Windows Phone 7 自定义事件

  在windows phone的应用开发里面，对于事件这种东西我们可以随处可见，本来就已经封装好了各种各样的事件机制，如按钮的单击事件等等的。在实际的开发中，我们需要自己去给相关的类自定义一些事件来满足业务的要求，特别在使用观察着模式的时候，在wp7中利用事件去实现是理所当然的。
    自定义事件步骤有下面的几个步骤：
1、继承eventargs类实现自己自定义的事件参数；
2、定义一个委托；
3、定义一个事件
4、添加事件。
下面来看一下一个demo对自定义事件的实现，这个demo只是对网络请求的状态进行一个简单的事件监控的调用处理：
自定义的事件参数类
statechangedeventargs.cs
using system;

namespace eventdemo
{
    /// <summary>
    /// 状态事件
    /// </summary>
    public class statechangedeventargs : eventargs
    {
        public readonly string newstate;
        public readonly datetime timestamp;

        public statechangedeventargs(string newstate)
        {
            this.newstate = newstate;
            this.timestamp = datetime.now;
        }
    }
}

在业务类里面定义事件：
nettask.cs
using system;
using system.net;
using system.threading;
using system.io;

namespace eventdemo
{
    public class nettask
    {
        //定义委托
        public delegate void statechanged(nettask sender, statechangedeventargs args);
        //定义事件
        public event statechanged onstatechanged;
        //出事状态
        public string nettaskname = "";

        /// <summary>
        /// 网络任务
        /// </summary>
        /// <param name="url"></param>
        public void startnettask(string url)
        {
            bool success = false;
            int attempt = 0;
            while (attempt < 3)
            {
                asynccallback callback = null;
                //开启线程等待
                manualresetevent webrequestwait = new manualresetevent(false);
                uri targeturi = new uri(url);
                httpwebrequest request = (httpwebrequest)webrequest.create(targeturi);
                request.method = "post";
                if (callback == null)
                {
                    callback = delegate(iasyncresult asrequest)
                    {
                        try
                        {
                            success = true;
                            webrequestwait.set();
                            //……
                        }
                        catch
                        {
                            onstatechanged(this, new statechangedeventargs("重试"));
                            webrequestwait.set();
                        }
                    };
                }
                request.begingetrequeststream(callback, request);

                //等待线程结束
                webrequestwait.waitone();
                if (success)
                {
                    break;
                }
                attempt++;
                thread.sleep(1000);
            }
            if (success)
            {
                onstatechanged(this, new statechangedeventargs("成功"));
                thread.sleep(50);
            }
            else
            {
                onstatechanged(this, new statechangedeventargs("失败"));
            }
        }
    }
}
 

简单的测试一下
        <grid x:name="contentpanel" grid.row="1" margin="12,0,12,0">
            <button content="测试网络" height="72" horizontalalignment="left" margin="143,105,0,0" name="button1" verticalalignment="top" width="202" click="button1_click" />
            <textblock height="50" horizontalalignment="left" margin="96,270,0,0" name="textblock1" text="网络的状态：" verticalalignment="top" width="126" />
            <textblock height="48" horizontalalignment="left" margin="34,326,0,0" name="textblock2" text="" verticalalignment="top" width="377" />
        </grid>

mainpage.xaml.cs
using system.windows;
using microsoft.phone.controls;

namespace eventdemo
{
    public partial class mainpage : phoneapplicationpage
    {
        public mainpage()
        {
            initializecomponent();
        }

        private void button1_click(object sender, routedeventargs e)
        {
            nettask nettask = new nettask();
            nettask.onstatechanged += onstatechanged;
            nettask.nettaskname = "测试网络";
            nettask.startnettask("");
        }

        public void onstatechanged(object sender, statechangedeventargs e)
        {
            nettask temp = sender as nettask;
            textblock2.text = temp.nettaskname + "," + e.newstate+","+e.timestamp.tolongtimestring();
        }
    }
}

 运行的效果如下：

  


摘自  linzheng