如何解决从后台线程问题更新UI
| 我正在编写一个类来移动和复制文件。当前文件进度和总进度更改时，我正在引发事件。当我在XP机器上测试代码时，它可以正常工作，但是当我在Windows 7 64位机器上运行它时，当前进度无法正确更新UI。当前进度ProgressBar仅获得一半，然后从下一个相同的文件开始。总进度ProgressBar更新正常。任何想法为什么会这样？ 编辑：Windows 7计算机正在运行四核，而XP正在运行双核。不知道这是否会有所作为。我只是一个业余爱好者，请原谅我的无知:) 编辑：添加的代码（背景）using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.IO;
using System.Threading;
using System.Timers;
using Timer = System.Timers.Timer;
namespace nGenSolutions.IO
{
public class FileTransporter
{
#region Delegates
public delegate void CurrentFileChangedEventHandler(string fileName);
public delegate void CurrentProgressChangedEventHandler(int percentComplete);
public delegate void CurrentWriteSpeedUpdatedEventHandler(long bytesPerSecond);
public delegate void TotalProgressChangedEventHandler(int percentComplete);
public delegate void TransportCompleteEventHandler(FileTransportResult result);
#endregion
private readonly List<string> _destinationFiles = new List<string>();
private readonly List<string> _sourceFiles = new List<string>();
private long _bytesCopiedSinceInterval;
private FileTransportResult _result;
private Timer _speedTimer;
private long _totalDataLength;
private BackgroundWorker _worker;
public bool TransportInProgress { get; private set; }
public event CurrentFileChangedEventHandler CurrentFileChanged;
public event CurrentProgressChangedEventHandler CurrentProgressChanged;
public event CurrentWriteSpeedUpdatedEventHandler CurrentWriteSpeedUpdated;
public event TotalProgressChangedEventHandler TotalProgressChanged;
public event TransportCompleteEventHandler TransportComplete;
public void AddFile(string sourceFile,string destinationFile)
{
if (!File.Exists(sourceFile))
throw new FileNotFoundException(\"The specified file does not exist!\",sourceFile);
var fileInfo = new FileInfo(sourceFile);
_totalDataLength += fileInfo.Length;
_sourceFiles.Add(sourceFile);
_destinationFiles.Add(destinationFile);
}
public void BeginTransport()
{
// update the write speed every 3 seconds
_speedTimer = new Timer {Interval = 3000};
_speedTimer.Elapsed += SpeedTimerElapsed;
_worker = new BackgroundWorker();
_worker.DoWork += DoTransport;
_worker.RunWorkerCompleted += WorkerCompleted;
_worker.RunWorkerAsync();
_speedTimer.Start();
TransportInProgress = true;
}
private void SpeedTimerElapsed(object sender,ElapsedEventArgs e)
{
InvokeCurrentSpeedUpdated(_bytesCopiedSinceInterval);
_bytesCopiedSinceInterval = 0;
}
private void WorkerCompleted(object sender,RunWorkerCompletedEventArgs e)
{
TransportInProgress = false;
InvokeTransportComplete(_result);
}
public void CancelTransport(bool rollbackChanges)
{
if (TransportInProgress == false)
throw new InvalidOperationException(\"You tried to stop the transport before you started it!\");
_result = FileTransportResult.Cancelled;
_worker.CancelAsync();
while (_worker.IsBusy)
{
// wait for worker to die an \'orrible death
}
// TODO: rollback changes if requested
}
private void DoTransport(object sender,DoWorkEventArgs e)
{
long totalBytesCopied = 0;
int totalPercentComplete = 0;
for (int i = 0; i < _sourceFiles.Count; i++)
{
string sourceFile = _sourceFiles[i];
string destinationFile = _destinationFiles[i];
long currentFileLength = new FileInfo(sourceFile).Length;
InvokeCurrentFileChanged(sourceFile);
using (var sourceStream = new FileStream(sourceFile,FileMode.Open,FileAccess.Read))
{
using (var destinationStream = new FileStream(destinationFile,FileMode.Create,FileAccess.Write))
{
using (var reader = new BinaryReader(sourceStream))
{
using (var writer = new BinaryWriter(destinationStream))
{
int lastPercentComplete = 0;
for (int j = 0; j < currentFileLength; j++)
{
writer.Write(reader.ReadByte());
totalBytesCopied += 1;
_bytesCopiedSinceInterval += 1;
int current = Convert.ToInt32((j/(double) currentFileLength)*100);
int total = Convert.ToInt32((totalBytesCopied/(double) _totalDataLength)*100);
// raise progress events every 3%
if (current%3 == 0)
{
// only raise the event if the progress has increased
if (current > lastPercentComplete)
{
lastPercentComplete = current;
InvokeCurrentProgressChanged(lastPercentComplete);
}
}
if (total%3 == 0)
{
// only raise the event if the progress has increased
if (total > totalPercentComplete)
{
totalPercentComplete = total;
InvokeTotalProgressChanged(totalPercentComplete);
}
}
}
}
InvokeCurrentProgressChanged(100);
}
}
}
}
InvokeTotalProgressChanged(100);
}
private void InvokeCurrentFileChanged(string fileName)
{
CurrentFileChangedEventHandler handler = CurrentFileChanged;
if (handler == null) return;
handler(fileName);
}
private void InvokeCurrentProgressChanged(int percentComplete)
{
CurrentProgressChangedEventHandler handler = CurrentProgressChanged;
if (handler == null) return;
handler(percentComplete);
}
private void InvokeCurrentSpeedUpdated(long bytesPerSecond)
{
CurrentWriteSpeedUpdatedEventHandler handler = CurrentWriteSpeedUpdated;
if (handler == null) return;
handler(bytesPerSecond);
}
private void InvokeTotalProgressChanged(int percentComplete)
{
TotalProgressChangedEventHandler handler = TotalProgressChanged;
if (handler == null) return;
handler(percentComplete);
}
private void InvokeTransportComplete(FileTransportResult result)
{
TransportCompleteEventHandler handler = TransportComplete;
if (handler == null) return;
handler(result);
}
}
using System;
using System.IO;
using System.Windows.Forms;
using ExtensionMethods;
using nGenSolutions.IO;
namespace TestApplication
{
public partial class ProgressForm : Form
{
public ProgressForm()
{
InitializeComponent();
}
private void ProgressForm_Load(object sender,EventArgs e)
{
var transporter = new FileTransporter();
foreach (string fileName in Directory.GetFiles(\"C:\\\\Temp\\\\\"))
{
transporter.AddFile(fileName,\"C:\\\\\" + Path.GetFileName(fileName));
}
transporter.CurrentFileChanged += transporter_CurrentFileChanged;
transporter.CurrentProgressChanged += transporter_CurrentProgressChanged;
transporter.TotalProgressChanged += transporter_TotalProgressChanged;
transporter.CurrentWriteSpeedUpdated += transporter_CurrentWriteSpeedUpdated;
transporter.TransportComplete += transporter_TransportComplete;
transporter.BeginTransport();
}
void transporter_TransportComplete(FileTransportResult result)
{
Close();
}
void transporter_CurrentWriteSpeedUpdated(long bytesPerSecond)
{
double megaBytesPerSecond = (double)bytesPerSecond/1024000;
currentSpeedLabel.SafeInvoke(x=> x.Text = string.Format(\"Transfer speed: {0:0.0} MB/s\",megaBytesPerSecond));
}
private void transporter_TotalProgressChanged(int percentComplete)
{
totalProgressBar.SafeInvoke(x => x.Value = percentComplete);
}
private void transporter_CurrentProgressChanged(int percentComplete)
{
currentProgressBar.SafeInvoke(x => x.Value = percentComplete);
}
private void transporter_CurrentFileChanged(string fileName)
{
this.SafeInvoke(x => x.Text = string.Format(\"Current file: {0}\",fileName));
}
}
public static void SafeInvoke<T>(this T @this,Action<T> action) where T : Control
{
if (@this.InvokeRequired)
{
@this.Invoke(action,new object[] {@this});
}
else
{
if (!@this.IsHandleCreated) return;
if (@this.IsDisposed)
throw new ObjectDisposedException(\"@this is disposed.\");
action(@this);
}
}
解决方法
好吧，如果transporter_CurrentProgressChanged获取正确的值，则程序可以正常运行。您可以尝试在进度值为100％时向InvokeCurrentProgressChanged（可能带有0参数）添加一些最小的Thread.Sleep调用，以获取UI更新自身的机会，但是在这种情况下，您会降低程序性能。最好不要更改程序，因为它可以按预期工作，并且更新了主进度条。
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