I am using the QML MapItemView component with a C++ QAbstractListModel-based model. The MapItemView is working fine when the model is reset, or whenever a new item is added or an existing item is removed. However, the MapItemView is not reflecting changes to already added items.
I have first experienced this issue with Qt 5.4 but I still face it after updating to Qt 5.5
The following example shows the issue with 2 different models : a C++ model based on QAbstractListModel and a QML ListModel.
It is possible to switch from one model to another, pressing the top-right button:
- When the QML model is used, clicking in the map will add a new element and modify the first element.
- The C++ model used a
QTimerto modify its content every seconds.
The MapItemView is not showing the model changes whatever the model type is. When switching from one model to another, one can see that the MapView gets updated.
I am probably missing something very obvious but I don't see what it is. Thank you in advance for your help.
The main.cpp code :
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include "playermodel.h"
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
PlayerModel playerModel;
engine.rootContext()->setContextProperty("playerModel", &playerModel);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}
The C++ model header (playermodel.h) :
#ifndef PLAYERMODEL_H
#define PLAYERMODEL_H
#include <QObject>
#include <QAbstractListModel>
#include <QGeoPositionInfoSource>
#include <QTimer>
#include <QDebug>
struct PlayerData
{
PlayerData(){ }
PlayerData(int _Azimuth, double lat, double lng){
Azimuth = _Azimuth;
Latitude = lat;
Longitude = lng;
}
int Azimuth = -1;
double Latitude = 0.;
double Longitude = 0.;
QVariant getRole(int role) const;
enum Roles{
RoleAzimuth = Qt::UserRole + 1,
RoleLatitude,
RoleLongitude
};
};
class PlayerModel : public QAbstractListModel
{
Q_OBJECT
public:
PlayerModel();
~PlayerModel();
int rowCount(const QModelIndex & parent = QModelIndex()) const;
QVariant data( const QModelIndex & index, int role = Qt::DisplayRole ) const;
Q_INVOKABLE Qt::ItemFlags flags(const QModelIndex &index) const Q_DECL_OVERRIDE;
virtual bool setData(const QModelIndex & index, const QVariant & value, int role = Qt::EditRole);
bool removeRows(int row, int count, const QModelIndex & parent = QModelIndex());
void resetModel();
void updateModel();
public slots:
void testUpdateModel();
protected:
QHash<int, QByteArray> roleNames() const;
private:
QTimer m_timer;
QVector< PlayerData> m_lstValues ;
};
#endif // PLAYERMODEL_H
The C++ model (playermodel.cpp)
#include "playermodel.h"
QVariant PlayerData::getRole(int role) const
{
switch (role)
{
case Roles::RoleAzimuth:
return Azimuth;
case Roles::RoleLatitude:
return Latitude;
case Roles::RoleLongitude:
return Longitude;
default:
return QVariant();
}
}
PlayerModel::PlayerModel()
{
resetModel();
connect(&m_timer, SIGNAL(timeout()), this, SLOT(testUpdateModel()));
m_timer.start(1000);
}
PlayerModel::~PlayerModel()
{
}
void PlayerModel::testUpdateModel()
{
updateModel();
}
int PlayerModel::rowCount(const QModelIndex & parent) const
{
Q_UNUSED(parent);
return m_lstValues.size();
}
QVariant PlayerModel::data( const QModelIndex & index, int role ) const
{
if ( (index.row() < 0) || (index.row() >= rowCount()) )
return QVariant();
return m_lstValues[ index.row()].getRole( role);
}
void PlayerModel::resetModel()
{
qDebug() << "Reset players model";
beginResetModel();
m_lstValues.clear();
//populate with dummy value
m_lstValues.push_back( PlayerData( 10, 47.1, -1.6 ));
m_lstValues.push_back( PlayerData( 20, 47.2, -1.6 ));
m_lstValues.push_back( PlayerData( 30, 47.1, -1.5 ));
m_lstValues.push_back( PlayerData( 40, 47.2, -1.5 ));
endResetModel();
}
void PlayerModel::updateModel()
{
qDebug() << "update players model upon timeout";
//change the Azimuth of every model items
int row = 0;
for (PlayerData player : m_lstValues)
{
setData( index(row), (player.Azimuth + 1) % 360, PlayerData::RoleAzimuth);
row++;
}
//qDebug() << "First element azimuth is now : " << data( index(0),PlayerData::RoleAzimuth).toInt() << "°";
}
bool PlayerModel::setData(const QModelIndex & index, const QVariant & value, int role)
{
if ( (index.row() < 0) || (index.row() >= rowCount()) ) return false;
PlayerData& player = m_lstValues[ index.row() ];
switch (role)
{
case PlayerData::RoleAzimuth:
player.Azimuth = value.toInt();
break;
case PlayerData::RoleLatitude:
player.Latitude = value.toDouble();
break;
case PlayerData::RoleLongitude:
player.Longitude = value.toDouble();
break;
}
emit dataChanged(index, index );//, QVector<int>( role));
return true;
}
bool PlayerModel::removeRows(int row, int count, const QModelIndex & parent)
{
Q_UNUSED(count);
Q_UNUSED(parent);
beginRemoveRows(QModelIndex(), row, row);
m_lstValues.remove( row);
endRemoveRows();
return true;
}
QHash<int, QByteArray> PlayerModel::roleNames() const
{
QHash<int, QByteArray> roles;
roles[PlayerData::Roles::RoleAzimuth] = "Azimuth";
roles[PlayerData::Roles::RoleLatitude] = "Latitude";
roles[PlayerData::Roles::RoleLongitude] = "Longitude";
return roles;
}
Qt::ItemFlags PlayerModel::flags(const QModelIndex &index) const
{
if (!index.isValid())
return 0;
return Qt::ItemIsEditable | QAbstractItemModel::flags(index);
}
and finally the QML file :
import QtQuick 2.4
import QtQuick.Window 2.2
import QtLocation 5.3
import QtPositioning 5.0
Window {
id:mainWnd
visible: true
width : 1024
height:768
property bool useQMLModel: true
Map {
id: map
anchors.fill: parent
anchors.margins: 50
plugin: Plugin{ name:"osm";}
center: QtPositioning.coordinate(47.1, -1.6)
zoomLevel: map.maximumZoomLevel
MapItemView{
id:mapItemView
model: mainWnd.useQMLModel ? qmlModel : playerModel
delegate: MapQuickItem {
//anchorPoint:
id:delegateMQI
rotation: model.Azimuth
sourceItem: Rectangle{
id:defaultDelegate
width:32
height:32
radius:16
opacity: 0.6
rotation:Azimuth
color:"blue"
Text{
text: Azimuth
anchors.centerIn : parent
}
}
coordinate: QtPositioning.coordinate(Latitude,Longitude)
}
}
MouseArea{
anchors.fill: parent
enabled : useQMLModel
//preventStealing: true
propagateComposedEvents: true
onClicked:
{
//Modify an item
var newAzim = Math.random()*360;
qmlModel.setProperty(0, "Azimuth", newAzim);
//Check modification
console.log("Azim:" + qmlModel.get(0).Azimuth );
qmlModel.setProperty(0, "Color", "blue");
//add a new item
qmlModel.append({"Latitude": 47.05 + Math.random() *0.2, "Longitude":-1.75 + Math.random() *0.3, "Azimuth":0, "Color":"red"})
console.log("Nb item:" + qmlModel.count );
map.update();
map.fitViewportToMapItems();
mouse.accepted = false
}
}
}
Connections{
target:mapItemView.model
onDataChanged:{
if (useQMLModel)
console.log("dataChanged signal Azim:" + qmlModel.get(0).Azimuth );
else
console.log("dataChanged signal Azim:" + playerModel.data( topLeft, 0x0101) );
}
}
ListModel{
id:qmlModel
ListElement {
Latitude: 47.1
Longitude: -1.6
Azimuth: 10.0
}
}
Rectangle{
anchors.top : parent.top
anchors.left : parent.left
width : 400
height : 300
radius: 10
color:"grey"
ListView{
id:lstView
model:mapItemView.model
anchors.fill:parent
delegate: Text{
width:parent.width
height:50
verticalAlignment: TextInput.AlignVCenter
fontSizeMode : Text.Fit
font.pixelSize: 42
minimumPixelSize: 5
text: "Latitude : " + Latitude + " - Longitude :" + Longitude + " - Azimuth : " + Azimuth
}
}
}
Rectangle{
anchors.right : parent.right
anchors.top : parent.top
radius : 10
color : "red"
width : 200
height : 50
Text{
anchors.centerIn: parent
text:"switch model"
}
MouseArea{
anchors.fill: parent
onClicked:{
mainWnd.useQMLModel = !mainWnd.useQMLModel;
}
}
}
}
Just in case that someone faces the same issue reported by the post's author, the problem was solved in Qt 5.6.0
Note that this is fixed by changeset Ib92252d18c2229bc6d43e11362b8f13cdb48f315 (https://codereview.qt-project.org/#/c/123660/ ) already merged in the 5.6 branch
来源：https://stackoverflow.com/questions/31536014/mapitemview-is-not-updated-after-a-datachanged-signal