How to dynamically add map objects to QML MAP element? Or how to create customised Map widget?
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Hi,
Thank you very much for the reply!
I am using qt mobility 1.1 beta, I wonder if there is version 1.2 for internal download and use?
I have read the documentation of qt mobility 1.2 related to location API part, and I am aware of the addMapObject(MapObject) and removeMapObject(MapObject). But I'm not quite sure whether they are really for adding/removing map objects dynamically...
It seems the parameter used in this two functions is MapObject, which is a QML element. And I understood that instead of putting the MapObject as a child element of Map element, you could have the MapObject outside Map element scope, and add the MapObject to the map at runtime. However, with this approach, one still needs to know how many map objects will be loaded at runtime, and predefine the MapObject element for them in QML. For example, one has to know there will be two map circles created at runtime , then create following qml:
@MapCircle {
id: circle1
center: coordinate1
radius: 100
color: "yellow"
}
MapCircle {
id: circle2
center: coordinate1
radius: 100
color: "yellow"
}...
onButton2Clicked: {
map.addMapObject(circle1)map.addMapObject(circle2)}@
And if you actually have 3 map circles need to be drawn, the addMapObject(MapObject) can not be used to add the circle3.
On the other hand, you could always have the two map circles as map child elements, and set the visibility at runtime, and make it looks like adding/removing object from map.
I am very grateful to be answered by Location API team, and could you clarify a bit more on how to use add/remove map object in QML Map element? I undertood the mobility API version 1.2 will be released pretty soon, and I can waite if it provides features which my application would need.
I prefer using qml map element to creating customised map widget, because I might run into some strange bugs if I use my own widget which I have no clue how to solve it. But I would also like to be clear what qml offers, and use it in a best way.
Regards,
Juan Feng
Contextual Solutions team
Nokia Research Center -
Hi Juan,
since I have been through the same pain I thought I should share my solution with you. It's probably a hack, but it works for me.
Basically I've created a subclass of QGraphicsGeoMap that mostly just wraps the API and exposes some methods to QML that are not available by default.
You are right that we need to have a parameter-less constructor to be able to use that widget within QML. Also you're right, QGraphicsGeoMap does not have a parameter-less constructor. I've solved that by having a static method that will provided the needed parameter. See MapWidget::createManager()
I'll simply paste my code below. Please note that I've not taken the time to make this code work stand-alone. It's ripped out of one of my projects and I removed as many unnecessary things to not further confuse you. I hope you can get the general idea from that code.
Have a look at addPoi() and removePoi() and createManager(). If you would like to use addPoi() directly from QML, you should change the signature to something like this:
@ Q_INVOCABLE void addPoi(double lat, double lon); @In my main.cpp I'm doing the following:
@ qmlRegisterType<MapWidget>("mywidgets", 1, 0, "TsMap"); @Have fun :)
@
// map_widget.h
#ifndef MAP_WIDGET_H
#define MAP_WIDGET_H#include <QGraphicsGeoMap>
#include <QGeoMappingManager>
#include <QGeoMapCircleObject>
#include <QGeoMapObject>
#include <QGeoMapPixmapObject>#include "poi_list_model.h"
#include "data_manager.h"QTM_USE_NAMESPACE
class MapWidget : public QGraphicsGeoMap
{
Q_OBJECTpublic:
MapWidget();
~MapWidget();void addPoi(PoiData *poi, bool active); void removePoi(PoiData *poi); void clearPois();signals:
void poiClicked(QString uuid);protected:
void mousePressEvent(QGraphicsSceneMouseEvent* event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent* event);
void mouseMoveEvent(QGraphicsSceneMouseEvent* event);private:
static QGeoMappingManager* createManager();
};#endif // MAP_WIDGET_H
@ -
@
// map_widget.cpp
#include <QDebug>
#include <QGeoServiceProvider>
#include <QGeoMappingManager>
#include <QGeoCoordinate>
#include <QGeoMapCircleObject>
#include <QGeoMapPixmapObject>
#include <QGeoMapGroupObject>
#include <QGraphicsSceneMouseEvent>
#include <QGeoBoundingBox>
#include <QtCore>#include "map_widget.h"
// A widget for QML, therefore we need the parameter-less constructor.
MapWidget::MapWidget() :
QGraphicsGeoMap(createManager())
{
setCenter(QGeoCoordinate(51.05, 13.73));
setZoomLevel(17);
}MapWidget::~MapWidget()
{
}// This method is a bit a heck. We actually call it before the object
// is completely created. We need to do this, because our parent class
// needs a QGeoMappingManager passed to its constructor.
QGeoMappingManager* MapWidget::createManager()
{
qDebug() << "INFO: Creating mapping manager";
// We have to access this as static member, because we can't get anything
// inside this object from the outside. The reason is, that this method
// is called by the constructor and that we cannot add values to the
// constructor, because QML always needs a parameter-less constructor.
QGeoServiceProvider *serviceProvider = new QGeoServiceProvider("osm", params);
QGeoMappingManager *mappingManager = serviceProvider->mappingManager();
if (mappingManager == 0) {
qDebug() << "WARN: Could not load 'osm' plugin. Falling back to 'nokia' plugin.";
serviceProvider = new QGeoServiceProvider("nokia");
mappingManager = serviceProvider->mappingManager();
}return mappingManager;}
void MapWidget::addPoi(PoiData *poi, bool active)
{
QGeoCoordinate coord(poi->getLat(), poi->getLon());QPixmap pixmap; if (active) { pixmap = QPixmap(":qml/Common/img/poi_active.png"); } else { pixmap = QPixmap(":qml/Common/img/poi_inactive.png"); } QGeoMapPixmapObject *pixMapObject = new QGeoMapPixmapObject(coord, QPoint(-26,-65), pixmap); pixMapObject->setProperty("uuid", poi->getUuid()); pixMapObject->setObjectName("poiMarker"); QGeoMapGroupObject *poiMarker = new QGeoMapGroupObject(); poiMarker->setProperty("uuid", poi->getUuid()); poiMarker->addChildObject(pixMapObject); if (active) { QGeoMapCircleObject *circle = new QGeoMapCircleObject(coord, poi->getRadius()); circle->setPen(QPen((poiColor))); circle->setBrush(QBrush(poiColor)); circle->setZValue(-1); poiMarker->addChildObject(circle); } addMapObject(poiMarker);}
void MapWidget::removePoi(PoiData *poi)
{
for (int i = 0; i < poiMarkers.length(); ++i) {
QGeoMapObject *marker = poiMarkers[i];
if (marker->property("uuid").toString() == poi->getUuid()) {
removeMapObject(marker);
return;
}
}
}void MapWidget::clearPois()
{
for (int i = 0; i < poiMarkers.length(); ++i) {
QGeoMapObject *obj = poiMarkers[i];
removeMapObject(obj);
}
}/*
- Remember the position. We use this in mouseReleaseEvent
/
void MapWidget::mousePressEvent(QGraphicsSceneMouseEvent event)
{
lastPos = event->pos();
}
/*
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If the mouse was moved by a maximum of 30px between press and release
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we look at the press coordinates and if there is a POI we emit a signal
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if there are several POIs, we only emit the signal for the first one.
/
void MapWidget::mouseReleaseEvent(QGraphicsSceneMouseEvent event)
{
QPointF newPos = event->pos();
QPointF diff = lastPos - newPos;if (qAbs(diff.x()) > 30 || qAbs(diff.y()) > 30) {
return;
}QList<QGeoMapObject*> objects = mapObjectsAtScreenPosition(lastPos);
if (objects.length() > 0) {
for (int i = 0; i < objects.length(); i++) {
QGeoMapObject *obj = objects[i];
if (obj->objectName() == "poiMarker") {
QString uuid = obj->property("uuid").toString();
emit poiClicked(uuid);
}
}
}
}
void MapWidget::mouseMoveEvent(QGraphicsSceneMouseEvent* event)
{
// Round to int
QPoint lastPos = event->lastPos().toPoint();
QPoint pos = event->pos().toPoint();int dx = lastPos.x() - pos.x(); int dy = lastPos.y() - pos.y(); pan(dx, dy); setFollowPosition(false);}
@ - Remember the position. We use this in mouseReleaseEvent
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Hi Conny,
Thank you very much!
Your approach does work! I think for developers who need to use more complicated features than what qml location plugin offers, probably a custimised map widget which extends QGraphicsGeoMap is the best option.
And it is also possible to develope own map widget, which subclasses QGraphicsWidget, by using QGeoMapData and QGeoMappingManager.
Thanks again!
Regards,
Juan -
Hi Jano,
if you're new with QML you should start by using the default map item. It has also much improved in QtM 1.2. Have a look here:
http://doc.qt.nokia.com/qtmobility-1.2/declarative-location-mapviewer-mapviewer-qml.html -
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Hi Conny,
I resolve issue. I'm gettin mouse events in simulator aswell.
Do you maybe know if is possible to add mapObject to the map so that onclick event can be handled?
Somehow extend QGeoMapObject?Unfortunatelly method mapObjectsAtScreenPosition(lastPos) does not work on devices. I'm retreiving empty objects lists.
I have latest Qt SDK 1.1.2 and usign Qt Mobility 1.1
Many Thanks for your help
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Yes you're right. Actually I've reported that bug. Unfortunately I don't know a way to get the mouse events on a devices with QtM < 1.2. I'm also waiting that QtM 1.2 will finally be available for devices.
On Maemo5 I've tested it with QtM 1.2 and it's actually working. On Symbian and for Ovi, we still have to wait :(
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Nice! I have also decided to give qml a try and of course are running into the same issues. I have started to make a minimal demo app from conny's example and would like to setup a wiki page or similar as i think we should document this a little bit, so others can re-use this.
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Ok, "here":http://wiki.meego.com/QML/QGraphicsGeoMap is the wiki page. Please contribute your findings and let's try to make this into a small complete guide for this. I e.g. found that the map doesn't scale when the window size changes.