为什么我要在我的活动中得到java.lang.NullpointerExcetion: uriString？

Question

嘿，我在filepath =Uri.parse(路径)处得到了一个错误“uriString: uriString”；位于onCreate内部。我试图将图像上传到firebase，为此我需要filepath，我做错了什么？，我在uploadImage()中使用了filepath作为图像的路径，在此活动中显示了来自数组的选定图像，我希望将选定的图像上传到防火墙，请参见代码：

private Uri filepath;
FirebaseStorage storage;
StorageReference storageReference;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_image_viewer);
    String path = null;
    filepath = Uri.parse(path);
    ImageView imageView = findViewById(R.id.imageView);
    storage = FirebaseStorage.getInstance();
    storageReference = storage.getReference();
    Intent intent = getIntent();
    if (intent != null) {
        Glide.with(ImageViewerActivity.this).load(intent.getStringExtra("image")).placeholder(R.drawable.ic_baseline_broken_image_24).into(imageView);
        path = intent.getStringExtra("image");
    }
    ImageButton uploadClicks = findViewById(R.id.UploadClicks);
    uploadClicks.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            uploadImage();
        }
    });

    ImageButton share = findViewById(R.id.shareImage);
    String finalPath = path;
    share.setOnClickListener(v -> new ShareCompat.IntentBuilder(ImageViewerActivity.this).setStream(Uri.parse(finalPath)).setType("image/*").setChooserTitle("Share Image").startChooser());

    ImageButton delete = findViewById(R.id.deleteImage);
    delete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            MaterialAlertDialogBuilder alertDialogBuilder = new MaterialAlertDialogBuilder(ImageViewerActivity.this);
            alertDialogBuilder.setMessage("Are you sure you want to delete this image ?");
            alertDialogBuilder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    String[] projection = new String[]{MediaStore.Images.Media._ID};
                    String selection = MediaStore.Images.Media.DATA + " = ?";
                    String[] selectionArgs = new String[]{new File(finalPath).getAbsolutePath()};
                    Uri queryUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                    ContentResolver contentResolver = getContentResolver();
                    Cursor cursor = contentResolver.query(queryUri, projection, selection, selectionArgs, null);
                    if (cursor.moveToFirst()) {
                        long id = cursor.getLong(cursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID));
                        Uri deleteUri = ContentUris.withAppendedId(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, id);
                        try {
                            contentResolver.delete(deleteUri, null, null);
                            boolean delete1 = new File(finalPath).delete();
                            Log.e("TAG", delete1 + "");
                            Toast.makeText(ImageViewerActivity.this, "Deleted Successfully", Toast.LENGTH_SHORT).show();
                            finish();
                        } catch (Exception e) {
                            e.printStackTrace();
                            Toast.makeText(ImageViewerActivity.this, "Error Deleting Video", Toast.LENGTH_SHORT).show();
                        }
                    } else {
                        Toast.makeText(ImageViewerActivity.this, "File Not Find", Toast.LENGTH_SHORT).show();
                    }
                    cursor.close();
                }
            });
            alertDialogBuilder.setNegativeButton("No", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                }
            });
            alertDialogBuilder.show();
        }
    });
}

private void uploadImage()
{
    if (filepath != null) {

        // Code for showing progressDialog while uploading
        ProgressDialog progressDialog
                = new ProgressDialog(this);
        progressDialog.setTitle("Uploading...");
        progressDialog.show();

        // Defining the child of storageReference
        StorageReference ref
                = storageReference
                .child(
                        "images/"
                                + UUID.randomUUID().toString());

        // adding listeners on upload
        // or failure of image
        ref.putFile(filepath)
                .addOnSuccessListener(
                        new OnSuccessListener<UploadTask.TaskSnapshot>() {

                            @Override
                            public void onSuccess(
                                    UploadTask.TaskSnapshot taskSnapshot)
                            {

                                // Image uploaded successfully
                                // Dismiss dialog
                                progressDialog.dismiss();
                                Toast
                                        .makeText(ImageViewerActivity.this,
                                                "Image Uploaded!!",
                                                Toast.LENGTH_SHORT)
                                        .show();
                            }
                        })

                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e)
                    {

                        // Error, Image not uploaded
                        progressDialog.dismiss();
                        Toast
                                .makeText(ImageViewerActivity.this,
                                        "Failed " + e.getMessage(),
                                        Toast.LENGTH_SHORT)
                                .show();
                    }
                })
                .addOnProgressListener(
                        new OnProgressListener<UploadTask.TaskSnapshot>() {

                            // Progress Listener for loading
                            // percentage on the dialog box
                            @Override
                            public void onProgress(
                                    UploadTask.TaskSnapshot taskSnapshot)
                            {
                                double progress
                                        = (100.0
                                        * taskSnapshot.getBytesTransferred()
                                        / taskSnapshot.getTotalByteCount());
                                progressDialog.setMessage(
                                        "Uploaded "
                                                + (int)progress + "%");
                            }
                        });
    }
}

}

Answer 1

你的代码说：

String path = null;
filepath = Uri.parse(path);

你会问为什么Uri.parse(path)会抛出一个NullPointerException。

答:因为path是null。

为什么？

答:因为您在前面的行中为它分配了null！

怎么修呢？

答:不要这样做。相反，从某个地方获取路径的非空值。

不幸的是，您的代码中没有足够的线索来确定它将从哪里获得值，因此恐怕您必须自己解决这个问题。