QML Maps with Pinch Zoom
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QML Map using PinchArea to zoom and MouseArea to pan
Qt Mobility's Location plugin provides a very nice QML Map item, but currently leaves navigation up to the developer to implement. Two common navigation methods are using a swipe gesture to pan the map around and using a pinch gesture to zoom in and out.
Having not found any solid examples of how to do these two things together, I thought I would post an example of some code which implement these two features. The code uses the "PinchArea":http://doc.qt.nokia.com/4.7-snapshot/qml-pincharea.html element which was introduced in Qt Quick 1.1.
I hope you find this helpful!
import QtQuick 1.1
import QtMobility.location 1.2
Rectangle {
id: pinchmap
property double defaultLatitude: 37.69
property double defaultLongitude: –97.33
property int defaultZoomLevel: 7
property alias mapType: map.mapType
width: 640
height: 350
Map {
id: map
anchors.fill: parent
zoomLevel: pinchmap.defaultZoomLevel
plugin: Plugin { name: "nokia" }
mapType: Map.StreetMap
center: Coordinate {
latitude: pinchmap.defaultLatitude
longitude: pinchmap.defaultLongitude
}
}
PinchArea {
id: pincharea
property double _''oldZoom
anchors.fill: parent
function calcZoomDelta(zoom, percent) {
return zoom + Math.log(percent)/Math.log(2)
}
onPinchStarted: {
oldZoom = map.zoomLevel
}
onPinchUpdated: {
map.zoomLevel = calcZoomDelta(oldZoom, pinch.scale)
}
onPinchFinished: {
map.zoomLevel = calcZoomDelta(oldZoom, pinch.scale)
}
}
MouseArea {
id: mousearea
property boolisPanning: false
property intlastX: –1
property intlastY: –1
anchors.fill : parent
onPressed: {
isPanning = true
lastX = mouse.x
lastY = mouse.y
}
onReleased: {
isPanning = false
}
onPositionChanged: {
if (isPanning) {
var dx = mouse.x -lastX
var dy = mouse.y -lastY
map.pan(-dx, -dy)
lastX = mouse.x
lastY = mouse.y
}
}
onCanceled: {
''_isPanning = false;
}
}
}