我正在尝试实现MDI Child窗口基类,根据to this reference详细说明说
我正在使用以下简单的基本模板类创建MDI子窗口,并实现上述语句以检索此指针。 (添加了一些评论)
basemdi.h
#pragma once
#include <Windows.h>
template <typename DERIVED_TYPE>
class BaseMDI
{
public:
inline HWND GetHandle() const;
BOOL Initialize(
PCTSTR szWindowName,
HWND hParent,
DWORD dwExStyle = WS_EX_MDICHILD, // THIS IS MDI WINDOW
DWORD dwStyle = 0,
int x = CW_USEDEFAULT,
int y = CW_USEDEFAULT,
int width = CW_USEDEFAULT,
int height = CW_USEDEFAULT,
HMENU hMenu = nullptr,
HINSTANCE hInstance = GetModuleHandle(nullptr),
LPVOID lpCreate = nullptr
);
protected:
virtual PCTSTR ClassName() const = 0;
static LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
virtual LRESULT HandleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam) = 0;
HWND m_hwnd = nullptr;
};
template<typename DERIVED_TYPE>
BOOL BaseMDI<DERIVED_TYPE>::Initialize(
PCTSTR szWindowName,
HWND hParent,
DWORD dwExStyle,
DWORD dwStyle,
int x,
int y,
int width,
int height,
HMENU hMenu,
HINSTANCE hInstance,
LPVOID lpCreate)
{
UNREFERENCED_PARAMETER(lpCreate);
WNDCLASSEX wc = { };
wc.cbClsExtra = 0;
wc.cbSize = sizeof(WNDCLASSEX);
wc.cbWndExtra = 0;
wc.hbrBackground = reinterpret_cast<HBRUSH>(GetStockObject(WHITE_BRUSH));
wc.hCursor = LoadCursor(nullptr, IDC_ARROW);
wc.hIcon = nullptr;
wc.hInstance = hInstance;
wc.lpfnWndProc = WindowProc;
wc.lpszClassName = ClassName();
wc.lpszMenuName = nullptr;
wc.style = CS_VREDRAW | CS_HREDRAW;
RegisterClassEx(&wc);
MDICREATESTRUCT mdicreate;
// ASSIGN POINTER TO THIS SO THAT WE LATER RETRIEVE IT
mdicreate.lParam = (LPARAM) this;
mdicreate.szClass = ClassName();
mdicreate.szTitle = TEXT("Hello");
mdicreate.hOwner = hInstance;
mdicreate.x = CW_USEDEFAULT;
mdicreate.y = CW_USEDEFAULT;
mdicreate.cx = CW_USEDEFAULT;
mdicreate.cy = CW_USEDEFAULT;
mdicreate.style = dwStyle;
m_hwnd = CreateWindowEx(
dwExStyle,
ClassName(),
szWindowName,
dwStyle,
x, y,
width,
height,
hParent,
hMenu,
hInstance,
&mdicreate // PASS ADDRESS OF MDICREATESTRUCT
);
return m_hwnd ? TRUE : FALSE;
}
// following base class WndProc calls derived class procedure,
// I retrive this pointer here to call correct procedure, but pThis is read acess vioalaiton
template<typename DERIVED_TYPE>
inline LRESULT BaseMDI<DERIVED_TYPE>::WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
DERIVED_TYPE* pThis = nullptr;
if (uMsg == WM_CREATE)
{
// RETRIEVE POINTER TO THIS
CREATESTRUCT* pCreate = reinterpret_cast<CREATESTRUCT*>(lParam);
MDICREATESTRUCT* pMdi = reinterpret_cast<MDICREATESTRUCT*>(pCreate->lpCreateParams);
pThis = reinterpret_cast<DERIVED_TYPE*>(pMdi->lParam);
SetWindowLongPtr(hWnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(pThis));
pThis->m_hwnd = hWnd;
}
else
{
pThis = reinterpret_cast<DERIVED_TYPE*>(GetWindowLongPtr(hWnd, GWLP_USERDATA));
}
if (pThis)
{
// EXCEPTION IS THROWN HERE
return pThis->HandleMessage(uMsg, wParam, lParam);
}
else
{
return DefMDIChildProc(hWnd, uMsg, wParam, lParam);
}
}
template <typename DERIVED_TYPE>
HWND BaseMDI<DERIVED_TYPE>::GetHandle() const
{
return m_hwnd;
}
这是我创建MDI子窗口对象的实际实例的方法,该类继承了模板化基类
mdiwindow.h
#pragma once
#include "mdibase.h"
class MDI : public BaseMDI<MDI>
{
public:
virtual LRESULT HandleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam) override;
private:
inline virtual PCTSTR ClassName() const override;
};
PCTSTR MDI::ClassName() const
{
return TEXT("MDIWindow");
}
mdiwindow.cpp
#include "mdiwindow.h"
LRESULT MDI::HandleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
default:
return DefMDIChildProc(m_hwnd, uMsg, wParam, lParam);
}
}
创建MDI子级时,我在basemdi.h中遇到异常,说pThis指针违反了读取访问权限。
我正在遵循有关如何检索传递给
MDICREATESTRUCT
的CreateWindowEx
的指针的msdn指令,该指针将this
的指针保存在lpCreateParams
中,但是由于某种原因,检索到的指针不起作用。您知道这可能是什么原因吗?
最佳答案
我设法解决了这个问题。
问题在于,MSDN正在讨论使用对子MDI窗口不起作用的CreateWindow
或CreateWindowEx
的可能性,需要改为使用CreateMDIWindow
!
这是上面示例中正在工作的Initialize函数,上面的其余代码很好:
template<typename DERIVED_TYPE>
BOOL BaseMDI<DERIVED_TYPE>::Initialize(
PCTSTR szWindowName,
HWND hParent,
DWORD dwExStyle,
DWORD dwStyle,
int x,
int y,
int width,
int height,
HMENU hMenu,
HINSTANCE hInstance,
LPVOID lpCreate)
{
UNREFERENCED_PARAMETER(lpCreate);
WNDCLASSEX wc = { };
wc.cbClsExtra = 0;
wc.cbSize = sizeof(WNDCLASSEX);
wc.cbWndExtra = 0;
wc.hbrBackground = reinterpret_cast<HBRUSH>(GetStockObject(WHITE_BRUSH));
wc.hCursor = LoadCursor(nullptr, IDC_ARROW);
wc.hIcon = nullptr;
wc.hInstance = hInstance;
wc.lpfnWndProc = WindowProc;
wc.lpszClassName = ClassName();
wc.lpszMenuName = nullptr;
wc.style = CS_VREDRAW | CS_HREDRAW;
if (!RegisterClassEx(&wc)) abort();
m_hwnd = CreateMDIWindow(
ClassName(),
szWindowName,
dwStyle,
x, y,
width,
height,
hParent,
hInstance,
(LPARAM)this);
if (!m_hwnd) abort();
return m_hwnd ? TRUE : FALSE;
}
关于c++ - MDI面向对象的方法,从MDICREATESTRUCT检索此指针,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/55547616/