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<html><head><script language="JavaScript"> function reset(){ for ( var i=0; i < document.Form1.elements.length; i++ ) { document.Form1.elements[i].options[0].selected=true }}function going(url){ parent.location=url; reset();}</script><style><!--A:link {text-decoration: none; color: #000000; font-family: 宋体}A:visited {text-decoration: none; color: #000000; font-family: 宋体}A:active {text-decoration: none; font-family: 宋体}A:hover {text-decoration: underline:#ffffff; color: #ff0000}body,table {font-size: 9pt; font-family: 宋体}.H1 {font-size: 9pt ; line-height:9pt; align=center}.ourfont {font-size: 9pt ; line-height:9pt; }.ourfont1 {font-size: 9pt ; line-height:9pt; }--></style><meta http-equiv="Content-Type" content="text/html; charset=gb2312"><title>在Delphi中侦测剪贴板的变化</title></head><body topmargin="0" leftmargin="0"><div align="center"><center><table border="0" cellPadding="0" cellSpacing="0" width="700"><tbody> <tr> <td><p class="content4"><span class="font"><img border="0" height="3" src="../../soft/pix.gif" width="700"></span></td> </tr></tbody></table></center></div><div align="center"><center><table border="0" cellPadding="0" cellSpacing="0" width="700"><tbody> <tr> <td bgColor="#3399ff" width="658"><p class="ourfont"><span class="font"> </span><a style="text-decoration: none; color: rgb(255,255,255)" href="../os/H00705-2.htm">操作系统</a><font color="#FFFFFF"><span class="font"><span> |</span></span></font><a style="color: rgb(255,255,255); text-decoration: none" href="../image/H00705-14.htm">图像处理</a><font color="#FFFFFF"><span>|<span class="font"> </span></span></font><a style="color: rgb(255,255,255); text-decoration: none" href="../autoCAD/H00705-19.htm">辅助设计</a><span class="font"><font color="#FFFFFF"><span> | </span></font></span><a style="color: rgb(255,255,255); text-decoration: none" href="../data/H00705-18.htm">数 据 库</a><span class="font"><font color="#FFFFFF"><span> | </span></font></span><a style="color: rgb(255,255,255); text-decoration: none" href="H00706-1.htm">高级编程</a><span class="font"><font color="#FFFFFF"><span> | </span></font></span><a style="color: rgb(255,255,255); text-decoration: none" href="../netuse/H00705-20.htm">网络应用</a><font color="#FFFFFF"><span><span class="font"> | </span></span></font><a style="color: rgb(255,255,255); text-decoration: none" href="../webpage/H00705-21.htm">网页制作</a><font color="#FFFFFF"><span><span class="font"> |</span></span></font> <a style="color: rgb(255,255,255); text-decoration: none" href="../technic/H00706-3.htm">技术交流 </a><a style="color: rgb(255,255,255); text-decoration: none" href="http://202.100.13.77/clslyb/default.asp?clsid=jiaoc"><font color="#FFFFFF"><strong>过客留言</strong></font></a></td> <td bgColor="#3399ff" width="32"><p align="center" class="ourfont"><a href="mailto:net@163.sn.cn"><img src="../../soft/email.gif" alt="email.gif (493 字节)" border="0" WIDTH="20" HEIGHT="19"></a></td> </tr></tbody></table></center></div><div align="center"><center><table border="1" cellSpacing="1" width="700" bordercolor="#3399FF"><tbody> <tr> <td align="left" bgColor="#FFFFFF" vAlign="top" width="700" bordercolor="#0000FF" bordercolorlight="#0000FF" bordercolordark="#0000FF"><p class="ourfont"> </p> <p align="center">在Delphi中侦测剪贴板的变化 <br> <br> (上海 钱可栋) </p> <p> 许多提供剪切、复制和粘贴功能的应用程序都有一个共同特点，那就是：工具栏上表示这三个功能的按钮会随着剪贴板的变化而变化，具体来说，粘贴按钮只有在剪贴板上有内容时才处于使能状态，而当剪贴板空时则变灰，也就是不能使用；相似地，剪切、复制按钮也只有在当前有文本或位图被选择时才有效。那么，这是怎么实现的呢？笔者曾经想在Delphi4.0中放置一个Timer控件，在其OnTimer事件中加入侦测剪贴板变化的代码，但最后放弃了，原因是Timer控件比较消耗系统资源，得不偿失，而且笔者也相信，那些应用程序的源代码也不是这么做的。其实，这个问题的关键在于怎么样响应Windows消息，这里就是响应剪贴板消息。Delphi体贴地将所有的Windows消息都重新定义，令我们可以方便地通过message关键字访问这些消息而不用理会恼人的API。下面，就用一个实例说明Delphi是怎么做的。<br> 程序需要一个ToolBar控件，在其上建立三个按钮；一个ImageList控件，为其加入三个小位图，分别表示剪切、复制和粘贴，将ImageList 赋予ToolBar的images属性；一个Memo控件，将其Lines属性置空。以下是程序清单：<br> unit Unit1;<br> interface<br> uses<br> Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,<br> StdCtrls,ClipBrd, ComCtrls, ImgList, ToolWin;<br> type<br> TForm1 = class(TForm)<br> ToolBar1: TToolBar;<br> ImageList1: TImageList;<br> ToolButton1: TToolButton;<br> ToolButton2: TToolButton;<br> ToolButton3: TToolButton;<br> Memo1: TMemo;<br> procedure FormCreate(Sender: TObject);<br> procedure FormDestroy(Sender: TObject);<br> procedure Memo1MouseUp(Sender: TObject; Button: TMouseButton;<br> Shift: TShiftState; X, Y: Integer);<br> procedure ToolButton1Click(Sender: TObject);<br> procedure ToolButton2Click(Sender: TObject);<br> procedure ToolButton3Click(Sender: TObject);<br> private<br> { Private declarations }<br> viewhandle:HWND;<br> procedure Change(var msg:TWMdrawclipboard);<br> message wm_drawclipboard;<br> public<br> { Public declarations }<br> end;<br> var<br> Form1: TForm1;<br> implementation<br> {＄R ＊.DFM}<br> procedure TForm1.FormCreate(Sender: TObject);<br> begin<br> Memo1.Align:=alClient;<br> ToolBar1.Flat:=True;<br> viewhandle:=SetClipboardviewer(Handle);<br> ToolButton1.Enabled:=False;<br> ToolButton2.Enabled:=False; <br> end;<br> procedure TForm1.FormDestroy(Sender: TObject);<br> begin<br> ChangeClipboardChain(Handle,viewhandle);<br> end;<br> procedure TForm1.Memo1MouseUp(Sender: TObject; Button: TMouseButton;<br> Shift: TShiftState; X, Y: Integer);<br> begin<br> if Memo1.SelText<>`` then<br> begin<br> ToolButton1.Enabled:=True;<br> ToolButton2.Enabled:=True;<br> end<br> else<br> begin<br> ToolButton1.Enabled:=False;<br> ToolButton2.Enabled:=False;<br> end<br> end;<br> procedure TForm1.ToolButton1Click(Sender: TObject);<br> begin<br> Memo1.CutToClipboard;<br> end;<br> procedure TForm1.ToolButton2Click(Sender: TObject);<br> begin<br> Memo1.CopyToClipboard;<br> end;<br> procedure TForm1.ToolButton3Click(Sender: TObject);<br> begin<br> Memo1.PasteFromClipboard;<br> end;<br> procedure TForm1.Change(var msg:TWMdrawclipboard);<br> begin<br> ToolButton3.Enabled:=Clipboard.Hasformat(cf_text)<br> end;<br> end.<br> 注意程序中的关键字：message，它使Change过程可以响应剪贴板消息，<br> 即剪贴板中有文本内容时粘贴按钮有效，反之无效；而剪切、复制按钮的状<br> 态在Memo1的MouseUp事件中响应。程序中的SetClipboardviewer函数用来登<br> 陆剪贴板，ChangeClipboardChain函数用来退出剪贴板。另外还有一点要说<br> 明的是：由于代码中有剪贴板类的操作，因此Uses子句中要加上ClipBrd。 </td> </tr></tbody></table></center></div><hr align="center" SIZE="1" width="700"><p align="center" class="ourfont"><span><span><font color="#000000"> <a style="color: rgb(0,0,0); 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