050.htm

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<p></font><font face="宋体" lang="ZH-CN" size="3">①</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">在</font><font face="Arial" size="3">Shape</font><font
face="宋体" lang="ZH-CN" size="3">控制的</font><font face="Arial" size="3">constructor</font><font
face="宋体" lang="ZH-CN" size="3">中创建</font><font face="Arial" size="3">Pen</font><font
face="宋体" lang="ZH-CN" size="3">和</font><font face="Arial" size="3">Brush</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p>constructor TSampleShape.Create(Aowner: TComponent);</p>
<p>begin</p>
<p>inherited Create(AOwner);</p>
<p>Width := 65;</p>
<p>Height := 65;</p>
<p>FPen := TPen.Create;</p>
<p>FBrush := TBrush.Create;</p>
<p>end;</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">②</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">在部件对象的声明中覆盖</font><font
face="Arial" size="3">destructor</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p>type</p>
<p>TSampleShape=class(TGraphicControl)</p>
<p>public</p>
<p>construstor.Create(Aowner: TComponent); override;</p>
<p>destructor.destroy; override;</p>
<p>end;</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">③</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">在库单元中的实现部分编写新的</font><font
face="Arial" size="3">destructor</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p>destructor TSampleShape.destroy;</p>
<p>begin</p>
<p>FPen.Free;</p>
<p>FBrush.Free;</p>
<p>inherited destroy;</p>
<p>end;</font><font face="宋体" lang="ZH-CN" size="3"></p>
<p>　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">④</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">设置</font><font face="Arial" size="3">Owned</font><font
face="宋体" lang="ZH-CN" size="3">对象的属性</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">处理</font><font face="Arial"
size="3">Pen</font><font face="宋体" lang="ZH-CN" size="3">和</font><font face="Arial"
size="3">Brush</font><font face="宋体" lang="ZH-CN" size="3">对象的最后一步是处理</font><font
face="Arial" size="3">Pen</font><font face="宋体" lang="ZH-CN" size="3">和</font><font
face="Arial" size="3">Brush</font><font face="宋体" lang="ZH-CN" size="3">发生改变时对</font><font
face="Arial" size="3">Shape</font><font face="宋体" lang="ZH-CN" size="3">控制的重画问题。</font><font
face="Arial" size="3">Pen</font><font face="宋体" lang="ZH-CN" size="3">和</font><font
face="Arial" size="3">Brush</font><font face="宋体" lang="ZH-CN" size="3">对象都有</font><font
face="Arial" size="3">OnChange</font><font face="宋体" lang="ZH-CN" size="3">事件，因此能够在</font><font
face="Arial" size="3">Shape</font><font face="宋体" lang="ZH-CN" size="3">控制中声明</font><font
face="Arial" size="3">OnChange</font><font face="宋体" lang="ZH-CN" size="3">事件指向的事件处理过程。</font><font
face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">下面给</font><font face="Arial"
size="3">Shape</font><font face="宋体" lang="ZH-CN" size="3">控制增加了该方法并更新了部件的</font><font
face="Arial" size="3">constructor</font><font face="宋体" lang="ZH-CN" size="3">以使</font><font
face="Arial" size="3">Pen</font><font face="宋体" lang="ZH-CN" size="3">和</font><font
face="Arial" size="3">Brush</font><font face="宋体" lang="ZH-CN" size="3">事件指向新方法：</p>
<p>　</font><font face="Arial" size="3"></p>
<p>type</p>
<p>TSampleShape = class(TGraphicControl)</p>
<p>published</p>
<p>procdeure StyleChanged(Sender: TObject);</p>
<p>end;</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p>implemintation</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p>constructor TSampleShape.Create(AOwner:TComponent);</p>
<p>begin </p>
<p>inherited Create(AOwner);</p>
<p>Width := 65;</p>
<p>Height := 65;</p>
<p>Fpen := TPen.Create;</p>
<p>FPen.OnChange := StyleChanged;</p>
<p>Fbrush := TBrush.Create;</p>
<p>FBrush.OnChange := StyleChanged;</p>
<p>end;</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p>procedure TSampleShape.StyleChanged(Sender: TObject);</p>
<p>begin</p>
<p>Invalidate(true);</p>
<p>end;</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">当变化发生时，部件重画以响应</font><font
face="Arial" size="3">Pen</font><font face="宋体" lang="ZH-CN" size="3">或</font><font
face="Arial" size="3">Brush</font><font face="宋体" lang="ZH-CN" size="3">的改变。</p>
<p>　</font><font face="Arial" size="3"></p>
<p>4. </font><font face="宋体" lang="ZH-CN" size="3">怎样画部件图形</font><font
face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">图形控制基本要素是在屏幕上画图形的方法。抽象类</font><font
face="Arial" size="3">TGraphicControl</font><font face="宋体" lang="ZH-CN" size="3">定义了名为</font><font
face="Arial" size="3">Paint</font><font face="宋体" lang="ZH-CN" size="3">的虚方法，可以覆盖该方法来画所要的图形。</font><font
face="Arial" size="3"></p>
<p>Shape</font><font face="宋体" lang="ZH-CN" size="3">控制的</font><font
face="Arial" size="3">paint</font><font face="宋体" lang="ZH-CN" size="3">方法需要做：</font><font
face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">●</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">使用用户选择的</font><font
face="Arial" size="3">Pen</font><font face="宋体" lang="ZH-CN" size="3">和</font><font
face="Arial" size="3">Brush</p>
<p></font><font face="宋体" lang="ZH-CN" size="3">●</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">使用所选的形状</font><font
face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">●</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">调整座标。这样，方形和圆可以使用相同的</font><font
face="Arial" size="3">Width</font><font face="宋体" lang="ZH-CN" size="3">和</font><font
face="Arial" size="3">Height</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">覆盖</font><font face="Arial"
size="3">paint</font><font face="宋体" lang="ZH-CN" size="3">方法需要两步：</font><font
face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">●</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">在部件声明中增加</font><font
face="Arial" size="3">Paint</font><font face="宋体" lang="ZH-CN" size="3">方法的声明</font><font
face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">●</font><font face="Arial" size="3">
</font><font face="宋体" lang="ZH-CN" size="3">在</font><font face="Arial" size="3">implementation</font><font
face="宋体" lang="ZH-CN" size="3">部分写</font><font face="Arial" size="3">Paint</font><font
face="宋体" lang="ZH-CN" size="3">方法的实现</p>
<p>　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">下面是</font><font face="Arial"
size="3">Paint</font><font face="宋体" lang="ZH-CN" size="3">方法的声明：</p>
<p>　</font><font face="Arial" size="3"></p>
<p>type</p>
<p>TSampleShape = class(TGraphicControl)</p>
<p>protected</p>
<p>procedure Paint; override;</p>
<p>end;</p>
<p></font><font size="3">　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">然后，编写</font><font
face="Arial" size="3">Paint</font><font face="宋体" lang="ZH-CN" size="3">的实现：</p>
<p>　</font><font face="Arial" size="3"></p>
<p>procedure TSampleShape.Paint;</p>
<p>begin</p>
<p>with Canvas do</p>
<p>begin</p>
<p>Pen := FPen;</p>
<p>Brush := FBrush;</p>
<p>case FShape of</p>
<p>sstRectangle, sstSquare :</p>
<p>Rectangle(0, 0, Width, Height);</p>
<p>sstRoundRect, sstRoundSquare: </p>
<p>RoundRect(0, 0, Width, Height, Width div 4, Height div 4);</p>
<p>sstCircle, sstEllipse :</p>
<p>Ellipse(0, 0, Width, Height);</p>
<p>end;</p>
<p>end;</p>
<p>end;</font><font size="3">　</font><font face="Arial" size="3"></p>
<p></font><font face="宋体" lang="ZH-CN" size="3">无论任何控制需要更新图形时，</font><font
face="Arial" size="3">Paint</font><font face="宋体" lang="ZH-CN" size="3">就被调用。当控制第一次出现，或者当控制前面的窗口消失时，</font><font
face="Arial" size="3">Windows</font><font face="宋体" lang="ZH-CN" size="3">会通知控制画自己。也可以通过调用</font><font
face="Arial" size="3">Invalidate</font><font face="宋体" lang="ZH-CN" size="3">方法强制重画，就象</font><font
face="Arial" size="3">StyleChanged</font><font face="宋体" lang="ZH-CN" size="3">方法所做的那样。</font></p>
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