值得注意的IsHitTestVisible

Posted 2020-08-11 普通的地球人

这个属性我们平时可能并不怎么用.先来看下MSDN上的解释:

解释的非常专业,然而我并没有看懂.

说说我的理解吧:把这个属性设置为false,看起来没有变化,但操作上已经把他完全忽视了,不触发事件,可以直接点到它下面的东西.

 

这个属性能方便的解决工作中常见的麻烦,比如下面这个例子:

注意上面那部分.效果很简单,就是个渐变的效果.但是这个渐变贯穿了两列,就使得处理起来有点小麻烦.

当然解决方案有很多:

可以写两个ListBoxItem的样式,第一个放顶部有渐变的背景,和右部保持一致,通过样式选择器来实现.这显然比较麻烦.

还可以在大背景下放个渐变,ListBoxItem的上半部分做成透明,这样相对简单,但不一定能实现理想的效果.

 

IsHitTestVisible属性就很好的解决了这个问题.直接在上层放个border,背景设置成渐变,IsHitTestVisible设置为false.这样就既能看到渐变效果,又能透过border,直接点到ListBoxItem.设置一个属性就解决了问题,非常方便.相当于在上面放了个蒙板,但是这个蒙板能看到却点不到.

 

类似的我还想到了一个场景:

 

这个效果顶层是个图片,IsHitTestVisible为false,透明为0.3.

并不是图片是个背景,然后所有控件都是半透明效果.

见代码:

 XMAL:

 1     <Grid>
 2         <Grid>
 3             <Grid.RowDefinitions>
 4                 <RowDefinition Height="70"></RowDefinition>
 5                 <RowDefinition></RowDefinition>
 6                 <RowDefinition Height="50"></RowDefinition>
 7             </Grid.RowDefinitions>
 8             <Border Background="#555F5F">
 9                 <Label Content="logo" Foreground="White"></Label>
10             </Border>
11             <Grid Grid.Row="1" Background="#AAAFAF">
12                 <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center" Button.Click="StackPanel_Click">
13                     <Button Width="132" Height="32" Content="金闪闪" Margin="10"></Button>
14                     <Button Width="132" Height="32" Content="小圆" Margin="10"></Button>
15                 </StackPanel>
16                 <Label Content="我不透明" Background="Green" Foreground="Blue" Width="100" Height="100" Margin="76,29,266,171"></Label>
17                 <Label Content="我不透明" Background="Red" Foreground="Blue" Width="100" Height="40" Margin="112,40,230,220"></Label>
18             </Grid>
19             <Border Grid.Row="2" Background="#555F5F">
20                 <Label Content="状态栏" Foreground="White"></Label>
21             </Border>
22         </Grid>
23         <Image Name="img" HorizontalAlignment="Center" VerticalAlignment="Center" Width="0" Height="0" Source="/Image/jinshanshan.jpg" Stretch="Fill" Opacity="0.1" IsHitTestVisible="False"></Image>
24     </Grid>

后台:

 

 1        private void StackPanel_Click(object sender, RoutedEventArgs e)
 2         {
 3             Button btn = (Button)e.OriginalSource;
 4             string content = btn.Content.ToString();
 5             if (content == "金闪闪")
 6             {
 7                 img.Source = new BitmapImage(new Uri(@"/Image/jinshanshan.jpg", UriKind.Relative));
 8             }
 9             if (content == "小圆")
10             {
11                 img.Source = new BitmapImage(new Uri(@"/Image/xiaoyuan.jpg", UriKind.Relative));
12             }
13 
14             DoubleAnimation daX = new DoubleAnimation();
15             daX.From = 0;
16             daX.To = 400;
17             daX.FillBehavior = FillBehavior.HoldEnd;
18             Storyboard.SetTarget(daX, img);
19             Storyboard.SetTargetProperty(daX, new PropertyPath(Image.WidthProperty));
20             DoubleAnimation daY = new DoubleAnimation();
21             daY.From = 0;
22             daY.To = 400;
23             daY.FillBehavior = FillBehavior.HoldEnd;
24             Storyboard.SetTarget(daY, img);
25             Storyboard.SetTargetProperty(daY, new PropertyPath(Image.HeightProperty));
26             DoubleAnimation daOp = new DoubleAnimation();
27             daOp.From = 1;
28             daOp.To = 0.3;
29             daOp.FillBehavior = FillBehavior.HoldEnd;
30             Storyboard.SetTarget(daOp, img);
31             Storyboard.SetTargetProperty(daOp, new PropertyPath(Image.OpacityProperty));
32 
33             Storyboard sb = new Storyboard();
34             sb.Children.Add(daX);
35             sb.Children.Add(daY);
36             sb.Children.Add(daOp);
37             sb.Begin();
38         }