new Thread(new Runnable() {
public void run() {
KeyEvent event = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_BACK);
new Instrumentation().sendKeySync(event);
KeyEvent event2 = new KeyEvent(KeyEvent.ACTION_UP, KeyEvent.KEYCODE_BACK);
new Instrumentation().sendKeySync(event2);
}
}).start();
위처럼 하셔도 됩니다.