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<title>OnMouseDown事件的处理</title>
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>> <a href="../cbuilder.htm">C++ Builder</a> >> </small><font>具体而微的绘图程式</font>·OnMouseDown事件的处理</p>
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</font><p><font SIZE="2"></font><font color="#FF0000" SIZE="2">·02-01 OnMouseDown事件的处理</font></p><font SIZE="2">
<p>首先我们先以一个最基本的画线程式来说明<font SIZE="2">OnMouseDown</font>事件的处理，当使用者按下滑鼠时，我们希望将笔移至事件发生时的坐标，因此我们可将程式写成如下：</p>
<p>void __fastcall TForm1::FormMouseDown(TObject *Sender, TMouseButton Button,</p>
<p>TShiftState Shift, int X, int Y)</p>
<p>{</p>
<p> Canvas->MoveTo(X,Y);</p>
<p>}</p>
<p>02-03 OnMouseUp事件的处理</p>
<p>同样地，我们可以再为这个<font SIZE="2">Form</font>加上<font SIZE="2">OnMouseUp</font>的事件处理函式，在收到<font SIZE="2">OnMouseUp</font>事件时，由滑鼠点下的坐标，画一条直线至现在的坐标。</p>
<p>void __fastcall TForm1::FormMouseUp(TObject *Sender, TMouseButton Button,</p>
<p>TShiftState Shift, int X, int Y)</p>
<p>{</p>
<p> Canvas->LineTo(X,Y);</p>
<p>}</p>
<p>在写完了以上两个事件处理函式之後，我们就可以在<font SIZE="2">Form</font>上面作画了，你可以用滑鼠在<font SIZE="2">Form</font>上面拖戈出一条条直线。其执行结果大致如图<font SIZE="2">01</font>：</p>
<p><img SRC="Image8.gif" WIDTH="348" HEIGHT="240">图<font SIZE="2">01</font></p>
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