如何使用手机默认打印机功能在Xamarin Android中打印从WebView打开的PDF内容

Question

Can any one help me with the problem, to print the url content. I am opening the PDF file in a web view of my application and then trying to print the document from there by placing separate button for printing. Please look at the code below.

    [Activity(Label = "PdfView")]
    public class PdfView : Activity
    {
        public static PdfView _context;
        Android.Content.Res.Resources res;
        private static string ErrorTitle, ErrorMsg;
        private static ProgressBar progressBar;

        WebView mWebView, Web_Print;
        RelativeLayout LL_Print,LL_input;
        string MyUrl;
        private WebClient _webClient = new WebClient();
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            _context = this;
            res = _context.Resources;
            SetContentView(Resource.Layout.web_pdf);
            ErrorTitle = res.GetString(Resource.String.error_title);
            ErrorMsg = res.GetString(Resource.String.Somethingwentwrong);
            progressBar = FindViewById<ProgressBar>(Resource.Id.progressBar1);
            LL_Print = FindViewById<RelativeLayout>(Resource.Id.LL_Print);
            LL_input = FindViewById<RelativeLayout>(Resource.Id.LL_input);
            Web_Print = FindViewById<WebView>(Resource.Id.Web_Print);
            Web_Print.Visibility = ViewStates.Gone;
            LL_Print.Visibility = ViewStates.Gone;
            var customWebViewClient = new WebViewLoaderClient();
            mWebView = FindViewById<WebView>(Resource.Id.Web);
            mWebView.Download += MWebview_Download;               
            mWebView.Settings.JavaScriptEnabled = true;
            mWebView.Settings.BuiltInZoomControls = true;
            mWebView.SetWebViewClient(customWebViewClient);
            mWebView.SetWebChromeClient(new WebChromeClient());
            String myPdfUrl = APIConstants.InvoicePdfUrl;
            MyUrl = "http://docs.google.com/gview?embedded=true&url=" + myPdfUrl;
            mWebView.LoadUrl(MyUrl);

            InitComonents();
        }

        private void MWebview_Download(object sender, DownloadEventArgs e)
        {
            mWebView.Visibility = ViewStates.Gone;
            LL_input.Visibility = ViewStates.Gone;
            LL_Print.Visibility = ViewStates.Visible;
            Web_Print.Visibility = ViewStates.Visible;
            var Url = e.Url;
            CustomWebViewClient client = new CustomWebViewClient(this);
            Web_Print.SetWebViewClient(client);
            Web_Print.SetWebChromeClient(new WebChromeClient());
            Web_Print.Settings.JavaScriptEnabled = true;
            Web_Print.LoadUrl(Url);
            Web_Print.Settings.UseWideViewPort = true;
            Web_Print.Settings.LoadWithOverviewMode = true;
        }


        #region // Initializing widgets
        public void InitComonents()
        {
            try
            {
                LinearLayout img_viw = FindViewById<LinearLayout>(Resource.Id.img_WV_back);
                LinearLayout img_viw_Home = FindViewById<LinearLayout>(Resource.Id.img_WV_home);

            }
            catch (Exception ex)
            {
                ex.Message.ToString();
            }
        }
        #endregion

        #region // Webview client
        public class WebViewLoaderClient : WebViewClient
        {
            public event EventHandler<bool> OnPageLoaded;
            public override bool ShouldOverrideUrlLoading(WebView view, string url)
            {
                view.LoadUrl(url);
                return true;
            }
            public override void OnPageStarted(WebView view, string url, Android.Graphics.Bitmap favicon)
            {
                base.OnPageStarted(view, url, favicon);
                progressBar.Visibility = ViewStates.Visible;
            }
            public override void OnPageFinished(WebView view, string url)
            {
                base.OnPageFinished(view, url);
                progressBar.Visibility = ViewStates.Gone;
            }
            public override void OnReceivedError(WebView view, ClientError errorCode, string description, string failingUrl)
            {
                base.OnReceivedError(view, errorCode, description, failingUrl);
                view.Visibility = ViewStates.Gone;
                Error();
            }
        }
        class MonkeyWebViewClient : WebViewClient
        {
            public override bool ShouldOverrideUrlLoading(WebView view, string url)
            {
                view.LoadUrl(url);
                return true;
            }
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl)
            {
                view.LoadUrl("file:///android_asset/myerrorpage.html");
            }
        }
        #endregion


        #region Error Message for Web View Error
        public static void Error()
        {
            AlertDialog.Builder alert = new AlertDialog.Builder(_context);
            alert.SetTitle(ErrorTitle);
            alert.SetMessage(ErrorMsg);
            alert.SetPositiveButton(Resource.String.ok, (senderAlert, args) =>
            {
                _context.Finish();
            });
            alert.SetCancelable(false);
            Dialog dialog = alert.Create();
            dialog.Show();
        }

        public void doWebViewPrint(string url)
        {
            PrintDocumentAdapter adapter;
            if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.Lollipop)
                adapter = mWebView.CreatePrintDocumentAdapter("test");
            else
                adapter = mWebView.CreatePrintDocumentAdapter();
            var printMgr = (PrintManager)GetSystemService(PrintService);
            printMgr.Print("printTest", adapter, null);
        }
        #endregion
    }

    public class CustomWebViewClient : WebViewClient
    {
        private PdfView myActivity;
        public bool shouldOverrideUrlLoading(WebView view, string url)
        {
            view.LoadUrl(url);
            return false;
        }
        public override void OnPageFinished(WebView view, string url)
        {
            Log.Debug("PRINT", "page finished loading " + url);
            myActivity.doWebViewPrint(url);
            //CreateWebPrintJob(view);
            base.OnPageFinished(view, url);
        }

        private void CreateWebPrintJob(WebView view)
        {
            throw new NotImplementedException();
        }

        public CustomWebViewClient(PdfView activity)
        {
            myActivity = activity;
        }
    }
}

This is able show the content of the PDF and open the printer function but the content of the PDF is not able to view in the printer function as preview ie, getting me as follows

So, Can any one help me with this problem to rectify and able to get the PDF content viewed in the web to print it.

Answer 1

Please see the following code which made it possible to print:: The complete game changer here is scale calculation,

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        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            _context = this;
            res = _context.Resources;
            SetContentView(Resource.Layout.xxxxxxxxxxxxxxxx);
            var customWebViewClient = new WebViewLoaderClient();
            mWebView = FindViewById<WebView>(Resource.Id.Web);
            //mWebView.Download += MWebview_Download;
            UserLoginDetailList = UserInfoDBServices.getUserLoginDetailsfromDBfordroid();
            ObjLangList = UserInfoDBServices.GetCurrentLanguageListfordroid();
            mWebView.Settings.JavaScriptEnabled = true;
            mWebView.Settings.BuiltInZoomControls = true;
            mWebView.SetWebViewClient(customWebViewClient);
            String myPdfUrl = APIConstants.InvoicePdfUrl;
            MyUrl = "http://docs.google.com/gview?embedded=true&url=" + myPdfUrl;//Here in myPdfUrl variable place the url of the pdf you are getting from your server
            mWebView.LoadUrl(MyUrl);
            InitComonents();
        }
        #region // Initializing widgets
        public void InitComonents()
        {
            try
            {
                Print = FindViewById<LinearLayout>(Resource.Id.ll_TNP_Pirnt);
                Print.Visibility = ViewStates.Visible;
                Print.Click += delegate
                  {
                      LL_Print.Clickable = false;
                      var printManager = (PrintManager)GetSystemService(Context.PrintService);
                      var content = FindViewById<LinearLayout>(Resource.Id.LL_input);
                      var printAdapter = new GenericPrintAdapter(this, content);

                      printManager.Print("MyPrintJob", printAdapter, null);
                  };
            }
            catch (Exception ex)
            {
                ex.Message.ToString();
            }
        }
        #endregion
        public class GenericPrintAdapter:PrintDocumentAdapter
        {
            View view;
            Context context;
            PrintedPdfDocument document;
            float scale;
            private DownloadPdfView downloadPdfView;
            private RelativeLayout content;

            public GenericPrintAdapter(DownloadPdfView downloadPdfView, View view)
            {
                this.downloadPdfView = downloadPdfView;
                this.view = view;
            }

            public override void OnLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras)
            {
                try
                {
                    document = new PrintedPdfDocument(context, newAttributes);

                    CalculateScale(newAttributes);

                    var printInfo = new PrintDocumentInfo
                        .Builder("Invoice.pdf")
                        .SetContentType(PrintContentType.Document)
                        .SetPageCount(1)
                        .Build();

                    callback.OnLayoutFinished(printInfo, true);
                }
                catch(Exception ex)
                {
                    ex.Message.ToString();
                }

            }

            public override void OnWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback)
            {

                try
                {
                    PrintedPdfDocument.Page page = document.StartPage(0);

                    page.Canvas.Scale(scale, scale);

                    view.Draw(page.Canvas);

                    document.FinishPage(page);

                    WritePrintedPdfDoc(destination);

                    document.Close();

                    document.Dispose();

                    callback.OnWriteFinished(pages);
                }
                catch (Exception ex)
                {
                    ex.Message.ToString();
                }

            }
            void CalculateScale(PrintAttributes newAttributes)
            {
                try
                {
                    int dpi = Math.Max(newAttributes.GetResolution().HorizontalDpi, newAttributes.GetResolution().VerticalDpi);

                    int leftMargin = (int)(dpi * (float)newAttributes.MinMargins.LeftMils / 1000);
                    int rightMargin = (int)(dpi * (float)newAttributes.MinMargins.RightMils / 1000);
                    int topMargin = (int)(dpi * (float)newAttributes.MinMargins.TopMils / 1000);
                    int bottomMargin = (int)(dpi * (float)newAttributes.MinMargins.BottomMils / 1000);

                    int w = (int)(dpi * (float)newAttributes.GetMediaSize().WidthMils / 3500) - leftMargin - rightMargin;
                    int h = (int)(dpi * (float)newAttributes.GetMediaSize().HeightMils / 3500) - topMargin - bottomMargin;

                    scale = Math.Min((float)document.PageContentRect.Width() / w, (float)document.PageContentRect.Height() / h);
                }
                catch (Exception ex)
                {
                    ex.Message.ToString();
                }

            }
            void WritePrintedPdfDoc(ParcelFileDescriptor destination)
            {
                try
                {
                    var javaStream = new Java.IO.FileOutputStream(destination.FileDescriptor);
                    var osi = new OutputStreamInvoker(javaStream);
                    using (var mem = new MemoryStream())
                    {
                        document.WriteTo(mem);
                        var bytes = mem.ToArray();
                        osi.Write(bytes, 0, bytes.Length);
                    }
                }
                catch (Exception ex)
                {
                    ex.Message.ToString();
                }
            }
        }

        #region // Webview client
        public class WebViewLoaderClient : WebViewClient
        {
            public event EventHandler<bool> OnPageLoaded;
            public override bool ShouldOverrideUrlLoading(WebView view, string url)
            {
                view.LoadUrl(url);
                return true;
            }
            public override void OnPageStarted(WebView view, string url, Android.Graphics.Bitmap favicon)
            {
                base.OnPageStarted(view, url, favicon);
                progressBar.Visibility = ViewStates.Visible;
            }
            public override void OnPageFinished(WebView view, string url)
            {
                base.OnPageFinished(view, url);
                progressBar.Visibility = ViewStates.Gone;
            }
            public override void OnReceivedError(WebView view, ClientError errorCode, string description, string failingUrl)
            {
                base.OnReceivedError(view, errorCode, description, failingUrl);
                view.Visibility = ViewStates.Gone;
                Error();
            }
        }
        class MonkeyWebViewClient : WebViewClient
        {
            public override bool ShouldOverrideUrlLoading(WebView view, string url)
            {
                view.LoadUrl(url);
                return true;
            }
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl)
            {
                view.LoadUrl("file:///android_asset/myerrorpage.html");
            }
        }
        #endregion

        #region Error Message for Web View Error
        public static void Error()
        {
            AlertDialog.Builder alert = new AlertDialog.Builder(_context);
            alert.SetTitle(ErrorTitle);
            alert.SetMessage(ErrorMsg);
            alert.SetPositiveButton(Resource.String.ok, (senderAlert, args) =>
            {
                _context.Finish();
            });
            alert.SetCancelable(false);
            Dialog dialog = alert.Create();
            dialog.Show();
        }
        #endregion
    }
}