Question

怎么消除Webbrowser控件切换时的闪烁

Answer 1

解决方法如下:

从WebBrowser派生一个新类

构造函数中添加DocumentCompleted事件响应

相关代码:
C# code
[DllImport("user32.dll")]
protected static extern int GetWindowLong(int hwindow, int unindex);
[DllImport("user32.dll")]
protected static extern int CallWindowProc(int lpPrevWndFunc, int hWnd, int Msg, int wParam, int lParam);
[DllImport("user32.dll")]
protected static extern int SetWindowLong(int hwindow, int unindex, CallWindowProcDelegate lnewvalue);

public static int oldWindow = 0;
public const int GWL_WNDPROC = -4;
public delegate int CallWindowProcDelegate(int Wnd, int Msg, int WParam, int LParam);
public CallWindowProcDelegate MyCallWindowProc;

bool add = false;

void ExtendWebBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
if(add)
{ return; }

add = true;
FindWindow fw = new FindWindow(this.Handle, "Internet Explorer_Server");
IntPtr hIE = fw.FoundHandle;

if (hIE.ToInt32() != 0)
{
oldWindow = (int)GetWindowLong(hIE.ToInt32(), GWL_WNDPROC);
MyCallWindowProc = new CallWindowProcDelegate(WndProc);
SetWindowLong(hIE.ToInt32(), GWL_WNDPROC, MyCallWindowProc);
}
}

private int WndProc(int Wnd, int Msg, int WParam, int LParam)
{
const int WM_ERASEBKGND = 0x14;

if (Msg == WM_ERASEBKGND)
{
return 1;
}

return CallWindowProc(oldWindow, Wnd, Msg, WParam, LParam);
}

/**/
/// <summary>
/// This class is to find the given window's child window accroding to the given child window's name.
/// The useage: FindWindow fw = new FindWindow(wndHandle, "ChildwndClassName"); IntPtr ip = fw.FoundHandle;
/// I adapt the code from Paul DiLascia,who is the MSDN Magazine's writer.
/// The original class is named CFindWnd which is written in C++, and you could get it on Internet.
/// www.pinvoke.net is a great website.It includes almost all the API fuctoin to be used in C#.
/// </summary>
class FindWindow
{
[DllImport("user32")]
[return: MarshalAs(UnmanagedType.Bool)]
//IMPORTANT : LPARAM must be a pointer (InterPtr) in VS2005, otherwise an exception will be thrown
private static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr i);
//the callback function for the EnumChildWindows
private delegate bool EnumWindowProc(IntPtr hWnd, IntPtr parameter);

//if found return the handle , otherwise return IntPtr.Zero
[DllImport("user32.dll", EntryPoint = "FindWindowEx")]
private static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

private string m_classname; // class name to look for

private IntPtr m_hWnd; // HWND if found
public IntPtr FoundHandle
{
get { return m_hWnd; }
}
// ctor does the work--just instantiate and go
public FindWindow(IntPtr hwndParent, string classname)
{
m_hWnd = IntPtr.Zero;
m_classname = classname;
FindChildClassHwnd(hwndParent, IntPtr.Zero);
}

//EnumChildWindows是API函数，能够遍历主窗口下所有子窗口。不过它的遍历过程是通过
//第二个参数即回调函数与程序员交互的。EnumChildWindows每找到一个窗口。就调用回调
//函数。回调函数如果返回false。遍历就会结束。

/**/
/// <summary>
/// Find the child window, if found m_classname will be assigned
/// </summary>
/// <param name="hwndParent">parent's handle</param>
/// <param name="lParam">the application value, nonuse</param>
/// <returns>found or not found</returns>
//The C++ code is that lParam is the instance of FindWindow class , if found assign the instance's m_hWnd
private bool FindChildClassHwnd(IntPtr hwndParent, IntPtr lParam)
{
EnumWindowProc childProc = new EnumWindowProc(FindChildClassHwnd);
IntPtr hwnd = FindWindowEx(hwndParent, IntPtr.Zero, this.m_classname, string.Empty);
if (hwnd != IntPtr.Zero)
{
this.m_hWnd = hwnd; // found: save it
return false; // stop enumerating
}
EnumChildWindows(hwndParent, childProc, IntPtr.Zero); // recurse redo FindChildClassHwnd
return true;// keep looking
}
}