Resume the Top Activity instead of starting the Launcher Activity

I use the following code in the LAUNCHER Activities of my apps to prevent the app from beeing started again when its still alive in the background and the icon is tapped

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

    if (!isTaskRoot()) {
        finish();
        return;
    }

    // Rest of your onCreate stuff goes here
}

This just finishes the LAUNCHER Activity and resumes the last used one.

Try using the following code in the onCreate method of the activity that is specified as the Launcher Activity in the Manifest, i.e. the ContentDownload activity from the original code posted in the question:

if ((getIntent().getFlags() & Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT) != 0) {
  finish();
  return;
}

This will finish your Launcher Activity before it is displayed by detecting that there is already a task running, and your app should instead resume to the last visible Activity.

See this page in the Android documentation regarding Android Manifest launchModes: http://developer.android.com/reference/android/R.styleable.html#AndroidManifestActivity_launchMode

You've got both your activities defined with launchMode="singleTask". This is the root of your problem. Remove that.