我怎么能笼络在C＃中的面板？ [英] How can I draw over a panel in C#?

问题描述

嘿，我需要做的比我在C＃中，但没有将panel1_Paint里面我的绘制代码面板图，我怎么能做到这一点？
顺便说一句，我使用的WinForms

Hey, I need to do my drawing over a panel in C# but without placing my drawing code inside "panel1_Paint", how can I do that ?? BTW, I'm using WinForms.

更新：我忘了，使一些清晰的，我不需要把我的画油漆处理程序中的代码，因为我要开始绘制根据按钮的事件。

Update : I forgot to make something clear, I need not to place my drawing code inside paint handler, because I need to start drawing depending on buttons' events.

推荐答案

通常你在所有你的图纸Paint事件处理程序。如果你想要做的任何更新（如果用户单击面板为例），你可以选择推迟采取行动：你存储所需要的数据（坐标用户点击的地方），并强制控制的重绘。这会导致油漆事件被解雇，在这里你就可以得出你之前存储的东西。

Usually you do all your drawings in the paint event handler. If you want to do any update (if a user clicks on the panel for example) you have to defer that action: you store the required data (coordinates where the user clicked) and force a redraw of the control. This causes the paint event to be fired, where you can then draw things you stored before.

另一种方式是（如果你真的想以'panel1_Paint外画'事件处理），以缓冲图像内画，将图像复制到图形的绘制事件处理程序对象控件

Another way would be (if you really want to draw outside of the 'panel1_Paint' event handler) to draw inside a buffer image, and copy the image to the controls graphics object in the paint event handler.

更新：

一个例子：

public class Form1 : Form
{
    private Bitmap buffer;

    public Form1()
    {
        InitializeComponent();

        // Initialize buffer
        panel1_Resize(this, null);
    }

    private void panel1_Resize(object sender, EventArgs e)
    {
        // Resize the buffer, if it is growing
        if (buffer == null || 
            buffer.Width < panel1.Width || 
            buffer.Height < panel1.Height)
        {
            Bitmap newBuffer = new Bitmap(panel1.Width, panel1.Height);
            if (buffer != null)
                using (Graphics bufferGrph = Graphics.FromImage(newBuffer))
                    bufferGrph.DrawImageUnscaled(buffer, Point.Empty);
            buffer = newBuffer;
        }
    }

    private void panel1_Paint(object sender, PaintEventArgs e)
    {
        // Draw the buffer into the panel
        e.Graphics.DrawImageUnscaled(buffer, Point.Empty);
    }



    private void button1_Click(object sender, EventArgs e)
    {
        // Draw into the buffer when button is clicked
        PaintBlueRectangle();
    }

    private void PaintBlueRectangle()
    {
        // Draw blue rectangle into the buffer
        using (Graphics bufferGrph = Graphics.FromImage(buffer))
        {
            bufferGrph.DrawRectangle(new Pen(Color.Blue, 1), 1, 1, 100, 100);
        }

        // Invalidate the panel. This will lead to a call of 'panel1_Paint'
        panel1.Invalidate();
    }
}

现在绘制的图像不会丢失，即使经过重绘控制的，因为它仅引出缓冲器（图像，保存在存储器中）。此外，您可以随时借鉴的东西一事件发生时，通过简单地画到缓冲区中。

Now the drawn images wont be lost, even after a redraw of the control, because it only draws out the buffer (the image, saved in the memory). Additionally you can draw things anytime a event occurs, by simply drawing into the buffer.

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