进度条未使用 BackgroundWorker 更新

Question

我正在尝试读取文件并在屏幕上显示进度。它应该显示在 Progress Bar（进度）和文本框（progress_text）上。

这是我正在使用的代码：

public partial class MainWindow : Window
{
    public static List<String> file = new List<String>();
    public long currentPosition = 0;
    String line;
    long length;
    public BackgroundWorker worker = new BackgroundWorker();


    public MainWindow()
    {
        InitializeComponent();

        worker.WorkerReportsProgress = true;
        worker.DoWork += worker_DoWork;
        worker.ProgressChanged += worker_ProgressChanged;
    }

    private void Start(object sender, RoutedEventArgs e)
    {
        worker.RunWorkerAsync();
    }

    void worker_DoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker bg = sender as BackgroundWorker;

        Dispatcher.Invoke(() =>
        {
            progress.Minimum = 0;
            progress.Maximum = 100;

            FileInfo fi = new FileInfo(upload.Text);
            length = fi.Length;

            int percent;


            using (StreamReader sr = new StreamReader(upload.Text, System.Text.Encoding.ASCII))
            {
                while (sr.EndOfStream == false)
                {
                    line = sr.ReadLine();
                    file.Add(line);
                    currentPosition += line.Count();

                    percent = (int)(100.0 / length * currentPosition);
                    bg.ReportProgress(percent);
                }
            }
        });
    }

    void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        progress.Value = e.ProgressPercentage;
        progress_text.Text = "reading " + currentPosition + " out of " + length;
    }
}

XAML:

<Window x:Class="ProgressBarUploadFile.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525"
    >
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="20*"/>
        <RowDefinition Height="20*"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="20*"/>
        <ColumnDefinition Width="20*"/>
    </Grid.ColumnDefinitions>
    <Button Grid.Row="0" Grid.Column="0" Content="Select File" FontSize="15" Click="Upload_file"/>
    <TextBox x:Name="upload" Grid.Row="0" Grid.Column="1" Text="" />
    <Button Grid.Row="1" Grid.Column="0" Content="Start upload" FontSize="15" Click="Start"/>
    <ProgressBar Name="progress" Grid.Row="1" Grid.Column="1" />
    <TextBlock Name="progress_text" Grid.Row="1" Grid.Column="1" VerticalAlignment="Bottom"/>
</Grid>

当我运行它处于调试状态时，它似乎可以正常工作。但是进度条和文本框只有在文件完全读取后才会更新。

我遵循了一些教程，例如：

https://msdn.microsoft.com/en-us/library/cc221403%28v=vs.95%29.aspx?f=255&MSPPError=-2147217396

http://www.wpf-tutorial.com/misc-controls/the-progressbar-control/

可是我想不通..

我觉得是个很小的东西，但是找不到。

谢谢！

Answer 1

试试这个代码：

private void Start(object sender, RoutedEventArgs e)
    {
 progress.Minimum = 0;
            progress.Maximum = 100;
        worker.RunWorkerAsync();
    }



BackgroundWorker bg = sender as BackgroundWorker;
            FileInfo fi = new FileInfo(@"File");
            length = fi.Length;

            int percent;


            using (StreamReader sr = new StreamReader(@"File", System.Text.Encoding.ASCII))
            {
                while (sr.EndOfStream == false)
                {
                    line = sr.ReadLine();
                    file.Add(line);
                    currentPosition += line.Count();

                    percent = (int)(currentPosition / length) * 100;
                    bg.ReportProgress(percent);
                    Thread.Sleep(100);
                }
            }

Answer 2

你的代码有这个问题：

(int)(a / b) * 100会先计算出a/b再转换成int再转换成*100，所以在a到达b之前， a/b 将始终为 0.*，(int)(a/b) 将始终为 0，因此最终值 0*100 将始终为 0。

突然当a=b然后(int)(a/b)变成1最后的值变为100。这就是为什么你的进度条在文件被完全读取之前不会更新

所以，你应该使用 percent = (int)(currentPosition * 100 / length);

或@jmc 在评论中建议：使用percent = (int)(100.0 / length * currentPosition);

进度条未使用 BackgroundWorker 更新

Progress Bar not updating using BackgroundWorker

c#

wpf

progress-bar