java - 照片压缩上传至数据库

Question

我正在尝试拍照然后将其上传到数据库，但是每次我拍照并尝试发布它时都会收到错误:java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“boolean android.graphics.Bitmap.compress(android.graphics.Bitmap$CompressFormat, int, java.io.OutputStream)”。

每当我拍照时，我都不会在 ImageView 中看到预览。

所以我假设我没有将照片正确添加到位图中，以便 ImageUploadImageToServerFunction() 存储图像。然而，它不起作用对我来说毫无意义。

这是我遇到问题的函数。

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();
    }

Answer 1

您可以使用此库来压缩图像

 compile 'id.zelory:compressor:2.1.0'

这是这个链接 https://android-arsenal.com/details/1/3758您可以自定义质量、高度、体重等。

compressedImageBitmap = new Compressor(this).compressToBitmap(actualImageFile);
compressedImageFile = new Compressor(this).compressToFile(actualImageFile);

如果您想要一些定制:

compressedImage = new Compressor(this)
            .setMaxWidth(640)
            .setMaxHeight(480)
            .setQuality(75)
            .setCompressFormat(Bitmap.CompressFormat.WEBP)
            .setDestinationDirectoryPath(Environment.getExternalStoragePublicDirectory(
              Environment.DIRECTORY_PICTURES).getAbsolutePath())
            .compressToFile(actualImage);