安卓相机 : Empty file in onActivityResult method

Question

我有一个 Activity 可以打开相机 Intent 并在 onActivityResult 方法中抓取照片。三台设备运行良好，没有错误，但仅在 一台设备 中，我在 file 变量上出现空错误。

“尝试在空对象引用上调用虚方法 java.lang.String java.io.File.getPath()”

这就是我实现它的方式。

A) 第一步:打开相机

单击按钮后，我运行以下代码。此代码将:

1. 创建一个新文件

2. 打开相机 Intent

       //create file
       imgName = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date()) + ".jpg";
       //global variable
       file = new File(Environment.getExternalStorageDirectory(), imgName);
   
       if(file != null){
          //save image here
   
          Uri relativePath = Uri.fromFile(file);
   
          //Open camera
          Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
          intent.putExtra(MediaStore.EXTRA_OUTPUT, relativePath);
          startActivityForResult(intent, Constant.CAMERA_PIC_REQUEST);
       }
   

B) 第二步:拍照并点击保存按钮

C) 第三步:在onActivityResult()方法中抓取图片

1. 检查常量 = Constant.CAMERA_PIC_REQUEST。

2. 从照片中获取EXIF数据，找出旋转照片所需的角度。

3. 设置宽度、高度和角度。创建 .jpg 照片

4. 将创建的图片名称和路径保存到imageArray中

5. 用imageArray设置 GridView

   public void onActivityResult(int requestCode, int resultCode, Intent data) {
   
   
   if (resultCode == RESULT_OK) {
   
       switch (requestCode) {
   
       case Constant.CAMERA_PIC_REQUEST:
           try {
   
               //Get EXIF data and rotate photo (1. file.getPath() has been used)
               ExifInterface exif = new ExifInterface(file.getPath());
               int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
   
               int angle = 0;// Landscape
   
               //rotate photo
               if (orientation == ExifInterface.ORIENTATION_ROTATE_90) {
                   angle = 90;
               } else if (orientation == ExifInterface.ORIENTATION_ROTATE_180) {
                   angle = 180;
               } else if (orientation == ExifInterface.ORIENTATION_ROTATE_270) {
                   angle = 270;
               }
   
               Matrix matrix = new Matrix();
               matrix.postRotate(angle);
   
   
               try {
   
                   //Create the rotated .jpg file (2. file.getPath() has been used)
                   Bitmap correctBmp = Func.decodeSampleBitmapFromFile(file.getPath(), Constant.PHOTO_WIDTH, Constant.PHOTO_HEIGHT);
                   correctBmp = Bitmap.createBitmap(correctBmp, 0, 0, correctBmp.getWidth(), correctBmp.getHeight(), matrix, true);
   
                   FileOutputStream fOut;
   
                   fOut = new FileOutputStream(file);
                   correctBmp.compress(Bitmap.CompressFormat.JPEG, 80, fOut);
                   fOut.flush();
                   fOut.close();
   
                   //image saved successfully - add photo name into reference array. Later I will use this
                   //(3. file.getPath() has been used)
                   Image img = new Image();
                   img.setImageName(imgName);
                   img.setAbsolutePath(file.getAbsolutePath());
                   img.setRelativePath(Uri.fromFile(file));
                   imageArray.add(img);//save in array
   
   
               } catch (FileNotFoundException e) {
                   Log.e("Error", e.getMessage());
   
               } catch (IOException e) {
                   Log.e("Error", e.getMessage());
   
               }
   
           } catch (Exception e) {
               //This exception is triggering.
               Log.e("Error 15", e.getMessage());
           }
   
           //set this photo in a grid view for user to see
           setGridView(imageArray);
           break;
   
       case Constant.POPUPFRAG:
           //something else
           break;
       default:
           //deafult
           break;
   
       }
   }
   }
   

错误 15(第三个异常)仅在一部手机中触发。我不确定为什么会这样。它显示了我在上面发布的空指针异常。

可以运行上述代码的三个设备至少具有 android v4.0 或更高版本。给我 null 异常的手机是 Samsung Galaxy Note 3 Android v5.0。 (虽然代码失败了，但我可以在手机图库中找到照片)

你能告诉我这里可能出什么问题吗？我错过了什么吗？无论如何要改进这段代码？

谢谢!

Answer 1

您可以这样使用，而不是直接使用 file.getPath()。

创建 Uri 的全局变量，然后在所有 Activity 中使用它。

private Uri imageToUploadUri;
file = new File(Environment.getExternalStorageDirectory(), imgName);

if(file != null){
   //save image here

   imageToUploadUri = Uri.fromFile(file);

   //Open camera
   Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
   intent.putExtra(MediaStore.EXTRA_OUTPUT, imageToUploadUri);
   startActivityForResult(intent, Constant.CAMERA_PIC_REQUEST);
}

然后在您的 onActivityResult() 中像这样使用:

public void onActivityResult(int requestCode, int resultCode, Intent data) {


if (resultCode == RESULT_OK) {

    switch (requestCode) {

    case Constant.CAMERA_PIC_REQUEST:
        try {


            ExifInterface exif = new ExifInterface(imageToUploadUri.getPath());
            int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);

            int angle = 0;// Landscape

            //rotate photo
            if (orientation == ExifInterface.ORIENTATION_ROTATE_90) {
                angle = 90;
            } else if (orientation == ExifInterface.ORIENTATION_ROTATE_180) {
                angle = 180;
            } else if (orientation == ExifInterface.ORIENTATION_ROTATE_270) {
                angle = 270;
            }

            Matrix matrix = new Matrix();
            matrix.postRotate(angle);


            try {

                //Create the rotated .jpg file (2. file.getPath() has been used)
                Bitmap correctBmp = Func.decodeSampleBitmapFromFile(imageToUploadUri.getPath(), Constant.PHOTO_WIDTH, Constant.PHOTO_HEIGHT);
                correctBmp = Bitmap.createBitmap(correctBmp, 0, 0, correctBmp.getWidth(), correctBmp.getHeight(), matrix, true);

                FileOutputStream fOut;

                fOut = new FileOutputStream(file);
                correctBmp.compress(Bitmap.CompressFormat.JPEG, 80, fOut);
                fOut.flush();
                fOut.close();

                //image saved successfully - add photo name into reference array. Later I will use this
                //(3. file.getPath() has been used)
                Image img = new Image();
                img.setImageName(imgName);
                img.setAbsolutePath(file.getAbsolutePath());
                img.setRelativePath(imageToUploadUri);
                imageArray.add(img);//save in array


            } catch (FileNotFoundException e) {
                Log.e("Error", e.getMessage());

            } catch (IOException e) {
                Log.e("Error", e.getMessage());

            }

        } catch (Exception e) {
            //This exception is triggering.
            Log.e("Error 15", e.getMessage());
        }

        //set this photo in a grid view for user to see
        setGridView(imageArray);
        break;

    case Constant.POPUPFRAG:
        //something else
        break;
    default:
        //deafult
        break;

    }
}
}

希望对你有帮助!