我的自定义RecyclerView适配器上的错误是什么？

Question

我正在使用Recycler View，我将所有设置都设置为ok（因为它接缝了），但是总是使活动崩溃，在进行一些调试之后，我发现了它发生的地方，但是从来没有弄清楚！这是我的RecyclerView适配器

在此处输入代码

public class StudentsAdapter extends RecyclerView.Adapter<StudentsAdapter.mHolder> {
    private  List<Student> mStudents;
    private  Context mContext;

    public StudentsAdapter(List<Student> students, Context mContext) {
        Log.d("StudentsAdapter", "in Constructor");
        this.mStudents = students;
        this.mContext = mContext;
    }

    @NonNull
    @Override
    public mHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        Log.d("StudentsAdapter", "in onCreateViewHolder");
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        View v = inflater.inflate(R.layout.note_list_students, parent, false);
        return new mHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull mHolder holder, int position) {
        Log.d("StudentsAdapter", "in onBindViewHolder");
        Student student = mStudents.get(position);
        Log.d("StudentsAdapter", "in getting Student Object");
        holder.nameTv.setText(student.getName());
        Log.d("StudentsAdapter", "in Setting Text name");
        holder.genderTv.setText(student.getGender());
        holder.birthdayTv.setText(student.getBirthday());
    }

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

    public class mHolder extends RecyclerView.ViewHolder {
        TextView nameTv, genderTv, birthdayTv;

        public mHolder(@NonNull View itemView) {
            super(itemView);
            Log.d("StudentsAdapter", "in View Holder");
            nameTv = itemView.findViewById(R.id.name);
            genderTv = itemView.findViewById(R.id.gender);
            birthdayTv = itemView.findViewById(R.id.birthday);

        }
    }
}

经过调试过程，这是我得到的：

2019-12-30 13:05:08.583 6169-6169/com.example.schooltendancemanager D/StudentsAdapter: in Constructor
2019-12-30 13:05:08.625 6169-6169/com.example.schooltendancemanager D/StudentsAdapter: in onCreateViewHolder
2019-12-30 13:05:08.638 6169-6169/com.example.schooltendancemanager D/StudentsAdapter: in View Holder
2019-12-30 13:05:08.638 6169-6169/com.example.schooltendancemanager D/StudentsAdapter: in onBindViewHolder
2019-12-30 13:05:08.638 6169-6169/com.example.schooltendancemanager D/StudentsAdapter: in getting Student Object
2019-12-30 13:05:08.642 6169-6169/com.example.schooltendancemanager E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.schooltendancemanager, PID: 6169
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
        at com.example.schooltendancemanager.ui.StudentsAdapter.onBindViewHolder(StudentsAdapter.java:43)
        at com.example.schooltendancemanager.ui.StudentsAdapter.onBindViewHolder(StudentsAdapter.java:18)
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6781)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6823)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5752)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6019)

Answer 1

检查以确保您的R.layout.note_list_students布局文件包含具有这些ID的Textview。

Answer 2

我认为您在下面这一行中使用了错误的ID，如果您有此ID（性别），请签入设计文件note_list_students.xml。>

genderTv = itemView.findViewById(R.id.gender);

Answer 3

由布局note_list_students引起的问题，即使TextViews匹配，但我曾经有两个版本的Layout，一个是标准版本note_list_students.xml，另一个是note_list_students.xml v21版本，因此我重新创建了它并使用了标准布局仅！