QML GridView contentItem children lenght doesn't match count - qt

Question

I'm experiencing issues with a GridView dinamically populated in a QtQuick app I'm developing.
The GridView is populated by the user input of a number of identical objects, except for some text.
GridView {
id: grid_fc
width : parent.width
height: parent.height / 2
model: ListModel {}
delegate: Fancoil {
objectName: nome
text: indirizzo
}
}
onNewNode:
{
grid_fc.model.append({nome: "fc_" + address, indirizzo: address})
}
At a certain signal the app need to change a property of these objects, so I search for each object by objectName and do the job.
onStatusChanged:
{
for(var i = 0; i <= grid_fc.count; i++)
{
if (grid_fc.contentItem.children[i].objectName === "fc_" + address)
{
if (online)
grid_fc.contentItem.children[i].status(Fancoil.Status.ONLINE)
else
grid_fc.contentItem.children[i].status(Fancoil.Status.OFFLINE)
break
}
}
}
If the number of object is "low" the GridView.count is equal to the GridView.contentItem.children lenght, but increasing the number, I get that the GridView.count it's correct, instead of the children lenght that is wrong.
Ex. Populating the GridView with 100 elements:
GridView.count = 100
GridView.contentItem.children = 74 (?!)
What's wrong with my code?

Answer 1

If the model has 100k elements, it is inefficient for the view to create 100k items if it is only going to show 100. In other words, the view dynamically creates the necessary items, so it is not recommended to access those elements through the "childrens", since these can change. Instead you should use the models:
ListModel{
id: gridview_model
}
GridView {
id: grid_fc
width : parent.width
height: parent.height / 2
model: gridview_model
delegate: Fancoil {
text: indirizzo
}
}
onNewNode:
{
gridview_model.append({status: Fancoil.Status.OFFLINE, indirizzo: address})
}
onStatusChanged: {
for(var i = 0; i <= gridview_model.count; i++)
{
var new_status = online ? Fancoil.Status.ONLINE : Fancoil.Status.OFFLINE
gridview_model.get(i).status = new_status
}
}

Answer 2

I get the point, but I tried this way and the result is the same.
Now, the model count is correct and I can see the code looping through all the nodes.
It seems like a rendering issue. Images out of sight seem not to catch the status update.
Also this happens: scrolling the gridview up and down causes some nodes to lose the red glow (status update to offline).
See the result of first time render