qml-maps.qdoc

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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
 
/*!
    \group qml-QtLocation5-maps
    \title QML Maps Plugin
    QML Support for the Qt Location API.
*/
 
 
/*!
\page qml-location5-maps.html
\title QML Maps
 
\brief Maps deals with maps, their contents and navigation.
 
\section1 Overview
 
The \l Map type allows the display of a map and placing objects within the map.
Various points of interest can be defined and added to the map for display.
Also the \l Map has features to control how the map is displayed. With the
Map item you can center the map, zoom, pinch and make the item flickable.
 
The places to be added to the map are
\l {Maps and Navigation (QML)#Putting Objects on a Map (Map Overlay Objects)}{MapItems}. The item's
position is defined by a \l [QtPositioning]{geoCoordinate} which includes
latitude, longitude and altitude. The item is then displayed automatically
after it is added to the \l Map.
 
\section2 Position on map
 
All position APIs are part of the \l {QtPositioning} module.
The basic piece of position information is the
\l [QtPositioning]{geoCoordinate}. A geoCoordinate encapsulates data for the
latitude, longitude and altitude of the location. Altitude is in meters. It
also has a method to determine distance to another geoCoordinate. The
\l [QtPositioning]{geoCoordinate} type may
also be held within a \l [QtPositioning]{Location} element, this will also have information
on a bounding box size to determine sufficient proximity to the location and a location address.
 
 
Here is an example of a client that uses a \l{PositionSource}{position source}
to center a \l{Map}{map} on the current position:
 
\code
    import QtPositioning
    import QtLocation
    ...
 
    Rectangle {
 
        Map {
            id: map
            // initialize map
            ...
        }
 
        PositionSource {
            onPositionChanged: {
                // center the map on the current position
                map.center = position.coordinate
            }
        }
    }
\endcode
 
\section2 Geocoding
 
\l {http://en.wikipedia.org/wiki/Geocoding}{Geocoding} is the derivation of
geographical coordinates (latitude and longitude) from other geographical references
to the locations. For example, this can be a street address. Reverse geocoding is also possible with
a street address being used to determine a geographical coordinate. Geocoding
is performed by using the \l [QML]{GeocodeModel} type.
 
The following code examples are a small part of the \c map component in the
\l {Map Viewer (QML)}{Map Viewer (QML)} example. The snippets
demonstrate the declaration of the \l GeocodeModel component.
 
In the snippet we see that the \l [QML]{GeocodeModel} contains the plugin
and two signal handlers. One for changes in status \l [QML]{GeocodeModel::status}{\c onStatusChanged} and
the other to update the centering of the Map object \l [QML]{GeocodeModel::locationsChanged}{\c onLocationsChanged}.
 
\snippet mapviewer/map/MapComponent.qml geocodemodel0
\codeline
\snippet mapviewer/map/MapComponent.qml geocodeview
 
The geocoding features are called from a higher level piece of code. In this
snippet we see an \l [QML]{Address} object filled with the desired parameters.
 
\snippet mapviewer/Main.qml geocode0
 
The \l [QML]{Address} is later used in a query for the \l GeocodeModel to
process and determine the geographical
\l [QtPositioning]{geoCoordinate}{coordinates}.
 
\snippet mapviewer/map/MapComponent.qml geocode1
 
 
\section2 Navigation
 
A very important function of the \l Map type is navigation
from one place to a destination with possible waypoints along the route. The
route will be divided up into a series of segments. At the end of each segment
is a vertex called a \e maneuver. The \e segments contain information about
the time and distance to the end of the segment. The \e maneuvers contain information
about what to do next, how to get onto the next segment, if there is one. So
a \e maneuver contains navigational information, for example "turn right now".
 
To find a suitable route we will need to use a \l RouteQuery to define the
selection criteria and adding any required waypoints.
The \l RouteModel should return a list of \l {routeSegment}s that defines the
route to the destination complete with navigation advice at the joins between
segments, called \l {routeManeuver}s
 
There are many options that you can add to the query to narrow the criteria.
The \l RouteQuery properties can include
 
\table 60%
    \row
        \li \l {RouteQuery::}{numberAlternativeRoutes}
        \li The number of alternative routes
    \row
        \li \l {RouteQuery::}{travelModes}
        \li Travel modes
    \row
        \li \l {RouteQuery::}{routeOptimizations}
        \li Required route optimizations
    \row
        \li \l {RouteQuery::}{segmentDetail}
        \li Level of detail in segments
    \row
        \li \l {RouteQuery::}{maneuverDetail}
        \li Level of detail in maneuvers between segments
    \row
        \li \l {RouteQuery::}{waypoints}
        \li A list of waypoints
    \row
        \li \l {RouteQuery::}{excludedAreas}
        \li A list of excluded areas that the route must not cross
    \row
        \li \l {RouteQuery::}{featureTypes}
        \li Relevant map features, for example highway, ferry
\endtable
 
 
In the following example a default \l [QML]{RouteQuery} is declared within \l [QML]{RouteModel}.
 
\snippet mapviewer/map/MapComponent.qml routemodel0
 
The user enters some information such as the starting point
of the route, some waypoints and the destination. All of these locations are
waypoints so the locations from start to finish will be entered as a sequence
of waypoints. Then other query properties can be set that may be specific to
this trip.
 
\snippet mapviewer/map/MapComponent.qml routerequest0
\snippet mapviewer/map/MapComponent.qml routerequest1
 
The \c routeInfoModel \l {Models and Views in Qt Quick#Models}{ListModel} is used to grab the
results of the query and construct a suitable list for display.
\snippet mapviewer/forms/RouteList.qml routeinfomodel0
\snippet mapviewer/forms/RouteList.qml routeinfomodel1
\snippet mapviewer/forms/RouteList.qml routeinfomodel3
 
The \l {Models and Views in Qt Quick#Models}{ListModel} \c routeInfoModel can be filled
with values using a code, that loops through the segments extracting the segment length,
instruction text and distance to the next instruction. The extracted data is formatted
for display as it is retrieved.
 
\snippet mapviewer/forms/RouteList.qml routeinfomodel2
 
For more information on the example see the \l {Map Viewer (QML)}{Map Viewer (QML)} example.
 
 
\section2  Zoom, Pinch and Flickable
 
The \l Map item also supports user interface interactions with the map using
tactile and mouse gestures. That is features such as swiping to pan,
pinching to zoom.
 
Enabling and configuring pinch and flickable is easy within the \l MapView type.
 
\snippet mapviewer/map/MapComponent.qml top
\snippet mapviewer/map/MapComponent.qml handler
\snippet mapviewer/map/MapComponent.qml end
 
Zoom can also be controlled by other objects like sliders, with binding
to the Map \l {QtLocation::Map::}{zoomLevel}.
 
\section1 QML Types
 
\section3 Maps
\annotatedlist qml-QtLocation5-maps
 
\section3 Geocoding
\annotatedlist qml-QtLocation5-geocoding
 
\section3 Routing
\annotatedlist qml-QtLocation5-routing
 
 
 
\section1 Example
 
The above snippets are taken from the \l {Map Viewer (QML)}{Map Viewer (QML)} example.
 
*/