java - List 不删除它包含在 RecyclerView 适配器中的 POJO 对象

Question

我正在从 Firebase 数据库中读取用户(姓名、年龄)的数据并将其显示在回收站 View 中。当用户长按一个项目时，该项目已成功从 firebase 中删除，但是当我尝试从 List of users 中删除该项目时，例如 List ，在子监听器的 onChildRemoved 方法中，用户未被删除。代码是:

mChildListener=new ChildEventListener() {
            @Override
            public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {

                User user=dataSnapshot.getValue(User.class);
                user.setUid(dataSnapshot.getKey());

                mDataList.add(user);
                mUserAdapter.notifyDataSetChanged();
                //passing the user returned to adapter but didn't work
                mUserAdapter.updateDataSet(user);
            }
            @Override
            public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {  
                User user=dataSnapshot.getValue(User.class);
                user.setUid(dataSnapshot.getKey());

                mDataList.remove(user);
                mUserAdapter.notifyDataSetChanged();
            }
        };

这是用户模型类:

public class User {
    private String uid;
    private String name;
    private int age;
    public User() {}
    public User(String uid, String name, int age) {
        this.uid = uid;
        this.name = name;
        this.age = age;
    }
    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getUid() {return uid;}
    public void setUid(String uid) {this.uid = uid;}
    public String getName() {return name;}
    public void setName(String name) {this.name = name;}
    public int getAge() {return age;}
    public void setAge(int age) {this.age = age;}
}

回收器 View 代码是这样的:

@Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

        User user=mDataList.get(position);

        holder.textView.setText(user.getName()+ "  |  "+user.getAge());

        holder.textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String uid=user.getUid();
                Intent intent=new Intent(mContext,DetailsActivity.class);
                intent.putExtra(USER_KEY,uid);
                mContext.startActivity(intent);
            }
        });
        holder.textView.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                //this line returns true
                boolean remove = mDataList.contains(user);
                //if I try to remove the user here, its removed
                //this line works as I want
//                mDataList.remove(user);
                Log.d(MainActivity.TAG, "updateDataSet: Contains: "+remove);
                Task<Void> removeUser = NetworkUtils.removeUser(user.getUid());
                removeUser.addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        Toast.makeText(mContext, "User removed", Toast.LENGTH_SHORT).show();
                        //mDataList.remove(user);
                        //notifyDataSetChanged();
                    }
                });
                return true;
            }
        });
    }

我还尝试将 onChildRemoved 中返回的用户传递给适配器，但效果不佳。

public void updateDataSet(User user){
        //this also returns false even the data of this user id displayed
        boolean contains=mDataList.contains(user);
        //this also does not works
        mDataList.remove(user);
        this.notifyDataSetChanged();
    }

我的问题是:

1) 我怎样才能从回收者 View 列表中删除在长时间点击项目时删除的项目？

2) 我有 List<User> mDataList在 MainActivity.java和一个 UserAdapter.java .我正在传递 mDataList在MainActivity到 UserAdapter .这两个在内存中是相同的还是不同的？如果不同，那么如何改变 List<user> mDataList在MainActivity (在 onChildAdded 中添加新项目)更改 List<User> mDataList在UserAdapter ？非常感谢。我已尽力解决我的问题。

Answer 1

使用 equals() 方法更新您的 User 类:

public class User {
    private String uid;
    private String name;
    private int age;
    public User() {}
    public User(String uid, String name, int age) {
        this.uid = uid;
        this.name = name;
        this.age = age;
    }
    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getUid() {return uid;}
    public void setUid(String uid) {this.uid = uid;}
    public String getName() {return name;}
    public void setName(String name) {this.name = name;}
    public int getAge() {return age;}
    public void setAge(int age) {this.age = age;}

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof User) {
            User user= (User) obj;
            return uid.equals(user.getUid());
        } else return false;
    }
}

现在更新您的 onChildRemoved 方法:

@Override
public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) { 
      User user=dataSnapshot.getValue(User.class);
      user.setUid(dataSnapshot.getKey());
      int index = mDataList.indexOf(user);
      mDataList.remove(index);
      mUserAdapter.notifyDataSetChanged();
    }

注意:如果uid在mDataList中不存在，则返回-1。