c# - c#中进度条上的文字

Question

我正在使用以下代码。

为什么它不能正常运行？

private void Form1_Shown(object sender, EventArgs e)
{
    for (int i = 1; i <= 100; i++)
    {
        Application.DoEvents();
        Thread.Sleep(200);

        progressBar1.Refresh();
        progressBar1.Value = i;
        progressBar1.CreateGraphics().DrawString(i.ToString() + "%",
            new Font("Arial", (float)8.25, FontStyle.Regular),
            Brushes.Black, new PointF(progressBar1.Width / 2 - 10,
                progressBar1.Height / 2 - 7));


    }
}

更新 ：

为什么不总是显示文字？

Answer 1

这行得通——尽管我将线程睡眠设置为超过 200 毫秒。您的问题是您在 UI 线程中完成了工作，因此它永远不会更新。为了更好的可见性，只需更改字体颜色：

 private void Form1_Load(object sender, EventArgs e)
{
  Task t = new Task(() => StartUpdate());
  t.Start();

  t.ContinueWith(task => Console.WriteLine("Done loading"));
}

 private void StartUpdate()
{
  for (int i = 1; i <= 100; i++)
  {
    UpdateProgressBar(i);
  }
}

private void UpdateProgressBar(int i)
{
  if (progressBar1.InvokeRequired)
  {
    progressBar1.Invoke(new Action<int>(UpdateProgressBar), new Object[] { i });
  }
  else
  {
    Thread.Sleep(200);
    progressBar1.Refresh();
    progressBar1.Value = i;
    progressBar1.CreateGraphics().DrawString(i.ToString() + "%", new Font("Arial",
                                          (float)10.25, FontStyle.Bold),
                                          Brushes.Red, new PointF(progressBar1.Width / 2 - 10, progressBar1.Height / 2 - 7));
  }
} 

Answer 2

用这个。有很好的方法可以做到这一点，但你的问题是它为什么不起作用，这是因为 Application.DoEvents();

    private void Main_Shown(object sender, EventArgs e)
    {
        for (int i = 1; i <= 100; i++)
        {
            progressBar1.Value = i;
            int percent = (int)(((double)(progressBar1.Value -progressBar1.Minimum) / (double)(progressBar1.Maximum - progressBar1.Minimum)) * 100);
            using (Graphics gr = progressBar1.CreateGraphics())
            {
                gr.DrawString(percent.ToString() + "%",  SystemFonts.DefaultFont, Brushes.Black, new PointF(progressBar1.Width / 2 - (gr.MeasureString(percent.ToString() + "%", SystemFonts.DefaultFont).Width / 2.0F), progressBar1.Height / 2 - (gr.MeasureString(percent.ToString() + "%", SystemFonts.DefaultFont).Height / 2.0F)));
            }
            System.Threading.Thread.Sleep(200);
        }
    }