图片已保存在图库中并尝试上传到服务器上

Question

我正在使用相机捕获图像并将其保存在图库中，然后我想将此图像发送到一个本地主机，尝试将其转换为base64字符串。谁能帮我这个？这是我的代码。

package com.accenture.kshitizgoyal.data_image;

import android.app.Activity;
import android.app.DownloadManager;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.util.Base64;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.net.URLConnection;
import java.sql.Timestamp;
import java.util.HashMap;
import java.util.Map;
import android.widget.EditText;




public class MainActivity extends AppCompatActivity {


    ImageView imageViewLoad;
    Button capturePhoto;
    Button submit;
    EditText PONumber, CustomerId;
    String CustID="";
    String PONum="";
    Bitmap photo;
    private static final int CAPTURE_PHOTO = 2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        CustomerId = (EditText) findViewById(R.id.editText1);
        PONumber = (EditText) findViewById(R.id.editText2);
        submit = (Button) findViewById(R.id.button);
        submit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                switch (v.getId()) {
                    case R.id.button:



                        new Thread(new Runnable() {
                            public void run() {

                                try {
                                    URL url = new URL("http://192.168.0.110:8080/SanjeevSir/Final_API");
                                    URLConnection connection = url.openConnection();

                                    String inputString1 = CustomerId.getText().toString();
                                    String inputString2 = PONumber.getText().toString();
                                    String inputString3= convertBitmapToString(photo);

                                    //inputString = URLEncoder.encode(inputString, "UTF-8");

                                    Log.d("inputString", inputString1);
                                    Log.d("inputString", inputString2);
                                    Log.d("inputString",inputString3);

                                    connection.setDoOutput(true);
                                    OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream());
                                    out.write(inputString1+","+inputString2);
                                    out.close();



                                    BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                                    String returnString1="";
                                    String returnString2="";
                                    String returnString3="";


                                    while (((returnString1 = in.readLine()) != null) && ((returnString2 = in.readLine()) != null))
                                    {
                                        CustID = returnString1;
                                        PONum  = returnString2;

                                    }
                                    in.close();




                                    runOnUiThread(new Runnable() {
                                        public void run() {

                                            CustomerId.setText(CustID.toString());
                                            PONumber.setText(PONum.toString());

                                        }
                                    });

                                } catch (Exception e) {
                                    Log.d("Exception", e.toString());
                                }

                            }
                        }).start();

                        break;
                }

            }
        });


        imageViewLoad = (ImageView) findViewById(R.id.imageView1);


        capturePhoto = (Button) findViewById(R.id.takephoto);

        //Clicking on TakePhoto Button
        capturePhoto.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent cameraIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
                startActivityForResult(cameraIntent, CAPTURE_PHOTO);

            }
        });
    }



    // The OnActivityResult helps to handle the functionality of the feature( After Capturing Photo/Video)
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent intent) {

        if (requestCode == CAPTURE_PHOTO && resultCode == Activity.RESULT_OK) {


            String appDirectoryName = "/FirstApp/";

            //Create folder in Gallery to store your Captured Images/Videos
            final File imageRoot = new File(Environment.getExternalStorageDirectory(), appDirectoryName);
            if (!imageRoot.exists()) {
                imageRoot.mkdir();
            }

            String dirName = Environment.getExternalStorageDirectory().getPath() + appDirectoryName;
            Toast.makeText(this, dirName, Toast.LENGTH_LONG).show();

            Bitmap photo = (Bitmap) intent.getExtras().get("data");



            Timestamp timestamp = new Timestamp(System.currentTimeMillis());

            File file = new File(dirName, "IMG" + timestamp.toString() + ".PNG");
            FileOutputStream fOut = null;
            try {
                fOut = new FileOutputStream(file);
                photo.compress(Bitmap.CompressFormat.PNG, 100, fOut);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }

            ContentValues values = new ContentValues();
            values.put("_data", file.getAbsolutePath());
            ContentResolver cr = getContentResolver();
            cr.insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, values);

            // displays the captured Photo on the app screen
            imageViewLoad.setImageBitmap(photo);
            }
    }
    public String convertBitmapToString(Bitmap photo){
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        photo.compress(Bitmap.CompressFormat.JPEG,0,stream); //compress to which format you want.
        byte[] byte_arr = stream.toByteArray();
        String imageStr = Base64.encodeToString(byte_arr,Base64.DEFAULT);
        return imageStr;
    }


}

我已经将位图转换为Base64字符串，并尝试使用Log语句在控制台中将其打印出来，但是什么也没看到，而是得到了空指针异常。我无法弄清楚该怎么做。预先感谢。