[英]updating UI thread using BackGroundWorker in C# Form application
我有一個耗時的任務,需要測試幾個網絡連接。 在下面的示例中,我將其限制為一個連接。 通常,連接會快速返回,但是可能會發生無法建立連接從而導致套接字超時的情況。 在此期間,我想在表單中顯示一個“ idler” gif,當連接成功時,應用程序應將“表單”中的“圖像”更改為一些綠色復選圖標,或者在連接失敗的情況下,將紅色圖標“ stopper”更改為顯示。
不知何故,我無法使惰輪gif變得可見並具有動畫效果。 要模擬失敗的連接,可以輸入無效的端口號或不存在的地址。
有什么線索我想念或做錯了什么嗎?
partial class Form1
{
/// <summary>
/// Required designer variable.
/// </summary>
///
#region BackgroundWorker
private System.ComponentModel.BackgroundWorker backgroundWorker = new System.ComponentModel.BackgroundWorker();
private delegate void SomeLongRunningMethodHandler(object sender, EventArgs e);
#endregion
private System.ComponentModel.IContainer components = null;
Button button,button2;
static Socket socket;
static bool success;
private static bool done;
private Label lbl1;
private Label lbl2;
private TextBox address;
private TextBox port;
private PictureBox p;
private static String port_number,host;
/// <summary>
/// Clean up any resources being used.
/// </summary>
/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
private void RunTest(object o,EventArgs e)
{
p.Visible = true;
SomeLongRunningMethodHandler synchronousFunctionHandler =
default(SomeLongRunningMethodHandler);
synchronousFunctionHandler =
TestConnection;
synchronousFunctionHandler.Invoke(o, e);
}
private void TestConnection(object o, EventArgs e)
{
host = address.Text;
port_number = port.Text;
if (null != socket)
{
socket.Close();
}
Thread.Sleep(1000);
IPEndPoint myEndpoint = new IPEndPoint(0, 0);
IPHostEntry remoteMachineInfo = Dns.GetHostEntry(host);
IPEndPoint serverEndpoint = new IPEndPoint(remoteMachineInfo.AddressList[0],
int.Parse(port_number));
socket = new Socket(myEndpoint.Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
try
{
socket.Connect(serverEndpoint);
success = true;
p.Image = global::BlockingUI.Properties.Resources.accept;
}
catch
{
success = false;
p.Image = global::BlockingUI.Properties.Resources.stopper;
}
done = true;
}
private void ExitApp(object o, EventArgs e)
{
Application.Exit();
}
}
如果您確實想使用BackgroundWorker
,那么它(或接近它的東西)應該為您指明正確的方向。 您正在創建BackgroundWorker
對象,但是對此不執行任何操作。 不允許BackgroundWorker
對象訪問UI元素,因為它們是UI線程所擁有的,但是您可以傳遞UI值,就像我在此處使用Tuple
(如果需要,您也可以創建自己的類來保存這些值),並且然后在工作程序完成后從UI線程修改UI。
private struct ConnectionProperties
{
public string Address;
public string Port;
}
private void RunTest(object o, EventArgs e)
{
BackgroundWorker worker = new System.ComponentModel.BackgroundWorker();
worker.RunWorkerCompleted += TestComplete;
worker.DoWork += TestConnection;
p.Visible = true;
//worker.RunWorkerAsync(new Tuple<string, string>(address.Text, port.Text));
worker.RunWorkerAsync(new ConnectionProperties{ Address = address.Text, Port = port.Text });
}
private void TestConnection(object sender, DoWorkEventArgs e)
{
bool success = false;
//var connection = e.Argument as Tuple<string, string>;
var connection = (ConnectionProperties)e.Argument;
if (null != socket)
{
socket.Close();
}
Thread.Sleep(1000);
IPEndPoint myEndpoint = new IPEndPoint(0, 0);
IPHostEntry remoteMachineInfo = Dns.GetHostEntry(connection.Address);
IPEndPoint serverEndpoint = new IPEndPoint(remoteMachineInfo.AddressList[0],
int.Parse(connection.Port));
socket = new Socket(myEndpoint.Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
try
{
socket.Connect(serverEndpoint);
success = true;
}
catch
{
success = false;
}
e.Result = success;
}
// Define other methods and classes here
private void TestComplete(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error == null)
{
var success = (bool)e.Result;
if (success)
{
p.Image = global::BlockingUI.Properties.Resources.accept;
}
else
{
p.Image = global::BlockingUI.Properties.Resources.stopper;
}
}
else
{
//unexpected error, show message or whatever
}
}
好吧,我是用自己的線程完成的。 通常,您使用長時間運行的任務運行線程,並在需要時調用Control.Invoke()並使用一個指向將在UI上運行的函數的委托。 看來您正在使用后台工作線程更改UI,這是不允許的。
此外,在Winforms中,必須調用Control.Invalidate()來強制重新繪制UI並顯示新圖標。
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