Activity传数据至Adapter后字符串显示为null问题求助

问题详情 #

已将数据从Activity传递至自定义RecyclerView Adapter，调试时确认传入Adapter构造函数的uniquesharedId参数存在正确数据，但执行this.uniquesharedIds = uniquesharedId;赋值后，成员变量uniquesharedIds显示为null，后续在onBindViewHolder中调用holder.Name.setText(uniquesharedIds)时显示空值。

相关代码 #

Activity的onCreate方法 #

myadapter = new Invite_Contributors_Adapter(contributorInviteList, getIntent().getStringExtra("uniquesharedId"));

Adapter完整代码 #

public class Invite_Contributors_Adapter extends RecyclerView.Adapter<Invite_Contributors_Adapter.myviewholder> {
    private ArrayList<Model_Invite_Contributors_List> model_invite_contributors_lists = new ArrayList<>();
    FirebaseAuth mAuth;
    private FirebaseUser currentuser;
    private DatabaseReference UsersReference;
    Context context;
    String uniquesharedIds;
    private InviteContributorsInterface inviteContributorsInterface;

    public Invite_Contributors_Adapter() {
    }

    public void updateInviteList (ArrayList list) {
        model_invite_contributors_lists .clear();
        model_invite_contributors_lists .addAll(list);
        notifyDataSetChanged();
    }

    public Invite_Contributors_Adapter(ArrayList<Model_Invite_Contributors_List>model_invite_contributors_lists, String uniquesharedId) {
        this.model_invite_contributors_lists = model_invite_contributors_lists;
        this.uniquesharedIds = uniquesharedId;
    }

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

    @Override
    public void onBindViewHolder(@NonNull myviewholder holder, int position) {
        holder.setData(model_invite_contributors_lists.get(position));
        mAuth = FirebaseAuth.getInstance();
        holder.Name.setText(uniquesharedIds);
    }


    @Override
    public int getItemCount() {
        return model_invite_contributors_lists.size();
    }


    static class myviewholder extends RecyclerView.ViewHolder implements DialogInterface.OnClickListener {
        TextView Name;
        CircleImageView profileImageView;

        public myviewholder(@NonNull View itemView) {
            super(itemView);
            Name = itemView.findViewById(R.id.contributor_name);
            profileImageView = itemView.findViewById(R.id.member_profile_picture);
        }

        @Override
        public void onClick(DialogInterface dialog, int which) {
        }

        public void setData(Model_Invite_Contributors_List model) {
            FirebaseUser currentuser;
            currentuser = FirebaseAuth.getInstance().getCurrentUser();
            DatabaseReference NameRef = FirebaseDatabase.getInstance().getReference(Strings.UsersReference);
            NameRef.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    if (dataSnapshot.exists()) {
                        // 隐藏当前用户的条目
                        if (currentuser.getUid().equals(model.getUser_Id())){
                            ViewGroup.LayoutParams params = itemView.getLayoutParams();
                            params.height = 0;
                            itemView.setLayoutParams(params);
                        } else {
                            for(DataSnapshot ds : dataSnapshot.getChildren())
                            {
                                itemView.setVisibility(View.VISIBLE);
                                String profileImageString;
                                profileImageString = model.getProfileimage();
                                Glide.with(profileImageView.getContext())
                                        .load(profileImageString)
                                        .placeholder(R.drawable.circle_placeholder)
                                        .error(R.drawable.circle_placeholder)
                                        .into(profileImageView);
                            }
                        }
                    }
                }

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

            });
        }
    }



    public void setInterface (Invite_Contributors_Adapter.InviteContributorsInterface inviteContributorsInterface) {
        this.inviteContributorsInterface = inviteContributorsInterface;
    }

    public interface InviteContributorsInterface{

    }
}

解决步骤 #

1. 排查空构造函数调用
   检查项目中是否存在其他地方通过空构造new Invite_Contributors_Adapter()实例化Adapter的情况。如果有，该实例的uniquesharedIds会是null，若后续将这个实例设置给RecyclerView，就会出现问题。确保所有Adapter实例都通过带参数的构造函数创建。

2. 添加日志确认赋值状态
   在带参数的构造函数中添加日志，验证赋值后uniquesharedIds的状态：

   public Invite_Contributors_Adapter(ArrayList<Model_Invite_Contributors_List>model_invite_contributors_lists, String uniquesharedId) {
       this.model_invite_contributors_lists = model_invite_contributors_lists;
       this.uniquesharedIds = uniquesharedId;
       Log.d("AdapterDebug", "构造函数赋值后uniquesharedIds: " + this.uniquesharedIds);
   }
   

   同时在onBindViewHolder中也添加日志：

   @Override
   public void onBindViewHolder(@NonNull myviewholder holder, int position) {
       holder.setData(model_invite_contributors_lists.get(position));
       Log.d("AdapterDebug", "onBindViewHolder中uniquesharedIds: " + uniquesharedIds);
       holder.Name.setText(uniquesharedIds);
   }
   

   通过日志判断是赋值时就出现问题，还是后续被修改为null。

3. 检查变量是否被意外覆盖
   全局搜索Adapter中对uniquesharedIds的赋值操作，确认没有其他代码将其设置为null。

4. 优化Adapter初始化逻辑
   将mAuth = FirebaseAuth.getInstance();移至Adapter的构造函数中，避免每次onBindViewHolder都重复初始化：

   public Invite_Contributors_Adapter(ArrayList<Model_Invite_Contributors_List>model_invite_contributors_lists, String uniquesharedId) {
       this.model_invite_contributors_lists = model_invite_contributors_lists;
       this.uniquesharedIds = uniquesharedId;
       this.mAuth = FirebaseAuth.getInstance();
   }
   

内容的提问来源于stack exchange，提问作者greenTea