Question

I am looking into JFace for Eclipse development. I made a plugin to act as a dummy content provider for a ComboViewer. This provider essentially provides the data model as an ArrayList of hardcoded values. Anyway, I tried to understand the approach.

I set the model on the ComboViewer via the comboViewer.setInput(list) method.
On the press of a button I call another object’s method that updates the list I passed as input to the ComboViewer (adds another element) and I call comboViewer.refresh to reflect the change, but nothing happens.

Turns out:

I need to call comboViewer.setInput(list) with the updated list to see the changes in the data (i.e. the previous addition) in my UI combo. I found that comboViewer.refresh reflects any updates only if I get the a hold of comboViewer‘s passed as input Object and modify that. I.e. if I do:

List<SomeObject> data = ((List<SomeObject>)(comboViewer.getInput()));  
data.add(new SomeObject("aaa","cccc"));  
comboViewer.refresh();    

Only like this the data are refreshed. But I don’t understand what is the proper way to use these APIs.
Am I supposed to ever get a hold and modify the object I pass in the setInput method? It feels I should not be doing it. So what is the purpose of refresh?

What is the proper way to do updates of the data that are provided to the Viewers?

Answer 1

The proper way to reflect changes is to call refresh. The list

String[] values = {"1","2","3"};
List<String> list = new ArrayList<String>(Arrays.asList(values));

create components

final ComboViewer comboViewer = new ComboViewer(shell, SWT.DROP_DOWN);
comboViewer.setLabelProvider(new LabelProvider());
comboViewer.setContentProvider(new ArrayContentProvider());
comboViewer.setInput(list);
Button button1 = new Button(shell, SWT.PUSH);
button1.setText("Button 5");
button1.addSelectionListener(new SelectionListener(){

  @Override
  public void widgetSelected(SelectionEvent e) {
     // TODO Auto-generated method stub
     System.out.println("Button 5");
     list.add("4");
     comboViewer.refresh();             
  }

  @Override
  public void widgetDefaultSelected(SelectionEvent e) {
     // TODO Auto-generated method stub     
  }

});

when you push the button the combo viewer is updated.