Backgroundworker 不会在单独的窗口中更新进度条

Question

我让它在 Indeterminate 模式下工作，但想显示实际进度。

当我尝试从 BackgroundWorker 中更新时，我收到错误消息“调用线程无法访问此对象，因为不同的线程拥有它。”但是，我看到的示例似乎正在做我想做的事情。大多数教程在主窗口中使用进度条，我希望在操作发生时出现一个单独的窗口。这是.Net 4

进度条窗口

<Window x:Class="WpfTest.ProgressBarPopup"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="ProgressBarPopup" Height="100" Width="300">
    <Grid Margin="20">
        <ProgressBar Minimum="0" Maximum="100" Height="20" x:Name="UpdateProgress" Value="10" IsIndeterminate="False" />
        <!-- {Binding Path=PercentDone}-->
    </Grid>
</Window>

后面的代码：

namespace WpfTest
{
    /// <summary>
    /// Interaction logic for ProgressBarPopup.xaml
    /// </summary>
    public partial class ProgressBarPopup : Window
    {
        public ProgressBarPopup()
        {
            InitializeComponent();
            UpdateProgress.Value = 60;
        }
    }
}

主窗口： （我删除了一些关于 ObservableCollection 的内容以整理代码。）

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel; // for background task
using System.Threading;    // for thread.sleep

namespace WpfTest
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {    
        ProgressBarPopup bar = new ProgressBarPopup();

        bool barExists = true;

        public MainWindow()
        {
            InitializeComponent();    
        }

        private void Progress_Click(object sender, RoutedEventArgs e)
        {
            if (!barExists)
            {
                bar = new ProgressBarPopup();
                barExists = false;
            }

            bar.Show();
#if true
            BackgroundWorker worker = new BackgroundWorker();
            worker.DoWork += new DoWorkEventHandler(worker_DoWork);
            worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunCompleted);

            worker.RunWorkerAsync();
#else       
            // this simple method of doing work in foreground doesn't work with progress bars
            for (int i = 0; i < 50; i++)
            {
                Thread.Sleep(100);
            }
            bar.Hide();
            bar.Close();  // need to clean up
#endif
        }

        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker worker = sender as BackgroundWorker;
            for (int i = 0; i < 50; i++)
            {
                bar.UpdateProgress.Value = i*2;       //  <<<=== gives Error here 
                Thread.Sleep(100);
            }
        }

        void worker_RunCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            bar.Hide();
            bar.Close();
            barExists = false;
        }
    }
}

Answer 1

您无法从 DoWork() 方法访问 UI 线程，因为该方法中的代码在单独的线程上运行。您必须为此使用BackgroundWorker.ProgressChanged 事件和BackgroundWorker.ReportProgress 方法...

Answer 2

您将不得不像这样调用控件。表单控件在自己的线程上运行。由于后台工作人员单独运行，它没有足够的权限来访问该控件。请查看 MethodInvoker 以将您的控件与后台工作人员分开。

void worker_RunCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
           _RunCompleted();
        }


private void _RunCompleted(){
MethodInvoker action = delegate
            {
           bar.Hide();
            bar.Close();
            barExists = false;
};
}