DrawString图形消失

Question

我正在尝试按照概述 here and here 在进度条上绘制一个字符串。进度条位于我的选项卡控件中的一系列选项卡页面之一。

这是我的代码：

int percent = 55;
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)));
}

没用。摆弄计时器后：

this.timer1.Enabled = true;
this.timer1.Tick += new System.EventHandler(this.timer1_Tick);

private void timer1_Tick(object sender, EventArgs e)
{
    progressBar1.PerformStep();
    System.Threading.Thread.Sleep(100);
    progressBar1.Refresh();
    int percent = (int)(((double)(progressBar1.Value - progressBar1.Minimum) / (double)(progressBar1.Maximum - progressBar1.Minimum)) * 100);
    progressBar1.CreateGraphics().DrawString(percent.ToString() + "%", new Font("Arial", (float)8.25, FontStyle.Regular), Brushes.Black, new PointF(progressBar1.Width / 2 - 10, progressBar1.Height / 2 - 7));
}

还有一些简单的：

private void button1_Click(object sender, EventArgs e)
{
    DrawProgress(); //this just calls the a method to do the DrawString
}

我发现它确实绘制了字符串，但在切换到另一个选项卡并返回后，字符串不再是 visible/there。

我什至将 "gr" 切换为 "progressBar1.CreateGraphics()" 并删除了 "using" 语句以查看它是否只是处理字符串，但即使使用：

progressBar1.CreateGraphics().DrawString(percent.ToString() + "%", SystemFonts.DefaultFont, Brushes.Black, new PointF(progressBar1.Width / 2 - (progressBar1.CreateGraphics().MeasureString(percent.ToString() + "%", SystemFonts.DefaultFont).Width / 2.0F), progressBar1.Height / 2 - (progressBar1.CreateGraphics().MeasureString(percent.ToString() + "%", SystemFonts.DefaultFont).Height / 2.0F)));

我也遇到了同样的问题

Answer 1

我认为，最好的解决方案是：您应该从 ProgressBar 派生并实现您自己的 Paint 处理程序。

这里有一个例子：（已测试）

// Custom paint progressbar
public class ProgressBarWithTitle : ProgressBar
{
    private Brush _barBrush;


    public ProgressBarWithTitle()
    {
        this.SetStyle(ControlStyles.UserPaint, true);
        this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);

        _barBrush = new SolidBrush(this.ForeColor);

    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        var rect = new RectangleF(0, 0, (float)(this.Width * (Value - Minimum) / Maximum), this.Height);
        e.Graphics.FillRectangle(_barBrush, rect);

        var valueString = base.Value.ToString() + "%";

        var textSize = e.Graphics.MeasureString(valueString, SystemFonts.DefaultFont);

        e.Graphics.DrawString(
            valueString,
            SystemFonts.DefaultFont,
            Brushes.Black,
            new PointF(
                (Width / 2) - ((int)textSize.Width / 2),
                (Height / 2) - ((int)textSize.Height / 2)));
    }


}

唯一的问题是，您必须自己绘制进度条。

DrawString图形消失

DrawString graphics dissappearing

c#

graphics

drawstring