ios - 上传图像时对象引用未设置为 object.postmethod POST 文件名文件的实例，但**与 Android 代码一起正常工作**

Question

当我向 ASP.net 服务器发送请求(来自 objective-c )时，我收到未设置对象引用到 object.postmethod POST 文件名文件的实例作为响应。

objective-c 代码

NSData *data = UIImagePNGRepresentation([UIImage imageNamed:@"arrow-next"]);

NSMutableURLRequest *request = [[NSMutableURLRequest alloc]
                                initWithURL:[NSURL URLWithString:@"http://aamc.kleward.com/OfflineCourse/iphone_Upload.aspx"]
                                cachePolicy:NSURLCacheStorageNotAllowed
                                timeoutInterval:120.0f];

[request addValue:@"text/plain; charset=utf-8" forHTTPHeaderField:@"Content-Type"];
[request setHTTPMethod:@"POST"];

[request addValue:[data base64Encoding] forHTTPHeaderField:@"file"];
[request addValue:@"myimage.png" forHTTPHeaderField:@"filename"];

[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

    if (!connectionError) {
        NSLog(@"response--%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
    }
    else{
        NSLog(@"error--%@",connectionError);
    }
}];

ASP.net代码

 private string UploadFile(byte[] file, string fileName)
{
    // the byte array argument contains the content of the file
    // the string argument contains the name and extension
    // of the file passed in the byte array
    string sJSON = "{\"Root\":[";
    try
    {
        // instance a memory stream and pass the
        // byte array to its constructor
        MemoryStream ms = new MemoryStream(file);
        // instance a filestream pointing to the
        // storage folder, use the original file name
        // to name the resulting file

        FileStream fs = new FileStream(//System.Web.Hosting.HostingEnvironment.MapPath
                    System.Configuration.ConfigurationManager.AppSettings["PDPointFile"].ToString() + fileName, FileMode.Create);

        // write the memory stream containing the original
        // file as a byte array to the filestream
        ms.WriteTo(fs);

        // clean up
        ms.Close();
        fs.Close();
        fs.Dispose();
        // return OK if we made it this far
        sJSON += "{\"Value\":\"True\",";
        sJSON += "\"File Path\":\"" + System.Configuration.ConfigurationManager.AppSettings["PDPointFilePath"].ToString() + fileName + "\"}]}";
        Response.Write(sJSON);
        return sJSON;
    }
    catch (Exception ex)
    {
        sJSON += "{\"Value\":\"False\",";
        sJSON += "\"File Path\":\"\"}]}";
        Response.Write(ex.Message);
        Response.Write(sJSON);
        return sJSON;
        // return the error message if the operation fails
        // return ex.Message.ToString();
    }
}

// getting value.

protected void Page_Load(object sender, EventArgs e)
 {
    try
    {
        postmethod = Request.HttpMethod;
        if (Request.HttpMethod == "POST")
        {
            str_filename = Request.Form["filename"].ToString();
            tokenID =  Server.UrlDecode(Request.Form["file"].ToString().Replace(" ", "+"));

           tokenID = tokenID.Replace(" ", "+");
           str_file = Convert.FromBase64String(tokenID);
           UploadFile(str_file, str_filename);
        }
    }
    catch (Exception ex)
    {
        Response.Write(ex.Message + "postmethod " + postmethod + " filename " + str_filename + " file " + tokenID);
    }
 }

编辑:

工作 Android 代码

HttpClient httpClient = new DefaultHttpClient();

mv = new MyVars();
myUrl = mv.upload_file + pick_image_name + "&file=" + imageEncoded ;
myUrl = myUrl.replaceAll("\n", "");
myUrl = myUrl.replaceAll(" ", "%20");
System.out.println("Complete Add statement url is : " + myUrl);
HttpPost httppost = new HttpPost("http://aamc.kleward.com/OfflineCourse/iphone_Upload.aspx"); // Setting URL link over here

try {
   // Add your data ... Adding data as a separate way ...
   List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
   nameValuePairs.add(new BasicNameValuePair("filename", pick_image_name));
   nameValuePairs.add(new BasicNameValuePair("file", imageEncoded));
   httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));


   System.out.println("================== URL HTTP ===============" + httppost.toString());

   // Execute HTTP Post Request
   HttpResponse response = httpClient.execute(httppost);

  // System.out.println("httpResponse"); // use this httpresponse for JSON Object.....
  InputStream inputStream = response.getEntity().getContent();
  InputStreamReader inputStreamReader = new InputStreamReader(
  inputStream);
  BufferedReader bufferedReader = new BufferedReader(
  inputStreamReader);
  StringBuilder stringBuilder = new StringBuilder();
  String bufferedStrChunk = null;
 while ((bufferedStrChunk = bufferedReader.readLine()) != null) {
  stringBuilder.append(bufferedStrChunk);
 }
 jsonString = stringBuilder.toString();
 System.out.println("Complete response is : " + jsonString);

 } catch (ClientProtocolException e) {
   // TODO Auto-generated catch block
} catch (IOException e) {
   // TODO Auto-generated catch block
}

我无法理解响应，任何人都可以告诉我这些响应的含义 Object reference not set to an instance of an object.postmethod POST filename file

为什么它与 Android 代码一起工作？

Answer 1

在您的 ASP.NET 页面中，您正在从发布的表单 中读取文件和文件名。

在您的 Android 代码中，您将文件和文件名添加到 form 并且您的 ASP.NET 页面能够读取它，所以没有问题。

但是，在您的 objective-c 代码中，您将文件和文件名添加到请求的 header 中，因此 ASP.NET 文件试图读取它们从表单中抛出异常，因为它试图读取 null 的表单变量。

只需尝试在 Objective C 代码中将文件和文件名添加到表单而不是标题，一切都会成功。

NSData *data = UIImagePNGRepresentation([UIImage imageNamed:@"arrow-next"]);
NSMutableURLRequest *request = [[NSMutableURLRequest alloc]
                            initWithURL:[NSURL URLWithString:@"http://aamc.kleward.com/OfflineCourse/iphone_Upload.aspx"]
                            cachePolicy:NSURLCacheStorageNotAllowed
                            timeoutInterval:120.0f];

[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[request setHTTPMethod:@"POST"];
NSString *postString = [NSString stringWithFormat:@"filename=%@&file=%@",@"myimage.png",[data base64Encoding]] ;
data = [postString dataUsingEncoding:NSUTF8StringEncoding];
NSString *postLength = [NSString stringWithFormat:@"%lu", (unsigned long)[data length]];
[request setValue:postLength forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody:data];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
    if (!connectionError) {
        NSLog(@"response--%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
    } else{
        NSLog(@"error--%@",connectionError);
    } 
}];