Drag PictureBox

Question

我想拖动一个PictureBox，并且已经成功做到了。但是我的应用程序执行起来不如Windows photo viewer顺利。我的意思是区别并不大，也没有任何区别，但值得注意。有什么我可以做的使它变得不那么混乱吗？这是我的简单代码：

int MOUSE_X = 0;
int MOUSE_Y = 0;

public Form1()
{
    InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
    picBox.Image = Image.FromFile(@"D:\test_big.png");
    picBox.Width = 3300;
    picBox.Height = 5100;
}

private void picBox_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        MOUSE_X = e.X;
        MOUSE_Y = e.Y;
    }
}

private void picBox_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        picBox.Left = picBox.Left + (e.X - MOUSE_X);
        picBox.Top = picBox.Top + (e.Y - MOUSE_Y);
    }
}

Answer 1

测试您的代码会产生：

而建议的代码：

using System.Runtime.InteropServices;
//...

private const int WM_SYSCOMMAND = 0x112;
private const int MOUSE_MOVE = 0xF012;

[DllImport("user32.dll")]
private static extern IntPtr SendMessage(
    IntPtr hWnd,
    int wMsg,
    IntPtr wParam,
    IntPtr lParam);

[DllImport("user32.dll")]
private static extern int ReleaseCapture(IntPtr hWnd);

private void picBox_MouseMove(object sender, MouseEventArgs e)
{
    if (!DesignMode && e.Button == MouseButtons.Left)
    {
        ReleaseCapture(picBox.Handle);
        SendMessage(picBox.Handle, WM_SYSCOMMAND, (IntPtr)MOUSE_MOVE, IntPtr.Zero);
    }
}

产品：

请注意，如果我这么说，我也会使用背景图片使情况变得更糟。但是，如果没有背景图片，则很难检测到使用了哪个代码段。