How to remove all the polylines from a map

问题:

Following

How to draw a path between two markers

I had to add lot of polylines between two markers, to make a path.

One of the markers is draggable, lets say source is draggable.

So, when user starts dragging the marker, the path previously drawn must be erased and a new path between new source and destination must be draw.

I am able to draw the new path, but how can i erase the previous path?

This is how the path is drawn:

    for (int z = 0; z < list.size() - 1; z++) {
        LatLng src = list.get(z);
        LatLng dest = list.get(z + 1);
        Polyline line = map.addPolyline(new PolylineOptions()
                .add(new LatLng(src.latitude, src.longitude),
                        new LatLng(dest.latitude, dest.longitude))
                .width(2).color(Color.RED).geodesic(true));
    }

One solution i can get is

map.clear();

To clear all the polylines, markers etc.. and add the markers again, then drawn the path.

But as soon as I start dragging, the marker is cleared, hence not visible on the map :(

Thank You

回答1:

Keep track of the Polyline as you add it to the map:

Polyline polyline = this.mMap.addPolyline(new PolylineOptions().....);

Then when you want to remove it:

polyline.remove();

If you have lots of Polylines, just add them to a List as they are put on the map:

List<Polyline> polylines = new ArrayList<Polyline>();

for(....)
{
    polylines.add(this.mMap.addPolyline(new PolylineOptions()....));
}

And when you want to delete:

for(Polyline line : polylines)
{
    line.remove();
}

polylines.clear();

The key is to keep a reference to the Polyline objects and call .remove() on each one.

回答2:

I know this is very old question but I noticed that this is very common need. I found another way and I wanted to share it.

Here is the basic idea:

Polyline polylineFinal;
PolylineOptions polylineOptions;

loop {

    polylineOptions.add( new LatLng( latitude, longitude ) );

}

polylineOptions.width(2);
polylineOptions.color(Color.RED);
polylineOptions.geodesic(true);

polylineFinal = map.addPolyline (polylineOptions);

Map's "addPolyline" method returns a single polyline which contains all the points. When I need to remove the points, I call polylineFinal's "remove" method.

polylineFinal.remove();

回答3:

I used this work :)

    private GoogleMap mMapView;

    SupportMapFragment myMapFragment = (SupportMapFragment)getSupportFragmentManager()
    .findFragmentById(R.id.mMapView3);
    mMapView = myMapFragment.getMap();

    PolylineOptions rectLine = new PolylineOptions()
                    .add(new LatLng(13.000000, 100.000000))
                    .add(new LatLng(13.010000, 100.000000));

            mMapView.addPolyline(rectLine);