List view getChildAt() is null

Question

My code

public class Products extends AppCompatActivity {
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.addproducts);
        FillList fillList = new FillList();
        fillList.execute("");

    }
    public class FillList extends AsyncTask<String, String, String> {

        List<Map<String, String>> prolist = new ArrayList<Map<String, String>>();
        @Override
        protected void onPreExecute() {

        }

        @Override
        protected void onPostExecute(String r) {


            String[] from = { "E","D", "C", "B","A"};
            int[] views = { R.id.lblMondeh,R.id.lblBes,R.id.lblBed,R.id.lblSharh,R.id.lblDate};
            final SimpleAdapter ADA = new SimpleAdapter(Products.this,
                    prolist, R.layout.lsttemplate, from,
                    views);
            lstSoratHesab.setAdapter(ADA);
            lstSoratHesab.setVisibility(View.VISIBLE);

        if(lstSoratHesab.getChildAt(0-lstSoratHesab.getFirstVisiblePosition())!=null)//all time this line is null
                lstSoratHesab.getChildAt(0).setBackgroundColor(Color.parseColor("#ff00aa63"));//i want change color first row

        }

        @Override
        protected String doInBackground(String... params) {

            Map<String, String> datanum = new HashMap<String, String>();

            datanum.put("E", "e");
            datanum.put("D", "d");
            datanum.put("C", "c");
            datanum.put("B", "b");
            datanum.put("A", "a");
            prolist.add(datanum);

        }
    }
}

I want set background color for first row.

why lstSoratHesab.getChildAt(0-lstSoratHesab.getFirstVisiblePosition()) or lstSoratHesab.getChildAt(0) all time is null?

But list view has 20 row

score 2 · Accepted Answer · answered Dec 21 '16 at 17:15

2

getChildAt(0) will retrieve the first row element, but you will need to get it in a thread to let the time for the layout to be displayed on screen, which can be set as:

lstSoratHesab.post(new Runnable() {
    @Override
    public void run() {
        if (lstSoratHesab.getChildAt(0) != null) {
            lstSoratHesab.getChildAt(0)
                    .setBackgroundColor(Color.parseColor("#ff00aa63"));
        }
    }
});

answered Dec 21 '16 at 17:15

Blo

11,903
5
45
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@ashkufaraz In `onPostExecute` as you did. – Blo Dec 21 '16 at 17:19
thank you this worked,can your more explain about this – ashkufaraz Dec 21 '16 at 17:31
1

There is [a perfect answer](http://stackoverflow.com/a/24035591/2668136) which is based on the issue for `View.getWidth()` and `View.getHeight()` which return null value. The solution #2 explains the problem that occurs and this above solution, @ashkufaraz. The `setAdapter()` can take a few time to displaying the list, therefore you attach on the view queue your changes. – Blo Dec 21 '16 at 17:40

score 0 · Answer 2 · answered Dec 21 '16 at 17:09

0

I suspect that 0-lstSoratHesab.getFirstVisiblePosition() is negative. getChildAt always returns null for negative values.

answered Dec 21 '16 at 17:09

F43nd1r

7,690
3
24
62

no,`lstSoratHesab.getChildAt(0)` still all time is null – ashkufaraz Dec 21 '16 at 17:10
`lstSoratHesab.getChildAt(0)` won't be called in your code if the condidtion is not true. – F43nd1r Dec 21 '16 at 17:13

List view getChildAt() is null

2 Answers2