从 Firebase 数据库获取和 ID 的 Intent 问题

Question

我对来自 class 的 Intent 有疑问，它发送带有 Course_ID 的额外字符串，如您在 Firebase 数据库图像中所见。有时在 class UploadFile.class 中，使用额外字符串（包含 Course_ID）获取意图的字符串会获取空值。如果你能推荐我一个新的方法来申请从 Firebase 获取这个 Course_ID，我将不胜感激。在此文本下方附有 Firebase 数据库的屏幕、我有时在 UploadFile.class 中遇到的错误以及 UploadFile.class 的代码和我发送此意图的 class 中的部分代码有额外的字符串。

UploadFile.class

public class UploadFile extends AppCompatActivity {

    EditText denumire_material;
    Button selectare_material;
    ImageView adaugare_material;
    DatabaseReference databaseReference;
    FirebaseAuth mFirebaseAuth;
    FirebaseDatabase reference;
    private FirebaseStorage storage;
    private StorageReference storageReference;
    private Uri pdfUri;
    String url;
    String generatedFilePath;
    Uri downloadUri;
    TeacherCoursesFragment teacherCoursesFragment = new TeacherCoursesFragment();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_upload_file);

        denumire_material = findViewById(R.id.editBoxDenumireMaterial);
        selectare_material = findViewById(R.id.btnSelectareMaterial);
        adaugare_material = findViewById(R.id.imgAddMaterial);
        mFirebaseAuth = FirebaseAuth.getInstance();


        storageReference = FirebaseStorage.getInstance().getReference();
        reference = FirebaseDatabase.getInstance();
        databaseReference = FirebaseDatabase.getInstance().getReference().child("Materials").child(mFirebaseAuth.getCurrentUser().getUid());

        selectare_material.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(ContextCompat.checkSelfPermission(UploadFile.this, Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED){
                    selectPDF();
                } else{
                    ActivityCompat.requestPermissions(UploadFile.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},9);

                }
            }
        });

        adaugare_material.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(pdfUri!=null){
                    uploadFile(pdfUri);
                    adaugareDateInFirebase();
                } else{}
            }
        });
    }

        private void adaugareDateInFirebase(){
            DatabaseReference reference1 = FirebaseDatabase.getInstance().getReference();
            Query query = reference1.child(mFirebaseAuth.getCurrentUser().getUid());
                    DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
                    Date date = new Date();
                    String datee = dateFormat.format(date).toString();
                    String course_id = getIntent().getExtras().getString("course id").toString();
                    HashMap<String, Object> firebase = new HashMap<>();
                    firebase.put("Denumire_material", denumire_material.getText().toString());
                    firebase.put("Locatie_material", generatedFilePath);
                    firebase.put("Teacher_ID", mFirebaseAuth.getCurrentUser().getUid());
                    firebase.put("Course_ID", course_id);
                    firebase.put("Data_adaugarii", datee);
                    databaseReference.push().setValue(firebase).addOnCompleteListener(new OnCompleteListener<Void>() {
                        @Override
                        public void onComplete(@NonNull Task<Void> task) {
                            if(task.isSuccessful()){

                            }
                        }
                    });
                }

        private void uploadFile(Uri pdfUri) {
        final String fileName = System.currentTimeMillis()+"";
        StorageReference storageReference = storage.getInstance().getReference();

        final StorageReference storageReference1 = storageReference.child("Materiale/" + mFirebaseAuth.getCurrentUser().getUid()+"/"+denumire_material.getText().toString());

        storageReference1.putFile(pdfUri).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
            @Override
            public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
                taskSnapshot.getStorage().getDownloadUrl().addOnCompleteListener(new OnCompleteListener<Uri>() {
                    @Override
                    public void onComplete(@NonNull Task<Uri> task) {
                        generatedFilePath = task.getResult().toString();
                    }
                });
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText(UploadFile.this, "File not succesfully uploaded", Toast.LENGTH_SHORT).show();
            }
        }).addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() {
            @Override
            public void onProgress(@NonNull UploadTask.TaskSnapshot taskSnapshot) {

            }
        });
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if(requestCode == 9 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
            selectPDF();
        } else{
            Toast.makeText(UploadFile.this, "Permission denied", Toast.LENGTH_SHORT).show();

        }
    }
    }

TeacherCoursesFragments.class - class 我从那里发送带有额外字符串的意图（当然它包含 id）。

public class TeacherCoursesFragment extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    v =  inflater.inflate(R.layout.fragment_teacher_courses, container, false);
    ImageView addCourseBtn = (ImageView) v.findViewById(R.id.btnAddCourse);

    recyclerView = v.findViewById(R.id.recyclerView_fragmentCourses);
    recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
    mAuth = FirebaseAuth.getInstance();
    FirebaseUser user = mAuth.getCurrentUser();
    String uid = user.getUid();
    createCourse = new CreateCourse();

    reference = FirebaseDatabase.getInstance().getReference().child("Courses").child("Teacher-Courses").child(uid);

    intent = new Intent(getActivity(), CreateCourse.class);
    addCourseBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(intent);
        }
    });


    return v;
}

@Override
public void onStart() {
    super.onStart();
    options = new FirebaseRecyclerOptions.Builder<Course>().setQuery(reference, Course.class).build();
    adapter = new FirebaseRecyclerAdapter<Course, CourseViewHolder>(options) {
        @Override
        protected void onBindViewHolder(@NonNull final CourseViewHolder courseViewHolder, int i, @NonNull final Course course) {
            courseViewHolder.courseRealName.setText(course.getCourse_name());
            String numberOfStudents = String.valueOf(course.getCourse_students());
            courseViewHolder.realNumberOfStudents.setText(numberOfStudents);
            courseViewHolder.detailsButtonCourse2.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent = new Intent(v.getContext(), CourseMaterial.class);
                    intent.putExtra("course id", course.getCourse_ID());
                    intent.putExtra("teacher id", course.getTeacher_ID());
                    startActivity(intent);
                }
            });

            courseViewHolder.course_chenar.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent = new Intent(v.getContext(), CourseOperations.class);
                    intent.putExtra("course name", course.getCourse_name());
                    intent.putExtra("course description", course.getCourse_description());
                    intent.putExtra("course points", String.valueOf(course.getCourse_points()));
                    intent.putExtra("course students", String.valueOf(course.getCourse_students()));
                    startActivity(intent);
                }
            });

            courseViewHolder.detailsButtonCourse.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent = new Intent(v.getContext(), UploadFile.class);
                    intent.putExtra("course id", course.getCourse_ID());
                    startActivity(intent);
                }
            });

        }

我是否应该创建 2 个 DatabaseReference，一个用于 Teacher-Courses，一个用于 Materials？我已经尝试过了，但是如果没有 Intent，我无法从 Teacher-Courses 中获取 Course_ID。我在 Whosebug 和 Google 上搜索过，但我根本没有找到任何解决方案。等待你的回应、建议或解决方案，如果你能给我一些。谢谢！

补充说明：课程名称和学生人数（第二个标题）是使用 RecyclerViewAdapter 和 RecyclerViewOptions 从 Firebase 数据库中提取的，如您在 TeacherCoursesFragment.class 中所见。第一个按钮重定向到 UploadFile.class，我在其中上传文件并为其建立名称以存储在 Firebase 存储中。第二个按钮将用户发送到另一个页面，用户可以在其中 select 从多个选项（删除等）。

Answer 1

也许在 UploadFile 中更改此设置：

String course_id = getIntent().getExtras().getString("course id").toString();

为此：

String course_id = getIntent().getStringExtra("course id");

更新：

我猜你应该在 onCreate():

中调用 getIntent()

在你的UploadFile

public class UploadFile extends AppCompatActivity {

........
//declare as member variable
private String course_id;


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_upload_file);

//get it here
course_id = getIntent().getStringExtra("course id");
.......
.......
.......

}




}

删除您正在使用的这一行：

String course_id = getIntent().getExtras().getString("course id").toString();

从 Firebase 数据库获取和 ID 的 Intent 问题

Problem with Intent that takes and ID from Firebase Database

android

android-intent

firebase

firebase-realtime-database