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inside custom component

Native Development

Posts: 206
Registered: ‎05-15-2012
My Device: None
My Carrier: Telus

QML ListView update item on data model change

[ Edited ]

If I have a list item in QML with a label in it that is made up of two elements of the data... ie.

 Label {
    id: scoreLabel                                        
    text: ListItemData.ups - ListItemData.downs

 The two items that make up the text are subject to change, however.


Firstly, how do I change the data model (on button press for example). The code:

ListItemData.ups = ListItemData.ups - 1;

 does not function.


Secondly, once I manage to change the data model, how can I have the label recalculate the "text" property. Will it automatically redraw, knowing it's underlying value has changed?


I've already implemented this successfully in a C++ list, but  I'm trying really hard not to rewrite a significant amount of QML in C++ just to solve what seems like a minor problem.


I guess this problem comes down to how to access and modify the list data model in QML.

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Posts: 1,524
Registered: ‎12-18-2012
My Device: Z30, Z10 LE, DevAlpha C, PlayBook

Re: QML ListView update item on data model change

[ Edited ]

You'll have to replace the entire datamodel element. I remember there was an example on this forum but couldn't find it so I hope I got the syntax right:

For GroupDataModel

var updatedItem = ListItemData;
updatedItem.ups = updatedItem.ups - 1;
dataModel.updateItem(indexPath, updatedItem)

For ArrayDataModel:
dataModel.replace(indexPath, updatedItem)

The list items will be updated automatically.

ListItemComponents have their own visibility scope. To access dataModel from them use:
where myItem is id of top-level item of ListItemComponent.

Example: http://supportforums.blackberry.com/t5/Cascades-Development/Access-ListView-model-from-ListItemCompo...

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