android:how to check if application is running in background

Update, see this first:

Checking if an Android application is running in the background

---

To check if your application is sent to background, you can call this code on onPause() on every activity in your application:

 /**
   * Checks if the application is being sent in the background (i.e behind
   * another application's Activity).
   * 
   * @param context the context
   * @return <code>true</code> if another application will be above this one.
   */
  public static boolean isApplicationSentToBackground(final Context context) {
    ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    List<RunningTaskInfo> tasks = am.getRunningTasks(1);
    if (!tasks.isEmpty()) {
      ComponentName topActivity = tasks.get(0).topActivity;
      if (!topActivity.getPackageName().equals(context.getPackageName())) {
        return true;
      }
    }

    return false;
  }

For this to work you should include this in your AndroidManifest.xml

<uses-permission android:name="android.permission.GET_TASKS" />