[英]Remove the last plotted line from Google Map Android
I have the following code which adds a PolylineOptions object to a Polyline array list. 我有以下代码将PolylineOptions对象添加到Polyline数组列表中。 The argument passed in is a series of points returned from a query to the Directions API. 传入的参数是从查询返回到Directions API的一系列点。
List<Polyline> polylines = new ArrayList<Polyline>();
public void drawPolylines(List<List<HashMap<String, String>>> result) {
PolylineOptions lineOptions = null;
// Traversing through all the routes
for (int i = 0; i < result.size(); i++) {
lineOptions = new PolylineOptions();
// Fetching i-th route
List<HashMap<String, String>> path = result.get(i);
// Fetching all the points in i-th route
for (int j = 0; j < path.size(); j++) {
HashMap<String, String> point = path.get(j);
double lat = Double.parseDouble(point.get("lat"));
double lng = Double.parseDouble(point.get("lng"));
LatLng position = new LatLng(lat, lng);
lineOptions.add(position).width(6).color(Color.BLUE);
}
polylines.add(mMap.addPolyline(lineOptions));
}
}
When I click on the undo button, I want it to remove the last line from the from the map, which is the last line on the polylines list. 当我单击撤消按钮时,我希望它从地图中删除最后一行,这是折线列表上的最后一行。 I have the following code, but nothing seems to be removed from the map whenever I run it. 我有以下代码,但是每次运行它似乎都不会从地图中删除任何内容。 Is there anything else I need to add in? 我还有什么需要补充的吗?
mButtonUndo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// create variable for the 2nd last point clicked and assign value form markerPoints array list
LatLng lastPoint;
lastPoint = markerPoints.get(markerPoints.size() - 2);
// animate camera to centre on the previously touched position
System.out.println("Centering camera to previous position at " + lastPoint.toString());
mMap.animateCamera(CameraUpdateFactory.newLatLng(lastPoint));
// remove line from the map
for (int i = 0; i == polylines.size(); i++) {
polylines.remove(polylines.size());
}
// remove value from the markerPoints array list
// update the distance text
double routeDistance = 0;
distanceCount.remove(distanceCount.size() - 1);
for (Double step : distanceCount) {
routeDistance += step;
}
System.out.println("Total Distance calculated in undo in m = " + routeDistance);
// output new value to ui
mDistanceCount.setText(routeDistance / 1000 + "km");
}
});
Found a solution by using a simple check in an enhanced for loop: 通过在增强的for循环中使用简单检查来找到解决方案:
mButtonUndo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// create variable for the 2nd last point clicked and assign value form markerPoints array list
LatLng lastPoint;
lastPoint = markerPoints.get(markerPoints.size() - 2);
// animate camera to centre on the previously touched position
System.out.println("Centering camera to previous position at " + lastPoint.toString());
mMap.animateCamera(CameraUpdateFactory.newLatLng(lastPoint));
// remove polyline object from the map
for (Polyline line : polylines) {
if (polylines.get(polylines.size() - 1).equals(line)) {
line.remove();
polylines.remove(line);
}
}
// remove last value from the markerPoints array list
markerPoints.remove(markerPoints.size() - 1);
// update the distance text
double routeDistance = 0;
distanceCount.remove(distanceCount.size() - 1);
for (Double step : distanceCount) {
routeDistance += step;
}
System.out.println("Total Distance calculated in undo in m = " + routeDistance);
// output new value to ui
mDistanceCount.setText(routeDistance / 1000 + "km");
}
});
您可以使用Map.clear()清除地图;
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