现在读写文件在Android原生态应该不在话下了。但是xamarin.forms应该如何用呢

1 //获取文件的名称含有后缀2 string strName = Path.GetFileName(strPath);3 strPath = "ftp://" + builder.UserName + ":" + builder.Password + "@" + builder.Host  + strPath;4 builder.AllPath = strPath;5 //global::Android.OS.Environment.ExternalStorageDirectory.AbsolutePath :得到安卓的根目录6 //Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData)：:得到安卓data目录7 var path = global::Android.OS.Environment.ExternalStorageDirectory.AbsolutePath + Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);8 //创建文件9 System.IO.Directory.CreateDirectory(path);

可是我运行半天在手机上都没有找到我文件。原来是没有权限。如何加权限呢！如下图在安卓项目里有个Properties的文件下有个AndroidManifest.xml的文件。在<application android:label="cardionNet2.Android"></application> 下加

1 
     2 
     

这两句就好。

 

之后如何用ftp下载文件呢。

1  FtpWebRequest reqFTP = null;//Ftp请求 2             FileStream saveStream = null;//Ftp文件流 3             Stream ftpStream = null;//Ftp传输流 4             FtpWebResponse response = null;//Ftp响应 5             try 6             { 7                 var sss = new Uri(builder.Path); 8   9                 //创建要保存的文件10                 saveStream = new FileStream(savePath, FileMode.Create);11                 //下载文件设置12                 reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(builder.AllPath)); 13                 reqFTP.Credentials = new NetworkCredential(builder.UserName, builder.Password);14                 reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;15                 reqFTP.UseBinary = true;16                 //开始请求17                 response = (FtpWebResponse)reqFTP.GetResponse();18                 //开始下载19                 ftpStream = response.GetResponseStream();20                 //将下载内容存入文件流21                 int bufferSize = 65535;22                 int readCount;23                 byte[] buffer = new byte[bufferSize];24                 readCount = ftpStream.Read(buffer, 0, bufferSize);25                 while (readCount > 0)26                 {27                     saveStream.Write(buffer, 0, readCount);28                     readCount = ftpStream.Read(buffer, 0, bufferSize);29                 }30  }31             catch (WebException webEx)32             {33                 throw webEx;34             }35             catch (Exception ex)36             {37                 throw ex;38             }39             finally40             {41                 //释放资源42                 if (ftpStream != null) ftpStream.Close();43                 if (saveStream != null) saveStream.Close();44                 if (response != null) response.Close();45             }

趋势xamarin的ftp下载文件和c#是一样的关键在于如何在手机上建立文件。