c# - 以编程方式将图像放入不活动的表单中？

Question

我想以编程方式将图像放入不活动的表单中。

Image myImage = new Image();
gfx = Form.ActiveForm.CreateGraphics();
gfx.DrawImage(myImage, 0,0);

只有在表单处于事件状态时它才会完美地工作，但是当表单处于非事件状态时它就没有意义了，只会返回一个错误:

In an instance of an object reference not set to an object.

如何处理我的应用程序中未激活的表单并为其添加图片？

更新 1

我做了实例，并打开了 DoubleBuffered 属性(true)但没有任何反应:

Form1 form = new Form1();
gfx = form.CreateGraphics();
gfx.DrawImage(bmp, 0, 0);

upd 2 More Source，是我加的类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Printing;

namespace testimg
{
    class doimg
    {

        public void picture()
        {

            // some staffs to get a picture, so it's in bmp object now.

            gfx = this. // watch picture below
            gfx.DrawImage(bmp, 0, 0);

            // I tried to use PictureBox, but it's the same issue (I can't handle it on a form)
            PictureBox pb = new PictureBox();
            pb.CreateGraphics();
            pb.DrawToBitmap(bmp,pb.ClientRectangle);

        }

    }
}

Arif Eqbal 解的图片:no graph methods for this (pic)

更新 3

我所拥有的完整资源(计时器为 10 秒)

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace testimg
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {

            doimg pic = new doimg();

            pic.picture();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            timer1.Enabled = true;
        }
     }
}

doimg.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Printing;


namespace testimg
{
    class doimg
    {

        public void picture()
        {

            // some staffs to get a picture, so it's in bmp object now.
            Bitmap bmp = new Bitmap(200, 200,    System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            Graphics gfx = Graphics.FromImage(bmp);
            gfx = Form1.ActiveForm.CreateGraphics(); // works well with active form
            gfx.DrawImage(bmp, 0, 0);


        }


     }
}

和项目的整个文件 http://www.filedropper.com/testimg

如您所见，程序处于事件状态时一切运行良好。仍然需要帮助。

Answer 1

在您的 Form2 上，尝试这样设置:

public partial class Form2 : Form {

  public Image MyImage { get; set; }

  public Form2() {
    InitializeComponent();
  }

  protected override void OnPaint(PaintEventArgs e) {
    if (MyImage != null) {
      e.Graphics.DrawImage(MyImage, 0, 0);
    }
    base.OnPaint(e);
  }
}

然后从你的事件表单中，你可以调用另一个表单来绘制它自己:

public partial class Form1 : Form {
  Form2 f2 = new Form2();

  public Form1() {
    InitializeComponent();
    f2.Show();
  }

  private void button1_Click(object sender, EventArgs e) {
    f2.MyImage = myImage;
    f2.Invalidate();
  }
}