The QGeoJson namespace contains functions to import and export geolocated information from and to GeoJson files. 更多...
| 头： | #include <QGeoJson> |
| qmake: | QT += location |
| QJsonDocument | exportGeoJson (const QVariantList & geoData ) |
| QVariantList | importGeoJson (const QJsonDocument & geoJson ) |
| QString | toString (const QVariantList & geoData ) |
The methods in the QGeoJson namespace can be used to convert between a GeoJSON document (see the Wikipedia page , RFC ) 和 QVariantList of QVariantMap elements ready to be used as Model in a MapItemView .
The
importGeoJson
() method accepts a
QJsonDocument
from which it extracts a single
JSON
object. The GeoJSON RFC expects that a valid GeoJSON Document has in its root a single JSON object. This method doesn't perform any validation on the input. The importer returns a
QVariantList
containing a single
QVariantMap
. This map has always at least 2 (key, value) pairs. The first one has
type
as key, and the corresponding value is a string identifying the GeoJSON type. This value can be one of the GeoJSON object types:
点
,
MultiPoint
,
LineString
,
MultiLineString
,
Polygon
,
MultiPolygon
,
GeometryCollection
,
FeatureCollection
. The second pair has
data
as key, and the corresponding value can be either a
QGeoShape
or a list, depending on the GeoJSON type. The next section provides details about the conversation form GeoJson objects to objects known in Qt Location. The
特征
type is converted into the type of the geometry contained within, with an additional (key, value) pair, where the key is
properties
and the value is a
QVariantMap
. Thus, a feature Map is distinguishable from the corresponding geometry, by looking for a
properties
member.
For the single type geometry objects (
点
,
LineString
，和
Polygon
), the value corresponding to the
data
key is a
QGeoShape
:
点
, the data is a
QGeoCircle
with the point coordinates stored in the center property.
For example, the following GeoJSON document contains a
点
geometry:
{
"type" : "Point",
"data" : [60.0, 11.0]
}
it is converted to a QVariantMap with the following structure:
{
type : "Point"
data : QGeoCircle({60.000, 11.000}, -1)
}
LineString
the data is a
QGeoPath
.
For example, the following GeoJSON document contains a
LineString
geometry:
{
"type" : "LineString",
"coordinates" : [[13.5, 43],[10.73, 59.92]]
}
it is converted to a QVariantMap with the following structure:
{
type : "LineString",
data : QGeoPath([{43.000, 13.500}, {59.920, 10.730}])
}
Polygon
, the data is a
QGeoPolygon
(holes are supported).
For example, the following GeoJSON document contains a
Polygon
geometry:
{
"type" : "Polygon",
"coordinates" : [
[[17.13, 51.11],
[30.54, 50.42],
[26.70, 58.36],
[17.13, 51.11]]
],
"bbox" : [60, 60, -60, -60]
}
it is converted to a QVariantMap with the following structure:
{
type : "Polygon"
data : QGeoPolygon([{51.110, 17.130}, {50.420,30.540}, {58.360, 26.700}, {51.110, 17.130}])
}
For the homogeneously typed multipart geometry objects (
MultiPoint
,
MultiLineString
,
MultiPolygon
) the value corresponding to the
data
key is a
QVariantList
. Each element of the list is a
QVariantMap
of one of the above listed types. The elements in this list will be all of the same GeoJSON type:
MultiPoint
, the data is a List of Points.
For example, the following GeoJSON document contains a
MultiPoint
geometry:
{
"type" : "MultiPoint",
"coordinates" : [
[11,60],
[5.5,60.3],
[5.7,58.90]
]
}
it is converted to a QVariantMap with the following structure:
{
type : "MultiPoint"
data : [
{
type : "Point"
data : QGeoCircle({60.000, 11.000}, -1)
},
{
type : "Point"
data : QGeoCircle({60.300, 5.500}, -1)
},
{
type : "Point"
data : QGeoCircle({58.900, 5.700}, -1)
}
]
}
MultiLineString
, the data is a List of LineStrings.
For example, the following GeoJSON document contains a
MultiLineString
geometry:
{
"type" : "MultiLineString",
"coordinates" : [
[[13.5, 43], [10.73, 59.92]],
[[9.15, 45], [-3.15, 58.90]]
]
}
it is converted to a QVariantMap with the following structure:
{
type : "MultiLineString"
data : [
{
type : "LineString"
data : QGeoPath([{45.000, 9.150}, {58.900, -3.150}])
},
{
type : "LineString"
data : QGeoPath([{43.000, 13.500}, {59.920, 10.730}])
}
]
}
MultiPolygon
, the data is a List of Polygons.
For example, the following GeoJSON document contains a
MultiPolygon
geometry:
{
"type" : "MultiPolygon",
"coordinates" : [
[
[
[17.13, 51.11],
[30.54, 50.42],
[26.74, 58.36],
[17.13, 51.11]
]
],
[
[
[19.84, 41.33],
[30.45, 49.26],
[17.07, 50.10],
[19.84, 41.33]
]
]
]
}
it is converted to a QVariantMap with the following structure:
{
type : "MultiPolygon"
data : [
{
type : "Polygon"
data : QGeoPolygon([{51.110, 17.130}, {50.420,30.540}, {58.360, 26.700}, {51.110, 17.130}])
},
{
type : "Polygon"
data : QGeoPolygon([{41.330, 19.840}, {49.260,30.450}, {50.100, 17.070}, {41.330, 19.840}])
}
]
}
The
GeometryCollection
is a heterogeneous composition of other geometry types. In the resulting
QVariantMap
, the value of the
data
member is a
QVariantList
populated by QVariantMaps of various geometries, including the GeometryCollection itself.
例如，以下
GeometryCollection
:
{
"type" : "GeometryCollection",
"geometries" : [
{
"type" : "MultiPoint",
"coordinates" : [
[11,60], [5.5,60.3], [5.7,58.90]
]
},
{
"type" : "MultiLineString",
"coordinates" : [
[[13.5, 43], [10.73, 59.92]],
[[9.15, 45], [-3.15, 58.90]]
]
},
{
"type" : "MultiPolygon",
"coordinates" : [
[
[[17.13, 51.11],
[30.54, 50.42],
[26.74, 58.36],
[17.13, 51.11]]
],
[
[[19.84, 41.33],
[30.45, 49.26],
[17.07, 50.10],
[19.84, 41.33]]
]
]
}
]
}
it is converted to a QVariantMap with the following structure:
{
type : "GeometryCollection"
data : [
{
type : "MultiPolygon"
data : [
{
type : "Polygon"
data : QGeoPolygon([{41.330, 19.840}, {49.260, 30.450}, {50.100, 17.070}, {41.330, 19.840}])
}
{
type : "Polygon"
data : QGeoPolygon([{51.110, 17.130}, {50.420, 30.540}, {58.360, 26.740}, {51.110, 17.130}])
}
]
}
{
type : "MultiLineString"
data : [
{
type : "LineString"
data : QGeoPath([{45.000, 9.150}, {58.900, -3.150}])
}
{
type : "LineString"
data : QGeoPath([{43.000, 13.500}, {59.920, 10.730}])
}
]
}
{
type : "MultiPoint"
data : [
{
type : Point
data : QGeoCircle({58.900, 5.700}, -1)
},
{
type : Point
data : QGeoCircle({60.300, 5.500}, -1)
},
{
type : Point
data : QGeoCircle({60.000, 11.000}, -1)
}
]
}
]
}
The
特征
object, which consists of one of the previous geometries together with related attributes, is structured like one of the 7 above mentioned geometry types, plus a
properties
member. The value of this member is a
QVariantMap
. The only way to distinguish a Feature from the included geometry is to check if a
properties
node is present in the
QVariantMap
.
例如，以下
特征
:
{
"type" : "Feature",
"id" : "Poly",
"properties" : {
"text" : "This is a Feature with a Polygon"
},
"geometry" : {
"type" : "Polygon",
"coordinates" : [
[[17.13, 51.11],
[30.54, 50.42],
[26.70, 58.36],
[17.13, 51.11]],
[[23.46, 54.36],
[20.52, 51.91],
[28.25, 51.50],
[26.80, 54.36],
[23.46, 54.36]]
]
}
}
it is converted to a QVariantMap with the following structure:
{
type : "Polygon"
data : QGeoPolygon([{51.110, 17.130}, {50.420,30.540}, {58.360, 26.700}, {51.110, 17.130}])
properties : {text : "This is a Feature with a Polygon"}
}
The
FeatureCollection
is a composition of Feature objects. The value of the
data
member in a FeatureCollection is a
QVariantList
populated by Feature type QVariantMaps.
例如，以下
FeatureCollection
:
{
"type" : "FeatureCollection",
"features" : [
{
"type" : "Feature",
"id" : "Poly",
"properties" : {
"text" : "This is a Feature with a Polygon"
},
"geometry" : {
"type" : "Polygon",
"coordinates" : [
[[17.13, 51.11],
[30.54, 50.42],
[26.70, 58.36],
[17.13, 51.11]],
[[23.46, 54.36],
[20.52, 51.91],
[28.25, 51.50],
[26.80, 54.36],
[23.46, 54.36]]
]
}
},
{
"type" : "Feature",
"id" : "MultiLine",
"properties" : {
"text" : "This is a Feature with a MultiLineString"
},
"geometry" : {
"type" : "MultiLineString",
"coordinates" : [
[[13.5, 43], [10.73, 59.92]],
[[9.15, 45], [-3.15, 58.90]]
]
}
}
]
}
it is converted to a QVariantMap with the following structure:
{
type : "FeatureCollection"
data : [
{
type : "MultiLineString"
data : [
{
type : "LineString"
data : QGeoPath([{45.000, 9.150}, {58.900, -3.150}])
}
{
type : "LineString"
data : QGeoPath([{43.000, 13.500}, {59.920, 10.730}])
}
]
properties : {text : "This is a Feature with a MultiLineString"}
},
{
type : "Polygon"
data : QGeoPolygon({51.110, 17.130}, {50.420, 30.540}, {58.360, 26.700}, {51.110, 17.130})
properties : {text : "This is a Feature with a Polygon"}
}
]
}
The exporter accepts the QVariantList returned by the importer , and returns a JSON document. The exporter is complementary to the importer because it executes the inverse action.
The toString outputs, for debugging purposes, the content of a QVariantList structured like importGeoJson does, to a QString using a prettyfied format.
This method exports the QVariantList geoData , expected to be structured like described in the section Importing GeoJSON , to a QJsonDocument containing the data converted to GeoJSON.
注意： This method performs no validation on the input.
另请参阅 importGeoJson .
This method imports the geoJson document, expected to contain valid GeoJSON data, into a QVariantList structured like described in the section Importing GeoJSON .
注意： This method performs no validation on the input.
另请参阅 exportGeoJson .
This method accepts the QVariantList geoData , structured as described in Importing GeoJSON , and returns a string containing the same data in a readable form.