c# - 离开文本框后，透明文本框不显示文本

Question

我为透明文本框创建了这个类

public partial class TransTextBox : TextBox
{
    public TransTextBox()
    {
        SetStyle(ControlStyles.SupportsTransparentBackColor |
                 ControlStyles.OptimizedDoubleBuffer |
                 ControlStyles.AllPaintingInWmPaint |
                 ControlStyles.ResizeRedraw |
                 ControlStyles.UserPaint, true);
        BackColor = Color.Transparent;
    }
}

但是当我离开文本框时，文本消失但仍然存在。如何解决？

Answer 1

您可以做的是删除 ControlStyles.OptimizedDoubleBuffer 标志，然后通过 OnPaint 事件上的 DrawString 重新绘制文本

类似这样的事情:

public partial class TransTextBox : TextBox {
    public TransTextBox() {
        SetStyle(ControlStyles.SupportsTransparentBackColor |
            //ControlStyles.OptimizedDoubleBuffer | //comment this flag out
                         ControlStyles.AllPaintingInWmPaint |
                         ControlStyles.ResizeRedraw |
                         ControlStyles.UserPaint, true);
        BackColor = Color.Transparent;
    }

    private void redrawText() {
        using (Graphics graphics = this.CreateGraphics())
        using (SolidBrush brush = new SolidBrush(this.ForeColor))
            graphics.DrawString(this.Text, this.Font, brush, 1, 1); //play around with how you draw string more to suit your original
    }

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

如果您使用DoubleBuffer，即使您重新绘制字符串，您的字符串也会被双倍“删除”。