android将文件上传到nodejs服务器

Question

我正在尝试将文件从我的Android设备上传到nodejs服务器，我正在使用okhttp发送帖子请求。请求到达服务器但我无法访问请求中的文件来保存它..我试图将我提供的数据放在标题中，但它们都是未定义的.....这里是代码：

MainActivity：

df

first  bar     baz     foo    
second one two one two one two
A        2   3   3   4  10   8
B       22  16   7   3   2  26
C        4   5   1   9   6   5

df.sum(level=0, axis=1)

first  bar  baz  foo
A        5    7   18
B       38   10   28
C        9   10   11

现在到nodeJs代码：      //在启动服务器后......

    package app.file_upload;

import android.Manifest;
import android.app.ProgressDialog;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.webkit.MimeTypeMap;
import android.widget.Button;

import com.nbsp.materialfilepicker.MaterialFilePicker;
import com.nbsp.materialfilepicker.ui.FilePickerActivity;

import java.io.File;
import java.io.IOException;

import okhttp3.MediaType;
import okhttp3.MultipartBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity {

    private Button button;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button);


        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
            if(ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
                requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},100);
                return;
            }
        }

        enable_button();
    }

    private void enable_button() {

            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    new MaterialFilePicker()
                            .withActivity(MainActivity.this)
                            .withRequestCode(10)
                            .start();

                }
            });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if(requestCode == 100 && (grantResults[0] == PackageManager.PERMISSION_GRANTED)){
            enable_button();
        }else {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},100);
            }
        }
    }

    ProgressDialog progress;

    @Override
    protected void onActivityResult(int requestCode, int resultCode, final Intent data) {
        if(requestCode == 10 && resultCode == RESULT_OK){

            progress = new ProgressDialog(MainActivity.this);
            progress.setTitle("Uploading");
            progress.setMessage("Please wait...");
            progress.show();

            Thread t = new Thread(new Runnable() {
                @Override
                public void run() {

                    File f  = new File(data.getStringExtra(FilePickerActivity.RESULT_FILE_PATH));
                    String content_type  = getMimeType(f.getPath());

                    String file_path = f.getAbsolutePath();
                    OkHttpClient client = new OkHttpClient();
                    RequestBody file_body = RequestBody.create(MediaType.parse(content_type),f);

                    RequestBody request_body = new MultipartBody.Builder()
                            .setType(MultipartBody.FORM)
                            .addFormDataPart("type",content_type)
                            .addFormDataPart("uploaded_file",file_path.substring(file_path.lastIndexOf("/")+1), file_body)
                            .build();

                    Request request = new Request.Builder()
                            .url("http://192.168.0.109:2999/upload_audio")
                            .post(request_body)
                            .build();

                    try {
                        Response response = client.newCall(request).execute();

                        if(!response.isSuccessful()){
                            throw new IOException("Error : "+response);
                        }

                        progress.dismiss();

                    } catch (IOException e) {
                        e.printStackTrace();
                    }


                }
            });

            t.start();




        }
    }

    private String getMimeType(String path) {

        String extension = MimeTypeMap.getFileExtensionFromUrl(path);

        return MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
    }
}