转载:http://blog.csdn.net/fhbcn/archive/2011/01/28/6167504.aspx
单线程的winfom程序中,设置一个控件的值是很easy的事情,直接 this.TextBox1.value = "Hello World!";就搞定了,但是如果在一个新线程中这么做,比如:
private void btnSet_Click(object sender, EventArgs e) { Thread t = new Thread(new ParameterizedThreadStart(SetTextBoxValue)); //当然也可以用匿名委托写成Thread t = new Thread(SetTextBoxValue); t.Start("Hello World"); }
void SetTextBoxValue(object obj) { this.textBox1.Text = obj.ToString(); } 运行时,会报出一个无情的错误: 线程间操作无效: 从不是创建控件“textBox1”的线程访问它。
究其原因,winform中的UI控件不是线程安全的,如果可以随意在任何线程中改变其值,你创建一个线程,我创建一个线程,大家都来抢着更改"TextBox1"的值,没有任何秩序的话,天下大乱...
解决办法: 1.掩耳盗铃法(Control.CheckForIllegalCrossThreadCalls = false;)--仅Winform有效
using System; using System.Threading; using System.Windows.Forms;
namespace ThreadTest { public partial class Form1 : Form {
public Form1() { InitializeComponent(); Control.CheckForIllegalCrossThreadCalls = false;//这一行是关键 }
private void btnSet_Click(object sender, EventArgs e) { Thread t = new Thread(new ParameterizedThreadStart(SetTextBoxValue)); t.Start("Hello World"); }
void SetTextBoxValue(object obj) { this.textBox1.Text = obj.ToString(); } } } 设置Control.CheckForIllegalCrossThreadCalls为false,相当于不检测线程之间的冲突,允许各路线程随便乱搞,当然最终TextBox1的值到底是啥难以预料,只有天知道,不过这也是最省力的办法
2.利用委托调用--最常见的办法(仅WinForm有效)
using System; using System.Threading; using System.Windows.Forms;
namespace ThreadTest { public partial class Form1 : Form { delegate void D(object obj);
public Form1() { InitializeComponent(); }
private void btnSet_Click(object sender, EventArgs e) { Thread t = new Thread(new ParameterizedThreadStart(SetTextBoxValue)); t.Start("Hello World"); }
void SetTextBoxValue(object obj) { if (textBox1.InvokeRequired) { D d = new D(); textBox1.Invoke(d,obj);
} else { this.textBox1.Text = obj.ToString(); } }
void DelegateSetValue(object obj) { this.textBox1.Text = obj.ToString(); } } } 3.利用SynchronizationContext上下文 -- 最神秘的方法(Winform/Silverlight能用)
之所以说它神秘,是因为msdn官方对它的解释据说也是不清不楚
using System; using System.Threading; using System.Windows.Forms;
namespace ThreadTest { public partial class Form1 : Form { public Form1() { InitializeComponent(); }
private void btnSet_Click(object sender, EventArgs e) { Thread t = new Thread(new ParameterizedThreadStart(Run)); MyPram _p = new MyPram() { context = SynchronizationContext.Current, parm = "Hello World" }; t.Start(_p); }
void Run(object obj) { MyPram p = obj as MyPram; p.context.Post(SetTextValue, p.parm); }
void SetTextValue(object obj) { this.textBox1.Text = obj.ToString(); } }
public class MyPram { public SynchronizationContext context { set; get; } public object parm { set; get; } } } 4.利用BackgroundWorker --最偷懒的办法(Winform/Silverlight通用)
BackgroundWorker会在主线程之外,另开一个后台线程,我们可以把一些处理放在后台线程中处理,完成之后,后台线程会把结果传递给主线程,同时结束自己。
using System; using System.ComponentModel; using System.Windows.Forms;
namespace ThreadTest { public partial class Form1 : Form { public Form1() { InitializeComponent(); }
private void btnSet_Click(object sender, EventArgs e) { //MessageBox.Show(Thread.CurrentThread.ManagedThreadId.ToString()); using (BackgroundWorker bw = new BackgroundWorker()) { bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted); bw.DoWork += new DoWorkEventHandler(bw_DoWork); bw.RunWorkerAsync("Hello World"); } }
void bw_DoWork(object sender, DoWorkEventArgs e) { //MessageBox.Show(Thread.CurrentThread.ManagedThreadId.ToString()); e.Result = e.Argument;//这里只是简单的把参数当做结果返回,当然您也可以在这里做复杂的处理后,再返回自己想要的结果(这里的操作是在另一个线程上完成的) }
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { //这时后台线程已经完成,并返回了主线程,所以可以直接使用UI控件了 this.textBox1.Text = e.Result.ToString(); //MessageBox.Show(Thread.CurrentThread.ManagedThreadId.ToString()); } } } 5.Dispatcher.BeginInvoke--Silverlight的独门秘籍
代码 using System.Threading; using System.Windows.Controls; using System.Windows.Input;
namespace ThreadTest { public partial class MainPage : UserControl { public MainPage() { InitializeComponent(); }
private void LayoutRoot_MouseLeftButtonDown(object sender, MouseButtonEventArgs e) { Thread t = new Thread(SetTextValue); t.Start("Hello World"); }
void SetTextValue(object text) { this.Dispatcher.BeginInvoke(() => { this.txt.Text = text.ToString(); }); } } }
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