Android：java TextView颜色

Question

I need a little help. I need change the color of a text view with java code.. I tried different way but it always gives me an error:

java.lang.NullPointerException

I tried:

TextView sts;
sts = (TextView) findViewById(R.id.stato);
sts.setTextColor(Color.rgb(12,255,0));

or..

sts.setTextColor(android.graphics.Color.GREEN);

but both ways give me the same error on start.. My Class extends ListActivity

how do I? thanks in advance

FULL CODE:

public class ProvaDatabase extends ListActivity{

    TextView sts;   
    private DatabaseHelper databaseHelper;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        sts = (TextView) findViewById(R.id.stato);
        sts.setTextColor(android.graphics.Color.GREEN);
        //sts.setTextColor(Color.rgb(12,255,0));

        super.onCreate(savedInstanceState);
        databaseHelper = new DatabaseHelper(this);
        SQLiteDatabase db = databaseHelper.getWritableDatabase();
        databaseHelper.insertdb(db, "sta", "25/11/2016", "SUCCESS", null, null, null);
        databaseHelper.insertdb(db, "ssis", "25/11/2016", "WAITING", null, null, null);
        databaseHelper.insertdb(db, "AAAAAAAA", "25/11/2016", "FAILED", null, null, null);
        databaseHelper.insertdb(db, "BBBB", "bBBBBBB", "SUCCESS", null, null, null);
        Cursor c = databaseHelper.getDB();
        startManagingCursor(c);
        setListAdapter(new SimpleCursorAdapter(this, R.layout.registryvista, c, new String[]
        { TabellaRegistry.TYPE, TabellaRegistry.DATE, TabellaRegistry.STATUS }, new int[]
        { R.id.tipo, R.id.data, R.id.stato }));


        setContentView(R.layout.main2);

Answer 1

Seems like your view R.id.stato wasn't found and so sts == null . Try check that sts is not null, or some your additional code needed

EDIT:

In case when you cannot access layout of your item in list instead of doing

setListAdapter(new SimpleCursorAdapter(this, R.layout.registryvista, c, new String[]
    { TabellaRegistry.TYPE, TabellaRegistry.DATE, TabellaRegistry.STATUS }, new int[]
    { R.id.tipo, R.id.data, R.id.stato }));

you can write your own adapter like this:

public class MyAdapter extends SimpleCursorAdapter
{
    //here goes methods that should be overriden

    //and method getView in which we can access layout of our list item
    @Override
    public View getView (int position, View convertView, ViewGroup parent)
    {
        View view = super.getView(postition, convertView, parent);
        TextView sts = (TextView) view.findViewById(R.id.stato);
        sts.setTextColor(android.graphics.Color.GREEN);
    }
}

I hope you got my idea

Answer 2

Are you setting the content view before you try to get sts? You need to have the content view set in your activity before you can retrieve views from it.