Printing 在Xamarin UWP中打印具有多个页面的WebView

我正在尝试用xamarin表单打印网页。我正在使用DependencyService打印webview，我已经在android中成功实现了它

对于Windows UWP， 我提到了这个链接：

此过程中使用的方法是仅打印网页的第一页。

编辑：
我创建了一个接口

IPrint

，只为函数提供html源代码

public interface IPrint
{
    void PrintAsync(string htmlSource);
}

在PrintAsync函数中（在Windows UWP项目中）

当WebView完全加载时

    private async void ViewToPrint_LoadCompleteAsync(object sender, Windows.UI.Xaml.Navigation.NavigationEventArgs e)
    {

        if (PrintDoc != null)
        {
            printDoc.AddPages -= PrintDoc_AddPages;
            printDoc.GetPreviewPage -= PrintDoc_GetPreviewPage;
            printDoc.Paginate -= PrintDoc_Paginate;
        }
        this.printDoc = new PrintDocument();
        try
        {
            printDoc.AddPages += PrintDoc_AddPages;
            printDoc.GetPreviewPage += PrintDoc_GetPreviewPage;
            printDoc.Paginate += PrintDoc_Paginate;

            bool showprint = await PrintManager.ShowPrintUIAsync();

        }
        catch (Exception ex)
        {
            Debug.WriteLine(ex.ToString());
        }
        PrintDoc = null;
        GC.Collect();
    }

要在PrintDocument中添加页面

    private void PrintDoc_AddPages(object sender, AddPagesEventArgs e)
    {          
        printDoc.AddPage(ViewToPrint);
        printDoc.AddPagesComplete();
    }

要实现多页打印， 我提到这个链接：

我将AddPages函数更改为以下内容，但它似乎对我不起作用

    private void PrintDoc_AddPages(object sender, AddPagesEventArgs e)
    {     
        rectangleList = GetWebPages(ViewToPrint,  new Windows.Foundation.Size(100d, 150d));
        foreach (Windows.UI.Xaml.Shapes.Rectangle rectangle in rectangleList)
        {
            printDoc.AddPage(rectangle);
        }                                                                                     
        printDoc.AddPagesComplete();
    }

您可以在这里找到GetWebPages（）函数

    List<Windows.UI.Xaml.Shapes.Rectangle> GetWebPages(Windows.UI.Xaml.Controls.WebView webView, Windows.Foundation.Size page)
    {
        // ask the content its width
        var _WidthString = webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollWidth.toString()" }).GetResults();
        int _ContentWidth;
        if (!int.TryParse(_WidthString, out _ContentWidth))
            throw new Exception(string.Format("failure/width:{0}", _WidthString));
        webView.Width = _ContentWidth;

        // ask the content its height
        var _HeightString = webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollHeight.toString()" }).GetResults();
        int _ContentHeight;
        if (!int.TryParse(_HeightString, out _ContentHeight))
            throw new Exception(string.Format("failure/height:{0}", _HeightString));
        webView.Height = _ContentHeight;

        // how many pages will there be?
        var _Scale = page.Width / _ContentWidth;
        var _ScaledHeight = (_ContentHeight * _Scale);
        var _PageCount = (double)_ScaledHeight / page.Height;
        _PageCount = _PageCount + ((_PageCount > (int)_PageCount) ? 1 : 0);

        // create the pages
        var _Pages = new List<Windows.UI.Xaml.Shapes.Rectangle>();
        for (int i = 0; i < (int)_PageCount; i++)
        {
            var _TranslateY = -page.Height * i;
            var _Page = new Windows.UI.Xaml.Shapes.Rectangle
            {
                Height = page.Height,
                Width = page.Width,
                Margin = new Windows.UI.Xaml.Thickness(5),
                Tag = new Windows.UI.Xaml.Media.TranslateTransform { Y = _TranslateY },
            };
            _Page.Loaded += (s, e) =>
            {
                var _Rectangle = s as Windows.UI.Xaml.Shapes.Rectangle;
                var _Brush = GetWebViewBrush(webView);
                _Brush.Stretch = Windows.UI.Xaml.Media.Stretch.UniformToFill;
                _Brush.AlignmentY = Windows.UI.Xaml.Media.AlignmentY.Top;
                _Brush.Transform = _Rectangle.Tag as Windows.UI.Xaml.Media.TranslateTransform;
                _Rectangle.Fill = _Brush;
            };
            _Pages.Add(_Page);
        }
        return _Pages;
    }

    WebViewBrush GetWebViewBrush(Windows.UI.Xaml.Controls.WebView webView)
    {
        // resize width to content
        var _OriginalWidth = webView.Width;
        var _WidthString = webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollWidth.toString()" }).GetResults();
        int _ContentWidth;
        if (!int.TryParse(_WidthString, out _ContentWidth))
            throw new Exception(string.Format("failure/width:{0}", _WidthString));
        webView.Width = _ContentWidth;

        // resize height to content
        var _OriginalHeight = webView.Height;
        var _HeightString = webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollHeight.toString()" }).GetResults();
        int _ContentHeight;
        if (!int.TryParse(_HeightString, out _ContentHeight))
            throw new Exception(string.Format("failure/height:{0}", _HeightString));
        webView.Height = _ContentHeight;

        // create brush
        var _OriginalVisibilty = webView.Visibility;
        webView.Visibility = Windows.UI.Xaml.Visibility.Visible;
        var _Brush = new WebViewBrush
        {
            SourceName = webView.Name,
            Stretch = Windows.UI.Xaml.Media.Stretch.Uniform
        };
        _Brush.Redraw();

        // reset, return
        webView.Width = _OriginalWidth;
        webView.Height = _OriginalHeight;
        webView.Visibility = _OriginalVisibilty;
        return _Brush;
    }

<代码>列表GETWebPage（Windows .U.XAML.Nealth.WebVIEW WebVIEW，Windows .Fask.Stage页面） { //询问内容的宽度 var\u WidthString=webView.InvokeScriptAsync（“eval”， 新建[]{“document.body.scrollWidth.toString（）”}）.GetResults（）； int_ContentWidth； if（！int.TryParse（_WidthString，out_ContentWidth）） 抛出新异常（string.Format（“failure/width:{0}”，_WidthString））； webView.Width=\u ContentWidth； //询问内容的高度 var\u HeightString=webView.InvokeScriptAsync（“eval”， 新建[]{“document.body.scrollHeight.toString（）”}）.GetResults（）； 内部内容高度； 如果（！int.TryParse（_HeightString，out_ContentHeight）） 抛出新异常（string.Format（“failure/height:{0}”，_HeightString））； webView.Height=\u ContentHeight； //有多少页？ var _Scale=页面宽度/_内容宽度； var _ScaledHeight=（_ContentHeight*_Scale）； var _PageCount=（双精度）_ScaledHeight/page.Height； _PageCount=PageCount+（PageCount>（int）PageCount）？1:0； //创建页面 var_Pages=新列表（）； 对于（int i=0；i<（int）\u PageCount；i++） { var_TranslateY=-page.Height*i； var_Page=new Windows.UI.Xaml.Shapes.Rectangle { 高度=页面高度， 宽度=页宽， 边距=新的Windows.UI.Xaml.Thickness（5）， Tag=new Windows.UI.Xaml.Media.TranslateTransform{Y=\u TranslateY}， }; _页面加载+=（s，e）=> { var_Rectangle=s作为Windows.UI.Xaml.Shapes.Rectangle； var_Brush=GetWebViewBrush（webView）； _Brush.Stretch=Windows.UI.Xaml.Media.Stretch.UniformToFill； _Brush.AlignmentY=Windows.UI.Xaml.Media.AlignmentY.Top； _Brush.Transform=_Rectangle.Tag为Windows.UI.Xaml.Media.TranslateTransform； _矩形填充=_画笔； }; _页面。添加（_页面）； } 返回页面； } WebViewBrush GetWebViewBrush（Windows.UI.Xaml.Controls.WebView WebView） { //根据内容调整宽度 var _OriginalWidth=webView.Width； var\u WidthString=webView.InvokeScriptAsync（“eval”， 新建[]{“document.body.scrollWidth.toString（）”}）.GetResults（）； int_ContentWidth； if（！int.TryParse（_WidthString，out_ContentWidth）） 抛出新异常（string.Format（“failure/width:{0}”，_WidthString））； webView.Width=\u ContentWidth； //根据内容调整高度 var _OriginalHeight=webView.Height； var\u HeightString=webView.InvokeScriptAsync（“eval”， 新建[]{“document.body.scrollHeight.toString（）”}）.GetResults（）； 内部内容高度； 如果（！int.TryParse（_HeightString，out_ContentHeight）） 抛出新异常（string.Format（“failure/height:{0}”，_HeightString））； webView.Height=\u ContentHeight； //创建笔刷 var _originalvisibility=webView.Visibility； webView.Visibility=Windows.UI.Xaml.Visibility.Visible； var\u Brush=新的WebViewBrush { SourceName=webView.Name， 拉伸=Windows.UI.Xaml.Media.Stretch.Uniform }; _画笔。重画（）； //复位，返回 宽度=_原始宽度； webView.Height=_原始高度； webView.Visibility=_originalVisibility； 回刷； }

---

@Jerry Nixon的方法对我来说很有效。因为他的代码示例大约在五年前发布在该线程上。对于当前的UWP API，我只做了一些更改（例如，

webView.InvokeScriptAsync

）。我还看到您在代码中调用了

webView.InvokeScriptAsync

方法。那很好。但是你调用

GetResults（）

方法，我不建议你调用

GetResults（）

方法。因为调用javascript代码有时会花费很多时间。您可能会得到异常

一个方法在意外时间被调用

然后，我也注意到你的打印流程有点混乱。请阅读以了解标准化印刷工艺

您可以查看官方代码示例以了解详细信息

以下是您的代码段的更新代码：

async Task<List<Windows.UI.Xaml.Shapes.Rectangle>> GetWebPages(Windows.UI.Xaml.Controls.WebView webView, Windows.Foundation.Size page)
{
        // ask the content its width
        var _WidthString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollWidth.toString()" });
        int _ContentWidth;
        if (!int.TryParse(_WidthString, out _ContentWidth))
            throw new Exception(string.Format("failure/width:{0}", _WidthString));
        webView.Width = _ContentWidth;

        // ask the content its height
        var _HeightString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollHeight.toString()" });
        int _ContentHeight;
        if (!int.TryParse(_HeightString, out _ContentHeight))
            throw new Exception(string.Format("failure/height:{0}", _HeightString));
        webView.Height = _ContentHeight;

        // how many pages will there be?
        var _Scale = page.Width / _ContentWidth;
        var _ScaledHeight = (_ContentHeight * _Scale);
        var _PageCount = (double)_ScaledHeight / page.Height;
        _PageCount = _PageCount + ((_PageCount > (int)_PageCount) ? 1 : 0);

        // create the pages
        var _Pages = new List<Windows.UI.Xaml.Shapes.Rectangle>();
        for (int i = 0; i < (int)_PageCount; i++)
        {
            var _TranslateY = -page.Height * i;
            var _Page = new Windows.UI.Xaml.Shapes.Rectangle
            {
                Height = page.Height,
                Width = page.Width,
                Margin = new Windows.UI.Xaml.Thickness(5),
                Tag = new Windows.UI.Xaml.Media.TranslateTransform { Y = _TranslateY },
            };
            _Page.Loaded +=async (s, e) =>
            {
                var _Rectangle = s as Windows.UI.Xaml.Shapes.Rectangle;
                var _Brush = await GetWebViewBrush(webView);
                _Brush.Stretch = Windows.UI.Xaml.Media.Stretch.UniformToFill;
                _Brush.AlignmentY = Windows.UI.Xaml.Media.AlignmentY.Top;
                _Brush.Transform = _Rectangle.Tag as Windows.UI.Xaml.Media.TranslateTransform;
                _Rectangle.Fill = _Brush;
            };
            _Pages.Add(_Page);
        }
        return _Pages;
}

    async Task<WebViewBrush> GetWebViewBrush(Windows.UI.Xaml.Controls.WebView webView)
    {
        // resize width to content
        var _OriginalWidth = webView.Width;
        var _WidthString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollWidth.toString()" });
        int _ContentWidth;
        if (!int.TryParse(_WidthString, out _ContentWidth))
            throw new Exception(string.Format("failure/width:{0}", _WidthString));
        webView.Width = _ContentWidth;

        // resize height to content
        var _OriginalHeight = webView.Height;
        var _HeightString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollHeight.toString()" });
        int _ContentHeight;
        if (!int.TryParse(_HeightString, out _ContentHeight))
            throw new Exception(string.Format("failure/height:{0}", _HeightString));
        webView.Height = _ContentHeight;

        // create brush
        var _OriginalVisibilty = webView.Visibility;
        webView.Visibility = Windows.UI.Xaml.Visibility.Visible;
        var _Brush = new WebViewBrush
        {
            SourceName = webView.Name,
            Stretch = Windows.UI.Xaml.Media.Stretch.Uniform
        };
        _Brush.Redraw();

        // reset, return
        webView.Width = _OriginalWidth;
        webView.Height = _OriginalHeight;
        webView.Visibility = _OriginalVisibilty;
        return _Brush;
    }

<代码>异步任务GETWebPage（Windows .U.XAML.Nealth.WebVIEW WebVIEW，WiDOW.Studio.Stage页面） { //询问内容的宽度 var\u WidthString=wait webView.InvokeScriptAsync（“eval”， 新[]{“document.body.scrollWidth.toString（）”}）； int_ContentWidth； if（！int.TryParse（_WidthString，out_ContentWidth）） 抛出新异常（string.Format（“failure/width:{0}”，_WidthString））； webView.Width=\u ContentWidth； //询问内容的高度 var\u HeightString=wait webView.InvokeScriptAsync（“eval”， 新[]{“document.body.scrollHeight.toString（）”}）； int

async Task<List<Windows.UI.Xaml.Shapes.Rectangle>> GetWebPages(Windows.UI.Xaml.Controls.WebView webView, Windows.Foundation.Size page)
{
        // ask the content its width
        var _WidthString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollWidth.toString()" });
        int _ContentWidth;
        if (!int.TryParse(_WidthString, out _ContentWidth))
            throw new Exception(string.Format("failure/width:{0}", _WidthString));
        webView.Width = _ContentWidth;

        // ask the content its height
        var _HeightString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollHeight.toString()" });
        int _ContentHeight;
        if (!int.TryParse(_HeightString, out _ContentHeight))
            throw new Exception(string.Format("failure/height:{0}", _HeightString));
        webView.Height = _ContentHeight;

        // how many pages will there be?
        var _Scale = page.Width / _ContentWidth;
        var _ScaledHeight = (_ContentHeight * _Scale);
        var _PageCount = (double)_ScaledHeight / page.Height;
        _PageCount = _PageCount + ((_PageCount > (int)_PageCount) ? 1 : 0);

        // create the pages
        var _Pages = new List<Windows.UI.Xaml.Shapes.Rectangle>();
        for (int i = 0; i < (int)_PageCount; i++)
        {
            var _TranslateY = -page.Height * i;
            var _Page = new Windows.UI.Xaml.Shapes.Rectangle
            {
                Height = page.Height,
                Width = page.Width,
                Margin = new Windows.UI.Xaml.Thickness(5),
                Tag = new Windows.UI.Xaml.Media.TranslateTransform { Y = _TranslateY },
            };
            _Page.Loaded +=async (s, e) =>
            {
                var _Rectangle = s as Windows.UI.Xaml.Shapes.Rectangle;
                var _Brush = await GetWebViewBrush(webView);
                _Brush.Stretch = Windows.UI.Xaml.Media.Stretch.UniformToFill;
                _Brush.AlignmentY = Windows.UI.Xaml.Media.AlignmentY.Top;
                _Brush.Transform = _Rectangle.Tag as Windows.UI.Xaml.Media.TranslateTransform;
                _Rectangle.Fill = _Brush;
            };
            _Pages.Add(_Page);
        }
        return _Pages;
}

    async Task<WebViewBrush> GetWebViewBrush(Windows.UI.Xaml.Controls.WebView webView)
    {
        // resize width to content
        var _OriginalWidth = webView.Width;
        var _WidthString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollWidth.toString()" });
        int _ContentWidth;
        if (!int.TryParse(_WidthString, out _ContentWidth))
            throw new Exception(string.Format("failure/width:{0}", _WidthString));
        webView.Width = _ContentWidth;

        // resize height to content
        var _OriginalHeight = webView.Height;
        var _HeightString = await webView.InvokeScriptAsync("eval",
            new[] { "document.body.scrollHeight.toString()" });
        int _ContentHeight;
        if (!int.TryParse(_HeightString, out _ContentHeight))
            throw new Exception(string.Format("failure/height:{0}", _HeightString));
        webView.Height = _ContentHeight;

        // create brush
        var _OriginalVisibilty = webView.Visibility;
        webView.Visibility = Windows.UI.Xaml.Visibility.Visible;
        var _Brush = new WebViewBrush
        {
            SourceName = webView.Name,
            Stretch = Windows.UI.Xaml.Media.Stretch.Uniform
        };
        _Brush.Redraw();

        // reset, return
        webView.Width = _OriginalWidth;
        webView.Height = _OriginalHeight;
        webView.Visibility = _OriginalVisibilty;
        return _Brush;
    }