WinCE下透明Label闪烁的问题及解决方案(vb.net)

之前写了一篇WINCE背景图上透明Label显示的解决方法，实际上就是在背景图片上将字体“画”上去，去除掉了标准控件不透明的丑恶面容。

随着项目的进一步开发，发现当背景图片上很多的情况下，改变某一个Label的内容时，其它的Lable跟着闪一下。在尝试各种方法后依然不能解决。在网上查下来的资料大都采用双缓冲的方法，即先在内存画板上将Label画好，然后dump到屏幕上。

具体的方法是在pictureBox的Paint事件中:

1，取得pictureBox的graphic句柄；

2，准备好新的bitmap,先画背景再一个一个地把Label画上去，

3，利用pictureBox的graphic句柄，将第二步的bitmap画到pictureBox中

具体代码如下：

Private Sub picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a>1_Paint(ByVal sender As Object,ByVal e As System.Windows.Forms.PaintEventArgs) Dim pic<a href="/tag/Box/" target="_blank" class="keywords">Box</a>Graphics As Graphics = e.Graphics Dim map As Bitmap = New Bitmap("/1.bmp") 'get memery graphics Dim bitmapGraphics As Graphics = Graphics.FromImage(map) 'draw to memery DrawLabel(Label1,Me,bitmapGraphics) DrawLabel(Label2,bitmapGraphics) 'draw to picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a> pic<a href="/tag/Box/" target="_blank" class="keywords">Box</a>Graphics.DrawImage(map,0) 'release resource bitmapGraphics.Dispose() map.Dispose() pic<a href="/tag/Box/" target="_blank" class="keywords">Box</a>Graphics.Dispose() End Sub@H_<a href="/tag/404/" target="_blank" class="keywords">404</a>_16@ </p> <p> 我承认: 这样做的好处是效率高，<a href="/tag/xianshisudu/" target="_blank" class="keywords">显示速度</a>快。</p> <p> 但是我的项目这样做之后，<span style="color: #ff0000;">屏幕闪烁的问题还是没有<a href="/tag/jiejue/" target="_blank" class="keywords">解决</a>呀</span> ！！</p> <p> 仔细分析下来，终有成果。闪烁的根源在哪呢？原来当需要改变某一个Label时，WINCE是这样做的:</p> <p> 1，稳定<a href="/tag/xianshi/" target="_blank" class="keywords">显示</a>各LABEL</p> <p> 2，有需求改变某一LABEL<a href="/tag/neirong/" target="_blank" class="keywords">内容</a>时，<a href="/tag/diaoyong/" target="_blank" class="keywords">调用</a>picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a>的refresh<a href="/tag/hanshu/" target="_blank" class="keywords">函数</a>，这时picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a>是<span style="color: #ff0000;">先绘背景</span> </p> <p> 3，当执行到paint事件时,背景已经准备好，<span style="color: #ff0000;">然<a href="/tag/houzhixing/" target="_blank" class="keywords">后执行</a>paint事件里<a href="/tag/yonghu/" target="_blank" class="keywords">用户</a>的画图命令</span> 。</p> <p> 这样问题就来了，Label在改变时，中间插了一帧干净的背景，如果背景颜色和其它LABEL颜色差别很大的话，闪烁更厉害。</p> <p> <span style="color: #ff0000;">所以<a href="/tag/jiejue/" target="_blank" class="keywords">解决</a>的思路就是避免插入干净的背景，而是直接将带有Label<a href="/tag/neirong/" target="_blank" class="keywords">内容</a>的背景画出来，这样才是<a href="/tag/jiejue/" target="_blank" class="keywords">解决</a>闪烁问题的关键！</span> </p> <p><span style="color: #ff0000;"> <span style="color: #000000;"><span style="background-color: #ffffff;">具体的做法是在执行picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a> refresh()之前，创建</span> </span> </span> <span style="color: #000000;"><span style="background-color: #ffffff;">带有Label 字的bitmap背景，然后将picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a>的image<a href="/tag/shuxing/" target="_blank" class="keywords">属性</a>换成这个bitmap背景。</span> </span> </p> <p><span style="color: #ff0000;"> <span style="color: #000000;">具体做法如下（在<a href="/tag/shangyipian/" target="_blank" class="keywords">上一篇</a>blog<wince下透明Label的实现>基础上）：</span> </span> </p> <p><span style="color: #000000;"> 1，去掉picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a> paint事件,orimap是纯背景</span> </p> <p><span style="color: #000000;"> 2，<a href="/tag/zengjia/" target="_blank" class="keywords">增加</a>新<a href="/tag/hanshu/" target="_blank" class="keywords">函数</a>UpdateShow()，取代Picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a>1.refresh()</span> </p> <p><span style="color: #ff0000;"><textarea cols="50" rows="15" name="code" class="vb:nogutter:collapse"> Private Sub UpdateShow() Try Dim map As Bitmap = orimap.Clone 'get memery graphics Dim bitmapGraphics As Graphics = Graphics.FromImage(map) 'draw to memery DrawLabel(Label1,bitmapGraphics) DrawLabel(Label2,bitmapGraphics) 'load new image Picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a>1.Image = map Picture<a href="/tag/Box/" target="_blank" class="keywords">Box</a>1.Refresh() 'release resource bitmapGraphics.Dispose() map.Dispose() Catch ex As Exception End Try End Sub@H_<a href="/tag/404/" target="_blank" class="keywords">404</a>_16@ <br> </span> </p> <p><span style="color: #ff0000;"> <br> </span> </p> <p> OK,这样每次画的背景都带有Label<a href="/tag/neirong/" target="_blank" class="keywords">内容</a>，如果Label<a href="/tag/neirong/" target="_blank" class="keywords">内容</a>不变，屏幕就不会闪啦。</p> <p> 下面的图是做的小实验，两个图标，一个图标<a href="/tag/neirong/" target="_blank" class="keywords">内容</a>不变，另一个图标是数字，每过1mm<a href="/tag/neirong/" target="_blank" class="keywords">内容</a>加一。</p> <p> 如果将<span style="color: #ff0000;">双缓冲做在paint事件里，那两个图标都闪得不行</span> 。如果<span style="color: #ff0000;">将双缓冲做在paint事件之外，废掉paint事件画图</span> （即上面的做法），这样<a href="/tag/neirong/" target="_blank" class="keywords">内容</a>不变的Label一点都不会闪的。</p> <p> </p> <p> </p></div> <div class="topcard-tags"></div> <ul class="list-group"> <li class="list-group-item"><a href="/vb/261804.html" title="VB动态添加执行代码完整版(三)">上一篇：VB动态添加执行代码完整版(三)</a><a href="/vb/261802.html" title="像素画点算法" class="text-muted pull-right">下一篇：像素画点算法</a> </li> </ul> </div> </div> </div>  <div class="row row-sm"> <div class="col-sm-12 col-md-12 col-lg-12"> <div 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