Android ListView examples

Krysztof Grajek: Custom ListView items and adapters

AppFulcrum:

-Load data from ArrayList

-Using Xml Resource File

-Simple Multiple Selection Checkboxes

-Custom Layout Checkbox, ImageButton, TextView

-Using Sqlite Database

Lars Vogel: Android ListView and ListActivity

2 dologra erdemes odafigyelni a sajat ArrayAdapterunkben. Egyreszt amikor a ListView egy sora lekerul a kijelzorol ezt a view-t megkapja az adapater es a getView(..) method convertView-jaban ujra megapjuk es fel tudjuk hasznalni. Masreszt a getView-ban hivott findViewByID() eleg koltseges ezert erdemes egy ViewHolder class-ban tarolni a findeViewByID() alltal talalt view-kat es ezt a convertView tag-jeben tarolni. Ezzel Lars Vogel szerint kb 175%-os performacianovekedeset erhetunk el. Valahogy igy:

// ViewHolder will buffer the assess to the individual fields of the row layout

static class ViewHolder {

public ImageView imageView;

public TextView textView;

}

@Override

public View getView(int position, View convertView, ViewGroup parent) {

ViewHolder holder;

if (null == convertView) {

LayoutInflater inflater = context.getLayoutInflater();

rowView = inflater.inflate(R.layout.rowlayout, null, true);

holder = new ViewHolder();

holder.textView = (TextView) rowView.findViewById(R.id.label);

holder.imageView = (ImageView) rowView.findViewById(R.id.icon);

rowView.setTag(holder);

} else {

holder = (ViewHolder) rowView.getTag();

}

holder.textView.setText("whatever text");

holder.imageView.setImageResource(R.drawable.testicon);

return convertView;

}