Android实现连续两次返回键退出

在activity中添加如下代码

转载：https://www.cnblogs.com/hzauxx/p/11008772.html

    //定义一个变量，来标识是否退出
    private static int isExit=0;

Handler handler=new Handler(){
        @Override
        public void handleMessage(Message msg){
            super.handleMessage(msg);
            isExit--;
        }
    };
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event){
        if(keyCode== KeyEvent.KEYCODE_BACK){
            isExit++;
            exit();
            return false;
        }
        return super.onKeyDown(keyCode,event);
    }

    private void exit(){
        if(isExit<2){
            Toast.makeText(getApplicationContext(),"再按一次退出",Toast.LENGTH_SHORT).show();

            //利用handler延迟发送更改状态信息
            handler.sendEmptyMessageDelayed(0,2000);

        }else{
            super.onBackPressed();
        }
    }