如何为控件及其子项暂停绘画？

Question

我有一个控件,我必须做大量修改.当我这样做时,我想完全阻止它重绘 - SuspendLayout和ResumeLayout是不够的.如何为控件及其子项暂停绘画？

Answer 1

在我之前的工作中,我们努力让我们丰富的UI应用程序能够即时,流畅地进行绘制.我们使用标准的.Net控件,自定义控件和devexpress控件.

经过大量的谷歌搜索和反射器使用后,我遇到了WM_SETREDRAW win32消息.这实际上会在您更新它们时停止控件绘制,并且可以应用于IIRC到父/包含面板.

这是一个非常简单的类,演示如何使用此消息:

class DrawingControl
{
    [DllImport("user32.dll")]
    public static extern int SendMessage(IntPtr hWnd, Int32 wMsg, bool wParam, Int32 lParam);

    private const int WM_SETREDRAW = 11; 

    public static void SuspendDrawing( Control parent )
    {
        SendMessage(parent.Handle, WM_SETREDRAW, false, 0);
    }

    public static void ResumeDrawing( Control parent )
    {
        SendMessage(parent.Handle, WM_SETREDRAW, true, 0);
        parent.Refresh();
    }
}

有关此问题的更全面的讨论 - 谷歌的C#和WM_SETREDRAW,例如

C#抖动

暂停布局

它可能涉及到谁,这是VB中的类似示例:

Public Module Extensions
    <DllImport("user32.dll")>
    Private Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Boolean, ByVal lParam As IntPtr) As Integer
    End Function

    Private Const WM_SETREDRAW As Integer = 11

    ' Extension methods for Control
    <Extension()>
    Public Sub ResumeDrawing(ByVal Target As Control, ByVal Redraw As Boolean)
        SendMessage(Target.Handle, WM_SETREDRAW, True, 0)
        If Redraw Then
            Target.Refresh()
        End If
    End Sub

    <Extension()>
    Public Sub SuspendDrawing(ByVal Target As Control)
        SendMessage(Target.Handle, WM_SETREDRAW, False, 0)
    End Sub

    <Extension()>
    Public Sub ResumeDrawing(ByVal Target As Control)
        ResumeDrawing(Target, True)
    End Sub
End Module

Answer 2

以下是ng5000的相同解决方案,但不使用P/Invoke.

public static class SuspendUpdate
{
    private const int WM_SETREDRAW = 0x000B;

    public static void Suspend(Control control)
    {
        Message msgSuspendUpdate = Message.Create(control.Handle, WM_SETREDRAW, IntPtr.Zero,
            IntPtr.Zero);

        NativeWindow window = NativeWindow.FromHandle(control.Handle);
        window.DefWndProc(ref msgSuspendUpdate);
    }

    public static void Resume(Control control)
    {
        // Create a C "true" boolean as an IntPtr
        IntPtr wparam = new IntPtr(1);
        Message msgResumeUpdate = Message.Create(control.Handle, WM_SETREDRAW, wparam,
            IntPtr.Zero);

        NativeWindow window = NativeWindow.FromHandle(control.Handle);
        window.DefWndProc(ref msgResumeUpdate);

        control.Invalidate();
    }
}

Answer 3

我通常使用ngLink 答案的一点修改版本.

public class MyControl : Control
{
    private int suspendCounter = 0;

    private void SuspendDrawing()
    {
        if(suspendCounter == 0) 
            SendMessage(this.Handle, WM_SETREDRAW, false, 0);
        suspendCounter++;
    }

    private void ResumeDrawing()
    {
        suspendCounter--; 
        if(suspendCounter == 0) 
        {
            SendMessage(this.Handle, WM_SETREDRAW, true, 0);
            this.Refresh();
        }
    }
}

这允许挂起/恢复调用.你必须确保每个都SuspendDrawing与a 匹配ResumeDrawing.因此,公开它们可能不是一个好主意.

Answer 4

为了帮助不忘记重新绘图:

public static void SuspendDrawing(Control control, Action action)
{
    SendMessage(control.Handle, WM_SETREDRAW, false, 0);
    action();
    SendMessage(control.Handle, WM_SETREDRAW, true, 0);
    control.Refresh();
}

用法:

SuspendDrawing(myControl, () =>
{
    somemethod();
});

Answer 5

不使用互操作的好方案:

与往常一样,只需在CustomControl上启用DoubleBuffered = true即可.然后,如果您有任何容器,如FlowLayoutPanel或TableLayoutPanel,从这些类型和构造函数中派生类,则启用双缓冲.现在,只需使用派生的容器而不是Windows.Forms容器.

class TableLayoutPanel : System.Windows.Forms.TableLayoutPanel
{
    public TableLayoutPanel()
    {
        DoubleBuffered = true;
    }
}

class FlowLayoutPanel : System.Windows.Forms.FlowLayoutPanel
{
    public FlowLayoutPanel()
    {
        DoubleBuffered = true;
    }
}

Answer 6

基于ng5000的答案，我喜欢使用以下扩展名：

        #region Suspend
        [DllImport("user32.dll")]
        private static extern int SendMessage(IntPtr hWnd, Int32 wMsg, bool wParam, Int32 lParam);
        private const int WM_SETREDRAW = 11;
        public static IDisposable BeginSuspendlock(this Control ctrl)
        {
            return new suspender(ctrl);
        }
        private class suspender : IDisposable
        {
            private Control _ctrl;
            public suspender(Control ctrl)
            {
                this._ctrl = ctrl;
                SendMessage(this._ctrl.Handle, WM_SETREDRAW, false, 0);
            }
            public void Dispose()
            {
                SendMessage(this._ctrl.Handle, WM_SETREDRAW, true, 0);
                this._ctrl.Refresh();
            }
        }
        #endregion

使用：

using (this.BeginSuspendlock())
{
    //update GUI
}