Question

Made a custom list view that includes an Image, two text views and a checkbox. I could identify the checkbox being checked/ unchecked, but the problem with this design is very slow scrolling. Will this get faster if I test it into the real device.

public class ListViewActivity extends ListActivity {

 protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    ArrayAdapter<Model> compositeAdapter = new CompositeAdapter(this,
            getModel());
    setListAdapter(compositeAdapter);
    ListView lv = getListView();
    lv.setFastScrollEnabled(true);
   }
}

private class CompositeAdapter extends ArrayAdapter<Model> {
    private final List<Model> list;
    private final Activity context;

    public CompositeAdapter(Activity context, List<Model> list) {
        super(context, R.layout.listviewactivitylayout, list);
        this.context = context;
        this.list = list;
    }

    private class ViewHolder{
        protected TextView textView1;
        protected TextView textView2;
        protected ImageView imageView;
        protected CheckBox ckBox;
    }
    public View getView (int position, View convertView, ViewGroup parent) {
        View view = null;
        final ViewHolder vh;
        if(convertView==null){
            LayoutInflater li = context.getLayoutInflater();
            view = li.inflate(R.layout.listviewactivitylayout, null);
             vh = new ViewHolder();
            vh.ckBox =(CheckBox) view.findViewById(R.id.list_view_layout_checkbox);
            vh.imageView = (ImageView) view.findViewById(R.id.listView_image_view);
            vh.textView1 = (TextView)view.findViewById(R.id.list_view_layout_text_view1);
            vh.textView2= (TextView)view.findViewById(R.id.list_view_text_view2);
            view.setTag(vh);
        }
        else{
            view= convertView;
            vh = (ViewHolder)view.getTag();
        }

/**
** sending text and images to the each of the list view
**
*/

Answer 1

You are loading images. that needs to be handled in a seperate thread and just placed on an imageView when it is decoded.

here is a excelent project that will help you do that.
Lazy load images

EDIT

by looking at your code there are few things i am noticing:

First: there isnt any place you are asigning a picture. (use the lazy loading adapter for that)

Second: your checkbox selections will get messed up. you need to keep track of the checked position with state and redraw in getView (hashmap or even better a sparse array for that)

Third is to get rid of the helper view you are using. you don’t need it. (it is market as View view in your code).

So, if convertView==null just use convertView=inflate... and return that one at the end.

And Fourth as a useful tip: move the adapter class to a new class java file. you are already keeping the activity reference and the list, you can reduce the amount of code in your activity.