android退出整个程序

public boolean onKeyDown(int keyCode, KeyEvent event) {
		// 当点击返回按钮时，退出程序
		if (keyCode == KeyEvent.KEYCODE_BACK) {
			android.os.Process.killProcess(android.os.Process.myPid());
		}
		return super.onKeyDown(keyCode, event);
	}