屏幕快照Xamarin.Forms

Question

我有以下Xaml代码：

<StackLayout>
        <Button Text="Take a picture" Clicked="Button_Clicked_1" />
        <Grid x:Name="MainPageBluePrintGrid" BackgroundColor="BlueViolet" HeightRequest="100">
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
                <ColumnDefinition/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition/>
                <RowDefinition/>
            </Grid.RowDefinitions>

            <Label Text="A" Grid.Row="0" Grid.Column="0"/>
            <Label Text="B" Grid.Row="0" Grid.Column="1"/>
            <Label Text="C" Grid.Row="0" Grid.Column="2"/>

            <Image x:Name="image1" Grid.Row="1" Grid.Column="0"/>
            <Image x:Name="image2" Grid.Row="1" Grid.Column="1"/>
            <Image x:Name="image3" Grid.Row="1" Grid.Column="2"/>
        </Grid>


        <StackLayout BackgroundColor="BurlyWood">
            <Image x:Name="CapturedImage"/>
        </StackLayout>
    </StackLayout>        

第二行是图像，由用户挑选。是否可以仅截取第二行GridView的屏幕截图，并将其显示在<Image x:Name="CapturedImage"/>中。我已经搜索了如何做到这一点，但我只遇到了全屏捕捉，这在我的情况下并不理想。

Answer 1

听起来你想要创建特定Xamarin.Forms.View的快照。你应该将第二个Grid.Row包裹在一个顶级的View中，它将包含作为孩子的图像。之后，您可以使用特定于平台的功能来创建快照。

Android的

public void MakeViewShot(Xamarin.Forms.View view)
{
    var nativeView = view.GetRenderer().View;
    var wasDrawingCacheEnabled = nativeView.DrawingCacheEnabled;
    nativeView.DrawingCacheEnabled = true;
    nativeView.BuildDrawingCache(false);
    var bitmap = nativeView.GetDrawingCache(false);
    // TODO: Save bitmap and return filepath
    nativeView.DrawingCacheEnabled = wasDrawingCacheEnabled;
}

iOS版

public void MakeViewShot(Xamarin.Forms.View view)
{
    var nativeView = Xamarin.Forms.Platform.iOS.Platform.GetRenderer(view).NativeView;
    UIGraphics.BeginImageContextWithOptions(nativeView.Bounds.Size, opaque: true, scale: 0);
    nativeView.DrawViewHierarchy(nativeView.Bounds, afterScreenUpdates: true);
    var image = UIGraphics.GetImageFromCurrentImageContext();
    UIGraphics.EndImageContext();
    // TODO: Save bitmap and return filepath
}

用法示例：

<StackLayout
    x:Name="secondRow"
    Grid.Row="1">
    <Image x:Name="image1" />
    <Image x:Name="image2" />
    <Image x:Name="image3" />
</StackLayout>

MakeViewShot(secondRow);