如何在.NET MAUI项目中与Android项目的Java代码进行互操作？

huangapple
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英文:

How can I interop with Android project java in .NET MAUI Project?

问题

我尝试在.NET MAUI Blazor混合项目中打印文档。在这个过程中，我注意到了在platform/android文件夹根目录下与Android操作系统进行交互的地方。以下是我在开发该打印代码时所遵循的文档：

  1. 在Android打印管理器中打印照片
  2. 在Android中打印自定义文档

在Android上打印照片是成功的，但现在我想打印自定义文档，因为我想打印PDF。以下是成功打印图像和不成功打印PDF的代码。PDF和图像都可以转换为Base64字符串。

以下是.NET中的接口代码：

  1. namespace PrintMAUI.Services
  2. {
  3.     public interface IPrintCalller
  4.     {
  5.         Task<bool> printImage(byte[] bitmapBytes);
  6.         Task<bool> printPDF(byte[] pdfBytes);
  7.     }
  8. }

在Android平台上创建的类代码：

  1. namespace PrintMAUI.Platforms
  2. {
  3.     public class PrintCaller : MauiAppCompatActivity, IPrintCalller
  4.     {
  5.         public async Task<bool> printImage(byte[] bitmapBytes)
  6.         {
  7.             try
  8.             {
  9.                 //Microsoft.Maui.ApplicationModel.Platform.CurrentActivity.Context
  10.                
  11.                 PrintHelper photoPrinter = new PrintHelper(Platform.CurrentActivity);
  12.                 photoPrinter.ScaleMode = PrintHelper.ScaleModeFill;
  14.                 Bitmap bitmap = await BitmapFactory.DecodeByteArrayAsync(bitmapBytes, 0, bitmapBytes.Length);
  16.                 photoPrinter.PrintBitmap("Testing Print for BL", bitmap);
  17.                 return true;
  18.             }
  19.             catch (Exception ex)
  20.             {
  21.                 return false;
  22.             }
  23.         }
  25.         public async Task<bool> printPDF(byte[] pdfBytes)
  26.         {
  27.             try
  28.             {
  29.                 
  30.                 PrintManager printManager = Platform.CurrentActivity.GetSystemService(Android.Content.Context.PrintService).JavaCast<PrintManager>();
  31.                 string jobName = "simple Print Job";
  32.                 printManager.Print(jobName, new CustomPrintDocumentAdapter(pdfBytes), null);
  33.                 return true;
  34.             }
  35.             catch (Exception ex)
  36.             {
  37.                 return false;
  38.             }
  39.         }
  40.     }
  41. }

自定义打印适配器代码：

  1. using Android.Graphics.Pdf;
  2. using Android.OS;
  3. using Android.Print;
  4. using Android.Print.Pdf;
  5. using Android.Runtime;
  6. using Java.IO;
  7. using System;
  8. using System.Collections.Generic;
  9. using System.Linq;
  10. using System.Text;
  11. using System.Threading.Tasks;
  12. using static Android.Print.PrintAttributes;
  14. namespace PrintMAUI.Platforms
  15. {
  16.     public class CustomPrintDocumentAdapter : PrintDocumentAdapter
  17.     {
  18.         //private byte[] data;
  19.         private int totalPages = 0;
  20.         PrintedPdfDocument pdfDocument;
  21.         public CustomPrintDocumentAdapter(byte[] data)
  22.         {
  23.             //this.data = data;
  24.         }
  25.         public override void OnLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras)
  26.         {
  27.             pdfDocument = new PrintedPdfDocument(Platform.CurrentActivity, newAttributes);
  29.             if (cancellationSignal.IsCanceled)
  30.             {
  31.                 callback.OnLayoutCancelled();
  32.                 return;
  33.             }
  35.             int pages = computePageCount(newAttributes);
  37.             if (pages > 0)
  38.             {
  39.                 PrintDocumentInfo pdi = new PrintDocumentInfo.Builder("PDF.pdf")
  40.                     .SetContentType(Android.Print.PrintContentType.Document)
  41.                     .SetPageCount(pages)
  42.                     .Build();
  43.                 callback.OnLayoutFinished(pdi, true);
  44.             }
  45.             else
  46.             {
  47.                 callback.OnLayoutFailed("Calculations Failed!");
  48.             }
  49.         }
  50.         private bool containsPage(PageRange[] pages, int num)
  51.         {
  52.             //TODO: you have to do it
  53.             return true;
  54.         }
  55.         public override void OnWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback)
  56.         {
  57.             for (int i = 0; i < totalPages; i++)
  58.             {
  59.                 // Check to see if this page is in the output range.
  60.                 if (containsPage(pages, i))
  61.                 {
  62.                     // If so, add it to writtenPagesArray. writtenPagesArray.size()
  63.                     // is used to compute the next output page index.
  64.                     //writtenPagesArray.append(writtenPagesArray.size(), i);
  65.                     PdfDocument.Page page = pdfDocument.StartPage(i);
  67.                     // check for cancellation
  68.                     if (cancellationSignal.IsCanceled)
  69.                     {
  70.                         callback.OnWriteCancelled();
  71.                         pdfDocument.Close();
  72.                         pdfDocument = null;
  73.                         return;
  74.                     }
  76.                     // Rendering is complete, so page can be finalized.
  77.                     pdfDocument.FinishPage(page);
  78.                 }
  79.             }
  81.             // Write PDF document to file
  82.             try
  83.             {
  84.                 //FileOutputStream stream = new FileOutputStream(destination.FileDescriptor);
  85.                 FileStream stream = new FileStream((string)destination.FileDescriptor, FileMode.Create, FileAccess.Write);
  86.                 pdfDocument.WriteTo(stream);
  87.             }
  88.             catch (Exception e)
  89.             {
  90.                 callback.OnWriteFailed(e.ToString());
  91.                 return;
  92.             }
  93.             finally
  94.             {
  95.                 pdfDocument.Close();
  96.                 pdfDocument = null;
  97.             }
  98.             //PageRange[] writtenPages = computeWrittenPages();
  99.            /// Signal the print framework the document is complete
  100.             callback.OnWriteFinished(pages);
  102.         }
  104.         private int computePageCount(PrintAttributes printAttributes)
  105.         {
  106.             int itemsPerPage = 4;
  108.             MediaSize pageSize = printAttributes.GetMediaSize();
  109.             if (!pageSize.IsPortrait)
  110.             {
  111.                 itemsPerPage = 6;
  112.             }
  114.             int printItemCount = 1;
  116.             return (int)Math.Ceiling((double)printItemCount/itemsPerPage);
  117.         }
  118.     }
  119. }

我的做法

  1. 首先，我尝试创建一个单独的项目，其中包含打印机SDK，并从MAUI应用程序调用它。但由于策略限制，这并不起作用。

  2. 然后我尝试将打印机SDK添加到MAUI项目中。但这也不起作用。

  3. 然后我尝试这种方法。我尝试使用Android打印管理器来打印文档。我成功地打印了图像，但我想从字节数组中打印PDF。

我的期望

在CustomPrintDocumentAdapter类中，以下代码行存在问题，无法修复。无论如何，我都会得到转换问题：

  1. FileStream stream = new FileStream((string)destination.FileDescriptor, FileMode.Create, FileAccess.Write);
  2. pdfDocument.WriteTo(stream);

我想知道如何修复它？

其次，我认为这段代码可能有一些需要理解的地方，即CustomPrintDocumentAdapter如何支持打印自定义文档。有人能解释一下吗？

Google文档中有这段代码：

  1. writtenPagesArray.append(writtenPages
  3. <details>
  4. <summary>英文:</summary>
  6. I tried to print documents over .NET MAUI Blazor hybrid Project. When I was doing it, I saw the place interop with android os in platform/android folder root. Here is the documentation I followed when developing that code to print,
  8. 1. [Printing Photos in android Print manager](https://developer.android.com/training/printing/photos)
  9. 2. [Printing Custom Document in android](https://developer.android.com/training/printing/custom-docs)
  11. Printing photos in android is a success, but now I want to print custom documents because I want to print PDF. Here is a code for successful image print and unsuccessful PDF Print. Both PDF and image can convert to base64 string.
  13. here is code of interface in .NET

namespace PrintMAUI.Services
{
public interface IPrintCalller
{
Task<bool> printImage(byte[] bitmapBytes);
Task<bool> printPDF(byte[] pdfBytes);
}
}

  2. Class Created for android platform

namespace PrintMAUI.Platforms
{
public class PrintCaller : MauiAppCompatActivity, IPrintCalller
{
public async Task<bool> printImage(byte[] bitmapBytes)
{
try
{
//Microsoft.Maui.ApplicationModel.Platform.CurrentActivity.Context

  1.             PrintHelper photoPrinter = new PrintHelper(Platform.CurrentActivity);
  2. photoPrinter.ScaleMode = PrintHelper.ScaleModeFill;
  3. Bitmap bitmap = await BitmapFactory.DecodeByteArrayAsync(bitmapBytes, 0, bitmapBytes.Length);
  4. photoPrinter.PrintBitmap(&quot;Testing Print for BL&quot;, bitmap);
  5. return true;
  6. }catch (Exception ex)
  7. {
  8. return false;
  9. }
  10. }
  11. public async Task&lt;bool&gt; printPDF(byte[] pdfBytes)
  12. {
  13. try
  14. {
  15. PrintManager printManager = Platform.CurrentActivity.GetSystemService(Android.Content.Context.PrintService).JavaCast&lt;PrintManager&gt;();
  16. string jobName = &quot;simple Print Job&quot;;
  17. printManager.Print(jobName, new CustomPrintDocumentAdapter(pdfBytes), null);
  18. return true;
  19. }catch(Exception ex)
  20. {
  21. return false;
  22. }
  23. }
  24. }

}

  2. Custom Print Adapter

using Android.Graphics.Pdf;
using Android.OS;
using Android.Print;
using Android.Print.Pdf;
using Android.Runtime;
using Java.IO;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using static Android.Print.PrintAttributes;

namespace PrintMAUI.Platforms
{
public class CustomPrintDocumentAdapter : PrintDocumentAdapter
{
//private byte[] data;
private int totalPages = 0;
PrintedPdfDocument pdfDocument;
public CustomPrintDocumentAdapter(byte[] data)
{
//this.data = data;
}
public override void OnLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras)
{
pdfDocument = new PrintedPdfDocument(Platform.CurrentActivity,newAttributes);

  1.         if (cancellationSignal.IsCanceled)
  2. {
  3. callback.OnLayoutCancelled();
  4. return;
  5. }
  6. int pages = computePageCount(newAttributes);
  7. if(pages &gt; 0)
  8. {
  9. PrintDocumentInfo pdi = new PrintDocumentInfo.Builder(&quot;PDF.pdf&quot;)
  10. .SetContentType(Android.Print.PrintContentType.Document)
  11. .SetPageCount(pages)
  12. .Build();
  13. callback.OnLayoutFinished(pdi, true);
  14. }
  15. else
  16. {
  17. callback.OnLayoutFailed(&quot;Calculations Failed!&quot;);
  18. }
  19. }
  20. private bool containsPage(PageRange[] pages,int num)
  21. {
  22. //TODO: you have to do it
  23. return true;
  24. }
  25. public override void OnWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback)
  26. {
  27. for (int i = 0; i &lt; totalPages; i++)
  28. {
  29. // Check to see if this page is in the output range.
  30. if (containsPage(pages, i))
  31. {
  32. // If so, add it to writtenPagesArray. writtenPagesArray.size()
  33. // is used to compute the next output page index.
  34. //writtenPagesArray.append(writtenPagesArray.size(), i);
  35. PdfDocument.Page page = pdfDocument.StartPage(i);
  36. // check for cancellation
  37. if (cancellationSignal.IsCanceled)
  38. {
  39. callback.OnWriteCancelled();
  40. pdfDocument.Close();
  41. pdfDocument = null;
  42. return;
  43. }
  44. // Rendering is complete, so page can be finalized.
  45. pdfDocument.FinishPage(page);
  46. }
  47. }
  48. // Write PDF document to file
  49. try
  50. {
  51. //FileOutputStream stream = new FileOutputStream(destination.FileDescriptor);
  52. FileStream stream = new FileStream((string)destination.FileDescriptor, FileMode.Create, FileAccess.Write);
  53. pdfDocument.WriteTo(stream);
  54. }
  55. catch (Exception e)
  56. {
  57. callback.OnWriteFailed(e.ToString());
  58. return;
  59. }
  60. finally
  61. {
  62. pdfDocument.Close();
  63. pdfDocument = null;
  64. }
  65. //PageRange[] writtenPages = computeWrittenPages();
  66. /// Signal the print framework the document is complete
  67. callback.OnWriteFinished(pages);
  68. }
  69. private int computePageCount(PrintAttributes printAttributes)
  70. {
  71. int itemsPerPage = 4;
  72. MediaSize pageSize = printAttributes.GetMediaSize();
  73. if (!pageSize.IsPortrait)
  74. {
  75. itemsPerPage = 6;
  76. }
  77. int printItemCount = 1;
  78. return (int)Math.Ceiling((double)printItemCount/itemsPerPage);
  79. }
  80. }

}

  2. ### What I does
  3. 1. First I try to create seperate project with printer SDK and call to it from MAUI app. but it didn&#39;s work because policy restrictions.
  4. 2. Then I try to add printer SDK to MAUI Project. It doesn&#39;t work
  5. 3. Then I try to this way.I try to use android print manager to print documents. I successful when printing image. but I want to print PDF from it&#39;s byte array. 
  6. ### What I Expecting
  7. these lines in customprintdocumentadapter class got issue that cannot be fixed. everyway I got casting issue

FileStream stream = new FileStream((string)destination.FileDescriptor, FileMode.Create, FileAccess.Write);
pdfDocument.WriteTo(stream);

  1. I want way to fix it?
  2. Second thing is I thaught this code may have some ponts that have to be understand how customprintdocumentadapter support to print custom document. can someone explain?
  3. google documentation have this code

writtenPagesArray.append(writtenPagesArray.size(), i);

  2. but I cant find where is coming from.
  3. </details>
  4. # 答案1
  5. **得分**: 0
  6. 实际上不想创建PrintedPdfDocument对象。我可以像这样将我的字节数组传递给文件流：
  7. ```csharp
  8. public class CustomPrintDocumentAdapter : PrintDocumentAdapter
  9. {
  10. private byte[] data;
  11. public CustomPrintDocumentAdapter(byte[] data)
  12. {
  13. this.data = data;
  14. }
  15. public override void OnLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras)
  16. {
  17. if (cancellationSignal.IsCanceled)
  18. {
  19. callback.OnLayoutCancelled();
  20. return;
  21. }
  22. int pages = 1;
  23. if (pages &gt; 0)
  24. {
  25. PrintDocumentInfo pdi = new PrintDocumentInfo.Builder(&quot;PDF.pdf&quot;)
  26. .SetContentType(Android.Print.PrintContentType.Document)
  27. .SetPageCount(pages)
  28. .Build();
  29. callback.OnLayoutFinished(pdi, true);
  30. }
  31. else
  32. {
  33. callback.OnLayoutFailed(&quot;Calculations Failed!&quot;);
  34. }
  35. }
  36. public override void OnWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback)
  37. {
  38. try
  39. {
  40. FileOutputStream stream = new FileOutputStream(destination.FileDescriptor);
  41. stream.Write(data);
  42. }
  43. catch (Exception e)
  44. {
  45. callback.OnWriteFailed(e.ToString());
  46. return;
  47. }
  48. callback.OnWriteFinished(pages);
  49. }
  50. }

然后问题得以解决。

英文:

Actually Not wanted to create PrintedPdfDocument Object. I could able to pass my byte array to filestream like this

  1. public class CustomPrintDocumentAdapter : PrintDocumentAdapter
  2. {
  3. private byte[] data;
  4. public CustomPrintDocumentAdapter(byte[] data)
  5. {
  6. this.data = data;
  7. }
  8. public override void OnLayout(PrintAttributes oldAttributes, PrintAttributes newAttributes, CancellationSignal cancellationSignal, LayoutResultCallback callback, Bundle extras)
  9. {
  10. if (cancellationSignal.IsCanceled)
  11. {
  12. callback.OnLayoutCancelled();
  13. return;
  14. }
  15. int pages = 1;
  16. if (pages &gt; 0)
  17. {
  18. PrintDocumentInfo pdi = new PrintDocumentInfo.Builder(&quot;PDF.pdf&quot;)
  19. .SetContentType(Android.Print.PrintContentType.Document)
  20. .SetPageCount(pages)
  21. .Build();
  22. callback.OnLayoutFinished(pdi, true);
  23. }
  24. else
  25. {
  26. callback.OnLayoutFailed(&quot;Calculations Failed!&quot;);
  27. }
  28. }
  29. public override void OnWrite(PageRange[] pages, ParcelFileDescriptor destination, CancellationSignal cancellationSignal, WriteResultCallback callback)
  30. {
  31. try
  32. {
  33. FileOutputStream stream = new FileOutputStream(destination.FileDescriptor);
  34. stream.Write(data);
  35. }
  36. catch (Exception e)
  37. {
  38. callback.OnWriteFailed(e.ToString());
  39. return;
  40. }
  41. callback.OnWriteFinished(pages);
  42. }
  43. }

Then Problem get solved

huangapple
  • 本文由 发表于 2023年6月22日 17:01:33
  • 转载请务必保留本文链接：https://go.coder-hub.com/76530206.html
  • .net
  • android
  • maui
  • printing
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