Android中连续按两次返回键退出应用

方法1：

private long exitTime;@Overridepublic boolean onKeyDown(int keyCode, KeyEvent event) {if (keyCode == KeyEvent.KEYCODE_BACK&& event.getAction() == KeyEvent.ACTION_DOWN) {if ((System.currentTimeMillis() - exitTime) > 2000) { // 两次按返回键时间间隔大于2秒，则不退出Toast.makeText(getApplicationContext(), "再按一次退出应用",Toast.LENGTH_SHORT).show();exitTime = System.currentTimeMillis();} else { // 否则在小于2秒时退出应用finish();// System.exit(0);}return true;}return super.onKeyDown(keyCode, event);} 

补充：finish()是Activity的方法，调用时会退出当前Activity，而System.exit(0)会退出整个应用。

方法2：

private int mBackKeyPressedTimes = 0;@Overridepublic void onBackPressed() {if (mBackKeyPressedTimes == 0) {Toast.makeText(this, "再按一次退出程序 ", Toast.LENGTH_SHORT).show();mBackKeyPressedTimes = 1;new Thread() { // 开线程延时2秒设置变量mBackKeyPressedTimes@Overridepublic void run() {try {Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();} finally {mBackKeyPressedTimes = 0;}}}.start();return;} else {finish();}super.onBackPressed();}