使用 ItemTouchHelper 从 RecyclerView 中删除项目时引发 UnsupportedOperationException

Question

When item is removed from studentList throws:

**java.lang.UnsupportedOperationException
at java.util.AbstractList.remove(AbstractList.java:161)
at com.sayedy.naweed.test.newtest.TestCase$2.onSwiped**

I implemented ItemTouchHelper.Callback as will but leads to same exception. I can swap studentList items using onMove( ) without any problem why can't delete item using onSwiped() ?

RecyclerView:

public class TestCase extends RecyclerView.Adapter<TestCase.PassedViewHolder> {
        private Context context;
        private List<Student> studentList;
        private ItemTouchHelper itemTouchHelper;
    
        public TestCase(Context context, List<Student> studentList) {
            this.context = context;
            this.studentList = studentList;
        }
    
        public void setItemTouchHelper(ItemTouchHelper itemTouchHelper) {
            this.itemTouchHelper = itemTouchHelper;
        }
    
        @NonNull
        @Override
        public PassedViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            StudentPassedRowBinding rowBinding = DataBindingUtil.inflate(
                    LayoutInflater.from(context),
                    R.layout.student_passed_row,
                    parent, false);
            return new PassedViewHolder(rowBinding.getRoot());
        }
    
        @Override
        public void onBindViewHolder(@NonNull PassedViewHolder holder, int position) {
            holder.passedRowBinding.setStudent(studentList.get(position));
            holder.passedRowBinding.getRoot().setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    itemTouchHelper.startDrag(holder);
                    return false;
                }
            });
        }
    
        @Override
        public int getItemCount() {
            return studentList.size();
        }
    
    
        class PassedViewHolder extends RecyclerView.ViewHolder {
            public StudentPassedRowBinding passedRowBinding;
    
            public PassedViewHolder(@NonNull View itemView) {
                super(itemView);
    
                passedRowBinding = DataBindingUtil.bind(itemView);
            }
        }
    
    
        public ItemTouchHelper.SimpleCallback simpleCallback = new ItemTouchHelper.SimpleCallback(ItemTouchHelper.DOWN | ItemTouchHelper.UP, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {
            @Override
            public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
                int currentPosition = viewHolder.getAdapterPosition();
                int targetPosition = target.getAdapterPosition();
                Collections.swap(studentList, currentPosition,targetPosition);
                
                notifyItemMoved(currentPosition, targetPosition);
                return true;
            }
    
            @Override
            public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
                studentList.remove(viewHolder.getAdapterPosition());
                notifyItemRemoved(viewHolder.getAdapterPosition());
            }
        };
    }

The fragment initializes RecyclerView:

public View onCreateView(@NonNull LayoutInflater inflater, 
                         @Nullable ViewGroup container, 
                         @Nullable Bundle savedInstanceState) {

    studentBinding = FragmentStudentBinding.inflate(inflater);

    // Data
    List<Student> students = Arrays.asList(
            new Student("Ahmad", 1, R.drawable.profile, "PASS"),
            new Student("Mahmood", 2, R.drawable.profile, "FAIL"),
            new Student("Zakir", 3, R.drawable.profile, "PASS"),
            new Student("Rezaq", 8, R.drawable.profile, "FAIL"),
            new Student("Zeya", 9, R.drawable.profile, "FAIL"),
            new Student("Rasool", 10, R.drawable.profile, "FAIL"),
            new Student("Parwiz", 11, R.drawable.profile, "FAIL"));

    TestCase testCase = new TestCase(getContext(), students);
    studentBinding.studentRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
    studentBinding.studentRecyclerView.setAdapter(testCase);

    ItemTouchHelper itemTouchHelper = new ItemTouchHelper(testCase.simpleCallback);
    testCase.setItemTouchHelper(itemTouchHelper);
    itemTouchHelper.attachToRecyclerView(studentBinding.studentRecyclerView);

    return studentBinding.getRoot();
}

Student class:

public class Student implements Parcelable {
    private String name;
    private int id;
    private int studentProfile;
    private String result;

    public Student(String name, int id, int studentProfile, String result) {
        this.name = name;
        this.id = id;
        this.studentProfile = studentProfile;
        this.result = result;
    }

    protected Student(Parcel in) {
        name = in.readString();
        id = in.readInt();
        studentProfile = in.readInt();
        result = in.readString();
    }

    public static final Creator<Student> CREATOR = new Creator<Student>() {
        @Override
        public Student createFromParcel(Parcel in) {
            return new Student(in);
        }

        @Override
        public Student[] newArray(int size) {
            return new Student[size];
        }
    };

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getStudentProfile() {
        return studentProfile;
    }

    public void setStudentProfile(int studentProfile) {
        this.studentProfile = studentProfile;
    }

    public String getResult() {
        return result;
    }

    public void setResult(String result) {
        this.result = result;
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeInt(id);
        dest.writeInt(studentProfile);
        dest.writeString(result);
    }
}

Answer 1

I solved the problem. The Arrays.asList() return a fixed-size list. This list allow you to do operations like get and set, but the add and remove operations will throw UnsupportedOperationException.