WP7开发中自定义事件的处理

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，系统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>
 /// <paramname="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：

<Gridx:Name="ContentPanel"Grid.Row="1"Margin="12,0,12,0">
<ButtonContent="测试网络"Height="72"HorizontalAlignment="Left"Margin="143,105,0,0"Name="button1"VerticalAlignment="Top"Width="202"Click="button1_Click"/>
<TextBlockHeight="50"HorizontalAlignment="Left"Margin="96,270,0,0"Name="textBlock1"Text="网络的状态："VerticalAlignment="Top"Width="126"/>
<TextBlockHeight="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();
 }
privatevoid button1_Click(object sender, RoutedEventArgs e)
 {
 NetTask netTask = new NetTask();
 netTask.OnStateChanged += OnStateChanged;
 netTask.NetTaskName = "测试网络";
 netTask.StartNetTask("http://www.cnblogs.com");
 }
publicvoid 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：