重写返回键==>1秒内按两次返回键才能退出

private long exitTime = 0; public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) { if ((System.currentTimeMillis() - exitTime) > 2000) { Toast.makeText(getApplicationContext(), "再按一次退出应用", Toast.LENGTH_SHORT).show(); exitTime = System.currentTimeMillis(); } else { ExitActivity.exit(); } return true; } return super.onKeyDown(keyCode, event); }