Question

你能帮我解决这段代码吗？我想学习使用Invalidate和Update，但我不知道如何使用它此代码不起作用。我想设置新文本，但它不“刷新”并且不写新字符串“Prova”。感谢

namespace Invalidate
{
public partial class Form1 : Form
{
    private String txt;
    private PointF xy;
    public Form1()
    {
        InitializeComponent();
    }

    private void panel1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawString("This is the text that prints!",
        this.Font, System.Drawing.Brushes.Azure, 0, 0);
    }
    private void Form1_Load(object sender, EventArgs e)
    {
        Panel pHText = new Panel();
        pHText.Name = "ctrId"; 
        pHText.Location = new Point(10, 10);
        pHText.Size = new Size(200, 200);
        pHText.BackColor = Color.White;
        pHText.Paint += paintingUrCtr;
        Controls.Add(pHText);
    }

    private void paintingUrCtr(object sender, PaintEventArgs e)
    {
        Font myFont = new Font("Arial", 14);
        e.Graphics.DrawLine(new Pen(Color.Black), 0, 0, 10, 10);
        e.Graphics.DrawString(this.txt, myFont, Brushes.Blue, 10, 10);
    }
    public void setText(String text, PointF pos)
    {
        this.txt = text;
        this.xy = pos;
    }
    private void button_Click(object sender, EventArgs e)
    {
        setText("Prova", new PointF(100, 100));
        this.Invalidate();
        this.Update();
    }
}
}

Answer 1

调用this.Invalidate();不会使子控件无效，您需要使用重载that takes in a bool并传入true

private void button_Click(object sender, EventArgs e)
{
    setText("Prova", new PointF(100, 100));
    this.Invalidate(true);
    this.Update();
}

编辑：正如评论中所提到的，您也可以使单个子控件无效并更新它。

private void button_Click(object sender, EventArgs e)
{
    setText("Prova", new PointF(100, 100));
    this.Controls["ctrId"].Invalidate(true);
    this.Controls["ctrId"].Update();
}

C＃ - Invalidate（）和Update（）

1 个答案: