Question

我无法在简单的表单上绘制图形。我的代码编译并运行，但目标红框不会显示。

我在Visual Studio 2010中使用完整的.NET Framework 4。

出了什么问题，怎么修好？

private void Form1_Load(object sender, EventArgs e)
{
    System.Drawing.Graphics graphicsObj;
    graphicsObj = this.CreateGraphics();
    Pen myPen = new Pen(System.Drawing.Color.Red, 5);
    Rectangle myRectangle = new Rectangle(20, 20, 250, 200);
    graphicsObj.DrawRectangle(myPen, myRectangle);
}

编辑：工作但代码慢

    void BatteryPaint(object sender, EventArgs e)
    {
        TabPage page = (TabPage)sender;
        if (!controlsSetup)
        {
            populateBatteryTab(page);
            controlsSetup = true;
        }
        //Create the items
        Rectangle busBar = new Rectangle();
        Rectangle batPack = new Rectangle();
        Rectangle pack1Outline = new Rectangle();
        Rectangle pack2Outline = new Rectangle();
        Rectangle pack3Outline = new Rectangle();
        Rectangle pack4Outline = new Rectangle();

        Color GreenZone = Color.FromArgb(150, 0, 255, 0);
        Color YellowZone = Color.FromArgb(150, 255, 255, 0);
        Color RedZone = Color.FromArgb(150, 255, 0, 0);
        Color greyZone = Color.FromArgb(200, 200, 200, 200);

        Graphics graphicControl = page.CreateGraphics();

        SolidBrush busBarBrush = new SolidBrush(Color.Peru);
        SolidBrush GreenBrush = new SolidBrush(GreenZone);
        SolidBrush GreyBrush = new SolidBrush(greyZone);

        Pen packPen = new Pen(Color.LightGray, (float)8);


        Point busBarTop = new Point(page.Width / 64, page.Height / 32);
        Point busBarBottom = new Point(busBarTop.X, busBarTop.Y + page.Height / 6);

        //change the properties
        //Bus Bar Top
        busBar.Width = page.Width*153 / 640;
        busBar.Height = page.Height / 64;
        busBar.Location = busBarTop;
        graphicControl.FillRectangle(busBarBrush, busBar);

        //Bus Bar Bottom
        busBar.Location = busBarBottom;
        graphicControl.FillRectangle(busBarBrush, busBar);



        //Pack 1
        batPack.Width = page.Width / 20;
        batPack.Height = (busBarBottom.Y + busBar.Height) - busBarTop.Y;
        batPack.Location = new Point(busBarTop.X + page.Width / packSpacingMultiplier, busBarTop.Y);
        pack1Outline.Width = batOutlineWidth;
        graphicControl.FillRectangle(GreenBrush, batPack);
        pack1Outline.Height = (3 * (Battery.Width + page.Width / batSpacingMultiplier) + page.Width / batSpacingMultiplier);
        pack1Outline.Location = new Point(BatPack1.X - (page.Width / batSpacingMultiplier), BatPack1.Y - (page.Width / batSpacingMultiplier));
        for(int numBats = 0; numBats < 30; numBats++)
        {
            Battery.Location = new Point(BatPack1.X + ((numBats % 10) * (Battery.Width + page.Width / batSpacingMultiplier)), BatPack1.Y + ((numBats / 10) * (Battery.Width + page.Width / batSpacingMultiplier)));
            graphicControl.FillEllipse(new SolidBrush(BatteryZone(0.00)), Battery);
        }

        //Pack 2
        batPack.Location = new Point(batPack.Location.X + batPack.Width + page.Width / packSpacingMultiplier, batPack.Location.Y);
        graphicControl.FillRectangle(GreenBrush, batPack);
        pack2Outline.Width = batOutlineWidth;
        pack2Outline.Height = (3 * (Battery.Width + page.Width / batSpacingMultiplier) + page.Width / batSpacingMultiplier);
        pack2Outline.Location = new Point(BatPack2.X - (page.Width / batSpacingMultiplier), BatPack2.Y - (page.Width / batSpacingMultiplier));
        for(int numBats = 0; numBats < 30; numBats++)
        {
            Battery.Location = new Point(BatPack2.X + ((numBats % 10) * (Battery.Width + page.Width / batSpacingMultiplier)), BatPack2.Y + ((numBats / 10) * (Battery.Width + page.Width / batSpacingMultiplier)));
            graphicControl.FillEllipse(new SolidBrush(BatteryZone(0.00)), Battery);
        }

        //Pack 3
        batPack.Location = new Point(batPack.Location.X + batPack.Width + page.Width / packSpacingMultiplier, batPack.Location.Y);
        graphicControl.FillRectangle(GreenBrush, batPack);
        pack3Outline.Width = batOutlineWidth;
        pack3Outline.Height = (3 * (Battery.Width + page.Width / batSpacingMultiplier) + page.Width / batSpacingMultiplier);
        pack3Outline.Location = new Point(BatPack3.X - (page.Width / batSpacingMultiplier), BatPack3.Y - (page.Width / batSpacingMultiplier));
        for(int numBats = 0; numBats < 30; numBats++)
        {
            Battery.Location = new Point(BatPack3.X + ((numBats % 10) * (Battery.Width + page.Width / batSpacingMultiplier)), BatPack3.Y + ((numBats / 10) * (Battery.Width + page.Width / batSpacingMultiplier)));
            graphicControl.FillEllipse(new SolidBrush(BatteryZone(0.00)), Battery);
        }

        //Pack 4
        batPack.Location = new Point(batPack.Location.X + batPack.Width + page.Width / packSpacingMultiplier, batPack.Location.Y);
        graphicControl.FillRectangle(GreyBrush, batPack);
        pack4Outline.Width = batOutlineWidth;
        pack4Outline.Height = (3 * (Battery.Width + page.Width / batSpacingMultiplier) + page.Width / batSpacingMultiplier);
        pack4Outline.Location = new Point(BatPack4.X - (page.Width / batSpacingMultiplier), BatPack4.Y - (page.Width / batSpacingMultiplier));
        for(int numBats = 0; numBats < 30; numBats++)
        {
            Battery.Location = new Point(BatPack4.X + ((numBats % 10) * (Battery.Width + page.Width / batSpacingMultiplier)), BatPack4.Y + ((numBats / 10) * (Battery.Width + page.Width / batSpacingMultiplier)));
            graphicControl.FillEllipse(new SolidBrush(BatteryZone(0.00)), Battery);
        }


        //add the controls
        graphicControl.DrawRectangle(packPen, pack1Outline);
        graphicControl.DrawRectangle(packPen, pack2Outline);
        graphicControl.DrawRectangle(packPen, pack3Outline);
        graphicControl.DrawRectangle(packPen, pack4Outline);
    }

Answer 1

您不应该在Load事件中进行绘制，这是在您的表单首次显示之前触发的事件。窗口在显示时重新绘制，清除您绘制的图形。如果您想要一个持久性矩形，请改为处理Paint事件：

private void Form1_Paint(object sender, PaintEventArgs e)
{
    System.Drawing.Graphics graphicsObj = e.Graphics;
    Pen myPen = new Pen(System.Drawing.Color.Red, 5);
    Rectangle myRectangle = new Rectangle(20, 20, 250, 200);
    graphicsObj.DrawRectangle(myPen, myRectangle);
}

如果您不想要一个持久性矩形（非常可疑，但仍然可能），请尝试处理Shown事件而不是Load事件。

如果显示的图片会经常更新（例如在游戏中），请务必将DoubleBuffered设置为true并覆盖OnPaint，而不是处理事件：

protected override void OnPaint(PaintEventArgs e)
{
    Graphics g = e.Graphics;
    Pen myPen = new Pen(Color.Red, 5);
    g.DrawRectangle(myPen, 20, 20, 250, 200);
}

麻烦绘图图形

1 个答案: