谁能帮我解决这个问题，打印 url 内容。 我在我的应用程序的 Web View 中打开 PDF 文件，然后尝试通过放置单独的打印按钮从那里打印文档。请看下面的代码。
[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;
}
}
}
这能够显示 PDF 的内容并打开打印机功能，但 PDF 的内容无法在打印机功能中作为预览查看，即，得到我如下 
所以，任何人都可以帮助我解决这个问题以纠正并能够在网络上查看 PDF 内容以打印它。
最佳答案
请看下面的代码，它使打印成为可能: 这里完全改变游戏规则的是规模计算，
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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
}
}
关于android - Xamarin Android如何使用手机默认打印机功能打印从WebView打开的PDF内容，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47033755/