Xamarin Mono Android实现“再按一次退出程序”

开始研究Android平台软件编程，Xamarin Mono for Android上手快，跨平台共享代码，代价是bug多多，是一味可口的毒药啊！

环境VS2012 + Xamarin Mono Android 4.10.01073

先实现个小功能热热身，建立一个新Android Application工程，修改Activity1.cs代码如下：

using System;using Android.App;using Android.Content;using Android.Runtime;using Android.Views;using Android.Widget;using Android.OS;namespace MyXamarinApp{    [Activity(Label = "MyXamarinApp", MainLauncher = true, Icon = "@drawable/icon")]    public class Activity1 : Activity    {        int count = 1;        DateTime? lastBackKeyDownTime;        protected override void OnCreate(Bundle bundle)        {            base.OnCreate(bundle);            // Set our view from the "main" layout resource            SetContentView(Resource.Layout.Main);            // Get our button from the layout resource,            // and attach an event to it            Button button = FindViewById<Button>(Resource.Id.MyButton);            button.Click += delegate { button.Text = string.Format("{0} clicks!", count++); };        }        public override bool OnKeyDown(Keycode keyCode, KeyEvent e)        {            if (keyCode == Keycode.Back && e.Action == KeyEventActions.Down)            {                if (!lastBackKeyDownTime.HasValue || DateTime.Now - lastBackKeyDownTime.Value > new TimeSpan(0, 0, 2))                {                    Toast.MakeText(this.ApplicationContext, "再按一次退出程序", ToastLength.Short).Show();                    lastBackKeyDownTime = DateTime.Now;                }                else                {                    Finish();                }                return true;            }            return base.OnKeyDown(keyCode, e);        }    }}

功能很简单，就不解释了。请参照：http://www.cnblogs.com/weizilong/archive/2013/08/15/3259452.html

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