这是一张QML地图:
Map {
anchors.fill: parent
plugin: osmMapPlugin
center: QtPositioning.coordinate(56.006355, 92.860984)
zoomLevel: 14
MapPolyline {
line.width: 3
line.color: 'red'
path: [
{ latitude: -27, longitude: 153.0 },
{ latitude: -27, longitude: 154.1 },
{ latitude: -28, longitude: 153.5 },
{ latitude: -29, longitude: 153.5 }
]
}
}
如何从C / qt改变路径?我试过这个:
QML:
Map {
anchors.fill: parent
plugin: osmMapPlugin
center: QtPositioning.coordinate(56.006355, 92.860984)
zoomLevel: 14
MapPolyline {
line.width: 3
line.color: 'red'
path: map_path
}
}
C :
map = new QQuickWidget();
map->setSource(QUrl("qrc:map.qml"));
QQmlContext *qml_map = map->rootContext();
QGeoPath *path = new QGeoPath();
path->addCoordinate(*(new QGeoCoordinate(56.0831528053, 92.8405031454)));
path->addCoordinate(*(new QGeoCoordinate(56.1, 93)));
qml_map->setContextProperty("map_path", path);
但我有一个例外:
calling a private constructor of class 'QVariant':
qml_map->setContextProperty("map_path", path);
和
attempted to use of deleted function:
qml_map->setContextProperty("map_path", path);
UPD:
@ hi-im-frogatto建议有必要这样做:
qml_map->setContextProperty("map_path", QVariant::fromValue(path));
它有所帮助,错误不再发生.但是没有画出这条线.得到错误:
qrc:map.qml:30: ReferenceError: map_path is not defined
qrc:map.qml:21:5: QML Map: Plugin is a write-once property, and cannot be set again.
解决方法:
正如它说@HiI’mFrogatto你应该使用QVariant :: fromValue(),但它不能直接在.qml端使用:
QGeoPath geopath;
geopath.addCoordinate(QGeoCoordinate(56.006355, 92.860984));
geopath.addCoordinate(QGeoCoordinate(56.1, 93));
geopath.addCoordinate(QGeoCoordinate(56.1, 92.777));
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("geopath", QVariant::fromValue(geopath));
你需要做的是通过循环访问每个元素:
Map {
anchors.fill: parent
plugin: osmMapPlugin
center: QtPositioning.coordinate(56.006355, 92.860984)
zoomLevel: 10
MapPolyline {
id: pl
line.width: 3
line.color: 'red'
}
Component.onCompleted: {
var lines = []
for(var i=0; i < geopath.size(); i++){
lines[i] = geopath.coordinateAt(i)
}
pl.path = lines
}
}
但是在这种情况下我们无法更新QGeoPath的值,因此可以实现一个继承自QObject并具有QGeoPath属性的类,因为您可以从C或QML中操作它.
main.cpp中
#include <QGeoPath>
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QTimer>
class PathController: public QObject{
Q_OBJECT
Q_PROPERTY(QGeoPath geopath READ geoPath WRITE setGeoPath NOTIFY geopathChanged)
public:
PathController(QObject *parent=0):QObject(parent){}
void test(){
mGeoPath.addCoordinate(QGeoCoordinate(56.006355, 92.860984));
mGeoPath.addCoordinate(QGeoCoordinate(56.1, 93));
mGeoPath.addCoordinate(QGeoCoordinate(56.1, 92.777));
QTimer *timer = new QTimer(this);
QObject::connect(timer, &QTimer::timeout, [this](){
mGeoPath.translate(0.001, -0.01);
emit geopathChanged();
});
timer->start(1000);
}
QGeoPath geoPath() const{return mGeoPath;}
void setGeoPath(const QGeoPath &geoPath){
if(geoPath == mGeoPath)
return;
mGeoPath = geoPath;
emit geopathChanged();
}
signals:
void geopathChanged();
private:
QGeoPath mGeoPath;
};
int main(int argc, char *argv[])
{
#if defined(Q_OS_WIN)
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
QGuiApplication app(argc, argv);
PathController controller;
controller.test();
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("pathController", &controller);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
return -1;
return app.exec();
}
#include "main.moc"
main.qml
import QtQuick 2.9
import QtQuick.Window 2.2
import QtLocation 5.6
import QtPositioning 5.6
Window {
visible: true
width: 640
height: 480
Plugin {
id: osmMapPlugin
name: "osm"
}
Map {
anchors.fill: parent
plugin: osmMapPlugin
center: QtPositioning.coordinate(56.006355, 92.860984)
zoomLevel: 10
MapPolyline {
id: pl
line.width: 10
line.color: 'red'
}
}
function loadPath(){
var lines = []
for(var i=0; i < pathController.geopath.size(); i++){
lines[i] = pathController.geopath.coordinateAt(i)
}
return lines;
}
Connections{
target: pathController
onGeopathChanged: pl.path = loadPath()
}
Component.onCompleted: pl.path = loadPath()
}
在这个link中,您将找到完整的示例.