java - 单击 "delete"按钮时如何删除数据库中的一项？

Question

我是 android studio 的新手，对于我的 android 应用程序，我使用的是 Firebase。我想在单击按钮 delete(btnDelete) 时从数据库中删除一项。

    String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
    Query query= FirebaseDatabase.getInstance()
            .getReference().child("users").child(uid).child("foto");



        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            foto_root=itemView.findViewById(R.id.foto_root);
            tvNameF=itemView.findViewById(R.id.tvNameF);
            tvPhoneF=itemView.findViewById(R.id.tvPhoneF);
            tvAdressF=itemView.findViewById(R.id.tvAdressF);
            tvMailF=itemView.findViewById(R.id.tvMailF);
            tvNoteF=itemView.findViewById(R.id.tvNoteF);
            btnDelete=itemView.findViewById(R.id.btnDelete);
        }

        public void setTvNameF(String tvNameFs){
            tvNameF.setText(tvNameFs);
        }
        public void setTvPhoneF(String tvPhoneFs){
            tvPhoneF.setText(tvPhoneFs);
        }

    }

    /*
    get on dataBase
     */
    private void fetch() {
        FirebaseRecyclerOptions<Foto> options=
                new FirebaseRecyclerOptions.Builder<Foto>().setQuery(query, snapshot -> new Foto(
                snapshot.child("id").getKey(),
                snapshot.child("name").getValue().toString(),
                snapshot.child("phone").getValue().toString(),
                snapshot.child("adress").getValue().toString(),
                snapshot.child("email").getValue().toString(),
                snapshot.child("note").getValue().toString())).build();
        adapter = new FirebaseRecyclerAdapter<Foto, FotoActivity.ViewHolder>(options) {

            @NonNull
            @Override
            public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.foto_item,parent,false);
                return new ViewHolder(view);
            }

            @Override
            protected void onBindViewHolder(@NonNull ViewHolder viewHolder, int i, @NonNull Foto foto) {
                viewHolder.setTvNameF(foto.getNameF());
                viewHolder.setTvPhoneF(foto.getPhoneF());
                viewHolder.setTvAdressF(foto.getAdressF());
                viewHolder.setTvMailF(foto.getEmailF());
                viewHolder.setTvNoteF(foto.getNoteF());
                viewHolder.btnDelete.setOnClickListener(v -> {
                    delete();
                });
            }

        };
        rvFoto.setAdapter(adapter);
        }

    private void delete() {


        Toast.makeText(FotoActivity.this, "remove", Toast.LENGTH_SHORT).show();
    }

    private void viewRecyclerViewFoto() {
        linearLayoutManager=new LinearLayoutManager(this);
        rvFoto.setLayoutManager(linearLayoutManager);
        rvFoto.setHasFixedSize(true);
    }
}    


// adapter class

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

private void setInfoFoto() {
        DatabaseReference databaseReference=
                FirebaseDatabase.getInstance().getReference().child("users").child(uid).child("foto").push();
        Map<String,Object> mapFoto=new HashMap<>();
        mapFoto.put("id",databaseReference.getKey());
        mapFoto.put("name",etNameF.getText().toString());
        mapFoto.put("phone",etPhoneF.getText().toString());
        mapFoto.put("adress",etAdressF.getText().toString());
        mapFoto.put("email",etMailF.getText().toString());
        mapFoto.put("note",etNoteF.getText().toString());

        databaseReference.setValue(mapFoto);

    }

我想从 foto 中删除一个项目而不是所有数据库。

Answer 1

只需在您的删除函数中使用以下代码，这将删除“phone”节点的值。您将需要知道要删除的用户的 uid，否则您可以将其替换为数据库节点引用，但这将从所有用户 ID 中删除电话。基本上，您将监听照片节点，获取所有推送 ID 并循环遍历推送 ID 以删除所需的节点。

声明变量

private static final String TAG = "TestActivity";
private DatabaseReference fbDbRef;

创建时

final String uid = "youruid";
fbDbRef = FirebaseDatabase.getInstance().getReference().child("users")
         .child(uid).child("foto");

你的函数

private void delete() {

fbDbRef.addListenerForSingleValueEvent(new ValueEventListener() {

        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            for (DataSnapshot snapshot : dataSnapshot.getChildren()) {

                final String pushKey = snapshot.getKey();
                Log.d(TAG, "pushKey: " + pushKey);
                fbDbRef.child(pushKey).child("phone").removeValue();

            }

        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });

}