C# Win.Form - 加载后图形消失

Question

我正在使用用户控件来显示两个日期之间的时间。我的问题是当应用程序启动时运行或每次我 Refresh() 用户控件时，所有图形都会消失，直到调整表单大小。

观察窗体在刷新时的行为，用户控件在消失前在屏幕上显示了几帧。

我一头雾水，希望你能帮我解开这个谜。

此致，马蒂亚斯

PS：这是我的用户控件代码：

public partial class CalendarView : UserControl
{
    [Category("Behavior")]
    //these reads the start and end date for the datastrip from the parent form
    public DateTime StartDateTime (...)
    public DateTime EndDateTime (...)
    public int Space
    {
        get
        {
            double totalDays = (EndDateTime - StartDateTime).TotalDays;
            if (totalDays == 0) { totalDays = 1; }
            return (int)(GraphicsWidth / totalDays);
        }
    }
    private int GraphicsWidth
    {
        get
        {
            return panelDateTimeStrip.Width - 2;
        }
    }

    public CalendarView()
    {
        InitializeComponent();
    }

    private void drawDates()
    {
        Pen darkGray = new Pen(SystemColors.ControlDarkDark);
        Pen lightGray = new Pen(Color.LightGray);
        Pen gray = new Pen(Color.Gray);
        SolidBrush brush = new SolidBrush(SystemColors.ControlDarkDark);
        StringFormat stringFormat = new StringFormat();
        stringFormat.Alignment = StringAlignment.Center;
        int graphicsHeight = panelDateTimeStrip.Height - 2;
        Graphics graphics = panelDateTimeStrip.CreateGraphics();

        //<-----drawing all graphics------>\

        graphics.Dispose();
        darkGray.Dispose();
        lightGray.Dispose();
        gray.Dispose();
    }

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

    private void CalendarView_Resize(object sender, EventArgs e)
    {
        Invalidate();
    }

    private void CalendarView_Load(object sender, EventArgs e)
    {
        drawDates();
    }
}

Answer 1

评论几乎回答了这个问题，但由于还没有人发布答案，因此您应该如何更改代码：

private void drawDates(Graphics graphics)
{
    // create pens and brushes
    // do not CreateGraphics, use the parameter instead

    //<-----drawing all graphics------>\

    // dispose pens and brushes; do not dispose graphics!
}

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

请注意，您在自己绘制之前调用了 base.OnPaint，并且您不再使用 CreateGraphics。

C# Win.Form - 加载后图形消失

C# Win.Form - graphics disappear after load

c#

graphics

user-controls

drawing

winforms