How can i fix my null pointer exception

Question

I\'ve been trying to fix this null pointer exception but I cant. I know its pointing to a null object but I don\'t how to fix it. I am beginner in Java programming so please don

Answer 1

Your itemsAdapter is never initialized. And it has no values at all. That's why you're getting a NullPointerException when you call your add().

Try to do this:

ArrayList data = new ArrayList<>();

// add some data to your ArrayList.

itemsAdapter = new ArrayAdapter(this,
android.R.layout.simple_list_item_1, data);

You can also use a String[] array instead of an ArrayList or any other List for that matter.

---

On your code it should look like:

private ArrayAdapter itemsAdapter;
private ArrayList data;

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

    //EditText
    final EditText etTask = (EditText) findViewById(R.id.editText);
    final String task = etTask.getText().toString();

    data = new ArrayList<>();

    itemsAdapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1, data);

    //Button
    Button btn = (Button) findViewById(R.id.button);



    //OnClickListeners
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            data.add(task);
            itemsAdapter.notifyDataSetChanged();
            etTask.setText("");

        }
    });

---

Edit: If you're creating that ArrayAdapter to use in something like a ListView. Where is it on your code? I guess you also forgot to get it.

Something like:

ListView lv = (ListView) findViewById(R.id.yourListView);
// initialize the adapter and stuff.
lv.setAdapter(itemsAdapter);

For further reading on ListView and adapters, take a look at this link, and this tutorial. Also, check the docs.