【发布时间】：2014-01-24 09:03:21
【问题描述】：
我有一项功能允许用户在设备上的前置摄像头和主摄像头之间切换。在切换过程中，我想向用户显示一个 ProgressBar 和 TextBlock。由于某种原因，我无法让这些显示在视图中，并且在切换过程中唯一显示的是未旋转 VideoBrush 的冻结图像
MainPage.xaml
<Grid.RowDefinitions>
<RowDefinition Height="72"/>
<RowDefinition Height="*"/>
<RowDefinition Height="68"/>
<RowDefinition Height="72"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="72"/>
<ColumnDefinition Width=".33*"/>
<ColumnDefinition Width=".33*"/>
<ColumnDefinition Width=".33*"/>
<ColumnDefinition Width="72"/>
</Grid.ColumnDefinitions>
<!-- Center this on the screen -->
<Canvas x:Name="VideoCanvas" Grid.Row="0" Grid.RowSpan="4" Grid.ColumnSpan="5"
VerticalAlignment="Center" HorizontalAlignment="Center">
<Canvas.Background>
<VideoBrush x:Name="videoBrush">
<VideoBrush.RelativeTransform>
<CompositeTransform x:Name="videoBrushTransform"
CenterX="0.5" CenterY="0.5"/>
</VideoBrush.RelativeTransform>
</VideoBrush>
</Canvas.Background>
</Canvas>
...
<StackPanel Grid.Row="1" Grid.ColumnSpan="5" VerticalAlignment="Center">
<ProgressBar x:Name="progressIndicator" IsIndeterminate="False" Background="Transparent"/>
<TextBlock x:Name="modeChangeTextBlock" Margin="12"
VerticalAlignment="Top" HorizontalAlignment="Center" FontSize="28"
Foreground="{StaticResource PhoneSubtleBrush}"/>
</StackPanel>
MainPage.xaml.cs
void sensor_Click(object sender, EventArgs e)
{
CameraType type = camera.CameraType;
//Switch to other camera, if available
if(type == CameraType.Primary)
{
if(PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing) == true)
{
ShowProgress("Switching cameras");
UninitializeCamera();
InitializeCamera(CameraType.FrontFacing);
HideProgress();
}
}
else
{
if(PhotoCamera.IsCameraTypeSupported(CameraType.Primary) == true)
{
ShowProgress("Switching cameras");
UninitializeCamera();
InitializeCamera(CameraType.Primary);
HideProgress();
}
}
}
...
private void ShowProgress(String msg)
{
progressIndicator.IsIndeterminate = true;
modeChangeTextBlock.Text = msg;
//progressIndicator.Visibility = Visibility.Visible;
}
private void HideProgress()
{
progressIndicator.IsIndeterminate = false;
modeChangeTextBlock.Text = "";
//progressIndicator.Visibility = Visibility.Collapsed;
}
EDIT * 添加在现有 xaml 代码下方用于测试
<Rectangle x:Name="cameraSwitchingFill" Visibility="Visible"
Fill="{StaticResource SelfiePageBackgroundColorBrush}"
Grid.Row="0" Grid.Column="0" Grid.RowSpan="4" Grid.ColumnSpan="5"/>
<StackPanel Grid.Row="1" Grid.ColumnSpan="5" VerticalAlignment="Center">
<ProgressBar x:Name="progressIndicator" IsIndeterminate="True" Background="Transparent"/>
<TextBlock x:Name="modeChangeTextBlock" Margin="12"
VerticalAlignment="Top" HorizontalAlignment="Center" FontSize="28"
Foreground="{StaticResource PhoneSubtleBrush}" Text="test"/>
</StackPanel>
添加的编辑是尝试查看为什么在相机切换期间进度条不显示。设置要在屏幕上看到的所有内容，当第一次导航到此页面时，我看到的只是cameraSwitchingFill 矩形，上面没有 ProgressBar 或 TextBlock（尽管在设计器中我可以看到这些很好）。切换相机后，（如预期的那样）我看到了矩形，但没有看到 ProgressBar 或 TextBlock。
然后我回去不显示编辑和修改
void sensor_Click(object sender, EventArgs e) { //切换到其他相机，如果可用 CameraType type = camera.CameraType;
if(type == CameraType.Primary)
{
if(PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing) == true)
{
ShowProgress(AppResources.CapturePage_SwitchingCameras);
cameraSwitchingFill.Visibility = Visibility.Visible;
UninitializeCamera();
InitializeCamera(CameraType.FrontFacing);
cameraSwitchingFill.Visibility = Visibility.Collapsed;
HideProgress();
}
}
else
{
if(PhotoCamera.IsCameraTypeSupported(CameraType.Primary) == true)
{
ShowProgress(AppResources.CapturePage_SwitchingCameras);
cameraSwitchingFill.Visibility = Visibility.Visible;
UninitializeCamera();
InitializeCamera(CameraType.Primary);
cameraSwitchingFill.Visibility = Visibility.Collapsed;
HideProgress();
}
}
}
所以结果是当我永久使矩形和进度条显示在屏幕上时，只有矩形显示，直到第一个相机切换点击事件发生，此后矩形或进度条都不会显示。此外，即使在 xaml 中的 videobrush 实现下方声明的矩形和进度条在此期间设置为可见，在切换期间冻结的图像仍保留在屏幕上。
【问题讨论】：
-
这只是一个想法 - 您可以使用叠加层
标签： c# xaml windows-phone-7 windows-phone-8 camera