用于上传到数据库的照片压缩

Question

我正在尝试拍照并将其上传到数据库但是每次拍照并尝试发布时我都会收到错误消息： java.lang.NullPointerException：尝试调用虚方法＆＃39; boolean android.graphics.Bitmap.compress（android.graphics.Bitmap $ CompressFormat，int，java.io.OutputStream）＆＃39;在null对象引用上。

每当我拍照时，我都看不到图像视图中的预览。

所以我假设我没有正确地将照片添加到位图中，以便ImageUploadImageToServerFunction（）存储图像。然而，对我来说没有用是没有意义的。

这是我遇到问题的功能。

Button CaptureImageFromCamera,UploadImageToServer;

ImageView ImageViewHolder;

EditText imageName;

ProgressDialog progressDialog ;

Intent intent ;

public  static final int RequestPermissionCode  = 1 ;

Bitmap bitmap;

boolean check = true;

String GetImageNameFromEditText;

String ImageNameFieldOnServer = "image_name" ;

String ImagePathFieldOnServer = "image_path" ;

String ImageUploadPathOnSever ="https://androidjsonblog.000webhostapp.com/capture_img_upload_to_server.php" ;


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

    CaptureImageFromCamera = (Button)findViewById(R.id.mapsPicButton);
    ImageViewHolder = (ImageView)findViewById(R.id.imageView);
    UploadImageToServer = (Button) findViewById(R.id.postPicBtn);
    imageName = (EditText)findViewById(R.id.editText);

    EnableRuntimePermissionToAccessCamera();

    CaptureImageFromCamera.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);

            startActivityForResult(intent, 7);

        }
    });

    UploadImageToServer.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            GetImageNameFromEditText = imageName.getText().toString();

            ImageUploadToServerFunction();

        }
    });
}

// Start activity for result method to Set captured image on image view after click.
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == 7 && resultCode == RESULT_OK && data != null && data.getData() != null) {

        Uri uri = data.getData();

        try {

            // Adding captured image in bitmap.
            bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), uri);

            // adding captured image in imageview.
            ImageViewHolder.setImageBitmap(bitmap);

        } catch (IOException e) {

            e.printStackTrace();
        }
    }

}

// Upload captured image online on server function.
    public void ImageUploadToServerFunction(){

        ByteArrayOutputStream byteArrayOutputStreamObject ;

        byteArrayOutputStreamObject = new ByteArrayOutputStream();

        // Converting bitmap image to jpeg format, so by default image will upload in jpeg format.
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, byteArrayOutputStreamObject);

        byte[] byteArrayVar = byteArrayOutputStreamObject.toByteArray();

        final String ConvertImage = Base64.encodeToString(byteArrayVar, Base64.DEFAULT);

        class AsyncTaskUploadClass extends AsyncTask<Void,Void,String> {

            @Override
            protected void onPreExecute() {

                super.onPreExecute();

                // Showing progress dialog at image upload time.
                progressDialog = ProgressDialog.show(Photo.this,"Image is Uploading","Please Wait",false,false);
            }

            @Override
            protected void onPostExecute(String string1) {

                super.onPostExecute(string1);

                // Dismiss the progress dialog after done uploading.
                progressDialog.dismiss();

                // Printing uploading success message coming from server on android app.
                Toast.makeText(Photo.this,string1,Toast.LENGTH_LONG).show();

                // Setting image as transparent after done uploading.
                ImageViewHolder.setImageResource(android.R.color.transparent);


            }

            @Override
            protected String doInBackground(Void... params) {

                ImageProcessClass imageProcessClass = new ImageProcessClass();

                HashMap<String,String> HashMapParams = new HashMap<String,String>();

                HashMapParams.put(ImageNameFieldOnServer, GetImageNameFromEditText);

                HashMapParams.put(ImagePathFieldOnServer, ConvertImage);

                String FinalData = imageProcessClass.ImageHttpRequest(ImageUploadPathOnSever, HashMapParams);

                return FinalData;
            }
        }
        AsyncTaskUploadClass AsyncTaskUploadClassOBJ = new AsyncTaskUploadClass();

        AsyncTaskUploadClassOBJ.execute();
    }