windows8中实现的线性化刷问题

<StackPanel>            

<Button Content="点我" FontSize="30" >                

<Button.Background>                    

<SolidColorBrush Color="Red"/>                

</Button.Background>            

</Button>            

 

<Button Content="线性画刷" HorizontalAlignment="Left" Margin="14,448,0,0" VerticalAlignment="Top" Width="650" Height="87">                 <Button.Background>                    

<LinearGradientBrush>

<GradientStop Color="Red" Offset="0.1"/>                        

<GradientStop Color="blue" Offset="0.1"/>                      

<GradientStop Color="Blue" Offset="0.5"/>                        

<GradientStop Color="Black" Offset="0.5"/>                       

<GradientStop Color="Black" Offset="1"/>                    

</LinearGradientBrush>                

</Button.Background>            

</Button>            

 

<TextBlock HorizontalAlignment="Left" TextWrapping="Wrap" Text="TextBlock" VerticalAlignment="Top"/>            

<TextBlock Text="我是一只小小鸟，想要飞，可惜翅膀断了" FontSize="30" >                

<TextBlock.Foreground>                    

<LinearGradientBrush>                        

<GradientStop x:Name="gs1" Color="Yellow" Offset="0.1"/>                        

<GradientStop x:Name="gs2" Color="Blue" Offset="0.1"/>                        

<GradientStop Color="Blue" Offset="1"/>                    

</LinearGradientBrush>                

</TextBlock.Foreground>            

</TextBlock>        

</StackPanel>

 

 

 

后台------------

protected override void OnNavigatedTo(NavigationEventArgs e)        

{            

DispatcherTimer timer = new DispatcherTimer();            

timer.Interval = TimeSpan.FromMilliseconds(700);            

timer.Tick += timer_Tick;            

timer.Start();        

}

void timer_Tick(object sender, object e)        

{            

gs1.Offset += 0.01;            

gs2.Offset += 0.01;        

}

<Canvas>            

<Button Content="点我" FontSize="30" Canvas.Left="281" Canvas.Top="188" Width="140" Height="80">                

<Button.RenderTransform>                    

<RotateTransform Angle="20" CenterX="70" CenterY="40"/>                

</Button.RenderTransform>            

</Button>            

<Button Content="动起来" FontSize="30" Canvas.Left="488" Canvas.Top="70" Height="60" Width="201" Click="Button_Click_1"/>        

</Canvas>