why getEdgeFlags() always return 0
<p>I want to detect the touch edge in onTouchEvent function for my view, but  getEdgeFlags() always return 0 in my Nexus S 4.1.1, anyone can help me? thanks advance.</p>

<pre><code>@Override
public boolean onTouchEvent(MotionEvent event) {
    int edgeFlags = event.getEdgeFlags();
    //edgeFlags alway 0!
    switch (edgeFlags) {
    case MotionEvent.EDGE_LEFT:
        Log.i("tag", "EDGE_LEFT");
        break;
    case MotionEvent.EDGE_RIGHT:
        Log.i("tag", "EDGE_RIGHT");
        break;
    case MotionEvent.EDGE_TOP:
        Log.i("tag", "EDGE_TOP");
        break;
    case MotionEvent.EDGE_BOTTOM:
        Log.i("tag", "EDGE_BOTTOM");
        break;
    default:
        Log.i("tag", "" + edgeFlags);
        break;
    }
return super.onTouchEvent(event);
}
</code></pre>
