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我正在尝试以 xamarin 形式打印网页。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，我参考了这个链接：
https
://forums.xamarin.com/discussion/91163/problem-with-printing-webview-in-uwp-phone 这里使用的方法是只打印第一页网页。

编辑：
我创建了一个界面IPrint，只提供函数的 html 源代码。

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

在 PrintAsync 函数中（在 Windows UWP 项目中），

    async void IPrint.PrintAsync(string htmlSource)
    {
        ViewToPrint.NavigateToString(htmlSource);
        ViewToPrint.LoadCompleted += ViewToPrint_LoadCompleteAsync;
    }

当 WebView 完全加载后，

    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();
    }


为了实现多页打印， 我参考了这个链接：https ://stackoverflow.com/a/17222629/6366591

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();
    }

您可以在此处找到 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;
    }
4

1 回答 1

0

@Jerry Nixon 的方法对我来说效果很好。由于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，我只是做了一些改动（例如，webView.InvokeScriptAsync）。我还看到您 webView.InvokeScriptAsync在代码中调用了该方法。那挺好的。但是你调用GetResults()方法，我不建议你调用GetResults()方法。因为调用 javascript 代码有时会花费你很多时间。您可能会遇到异常A method was called at an unexpected time。

然后，我还注意到您的打印流程有点混乱。请从您的应用程序中阅读 Print以了解标准化的打印流程。

您可以查看官方代码示例打印示例以获取详细信息。

以下是您的代码片段的更新代码：

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;
    }

我使用了打印示例并将上面更新的代码放入其中并进行了一些相关更改，然后我可以成功打印所有网页。

于 2018-05-24T08:35:50.453 回答