Question

I am trying to get a handle on the RelativeLayout that defines how a row in a ListView should be laid out. I am getting null and I believe it is because one of two things.

Possibility one is that it is not inflated yet so it returns null….While I’ve read about this one I am very shaky on the inflation concept. I have been programming in Java for 3 weeks now (from C#).
So I’m not sure how to test, much less handle. For example all I do is set the adapter to the list view….not sure what event or when exactly the inflation happens under the covers.

Possibility two is that I’m not walking the tree properly.

My Parent:

<RelativeLayout 
    android:minHeight="320dp" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:id="@+id/rlay_LftDataParent" 
    android:orientation="vertical" >

<ListView 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:id="@+id/lstvw_LiftData" />

The row definition (the layout I am trying to set the min height for)

<RelativeLayout 
    android:layout_width="fill_parent"
    android:orientation="vertical" 
    android:id="@+id/rlay_LftDataRw" 
    android:layout_height="fill_parent" 
    android:background="@drawable/background">
...
</RelativeLayout>

In the Activity I’ve tried: (lstvw_LiftData is my ListView object)

RelativeLayout RowLayout = (RelativeLayout)lstvw_LiftData.findViewById(R.id.rlay_LftDataRw);

and

RelativeLayout RowLayout = (RelativeLayout)findViewById(R.id.rlay_LftDataRw);

If you are curious to know the bigger picture this is a follow on question from this post Using RelativeLayout to control a ListView row height where I’m trying to get the row layout to fill the screen.

Answer 1

You don’t access a View from the ListView row with findViewById. Instead use the adapter to get a reference of your RelativeLayout in the getView method and there set the width and height. You didn’t say what adapter do you use so here is a simple example for the basic ArrayAdapter:

Edit:
You don’t call the getView() method yourself, the adapter will call the getView method automatically when it’s time to show a new row. Regarding the question from your last comment, if the custom Adapter class is a inner class in the Activity where you’ll use it:

public class SomeActivity extends ListActivity {

     private int mHeight, mWidth;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // ...do what ever stuff you need in this activity
       // find out the height/width values:
        DisplayMetrics metrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(metrics);

        mHeight = metrics.heightPixels;
        mWidth = metrics.widthPixels;   
        // set the adapter
        setListAdapter(new CustomAdapter(this,
                R.layout.adapters_listview_rowheight, R.id.textView1, items));
    }

    //you use your own adapter class
    private class CustomAdapter extends ArrayAdapter<String> {

        public CustomAdapter(Context context, int resource,
                int textViewResourceId, String[] objects) {
            super(context, resource, textViewResourceId, objects);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
                    //do whatever logic you need here
                    // finally you end up with the RelativeLayout you'll return as the view for the row
                    // before you return set the desired values for its width and height
            rl.getLayoutParams().height = mHeight;
            rl.getLayoutParams().width = mWidth;
            return rl;
        }


    }

}

If you Adapter class is in another file then make the constructor of that adapter to take two int values representing the width and height:

//the constructor
public CustomAdapter(/*whatever parameters you already have*/, int height, int width) {
    //do stuff
    //now you also have a reference for the width and height that you can use in the getView method.
}

and in your Activity(with the same code for the onCreate method):

setListAdapter(new CustomAdapter(/*whatever parameters you already have*/, mHeight, mWidth));

I don’t know if this is what you want.