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      <font color="#800080">VC知识库（五）</font>
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      <font color="#800080">www.vckbase.com</font>
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      <big>可以使用Drag&amp;Drop的CTreeView</big>
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      <big><strong>闻怡洋译</strong></big>
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<p><font color="#000000" size="3"><tt>CTreeViewExt是MFC使用者可重用的类，该类由CTreeView派生，可以用在文档-视结构的应用程序中，并且支持Drag&amp;Drop。</tt></font></p>



<p><font color="#000000" size="3"><tt>使用者所需要做的仅仅是将文件加到AppWizard产生的工程中，(CTreeView为基类)并且将CTreeView替换为CTreeViewExt。并重载三个Virtual  
 
Function。</tt></font></p> 
 
 
 
<p><tt><font color="#000000"><font size="3">WenYY:这很简单吧，下面是源代码，我会在必要的地方加上注释，但由于原作者并未加，所以如果有出入请原谅，作者定义了三处虚拟函数，其作用是让使用者重载后，加入自己的</font></font><font size="3"><font

color="#FF0000">判断条件</font><font color="#000000">和</font><font color="#FF0000">结果处理</font><font

color="#000000">的功能，很巧妙的思想：</font></font></tt></p>



<p><font color="#990000"><tt><font size="3">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CopyItemProperties<br>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; IsItemCanBeDroppedOn(HTREEITEM hSource, HTREEITEM hTarget);<br> 
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; BOOL ItemCanBeDragged(HTREEITEM hItem);//检查是否可以对该ITEM实施Drag&amp;Drop</font> 
 
</tt></font></p> 
 
 
 
<p><font color="#990000"><tt><font size="3"><br>

</font>

</tt></font><font size="3">Header file</font></p> 
 
 
 
<pre><tt><font size="3"><font color="#990000">#if !defined(AFX_TREEVIEWEXT_H__99D8F6F8_79F0_11D1_8DC6_0000E8125FE5__INCLUDED_)

#define AFX_TREEVIEWEXT_H__99D8F6F8_79F0_11D1_8DC6_0000E8125FE5__INCLUDED_

#if _MSC_VER &gt;= 1000

#pragma once

#endif // _MSC_VER &gt;= 1000

// TreeViewExt.h : header file

//



/////////////////////////////////////////////////////////////////////////////

// CTreeViewExt view



class CTreeViewExt : public CTreeView

{

protected:

	CTreeViewExt();           // protected constructor used by dynamic creation

	DECLARE_DYNCREATE(CTreeViewExt)



// Attributes

public:



// Operations

public:



// Overrides

	// ClassWizard generated virtual function overrides

	//{{AFX_VIRTUAL(CTreeViewExt)

	protected:

	virtual void OnDraw(CDC* pDC);      // overridden to draw this view

	//}}AFX_VIRTUAL



// Implementation

protected:

	HTREEITEM m_hDraggedItem;

	BOOL m_bDraggingNow;   //标记

	CImageList *m_pDragImageList;

	virtual ~CTreeViewExt();

#ifdef _DEBUG

	virtual void AssertValid() const;

	virtual void Dump(CDumpContext&amp; dc) const;

#endif



	// Generated message map functions

protected:

	virtual void CopyItemProperties(HTREEITEM hNewItem, HTREEITEM hDraggedItem);

	virtual BOOL IsItemCanBeDroppedOn(HTREEITEM hSource, HTREEITEM hTarget);

	virtual BOOL ItemCanBeDragged(HTREEITEM hItem);</font><font

color="#0000FF">//检查是否可以对该ITEM实施Drag&amp;Drop</font><font

color="#990000">

	//{{AFX_MSG(CTreeViewExt)

	afx_msg void OnBegindrag(NMHDR* pNMHDR, LRESULT* pResult);//必须重载的函数

	afx_msg void OnMouseMove(UINT nFlags, CPoint point);

	afx_msg void OnLButtonUp(UINT nFlags, CPoint point);

	//}}AFX_MSG

	DECLARE_MESSAGE_MAP()

};



/////////////////////////////////////////////////////////////////////////////



//{{AFX_INSERT_LOCATION}}

// Microsoft Developer Studio will insert additional declarations immediately before the previous line.



#endif // !defined(AFX_TREEVIEWEXT_H__99D8F6F8_79F0_11D1_8DC6_0000E8125FE5__INCLUDED_)

</font></font></tt></pre>



<h4><font size="3">Implementation file</font></h4> 
 
 
 
<pre><tt><font size="3"><font color="#990000">

// TreeViewExt.cpp : implementation file

//



#include &quot;stdafx.h&quot;

#include &quot;TreeViewExt.h&quot;



#ifdef _DEBUG

#define new DEBUG_NEW

#undef THIS_FILE

static char THIS_FILE[] = __FILE__;

#endif



/////////////////////////////////////////////////////////////////////////////

// CTreeViewExt



IMPLEMENT_DYNCREATE(CTreeViewExt, CTreeView)



CTreeViewExt::CTreeViewExt()

{

	m_bDraggingNow		= FALSE;

	m_hDraggedItem		= NULL;

	m_pDragImageList	= NULL;

}



CTreeViewExt::~CTreeViewExt()

{

}





BEGIN_MESSAGE_MAP(CTreeViewExt, CTreeView)

	//{{AFX_MSG_MAP(CTreeViewExt)

	ON_NOTIFY_REFLECT(TVN_BEGINDRAG, OnBegindrag)

	ON_WM_MOUSEMOVE()

	ON_WM_LBUTTONUP()

	//}}AFX_MSG_MAP

END_MESSAGE_MAP()



/////////////////////////////////////////////////////////////////////////////

// CTreeViewExt drawing



void CTreeViewExt::OnDraw(CDC* pDC)

{

	CDocument* pDoc = GetDocument();

	// TODO: add draw code here

}



/////////////////////////////////////////////////////////////////////////////

// CTreeViewExt diagnostics



#ifdef _DEBUG

void CTreeViewExt::AssertValid() const

{

	CTreeView::AssertValid();

}



void CTreeViewExt::Dump(CDumpContext&amp; dc) const

{

	CTreeView::Dump(dc);

}

#endif //_DEBUG



/////////////////////////////////////////////////////////////////////////////

// CTreeViewExt message handlers



void CTreeViewExt::OnBegindrag(NMHDR* pNMHDR, LRESULT* pResult) 

{

	NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;



	if (!m_bDraggingNow)

	{//先检查是否正在过程中

		if (</font><strong><font

color="#FF0000">ItemCanBeDragged</font></strong><font color="#990000">(pNMTreeView-&gt;itemNew.hItem))

		{</font><font

color="#0000FF">//查询条件，是否允许Drag&amp;Drop</font><font color="#990000">

			CTreeCtrl&amp; tree = GetTreeCtrl();

			tree.SetCapture();

			m_bDraggingNow = TRUE;

			m_hDraggedItem = pNMTreeView-&gt;itemNew.hItem;</font><font

color="#0000FF">//保存变量</font><font color="#990000">

			tree.Select(m_hDraggedItem, TVGN_CARET);

			m_pDragImageList = tree.CreateDragImage(m_hDraggedItem);

			m_pDragImageList-&gt;DragEnter(&amp;tree, pNMTreeView-&gt;ptDrag);

			m_pDragImageList-&gt;BeginDrag(0, CPoint(0, 0));

		}

	}

	

	*pResult = 0;

}



void CTreeViewExt::OnMouseMove(UINT nFlags, CPoint point) 

{

	if (m_bDraggingNow)

	{

		CTreeCtrl&amp; tree = GetTreeCtrl();

		m_pDragImageList-&gt;DragEnter(&amp;tree, point);

		m_pDragImageList-&gt;DragMove(point);

	}

	

	CTreeView::OnMouseMove(nFlags, point);

}



void CTreeViewExt::OnLButtonUp(UINT nFlags, CPoint point) 

{

	if (m_bDraggingNow)

	{

		ReleaseCapture();



		m_bDraggingNow = FALSE;

		m_pDragImageList-&gt;EndDrag();

		delete m_pDragImageList;

		m_pDragImageList = NULL;



		CTreeCtrl&amp; tree = GetTreeCtrl();

		UINT flags;

		HTREEITEM hTargetItem = tree.HitTest(point, &amp;flags);//得到目标

		if (hTargetItem != NULL &amp;&amp; </font><strong><font

color="#FF0000">IsItemCanBeDroppedOn</font></strong><font color="#990000">(m_hDraggedItem, hTargetItem))

		{</font><font

color="#0000FF">//查询是否可以成功完成,条件是开始时选中的Item和结束使选中的ITEM是否满足你的条件</font><font

color="#990000">

			HTREEITEM hNewItem = tree.InsertItem(&quot;Untitled&quot;, hTargetItem);

			</font><strong><font

color="#FF0000">CopyItemProperties</font></strong><font color="#990000">(hNewItem, m_hDraggedItem);</font><font

color="#0000FF">//进行处理</font><font color="#990000">

			if (nFlags != MK_CONTROL)

				tree.DeleteItem(m_hDraggedItem);

		}	



		m_hDraggedItem = NULL;

	}


	CTreeView::OnLButtonUp(nFlags, point);

}

BOOL CTreeViewExt::ItemCanBeDragged(HTREEITEM hItem)

{</font><font

color="#0000FF">//作用为决定现在是否能开始,可以作为一种运行时的选项</font><font

color="#990000">

	return FALSE;

}



BOOL CTreeViewExt::IsItemCanBeDroppedOn(HTREEITEM hSource, HTREEITEM hTarget)

{</font><font

color="#0000FF">//决定现在结束条件是否正常，如不正常则放弃这次操作</font><font

color="#990000">

	return FALSE;

}
void CTreeViewExt::CopyItemProperties(HTREEITEM hNewItem, HTREEITEM hDraggedItem)
{</font><font

color="#0000FF">//按照你的需要对两个ITEM进行处理。</font><font

color="#990000">

}</font></font></tt></pre>



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