如何使用沿折线的实时位置来更新标记? [英] How to update marker using live location along a polyline?
问题描述
我的问题标题似乎已经存在，但这是我的完整情况.
My question titles seems to be an existing one, but here is my complete scenario.
我有一个针对基于Map的操作的活动，该活动沿着一条道路绘制一条折线，比方说两个位置之间的路线.基本上，该应用跟踪用户的当前位置(乘车旅行).因此，直到零件一切正常为止，例如正确显示了路线，设备Location API正在提供位置更新(有点准确)，而且我还能够顺利地更改位置更新，
I have an activity for Map based operations, where am drawing a polyline along a road, lets say a route between two locations. Basically the app tracks the users current location (Traveling by car). So till part everything is working, as in, the route is properly shown, device Location API is giving location updates (kindof exact), and also i was able to change the location updates smoothly,
问题是，位置更新有时呈锯齿状，有时可能不碰路，位置更新将遍及整个地方.
So the issue is, the locations updates are sometimes zig zag, it might not touch the road sometimes, the location updates will be going all over the place.
我也研究了ROAD api，但是即使从以前的一些问题中也没有得到正确的帮助.
I have looked into ROAD api also, but am not getting the correct help, even from some previously asked questions.
是否可以使标记仅沿道路移动?
Will it be possible to make the marker move only along the road?
任何帮助将不胜感激.
推荐答案
您可以通过将标记投影在最近的路径段上来将标记捕捉到路径.您可以通过
You can snap marker to the path by projection of marker on nearest path segment. Nearest segment you can find via PolyUtil.isLocationOnPath():
PolyUtil.isLocationOnPath(carPos, segment, true, 30)
该段的标记投影:
Point carPosOnScreen = projection.toScreenLocation(carPos);
Point p1 = projection.toScreenLocation(segment.get(0));
Point p2 = projection.toScreenLocation(segment.get(1));
Point carPosOnSegment = new Point();
float denominator = (p2.x - p1.x) * (p2.x - p1.x) + (p2.y - p1.y) * (p2.y - p1.y);
// p1 and p2 are the same
if (Math.abs(denominator) <= 1E-10) {
markerProjection = segment.get(0);
} else {
float t = (carPosOnScreen.x * (p2.x - p1.x) - (p2.x - p1.x) * p1.x
+ carPosOnScreen.y * (p2.y - p1.y) - (p2.y - p1.y) * p1.y) / denominator;
carPosOnSegment.x = (int) (p1.x + (p2.x - p1.x) * t);
carPosOnSegment.y = (int) (p1.y + (p2.y - p1.y) * t);
markerProjection = projection.fromScreenLocation(carPosOnSegment);
}
具有完整的源代码:
public class MainActivity extends AppCompatActivity implements OnMapReadyCallback {
private GoogleMap mGoogleMap;
private MapFragment mapFragment;
private Button mButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mapFragment = (MapFragment) getFragmentManager()
.findFragmentById(R.id.map_fragment);
mapFragment.getMapAsync(this);
mButton = (Button) findViewById(R.id.button);
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
}
});
}
@Override
public void onMapReady(GoogleMap googleMap) {
mGoogleMap = googleMap;
mGoogleMap.setOnMapLoadedCallback(new GoogleMap.OnMapLoadedCallback() {
@Override
public void onMapLoaded() {
List<LatLng> sourcePoints = new ArrayList<>();
PolylineOptions polyLineOptions;
LatLng carPos;
sourcePoints.add(new LatLng(-35.27801,149.12958));
sourcePoints.add(new LatLng(-35.28032,149.12907));
sourcePoints.add(new LatLng(-35.28099,149.12929));
sourcePoints.add(new LatLng(-35.28144,149.12984));
sourcePoints.add(new LatLng(-35.28194,149.13003));
sourcePoints.add(new LatLng(-35.28282,149.12956));
sourcePoints.add(new LatLng(-35.28302,149.12881));
sourcePoints.add(new LatLng(-35.28473,149.12836));
polyLineOptions = new PolylineOptions();
polyLineOptions.addAll(sourcePoints);
polyLineOptions.width(10);
polyLineOptions.color(Color.BLUE);
mGoogleMap.addPolyline(polyLineOptions);
carPos = new LatLng(-35.281120, 149.129721);
addMarker(carPos);
mGoogleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(sourcePoints.get(0), 15));
for (int i = 0; i < sourcePoints.size() - 1; i++) {
LatLng segmentP1 = sourcePoints.get(i);
LatLng segmentP2 = sourcePoints.get(i+1);
List<LatLng> segment = new ArrayList<>(2);
segment.add(segmentP1);
segment.add(segmentP2);
if (PolyUtil.isLocationOnPath(carPos, segment, true, 30)) {
polyLineOptions = new PolylineOptions();
polyLineOptions.addAll(segment);
polyLineOptions.width(10);
polyLineOptions.color(Color.RED);
mGoogleMap.addPolyline(polyLineOptions);
LatLng snappedToSegment = getMarkerProjectionOnSegment(carPos, segment, mGoogleMap.getProjection());
addMarker(snappedToSegment);
break;
}
}
}
});
mGoogleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(sourcePoints.get(0), 15));
}
private LatLng getMarkerProjectionOnSegment(LatLng carPos, List<LatLng> segment, Projection projection) {
LatLng markerProjection = null;
Point carPosOnScreen = projection.toScreenLocation(carPos);
Point p1 = projection.toScreenLocation(segment.get(0));
Point p2 = projection.toScreenLocation(segment.get(1));
Point carPosOnSegment = new Point();
float denominator = (p2.x - p1.x) * (p2.x - p1.x) + (p2.y - p1.y) * (p2.y - p1.y);
// p1 and p2 are the same
if (Math.abs(denominator) <= 1E-10) {
markerProjection = segment.get(0);
} else {
float t = (carPosOnScreen.x * (p2.x - p1.x) - (p2.x - p1.x) * p1.x
+ carPosOnScreen.y * (p2.y - p1.y) - (p2.y - p1.y) * p1.y) / denominator;
carPosOnSegment.x = (int) (p1.x + (p2.x - p1.x) * t);
carPosOnSegment.y = (int) (p1.y + (p2.y - p1.y) * t);
markerProjection = projection.fromScreenLocation(carPosOnSegment);
}
return markerProjection;
}
public void addMarker(LatLng latLng) {
mGoogleMap.addMarker(new MarkerOptions()
.position(latLng)
);
}
}
您会得到类似的东西:
But better way is to calculate car distance from start of the path and find it position on path via SphericalUtil.interpolate() because if several path segments is close one to another (e.g. on different lanes of same road) like that:
与当前汽车位置最接近的错误"部分.因此，请从路线起点算起汽车的距离，然后使用
to current car position may be closest "wrong" segment. So, calculate distance of the car from the start of the route and use SphericalUtil.interpolate() for determine point exactly on path.
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