App crashing when trying to use RecyclerView With LayoutManager

Question

I'm trying to show a data in RecyclerView but application crass Error:

Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference

Declaration of RecyclerView :

RecyclerView rvTodos;

findViewByid of RecyclerView:

rvTodos = (RecyclerView) findViewById(R.id.rvTodos);

Here is my SetAdapter class:

private void setAdapters() {
        todosAdapter = new TodosAdapter(toDoList);
        RecyclerView.LayoutManager mLayoutManager1 = new LinearLayoutManager(getApplicationContext());
        rvTodos.setLayoutManager(mLayoutManager1);
        rvTodos.setItemAnimator(new DefaultItemAnimator());
        rvTodos.setAdapter(todosAdapter);
    }

Open Logcat and show the error and i click on error then it's go in this line:

rvTodos.setItemAnimator(new DefaultItemAnimator());

Here is my TodosListActivity.class

public class TodosListActivity extends AppCompatActivity implements View.OnClickListener{

    TextView txtTitle, txtClose, txtSave, txtAdd;

    String label_todos, text_add_todo;

    RecyclerView rvTodos;

    private List<ToDo> toDoList = new ArrayList<>();
    private TodosAdapter todosAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_events_list);

        init();
    }

    private void init() {

        txtTitle = (TextView) findViewById(R.id.txtTitle);
        label_todos = getResources().getString(R.string.label_todos);
        txtTitle.setText(label_todos);

        txtSave = (TextView) findViewById(R.id.txtSave);
        txtSave.setVisibility(View.GONE);

        txtClose = (TextView) findViewById(R.id.txtClose);
        txtClose.setOnClickListener(this);
        txtAdd = (TextView) findViewById(R.id.txtAdd);
        txtAdd.setOnClickListener(this);
        text_add_todo = getResources().getString(R.string.text_add_todo);
        txtAdd.setText(text_add_todo);

        rvTodos = (RecyclerView) findViewById(R.id.rvTodos);

        setAdapters();
        prepareToDOData();
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {

            case R.id.txtAdd:
                Intent intent = new Intent(this, AddTodoActivity.class);
                startActivity(intent);
                break;

            case R.id.txtClose:
                finish();
                break;

        }

    }

    private void setAdapters() {
        todosAdapter = new TodosAdapter(toDoList);
        RecyclerView.LayoutManager mLayoutManager1 = new LinearLayoutManager(getApplicationContext());
        rvTodos.setLayoutManager(mLayoutManager1);
        rvTodos.setItemAnimator(new DefaultItemAnimator());
        rvTodos.setAdapter(todosAdapter);
    }

    private void prepareToDOData() {
        ToDo data = new ToDo("David Cummings", "26/10/2017 2:25PM");
        toDoList.add(data);

        data = new ToDo("Lawrence Cummings", "26/10/2017 2:25PM");
        toDoList.add(data);


        data = new ToDo("Ketul Inc.", "11/11/2017 3:46 PM");
        toDoList.add(data);

        //notesAdapter.notifyDataSetChanged();
        todosAdapter.notifyDataSetChanged();
    }
}

I refer this link but it's not work for me : App crashing when trying to use RecyclerView on android 5.0

It's not duplicate with What is a NullPointerException, and how do I fix it?

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — AskNilesh, Feb 20 '18 at 08:08
Firstly make sure you are calling findViewById in onCreate or later and that the resource id is valid — sshashank124, Feb 20 '18 at 08:09
@NileshRathod plz remove your comment of duplicate if anyone to know it's a same question i fully challenging the every one solve my error using this link : https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it if not then why you assign this question is duplicate — Ali, Feb 20 '18 at 12:09
ya bro but it's not necessary to every `java.lanf.NullpointerExceptio` same in my error it's a different problem — Ali, Feb 20 '18 at 12:14

score 1 · Accepted Answer · edited Feb 20 '18 at 10:08

1

As you mentioned you are using two reyclerView so please check your recyclerview Id is it there perfect recyclerview id or you are assign same id for both of the recyclerview .

Reference Code :

Reference : https://www.androidhive.info/2016/01/android-working-with-recycler-view/

call prepareToDOData(); inside setAdapters()

     private void setAdapters() {
        todosAdapter = new TodosAdapter(toDoList);
        RecyclerView.LayoutManager mLayoutManager1 = new LinearLayoutManager(getApplicationContext());
        rvTodos.setLayoutManager(mLayoutManager1);
        rvTodos.setItemAnimator(new DefaultItemAnimator());
        rvTodos.setAdapter(todosAdapter);

        prepareToDOData();//call here
    }


 private void prepareToDOData() {
        ToDo data = new ToDo("David Cummings", "26/10/2017 2:25PM");
        toDoList.add(data);

        data = new ToDo("Lawrence Cummings", "26/10/2017 2:25PM");
        toDoList.add(data);


        data = new ToDo("Ketul Inc.", "11/11/2017 3:46 PM");
        toDoList.add(data);

        //notesAdapter.notifyDataSetChanged();
        todosAdapter.notifyDataSetChanged();
    }

edited Feb 20 '18 at 10:08

Ali

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answered Feb 20 '18 at 08:26

Abhishek kumar

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Why `prepareToDOData()` have to call inside `setAdapters()`? what will happen if not? – Abu Yousuf Feb 20 '18 at 08:43
i have other class and i declare same way or class work perfectly so this is not correct answer – Ali Feb 20 '18 at 08:57
Are you getting runtime Exception or compile time @MohammadAli – Abhishek kumar Feb 20 '18 at 09:13
2

@MohammadAli, comment that line and check are you getting any other issue ? – Abhishek kumar Feb 20 '18 at 09:43
i got my solution in this line `rvTodos = (RecyclerView) findViewById(R.id.rvTodos);` i pass the wrong id so it's generate the error @Abhishekkumar – Ali Feb 20 '18 at 09:51
it mean you are using same id for both of your recyclerview. Thats Why i told you to comment and check it may be some other reason for error. @MohammadAli – Abhishek kumar Feb 20 '18 at 09:53
Welcome @MohammadAli , and also use flow as i mentioned in my answer code , happy to help you. – Abhishek kumar Feb 20 '18 at 09:55
you update your answer with the problem so other user can access this answer @Abhishekkumar – Ali Feb 20 '18 at 09:59

App crashing when trying to use RecyclerView With LayoutManager

1 Answers1