Erratic behaviour of listview (Android)

Question

In my listview I have a custom Adapter, which I build using a TreeMap, I defined the getView method which is as follows. I am trying to strike out the text in a certian textview of the listview on click, only those textviews will be striken off which contain a certain pattern of characters (y@y). However on clicking one row in the listview I am getting strike out effect on some other row.

    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);



        if (convertView == null) { 
            convertView = inflater.inflate(R.layout.chklistlayout, parent, false); 
        }
        TextView textView = ((TextView) convertView.findViewById(R.id.textView1));
        TextView imageview = ((TextView) convertView.findViewById(R.id.textView2));
        textView.setText(values[position]);
        imageview.setText(mValues[position]);


        String s = mValues[position];
        if (s.contains("y@y")) {
            System.out.println("In if of getview");
            System.out.println(s);
            imageview.setPaintFlags(imageview.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
        } else {

        }

        return convertView;
    }
}

I tried using a holder pattern too, using a static holder class, but the problem seems to persist. Any pointers?

use else block to handle this, `imageview.setPaintFlags()` not to strike — Muhammad Babar, Sep 03 '13 at 10:19
What is the reason behind this behaviour, though leaving else empty should have worked? I changed it, can you enlighten me on what argument I pass to .setPaintFlags(), its asking me for an int parameter. — Skynet, Sep 03 '13 at 10:22
Because of the convertView. When you scroll the list the same view that was used before is give back to getView method. So the same imageView that you painted with StrikeThrough before is still painted with it. So you have to revert that action. — Budius, Sep 03 '13 at 10:26
Okay guys this works for me, post an answer and I will accept that! — Skynet, Sep 03 '13 at 10:28
The reason behind this is recycling, i don't know about the `Paint` *flags*, what i meant to say is in your **else** block try to remove the flag that is striking and for more details about `ListView` *recycler* refer this http://stackoverflow.com/a/14108676/1939564 — Muhammad Babar, Sep 03 '13 at 10:29
imageview.setPaintFlags( imageview.getPaintFlags() & (~ Paint.STRIKE_THRU_TEXT_FLAG)); — Skynet, Sep 03 '13 at 10:34

score 2 · Accepted Answer · answered Sep 03 '13 at 10:37

this answer is half mine and half from Muhammad Babar that we both commented on the question making together a quite nice answer:

use else block to handle this, imageview.setPaintFlags() not to strike

that happens

Because of the convertView. When you scroll the list the same view that was used before is give back to getView method. So the same imageView that you painted with StrikeThrough before is still painted with it. So you have to revert that action.

more over, because of this recycling, usually dealing with Adapters you must ALWAYS undo/revert/repaint/change text/change image to all the elements to make sure it will be on screen the way you want.

ps.: now you should apply a Holder pattern to get better performance.

I was previously using a holder pattern, but with this erratic behavior I listened to Romain guy for over an hour in the YouTube video "The world of listview". Now as I know the problem, I will revert back to the holder pattern. — Skynet, Sep 03 '13 at 10:43

Erratic behaviour of listview (Android)

1 Answers1