Android 返回键连续点击两次退出应用

返回键连续点击两次退出应用，一般大家都是使用时间差来实现功能，现在推荐使用handler来实现，看代码

使用工具类[b]DoubleClickExitHelper[/b]

public class DoubleClickExitHelper {
	private final Activity mActivity;
	private boolean isOnKeyBacking;
	private Handler mHandler;
	private Toast mBackToast;

	public DoubleClickExitHelper(Activity activity) {
		mActivity = activity;
		mHandler = new Handler(Looper.getMainLooper());
	}

	/**
	 * Activity onKeyDown事件
	 * */
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if(keyCode != KeyEvent.KEYCODE_BACK) {
			return false;
		}
		if(isOnKeyBacking) {
			mHandler.removeCallbacks(onBackTimeRunnable);
			if(mBackToast != null){
				mBackToast.cancel();
			}
			mActivity.finish();
			return true;
		} else {
			isOnKeyBacking = true;
			if(mBackToast == null) {
				mBackToast = Toast.makeText(mActivity, "再按一次返回", 2000);
			}
			mBackToast.show();
			//延迟两秒的时间，把Runable发出去
			mHandler.postDelayed(onBackTimeRunnable, 2000);
			return true;
		}
	}

	private Runnable onBackTimeRunnable = new Runnable() {

		@Override
		public void run() {
			isOnKeyBacking = false;
			if(mBackToast != null){
				mBackToast.cancel();
			}
		}
	};
}

[b]接下来我们只需要在回调onKeyDown中加入该工具方法即可，当然使用前要初始化下[/b]

DoubleClickExitHelper doubleClick = new DoubleClickExitHelper(this);

[b]接下来重写onKeyDown:[/b]

/**
	 * Returns: 
	 * Return
	 * true to prevent this event from being propagated further, or false to
	 * indicate that you have not handled this event and it should continue to
	 * be propagated.
	 */
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {

		if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
			return doubleClick.onKeyDown(keyCode, event);
		}
		return super.onKeyDown(keyCode, event);
	}

[b]完成，方便简单[/b]