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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>

第二行是用户选择的图片。是否可以只截取GridView第二行的截图，并显示在<Image x:Name="CapturedImage"/>中。我搜索了如何操作，但我只遇到了全屏捕获，这对我来说并不理想。

Answer 1

听起来您想创建特定 Xamarin.Forms.View 的快照。您应该将第二个 Grid.Row 包裹在一个顶层 View 中，该层将包含子图像。之后，您可以使用特定于平台的功能来创建快照。

Android

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

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);

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