在WPF BackgroundWorker的更新进度 [英] Update progressbar from a backgroundworker in WPF

问题描述

我试图使用的BackgroundWorker 来做出提前进度。最终的目标是展示一个背景搜索的进步，但我首先要了解做一个简单的模拟进度条。这是代码：

I'm trying to make a progressbar advance using a BackgroundWorker. The final goal is to show the progress of a background search, but I first want to get to know the progress bar by doing a simple simulation. This is the code:

    public MainWindow()
    {
        InitializeComponent();

        worker = new BackgroundWorker(); // variable declared in the class
        worker.WorkerReportsProgress = true;
        worker.DoWork += new DoWorkEventHandler(worker_DoWork);
        worker.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
        worker.RunWorkerCompleted += worker_RunWorkerCompleted;
    }

    private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        this.Title += " DONE";
    }

    private void worker_DoWork(object sender, DoWorkEventArgs e)
    {
        for(int j = 0; j <= 100; j++)
        {
            worker.ReportProgress(j);
            Title += j.ToString();
            Thread.Sleep(50);
        }
    }

    void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        searchProgressBar.Value = e.ProgressPercentage;
    }

但是当我运行它，它会跳过对末端，而不会改变进度以任何方式。当我调试它一步一步，最后一步，我得到的就是 worker.ReportProgress（J）; ，则控制返回给程序和 worker_RunWorkerCompleted 被调用。为什么呢？

But when I run it, it skips right to the end, without altering the progressbar in any way. When I debug it step-by-step, the last step I get to is worker.ReportProgress(j);, then control returns to the program and worker_RunWorkerCompleted is called. Why?

推荐答案

如果你想修改 UI内容，你应该把 UI调度呼叫。您不能从后台线程修改UI对象。

In case you trying to change the UI content, you should put the calls on UI Dispatcher. You can't modify UI objects from background thread. Replace your lines with these -

App.Current.Dispatcher.Invoke((Action)delegate()
        {
            Title += j.ToString();
        });

和

App.Current.Dispatcher.Invoke((Action)delegate()
        {
            Title = "Done";
        });

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