在WPF上，ProgressBar值正在改变，但gui没有改变
本文关键字：改变 gui WPF ProgressBar | 更新日期: 2023-09-27 18:05:47
我正在尝试实现一个ProgressBar，它将在文件传输期间显示。
文件传输是通过BackgroundWorker完成的。
只是为了检查功能，我试图从主线程取得进展，但什么也没发生。
代码:
myProgressBar.Minimum = 0;
myProgressBar.Maximum = numOfPackets;
这是后台工作代码…
然后:
myProgressBar.IsEnabled = true;
for (int i = 0; i < buff.Length; i++)
{
myProgressBar.Value = i;
myProgressBar.UpdateDefaultStyle();
}
为什么什么都没变?
在后台线程上做IO或文件传输是非常糟糕的，因为在文件传输或IO操作期间CPU没有被使用，所以你的后台线程除了等待IO完成之外什么都不做，你浪费了一个线程，这反过来又导致内存的浪费。另一个缺点是你的UI将变得无响应文件传输需要相当多的时间，即使你在后台线程上做它。
我可以继续写在后台线程上做IO工作的缺点，但你应该要求一个关于在异步中做IO的文档。网后台线程用于CPU密集型工作，比如一些涉及CPU的繁重计算。
你应该使用异步IO。使用async和await。请阅读异步IO。我有一个例子，无论你是做纯异步IO与进度条和响应式UI。我明天写。
* *下面是异步io文件传输代码，假设用于进度更新的所有文件大小相同下面提到的代码将工作和应用程序不会挂起，即使你移动窗口，而文件正在传输。* *
MainWindow.xaml
<Window x:Class="asyncawait.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="514" Width="674">
<Grid Margin="0,0,0,4">
<ScrollViewer Name="scrv_Log" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto" HorizontalAlignment="Left" Width="397" Margin="33,61,0,67">
<ListBox VirtualizingPanel.VirtualizationMode="Recycling" ItemsSource="{Binding Datas,Mode=OneWay}" Background="White" Foreground="Red"/>
</ScrollViewer>
<TextBlock Height="40" Width="70" FontSize="10" Foreground="Green" Text="{Binding FileCounter,Mode=OneWay}" Margin="540,281,56,158"></TextBlock>
<Button Foreground="Black" IsEnabled="{Binding IsButtonEnabled}" Click="Button_Click" Height="40" Width="40" RenderTransformOrigin="4.65,0.425" Margin="540,210,86,229"></Button>
<ProgressBar Value="{Binding Progressvalue,Mode=OneWay}" Name="prg" Foreground="Green" Height="20" Width="600" Margin="23,453,44.2,7"></ProgressBar>
<Label Content="{Binding ElementName=prg,Path=Value}" ContentStringFormat="{}{0}%" Height="25" Margin="253,0,295.2,22" VerticalContentAlignment="Center" VerticalAlignment="Bottom"/>
<TextBox Background='AliceBlue' HorizontalAlignment="Left" Height="23" Margin="525,109,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="97"/>
</Grid>
</Window>
****下面是执行异步IO的代码**
public partial class MainWindow: Window,INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
this.DataContext = this;
}
public double Progressvalue
{
get
{
return _Progressvalue;
}
set
{
if(value!=_Progressvalue)
{
_Progressvalue=value;
OnPropertyChanged();
}
}
}
private Double _Progressvalue=0;
private bool _IsEnabled=true;
public Boolean IsButtonEnabled {
get
{
return _IsEnabled;
}
set
{
if(value!=_IsEnabled)
{
_IsEnabled = value;
OnPropertyChanged();
}
}
}
private async void Button_Click(object sender, RoutedEventArgs e)
{
IsButtonEnabled = false;
await AsyncTransferFiles();
IsButtonEnabled = true;
scrv_Log.ScrollToBottom();
}
private String fileCounter;
public String FileCounter
{
get
{ return fileCounter; }
set
{
if (value != fileCounter)
{
fileCounter = value;
OnPropertyChanged();
}
}
}
private ObservableCollection<String> _Datas = new ObservableCollection<string>();
public ObservableCollection<String> Datas
{
get
{
return _Datas;
}
}
private async Task AsyncTransferFiles()
{
var fileNames = Directory.GetFiles("C:''Data1").ToList();
int totalCount = fileNames.Count;
pr = (double)1 / totalCount;
int counter = 0;
var progress = new Progress<double>();
progress.ProgressChanged += (sender, e) =>
{
Progressvalue = Double.Parse(e.ToString());
};
foreach (var fileName in fileNames)
{
await (CopyFileAsync(fileName, "C:''GradebookTemp1''" + fileName.Split('''')[2], progress, ++counter));
}
}
double pr = 0.0;
public async Task CopyFileAsync(string sourcePath, string destinationPath,IProgress<double> progress ,int fileCounter)
{
using (Stream source = File.Open(sourcePath,FileMode.Open))
{
using (Stream destination = File.Create(destinationPath))
{
await source.CopyToAsync(destination);
progress.Report((int)(pr*fileCounter*100));
FileCounter = fileCounter.ToString();
Datas.Add("Copied File: " + sourcePath);
scrv_Log.ScrollToBottom();
}
}
}
private void EnableButton()
{
IsButtonEnabled = true;
}
private void OnPropertyChanged([CallerMemberName] String propertyName=null)
{
var handler = PropertyChanged;
if(null!=handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
这个解决方案曾经对我有效:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void button_Click(object sender, RoutedEventArgs e)
{
for (int i = 0; i < 100; i++)
{
progBar.Value = i;
progBar.Refresh();
Thread.Sleep(10);
}
}
}
public static class ExtensionMethods
{
private static Action EmptyDelegate = delegate () { };
public static void Refresh(this UIElement uiElement)
{
uiElement.Dispatcher.Invoke(DispatcherPriority.Render, EmptyDelegate);
}
}
我的相关示例- xaml基本上包含:
<Grid>
<ProgressBar x:Name="progBar" HorizontalAlignment="Left" Height="10" Margin="116,175,0,0" VerticalAlignment="Top" Width="100"/>
<Button x:Name="button" Content="Button" HorizontalAlignment="Left" Margin="156,51,0,0" VerticalAlignment="Top" Width="75" Click="button_Click"/>
</Grid>
但是我认为这对于理解是没有必要的-我认为你已经明白了代码的意思，它是非常自我描述的
对于wpf，可以这样使用:
this.Dispacher.BeginInvoke(new Action(()=> { for(int i...)...; }));
Just Refresh The Control:
myProgressBar.Refresh();