阻止Firebase中的重复数据条目？

Question

我有一个应用程序，允许用户上传汽车图像和汽车的一些细节。现在我想确保每个汽车模型只能输入一个条目，所以我想运行一个方法来检查CarModel是否存在，以及是否阻止用户上传。 我该怎么做？

这是我上传图片和汽车详细信息的代码：

    // Creating UploadImageFileToFirebaseStorage method to upload image on storage.
public void UploadImageFileToFirebaseStorage() {

    // Checking whether FilePathUri Is empty or not.
    if (FilePathUri != null) {

        // Setting progressDialog Title.
        progressDialog.setTitle("Image is Uploading...");

        // Showing progressDialog.
        progressDialog.show();

        // Creating second StorageReference.
        StorageReference storageReference2nd = storageReference.child(Storage_Path + System.currentTimeMillis() + "." + GetFileExtension(FilePathUri));

        // Adding addOnSuccessListener to second StorageReference.
        storageReference2nd.putFile(FilePathUri)
                .addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
                    @Override
                    public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {

                        // Getting image name from EditText and store into string variable.
                        String CarMake = carMake.getText().toString().trim();
                        String CarModel = carModel.getText().toString().trim();

                        // Hiding the progressDialog after done uploading.
                        progressDialog.dismiss();

                        // Showing toast message after done uploading.
                        Toast.makeText(getApplicationContext(), "Image Uploaded Successfully ", Toast.LENGTH_LONG).show();

                        @SuppressWarnings("VisibleForTests")
                        ImageUploadInfo imageUploadInfo = new ImageUploadInfo(taskSnapshot.getDownloadUrl().toString(), CarMake, CarModel);

                        // Getting image upload ID.
                        String ImageUploadId = databaseReference.push().getKey();

                        // Adding image upload id s child element into databaseReference.
                        databaseReference.child(ImageUploadId).setValue(imageUploadInfo);
                    }
                })
                // If something goes wrong .
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception exception) {

                        // Hiding the progressDialog.
                        progressDialog.dismiss();

                        // Showing exception erro message.
                        Toast.makeText(uploadActivity.this, exception.getMessage(), Toast.LENGTH_LONG).show();
                    }
                })

                // On progress change upload time.
                .addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() {
                    @Override
                    public void onProgress(UploadTask.TaskSnapshot taskSnapshot) {

                        // Setting progressDialog Title.
                        progressDialog.setTitle("Image is Uploading...");

                    }
                });


    }
    else {

        Toast.makeText(uploadActivity.this, "Please Select Image or Enter Car Details", Toast.LENGTH_LONG).show();

    }
}

我还有另一种检查重复项的方法：

public void duplicateCheck(){

    databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(final DataSnapshot dataSnapshot) {
            for (DataSnapshot data : dataSnapshot.getChildren()) {
                //If email exists then toast shows else store the data on new key
                if (!data.getValue(Car.class).getCarModel().equals(carModel)) {
                    databaseReference.child(databaseReference.push().getKey()).setValue(new Car(carMake, carModel));
                } else {
                    Toast.makeText(uploadActivity.this, "Car Model Already Exists.", Toast.LENGTH_SHORT).show();
                }
            }
        }

        @Override
        public void onCancelled(final DatabaseError databaseError) {
        }
    });
}

我在上传按钮上调用这两种方法：

// Adding click listener to Upload image button.
    UploadButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            // Calling method to upload selected image on Firebase storage.
            UploadImageFileToFirebaseStorage();
            duplicateCheck();

        }
    });