Java 除最后一个对象外,RecyclerView在删除对象时更新视图
在我的应用程序中,我有一个活动,在RecyclerView中显示学生的数组列表。学生存储在Firebase实时数据库中。用户可以添加或删除学生。当用户删除一名学生时,RecyclerView将更新并显示剩余的学生 但我有个问题。例如,假设我有5个学生。我想删除所有5个,所以我一个接一个地删除它们。4名学生正确删除,RecyclerView更新并反映了这一点。只有当我删除最后一个学生时,RecyclerView才会更新,学生卡视图才会保留在那里。我收到一条祝酒词,确认该学生已被删除,我可以看到他们已在数据库中被删除。如果我导航回仪表板并返回学生列表,则CardView将消失。奇怪 每次删除后,我都会再次尝试调用onStart,但这没有帮助。有什么想法吗 我的活动:Java 除最后一个对象外,RecyclerView在删除对象时更新视图,java,android,firebase-realtime-database,arraylist,android-recyclerview,Java,Android,Firebase Realtime Database,Arraylist,Android Recyclerview,在我的应用程序中,我有一个活动,在RecyclerView中显示学生的数组列表。学生存储在Firebase实时数据库中。用户可以添加或删除学生。当用户删除一名学生时,RecyclerView将更新并显示剩余的学生 但我有个问题。例如,假设我有5个学生。我想删除所有5个,所以我一个接一个地删除它们。4名学生正确删除,RecyclerView更新并反映了这一点。只有当我删除最后一个学生时,RecyclerView才会更新,学生卡视图才会保留在那里。我收到一条祝酒词,确认该学生已被删除,我可以看到他们
public class StudentListActivity extends AppCompatActivity {
//firebase auth
private FirebaseAuth mAuth;
//public variables
public String currentUserAccount;
public String teacherAccountNav = "Teacher";
public String currentUserId;
//recyclerView variables
DatabaseReference ref;
ArrayList<Student> list;
RecyclerView recyclerView;
SearchView searchView;
@RequiresApi(api = Build.VERSION_CODES.KITKAT)
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_student_list);
//get current user
mAuth = FirebaseAuth.getInstance();
FirebaseUser user = mAuth.getCurrentUser();
//assert current user is not null and get current users id
assert user != null;
currentUserId = user.getUid();
//getting firebase reference of current users students
ref = FirebaseDatabase.getInstance().getReference().child("students").child(currentUserId);
//initialise views
recyclerView = findViewById(R.id.rv);
recyclerView.setHasFixedSize(true);
searchView = findViewById(R.id.searchView);
}
@Override
protected void onStart() {
super.onStart();
if(ref != null){
ref.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
//add students from firebase to an array list
if(dataSnapshot.exists()){
list = new ArrayList<>();
for(DataSnapshot ds : dataSnapshot.getChildren()){
list.add(ds.getValue(Student.class));
}
//sort by name
Collections.sort(list, Student.myName);
//make recycler view
recyclerView.setLayoutManager(new LinearLayoutManager(StudentListActivity.this));
StudentAdapterClass studentAdapterClass = new StudentAdapterClass(list);
recyclerView.setAdapter(studentAdapterClass);
//click listeners for buttons
studentAdapterClass.setOnItemClickListener(new StudentAdapterClass.OnItemClickListener() {
@Override
public void onUpdateClick(int position) {
//handle update click in here
Student student = list.get(position);
//show update dialog here
showUpdateDialog(student.getStudentId(), student.getStudentName(), student.getStudentEmail());
}
@Override
public void onDeleteClick(int position){
//handle delete click in here
Student student = list.get(position);
//show delete dialog here
showDeleteDialog(student.getStudentId());
}
});
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(StudentListActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}//if
}
//dialog box for deleting student
private void showDeleteDialog(final String studentId){
AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
LayoutInflater inflater = getLayoutInflater();
//dialog XML
final View dialogView = inflater.inflate(R.layout.delete_student_dialog, null);
dialogBuilder.setView(dialogView);
final ImageButton buttonNo = dialogView.findViewById(R.id.imageButtonNo);
final ImageButton buttonYes = dialogView.findViewById(R.id.imageButtonYes);
final AlertDialog alertDialog = dialogBuilder.create();
alertDialog.show();
buttonNo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
alertDialog.dismiss();
}
});
buttonYes.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
deleteStudent(studentId);
alertDialog.dismiss();
}
});
}
//delete student method
private void deleteStudent(String id){
//get current user
mAuth = FirebaseAuth.getInstance();
FirebaseUser user = mAuth.getCurrentUser();
//assert current user is not null and get current users id
assert user != null;
currentUserId = user.getUid();
DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("students").child(currentUserId).child(id);
databaseReference.removeValue();
Toast.makeText(this, "Student Deleted", Toast.LENGTH_LONG).show();
//clear and get new list
onStart();
}
公共类StudentListActivity扩展了AppCompatActivity{
//火基认证
私人消防队;
//公共变量
公共字符串currentUserAccount;
公共字符串teacherAccountNav=“Teacher”;
公共字符串currentUserId;
//循环视图变量
数据库参考文献;
数组列表;
回收视图回收视图;
搜索视图搜索视图;
@RequiresApi(api=Build.VERSION\u CODES.KITKAT)
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u student\u list);
//获取当前用户
mAuth=FirebaseAuth.getInstance();
FirebaseUser=mAuth.getCurrentUser();
//断言当前用户不为null并获取当前用户id
断言用户!=null;
currentUserId=user.getUid();
//获取当前用户和学生的firebase参考
ref=FirebaseDatabase.getInstance().getReference().child(“学生”).child(currentUserId);
//初始化视图
recyclerView=findViewById(R.id.rv);
recyclerView.setHasFixedSize(true);
searchView=findviewbyd(R.id.searchView);
}
@凌驾
受保护的void onStart(){
super.onStart();
如果(ref!=null){
ref.addValueEventListener(新的ValueEventListener(){
@凌驾
public void onDataChange(@NonNull DataSnapshot DataSnapshot){
//将firebase中的学员添加到数组列表
if(dataSnapshot.exists()){
列表=新的ArrayList();
对于(DataSnapshot ds:DataSnapshot.getChildren()){
添加(ds.getValue(Student.class));
}
//按名称排序
Collections.sort(list,Student.myName);
//创建回收者视图
setLayoutManager(新的LinearLayoutManager(StudentListActivity.this));
StudentAdapterClass StudentAdapterClass=新的StudentAdapterClass(列表);
setAdapter(studentAdapterClass);
//单击按钮的侦听器
studentAdapterClass.setOnItemClickListener(新的studentAdapterClass.OnItemClickListener(){
@凌驾
更新点击时的公共无效(内部位置){
//处理更新点击这里
学生=列表。获取(位置);
//在此处显示更新对话框
showUpdateDialog(student.getStudentId(),student.getStudentName(),student.getStudentEmail());
}
@凌驾
公共位置单击(内部位置){
//处理删除点击这里
学生=列表。获取(位置);
//在此处显示删除对话框
showDeleteDialog(student.getStudentId());
}
});
}
}
@凌驾
已取消的公共void(@NonNull DatabaseError DatabaseError){
Toast.makeText(StudentListActivity.this,databaseError.getMessage(),Toast.LENGTH_SHORT.show();
}
});
}//如果
}
//用于删除学生的对话框
私有void showDeleteDialog(最终字符串studentId){
AlertDialog.Builder dialogBuilder=新建AlertDialog.Builder(此);
LayoutInflater充气机=getLayoutInflater();
//对话框XML
最终视图对话框视图=充气机。充气(R.layout.delete\u student\u对话框,空);
dialogBuilder.setView(dialogView);
final ImageButton buttonNo=dialogView.findViewById(R.id.imageButtonNo);
final ImageButton buttonYes=dialogView.findViewById(R.id.imageButtonYes);
final AlertDialog AlertDialog=dialogBuilder.create();
alertDialog.show();
buttonNo.setOnClickListener(新视图.OnClickListener(){
@凌驾
公共void onClick(视图v){
alertDialog.disclose();
}
});
setOnClickListener(新视图.OnClickListener(){
@凌驾
公共void onClick(视图v){
删除学生(学生ID);
alertDialog.disclose();
}
});
}
//删除学生方法
私有无效删除学生(字符串id){
//获取当前用户
mAuth=FirebaseAuth.getInstance();
FirebaseUser=mAuth.getCurrentUser();
//断言当前用户不为null并获取当前用户id
断言用户!=null;
currentUserId=user.getUid();
DatabaseReference DatabaseReference=FirebaseDatabase.getInstance().getReference(“学生”).child(currentUserId).child(id);
databaseReference.removeValue();
Toast.makeText(此“学生已删除”,Toast.LENGTH_LONG).show();
//清除并获取新列表
onStart();
}
我的适配器:
public class StudentAdapterClass extends RecyclerView.Adapter<StudentAdapterClass.MyViewHolder> {
private ArrayList<Student> list;
private OnItemClickListener mListener;
public interface OnItemClickListener{
//click method for update button
void onUpdateClick(int position);
//click method for delete button
void onDeleteClick(int position);
}
public void setOnItemClickListener(OnItemClickListener listener){
mListener = listener;
}
public StudentAdapterClass(ArrayList<Student> list){
this.list = list;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.card_holder, viewGroup, false);
return new MyViewHolder(view, mListener);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder myViewHolder, int i) {
myViewHolder.name.setText(list.get(i).getStudentName());
myViewHolder.email.setText(list.get(i).getStudentEmail());
}
@Override
public int getItemCount() {
return list.size();
}
static class MyViewHolder extends RecyclerView.ViewHolder {
TextView name, email;
ImageButton update, delete;
MyViewHolder(@NonNull View itemView, final OnItemClickListener listener) {
super(itemView);
name = itemView.findViewById(R.id.studentName);
email = itemView.findViewById(R.id.studentEmail);
update = itemView.findViewById(R.id.updateButton);
delete = itemView.findViewById(R.id.deleteButton);
//update click listener
update.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (listener != null){
int position = getAdapterPosition();
if(position != RecyclerView.NO_POSITION){
listener.onUpdateClick(position);
}
}
}
});
delete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (listener != null){
int position = getAdapterPosition();
if(position != RecyclerView.NO_POSITION){
listener.onDeleteClick(position);
}
}
}
});
}
}
公共类StudentAdapterClass扩展了RecyclerView.Adapter{
私有数组列表;
私人监听
recyclerView.getAdapter().notifyDataSetChanged()