======两秒之内两次back就finish======

/**
	 * 两秒之内，按两次回退键才会推出app
	 */
	public static boolean isToFinish = false;
	public static boolean isFirst = true;
	public static boolean finishTwoBack(Context mContext){
		
		
		Handler handler = new Handler();
		Runnable r = new Runnable() {
			
			@Override
			public void run() {
				isFirst = true;
				isToFinish = false;
			}
		};
		if(isFirst){
			
			isFirst = false;
			handler.postDelayed(r, 2000);
			Toast.makeText(mContext, "再按一次退出程序", Toast.LENGTH_SHORT).show();
			
		}else{
			
			isToFinish = true;
		}
		return isToFinish;
		
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if(keyCode == KeyEvent.KEYCODE_BACK){

			if(ComUtils.finishTwoBack(this)){

				return super.onKeyDown(keyCode, event);
			};

			return true;
		}
		return super.onKeyDown(keyCode, event);
	}

======两秒之内两次back就finish======

原文：http://blog.csdn.net/soulofandroid/article/details/42964801