android, why say var is null

Question

I have a extended class, in class have a var, I define this by value, but say this is null !!!!

public class CalendarCell extends TextView
{

    public static final String TAG = "CalendarCell";

    protected ArrayList<Integer> cellStates = new ArrayList<>();

public CalendarCell(Context context)
{
    super(context);
}

public CalendarCell(Context context, AttributeSet attrs)
{
    super(context, attrs);
}

public CalendarCell(Context context, AttributeSet attrs, int defStyle)
{
    super(context, attrs, defStyle);
}

@Override
protected int[] onCreateDrawableState(int states)
{
    int newStatesSize = cellStates.size();  // Error here (null)
    if (newStatesSize > 0)
    {

        ...
    }
    else
    {
        return super.onCreateDrawableState(states);
    }
}

public void resetStates()
{
    cellStates.clear();
}

public void addState(int state)
{
    if(!cellStates.contains(state))
        cellStates.add(state);
    }
}

I defined 'cellStates' by value.but say this is null. Why???

java.lang.NullPointerException
 at yaran.CalendarSection.ViewSection.CalendarCell.onCreateDrawableState(CalendarCell.java:44)

Please edit and show the full stack trace of the exception. I wonder if this is actually being called from the super class constructor. — Andy Turner, Sep 02 '17 at 13:28

score 0 · Answer 1 · answered Sep 02 '17 at 13:08

0

Make cellStates final like so:

protected final ArrayList<Integer> cellStates = new ArrayList<>();

answered Sep 02 '17 at 13:08

devgianlu

1,547
13
25

I add final, but I get error so – ali Sep 02 '17 at 13:25
@ali It's pretty much impossible, a final field can't be changed and you're initializing it in declaration. There must be something else in the code that's not working. – devgianlu Sep 02 '17 at 13:27
When i add blow code ,its resolve problem. if(cellStates == null) cellStates = new ArrayList<>(); but for increment speed i want remove this pice – ali Sep 02 '17 at 14:32
1

@ali You must be missing something. Try debugging the code and checking for value assignation to your field. – devgianlu Sep 02 '17 at 15:25

android, why say var is null

1 Answers1