
      SystemClock.sleep(1);
      Intent intent = new Intent(context, MyActivity.class);
      intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_NO_USER_ACTION);
      context.startActivity(intent);
    }

  }

}

Here’s the code for MyActivity:

public class MyActivity extends Activity {
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_my);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL);
  }
}

And here’s the layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:windowBackground="@android:color/transparent" 
    android:windowIsTranslucent="true" 
    android:windowAnimationStyle="@android:style/Animation.Translucent" >
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/incoming_call"
        tools:context=".MyActivity" />
</RelativeLayout>

This successfully pops up a screen with my message on it, but it does so with a white background instead of a transparent background. Any idea what I might be doing wrong? I’m using the emulator with the Android 2.2 SDK.

Answer 1

I think the issue may be in the confusion between the window and the contentView.

android:windowBackground="@android:color/transparent" 
android:windowIsTranslucent="true" 
android:windowAnimationStyle="@android:style/Animation.Translucent"
android:windowNoTitle="true"
android:windowFrame="@null"

These attributes probably won’t be respected by RelativeLayout and whatever you put in the content view, in general.

The window attributes are a property of the Window. You can change the Window in code or in the setup of your activity using a Theme.

<activity android:name="....YourActivity" android:theme="@style/MyTransparentTheme"/>

Then in some res file:

Project/res/values/themes.xml

<resources ....>
 ....
<style android:name="MyTransparentTheme" parent="@android:style/Theme">
  <item name="android:windowBackground">@android:color/transparent</item>
  <item name="android:windowIsTranslucent">true</item>
  <item name="android:windowAnimationStyle">@android:style/Animation.Translucent</item>
  <item name="android:windowNoTitle">true</item>
  <item name="android:windowFrame">@null</item>
</style>
....

You could also set it up by setting these properties on the Window of the activity directly, similar to how you set getWindow().addFlags(WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE); You can also just set the window to have a transparent background.