onActivityResult() 在 Android 4.1.2 中捕获图像后给出空值

Question

我想捕获图像，将其保存到外部存储并显示在 ImageView 中。成功捕获并保存图像，但在执行onActivityResult() 时未显示在ImageView 中。它给出null 值。

请告诉我为什么它给了我空值。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    imageView = (ImageView) findViewById(R.id.imageView);

    //camera stuff
    Intent imageIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
    timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());

    //folder stuff
    imagesFolder = new File(Environment.getExternalStorageDirectory(), "MyImages");
    imagesFolder.mkdirs();

    File image = new File(imagesFolder, "QR_" + timeStamp + ".png");
    uriSavedImage = Uri.fromFile(image);

    imageIntent.putExtra(MediaStore.EXTRA_OUTPUT, uriSavedImage);
    startActivityForResult(imageIntent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    try {
        if (requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {
            if (resultCode == RESULT_OK) {
                Toast.makeText(this, "Image saved to:\n", Toast.LENGTH_LONG).show();
                Bitmap bitmap = (Bitmap) data.getExtras().get(MediaStore.EXTRA_OUTPUT);
                imageView.setImageBitmap(bitmap);

            } else if (resultCode == RESULT_CANCELED) {
                // User cancelled the image capture
            } else {
                // Image capture failed, advise user
            }
        }
    } catch (Exception e) {
        Log.d("onActivityResult", " error "+e.getMessage());
    }
}

日志错误：

10-01 10:57:14.008 18530-18530/com.example.zohaibsiddique.camera D/onActivityResult:  error null

Answer 1

如果您将额外参数MediaStore.EXTRA_OUTPUT 与相机意图一起传递，那么相机活动会将捕获的图像写入该路径，并且不会在onActivityResult 方法中返回位图。

如果您检查您所传递的路径，那么您将知道实际上相机已将捕获的文件写入该路径。

如需了解更多信息，您可以关注this、this 和this

Answer 2

您有两个选项来获取图像，从图库和从相机拍摄。如果您将EXTRA_OUTPUT 放入意图中，它不会返回Bitmap。那么你必须使用Uri。

用这两种方法startActivityForResult。

private void selectFromCamera() {

    try {
        File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "DCIM");
        if (!file.exists()) {
            file.mkdirs();
        }

        File localFile = new File(file + File.separator + "IMG_" + String.valueOf(System.currentTimeMillis()) + ".jpg");
        imageUri = Uri.fromFile(localFile);

        Intent cameraIntent = new Intent("android.media.action.IMAGE_CAPTURE");

        cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            cameraIntent.setClipData(ClipData.newRawUri(null, Uri.fromFile(localFile)));
        }

        startActivityForResult(cameraIntent, REQUEST_CAMERA);
    } catch (Exception localException) {
        Toast.makeText(ActivityAddMemory.this, "Exception:" + localException, Toast.LENGTH_SHORT).show();
    }
}

private void selectFromGallery() {
    Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    intent.setType("image/*");
    startActivityForResult(Intent.createChooser(intent, "Select File"), SELECT_FILE);
}

现在在onActivityForResult里面

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
    super.onActivityResult(requestCode, resultCode, intent);

    if(resultCode == RESULT_OK) {
        String path=null;
        Uri uri;
        if (intent == null || intent.getData() == null)
            uri = this.imageUri;
        else
            uri = intent.getData();

        if(requestCode == SELECT_FILE) {
            path = getRealPathFromURI(uri);
        } else if(requestCode == REQUEST_CAMERA){
            path = uri.getEncodedPath();
        }

    imageView.setImageBitmap(BitmapFactory.decodeFile(path));
}

下面是getRealPathFromUri

public String getRealPathFromURI(Uri uri){
    String filePath = "";
    String[] filePahColumn = {MediaStore.Images.Media.DATA};
    Cursor cursor = getContentResolver().query(uri, filePahColumn, null, null, null);
    if (cursor != null) {
        if(cursor.moveToFirst()){
            int columnIndex = cursor.getColumnIndex(filePahColumn[0]);
            filePath = cursor.getString(columnIndex);
        }
        cursor.close();
    }
    return filePath;
}

Answer 3

在 onCreate() 中调用这个方法

public void startCameraIntent() {
        File imageFile = new File("YOUR PATH");
        Uri imageFileUri = Uri.fromFile(imageFile); // convert path to Uri

        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        intent.putExtra(MediaStore.EXTRA_OUTPUT, imageFileUri);   // set the image file name
        startActivityForResult(intent, 02);
    }

将这些行放在 onActivityResult() 中

new ImageCompression(this).execute("PATH");

创建类：

public class ImageCompression extends AsyncTask<String, Void, String> {

        private Context context;
        private static final float maxHeight = 1280.0f;
        private static final float maxWidth = 1280.0f;


        public ImageCompression(Context context) {
            this.context = context;
        }

        @Override
        protected String doInBackground(String... strings) {
            if (strings.length == 0 || strings[0] == null)
                return null;

            return compressImage(strings[0]);
        }

        protected void onPostExecute(String imagePath) {
            // imagePath is path of new compressed image.
            imageView.setImageBitmap(BitmapFactory.decodeFile(new File(imagePath).getAbsolutePath()));
        }


        public String compressImage(String imagePath) {
            Bitmap scaledBitmap = null;

            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inJustDecodeBounds = true;
            Bitmap bmp = BitmapFactory.decodeFile("YOUR PATH", options);

            int actualHeight = options.outHeight;
            int actualWidth = options.outWidth;

            float imgRatio = (float) actualWidth / (float) actualHeight;
            float maxRatio = maxWidth / maxHeight;

            if (actualHeight > maxHeight || actualWidth > maxWidth) {
                if (imgRatio < maxRatio) {
                    imgRatio = maxHeight / actualHeight;
                    actualWidth = (int) (imgRatio * actualWidth);
                    actualHeight = (int) maxHeight;
                } else if (imgRatio > maxRatio) {
                    imgRatio = maxWidth / actualWidth;
                    actualHeight = (int) (imgRatio * actualHeight);
                    actualWidth = (int) maxWidth;
                } else {
                    actualHeight = (int) maxHeight;
                    actualWidth = (int) maxWidth;

                }
            }

            options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);
            options.inJustDecodeBounds = false;
            options.inDither = false;
            options.inPurgeable = true;
            options.inInputShareable = true;
            options.inTempStorage = new byte[16 * 1024];

            try {
                bmp = BitmapFactory.decodeFile(imagePath, options);
            } catch (OutOfMemoryError exception) {
                exception.printStackTrace();

            }
            try {
                scaledBitmap = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.RGB_565);
            } catch (OutOfMemoryError exception) {
                exception.printStackTrace();
            }

            float ratioX = actualWidth / (float) options.outWidth;
            float ratioY = actualHeight / (float) options.outHeight;
            float middleX = actualWidth / 2.0f;
            float middleY = actualHeight / 2.0f;

            Matrix scaleMatrix = new Matrix();
            scaleMatrix.setScale(ratioX, ratioY, middleX, middleY);

            Canvas canvas = new Canvas(scaledBitmap);
            canvas.setMatrix(scaleMatrix);
            canvas.drawBitmap(bmp, middleX - bmp.getWidth() / 2, middleY - bmp.getHeight() / 2, new Paint(Paint.FILTER_BITMAP_FLAG));

            if (bmp != null) {
                bmp.recycle();
            }

            ExifInterface exif;
            try {
                exif = new ExifInterface(imagePath);
                int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, 0);
                Matrix matrix = new Matrix();
                if (orientation == 6) {
                    matrix.postRotate(90);
                } else if (orientation == 3) {
                    matrix.postRotate(180);
                } else if (orientation == 8) {
                    matrix.postRotate(270);
                }
                scaledBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);
            } catch (IOException e) {
                e.printStackTrace();
            }
            FileOutputStream out = null;
            String filepath = getFilename();
            try {
                new File("YOUR PATH").delete();
                out = new FileOutputStream(filepath);

                //write the compressed bitmap at the destination specified by filename.
                scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);
/*

                Uri uri = Uri.parse(filepath + "/tmp.x");
                sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, uri));

*/
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }

            return filepath;
        }

        public int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
            final int height = options.outHeight;
            final int width = options.outWidth;
            int inSampleSize = 1;

            if (height > reqHeight || width > reqWidth) {
                final int heightRatio = Math.round((float) height / (float) reqHeight);
                final int widthRatio = Math.round((float) width / (float) reqWidth);
                inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
            }
            final float totalPixels = width * height;
            final float totalReqPixelsCap = reqWidth * reqHeight * 2;

            while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
                inSampleSize++;
            }

            return inSampleSize;
        }
    }

比活动类中的创建方法：

public String getFilename() {
    File mediaStorageDir = new File(Environment.getExternalStorageDirectory()
            + "/Tax Images");

    MediaScannerConnection.scanFile(this, new String[]{mediaStorageDir.toString()}, null, null);
    // Create the storage directory if it does not exist
    if (!mediaStorageDir.exists()) {
        mediaStorageDir.mkdirs();
    }


    String uriString = (mediaStorageDir.getAbsolutePath() + "/" + "IMAGE_NAME");

    return uriString;
}