How do I use setText from within a callback?

Question

In my code below I am able to edit a text from my first setText() call but not from within the callback.
The error I receive is a NullPointerException for title in the callback.
How do I set this up so I can edit the text from within the callback?

public class ListingActivity extends AppCompatActivity {
    final String TAG = "ListingActivity";
    TextView title;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        title = (TextView)findViewById(R.id.tvTitle);

        Intent intent = getIntent();
        final String listingId = intent.getStringExtra("ObjectId");

        setContentView(R.layout.listing_activity);
        Log.e(TAG, "listingId: " + listingId);

        title.setText("listingId");//fine

        ListingManager.getListing(listingId, new ListingCB() {
            @Override
            public void done(String error, Listing listing) {
                title.setText("listingId");//null pointer error
            }
        });
    }
}

Below answers are right, but you should also make sure that the callback runs on main thread. — Kise, Feb 27 '17 at 04:59

score 3 · Accepted Answer · answered Feb 27 '17 at 04:52

Your setContentView() method must be called before giving references using findViewById() method, so your code will be -

    public class ListingActivity extends AppCompatActivity {
    final String TAG = "ListingActivity";
    TextView title;

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

        title = (TextView)findViewById(R.id.tvTitle);

        Intent intent = getIntent();
        final String listingId = intent.getStringExtra("ObjectId");

        Log.e(TAG, "listingId: " + listingId);

        title.setText("listingId");//fine

        ListingManager.getListing(listingId, new ListingCB() {
            @Override
            public void done(String error, Listing listing) {
                title.setText("listingId");//null pointer error
            }
        });
    }
}

score 1 · Answer 2 · answered Feb 27 '17 at 04:52

1

title.setText("listingId");//fine

That shouldn't be fine...

You must put setContentView before any findViewById. That is number one reason why your TextView is null.

Your callback is fine.

answered Feb 27 '17 at 04:52

OneCricketeer

179,855
19
132
245

How do I use setText from within a callback?

2 Answers2

Linked