LWUIT列表的运行速度非常慢

Question

I've faced with the well-known problem in LWUIT. My list component with the checkbox renderer scrolls very slow. If to test my application on emulator it runs quite smoothly (nevertheless I see CPU utilization splashes up to 60% during scroll action), but if to run it on mobile phone it takes a couple of seconds between focus movements.

There's a code of renderer:

public class CheckBoxMultiselectRenderer extends CheckBox implements ListCellRenderer {

public CheckBoxMultiselectRenderer() {
    super("");
}

//override
public void repaint() {
}

public Component getListCellRendererComponent(List list, Object value, 
 int index,boolean isSelected) {
    Location loc = (Location)value;
    setText(loc.getLocationName());
    setFocus(isSelected);
    setSelected(loc.isSelected());

    return this;
}

public Component getListFocusComponent(List list) {
    setText("");
    setFocus(true);
    getStyle().setBgTransparency(Consts.BG_TRANSPARENCY);
    return this;
}
}

that's the code of my form containing the list:

protected void createMarkup() {
    Form form = getForm();
    form.setLayout(new BorderLayout());
    form.setScrollable(false);

    Label title = new Label("Choose location zone:");
    title.getStyle().setMargin(5, 5, 0, 0);
    title.getStyle().setBgTransparency(Consts.BG_TRANSPARENCY);
    title.setAlignment(Component.CENTER);

    form.addComponent(BorderLayout.NORTH, title);

    list = new List(StateKeeper.getLocationsAsList());
    list.setFixedSelection(List.FIXED_NONE_CYCLIC);
//        list.setSmoothScrolling(true);
    list.getStyle().setBgTransparency(0);
    list.setListCellRenderer(new CheckBoxMultiselectRenderer());
    list.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent ae){
//                List l = (List)ae.getSource();
//                l.requestFocus();
//                l.setHandlesInput(true);
            Location selItem = (Location)list.getSelectedItem();
            selItem.setSelected(!selItem.isSelected());
        }
    });

    form.addComponent(BorderLayout.CENTER, list);
}

I would be very thankful for any help!

Answer 1

We must be so carefull building lwuit List . If we have made something wrong they can work worse than expected. I recommend you to take a look on this

LWUIT Blog ListRender

You can also rewrite your paint method. You list's speed will be increased.