Xamarin的.Android pdf生成器

首先确保在Manifest文件中允许WriteExternalStorage

为了在外部存储器上读写文件，你的应用程序必须获取READ_EXTERNAL_STORAGE或WRITE_EXTERNAL_STORAGE系统权限。例如:

 <manifest ...>
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 </manifest>

FileStream构造函数(众多构造函数之一)接受字符串作为路径和FileMode，因此一个示例解决方案将是。

  var directory = new Java.IO.File(Android.OS.Environment.ExternalStorageDirectory, "pdf").ToString();
  if (!Directory.Exists(directory))
  {
      Directory.CreateDirectory(directory);
  }
  var path = Path.Combine(directory, "myTestFile.pdf");
  var fs = new FileStream(path, FileMode.Create);

这将创建名为"pdf"的文件夹到外部存储，然后创建pdf文件。在创建文件之前，可以包含额外的代码来检查文件是否存在。

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);
            var directory = new Java.IO.File(Android.OS.Environment.ExternalStorageDirectory, "pdf").ToString();
            if (!Directory.Exists(directory))
            {
                Directory.CreateDirectory(directory);
            }
            var path = Path.Combine(directory, "myTestFile.pdf");
            if (File.Exists(path))
            {
                File.Delete(path);
            }
            var fs = new FileStream(path, FileMode.Create);
            Document document = new Document(PageSize.A4, 25, 25, 30, 30);
            PdfWriter writer = PdfWriter.GetInstance(document, fs);
            document.Open();
            document.Add(new Paragraph("Hello World"));
            document.Close();
            writer.Close();
            fs.Close();
            Java.IO.File file = new Java.IO.File(path);
            Intent intent = new Intent(Intent.ActionView);
            intent.SetDataAndType(Android.Net.Uri.FromFile(file), "application/pdf");
            StartActivity(intent);
        }

如果您正在进行跨平台开发，最好在注释处生成PDF。请参阅以下使用iTEXT sharp在PCL中创建PDF的代码。iTEXT PDF

这里我使用PCL存储库进行IO访问，这对PCL非常有用。你可以在这里找到更多信息PCL存储

1. 将PCL存储库添加到您的PCL项目中，以及使用nuget的相关平台。

安装包PCLStorage

public class PdfHelper
{
  public async Task PCLGenaratePdf(string path)
  {
    IFolder rootFolder = await FileSystem.Current.GetFolderFromPathAsync(path);
    IFolder folder = await rootFolder.CreateFolderAsync("folder", CreationCollisionOption.OpenIfExists);
    IFile file = await folder.CreateFileAsync("file.pdf", CreationCollisionOption.ReplaceExisting);
    using (var fs = await file.OpenAsync(FileAccess.ReadAndWrite))
    {
        var document = new Document(PageSize.A4, 25, 25, 30, 30);
        PdfWriter writer = PdfWriter.GetInstance(document, fs);
        document.Open();
        document.Add(new Paragraph("heloo everyone"));
        document.Close();
        writer.Close();
    }
 }
 public async Task<string> PCLReadFile(string path)
 {
    IFile file = await FileSystem.Current.GetFileFromPathAsync(path);
    return file.Path;
 }
}

    private async void Genarate(string path)
    {
        var creator = new PdfHelper();
        await creator.PCLGenaratePdf(path);
    }

    private async void ReadPDF(object sender, EventArgs e)
     {
        String sdCardPath = Environment.ExternalStorageDirectory.AbsolutePath;
        String fullpath = Path.Combine(sdCardPath, "folder/" + "file.pdf");
        var creator = new PdfHelper();
        string filePath = await creator.PCLReadFile(fullpath);
        Uri pdfPath = Uri.FromFile(new File(filePath));
        Intent intent = new Intent(Intent.ActionView);
        intent.SetDataAndType(pdfPath, "application/pdf");
        intent.SetFlags(ActivityFlags.NewTask);
        Application.Context.StartActivity(intent);
    }