Windows Phone 7 自訂事件

     在Windows Phone的應用開發裡面，對於事件這種東西我們可以隨處可見，系統本來就已經封裝好了各種各樣的事件機制，如按鈕的單擊事件等等的。在實際的開發中，我們需要自己去給相關的類自訂一些事件來滿足業務的要求，特別在使用觀察著模式的時候，在wp7中利用事件去實現是理所當然的。

    自訂事件步驟有下面的幾個步驟：

1、繼承EventArgs類實現自己自訂的事件參數；

2、定義一個委託；

3、定義一個事件

4、添加事件。

下面來看一下一個Demo對自訂事件的實現，這個Demo只是對網路請求的狀態進行一個簡單的事件監控的調用處理：

自訂的事件參數類

StateChangedEventArgs.cs

using System;

namespace EventDemo
{
/// <summary>
/// 狀態事件
/// </summary>
    public class StateChangedEventArgs : EventArgs
    {
public readonly string NewState;
public readonly DateTime Timestamp;

public StateChangedEventArgs(string newstate)
        {
this.NewState = newstate;
this.Timestamp = DateTime.Now;
        }
    }
}

在業務類裡面定義事件：

NetTask.cs

using System;
using System.Net;
using System.Threading;
using System.IO;

namespace EventDemo
{
public class NetTask
    {
//定義委託
        public delegate void StateChanged(NetTask sender, StateChangedEventArgs args);
//定義事件
        public event StateChanged OnStateChanged;
//出事狀態
        public string NetTaskName = "";

/// <summary>
/// 網路任務
/// </summary>
/// <param name="url"></param>
        public void StartNetTask(string url)
        {
bool success = false;
int attempt = 0;
while (attempt < 3)
            {
                AsyncCallback callback = null;
//開啟線程等待
                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("重試"));
                            webRequestWait.Set();
                        }
                    };
                }
                request.BeginGetRequestStream(callback, request);

//等待線程結束
                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("失敗"));
            }
        }
    }
}

簡單的測試一下

        <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<Button Content="測試網路" 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="網路的狀態：" 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 = "測試網路";
            netTask.StartNetTask("http://www.cnblogs.com");
        }

public void OnStateChanged(object sender, StateChangedEventArgs e)
        {
            NetTask temp = sender as NetTask;
            textBlock2.Text = temp.NetTaskName + "," + e.NewState+","+e.Timestamp.ToLongTimeString();
        }
    }
}

 啟動並執行效果如下：