Setting textview text in code

Question

Can someone tell me where I am going wrong?

I'm trying to change my textview called MyText to something else, but when I try I get the error:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference at android.app.Activity.findViewById(Activity.java:2071)

public class MainScreen extends Activity {
    TextView texting = (TextView) findViewById(R.id.MyText);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_screen);
        texting.setText("Test");

};
}

Mike · Accepted Answer · 2014-10-21 18:18:45Z

4

This is how your code should look like:

public class MainScreen extends Activity {

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

        // If you're not using this view anywhere, you don't have to declare it globally. Use only a local variables
        TextView texting = (TextView) findViewById(R.id.MyText);
        texting.setText("Test");

    };
}

You should ALWAYS initialize your views after you have your root layout. In this case, right after you did setContentView(R.layout.activity_main_screen); This scenario applies to Activites.

In case you use a fragment you should do this right after you inflated your root layout in the onCreateView method. Something like:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = (LinearLayout) inflater.inflate(R.layout.my_fragment, container, false);
    // THIS is where you start initializing your views
    return view;
}

edited Oct 21, 2014 at 18:18

answered Oct 21, 2014 at 18:04

Mike

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1 Comment

Imsopov Over a year ago

Thank you, this was doing my head in.

Wagner DosAnjos · Accepted Answer · 2014-10-21 18:04:08Z

1

The TextView is not available until after setContentView is called. So, findViewById will return null when MainScreen is instantiated. The solution is to move the findViewById call to the onCreate method as follows:

public class MainScreen extends Activity {
    TextView texting;

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

        texting = (TextView) findViewById(R.id.MyText);

        texting.setText("Test");

    }
}

answered Oct 21, 2014 at 18:04

Wagner DosAnjos

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Comments

RizJa · Accepted Answer · 2014-10-21 18:05:47Z

1

Do the following:

public class MainScreen extends Activity {
    TextView texting;

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

        texting = = (TextView) findViewById(R.id.MyText);
        texting.setText("Test");

    };
}

You have to initialize your TextView object inside your onCreate method.

answered Oct 21, 2014 at 18:05

RizJa

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