Android - 显示多段线 [英] Android - Display Polylines

问题描述

我有两个活动的应用程序。在第一个活动中，用户可以在地图上设置两个标记，并在两个标记之间绘制路径。在第二个活动中，我想显示在第一个活动中绘制的所有路径。为此，我保存Firebase实时数据库中路径的路标，并在第二个活动中检索数据。

截至目前，第二个活动仅显示一条路径从数据库。我想要做的是在第二个活动中显示用户在第一个活动（保存在数据库中）中制作的所有路径。我假设我必须做一些循环来做到这一点。任何想法如何做到这一点？

POJO类 - 路线：

  public class Route {
 
 private ArrayList< Location>位置; 
 
 public Route（）{
} 
 
 public ArrayList< Location> getLocations（）{
返回位置; 
 
 
 public void setLocations（ArrayList< Location> locations）{
 this.locations = locations; 
 
 
 $ / code $ / pre 
 
 
 POJO类 - 位置：
  public static class Location {
 private Double latitude; 
私人双倍经度; 
 $ b public Location（）{
} 
 
 public double getLatitude（）{
 return latitude; 
} 
 
 public void setLatitude（Double latitude）{
 this.latitude = latitude; 
} 
 
 public Double getLongitude（）{
 return longitude; 
} 
 
 public void setLongitude（Double longitude）{
 this.longitude = longitude; 
 
 
 $ / code $ / pre 
 $ b $ p我的数据库
 
 
  
 
 
 
我如何检索数据并添加多段线来映射：
  userRef.child（sharedPreferences.getString（school，null））。child（routes）。child（sh.getString（key ，null））。addListenerForSingleValueEvent（new ValueEventListener（）{
 @Override $ b $ public void onDataChange（DataSnapshot dataSnapshot）{
 Route route = dataSnapshot.getValue（Route.class）; 
 for（Location location：route.getLocations（））{
 double lat = location.getLatitude（）; 
 double lng = location.getLongitude（）; 
 position = new LatLng（lat，lng ）; 
 points.add（position）; 
} 
} 
 
 
 PolylineOpt离子lineOptions =新的PolylineOptions（）; （LatLng point：points）
（
 lineOptions.add（point）; 
} 
 lineOptions.width（12）; 
 lineOptions.clickable（true）; 
 lineOptions.color（Color.RED）; 
 mMap.addPolyline（lineOptions）; 
  
 
 
解决方案
在当前的例子中，到 $ school / routes 下的单个节点，所以它只会检索那个节点。
 
 
 
如果你需要一次检索所有的路由，你需要附加一个监听器到 routes 节点，并且逐个遍历这些子节点。有关处理数据列表的文档：  
 $ b 
 
 
将ValueEventListener附加到数据列表中会将整个数据列表作为单个DataSnapshot返回，然后您可以循环访问个人的孩子。
 
类似这样的工作应该可以完成这项工作： 
 
 <$ p $ （）;} $ {code} public void drawAllRoutes（）{
 userRef.child（sharedPreferences.getString（school，null））。child（routes）。addListenerForSingleValueEvent（new ValueEventListener（）{$ b （DataSnapshot child：dataSnapshot.getChildren（））{
路由路径= child.getValue（Route.class）; $ b $覆盖$ b $公共无效onDataChange（DataSnapshot dataSnapshot）{
 $ b drawRoute（route）; 
} 
} 
 
 @Override 
 public void onCancelled（DatabaseError databaseError）{} 
}）; 
 
 
 public void drawRoute（Route route）{
 PolylineOptions lineOptions = new PolylineOptions（）; 
 
（位置位置：route.getLocations（））{
 double lat = location.getLatitude（）; 
 double lng = location.getLongitude（）; 
 lineOptions.add（new LatLng（lat，lng））; 
} 
 
 lineOptions.width（12）; 
 lineOptions.clickable（true）; 
 lineOptions.color（Color.RED）; 
 
 mMap.addPolyline（lineOptions）; 
 
  
 
 
  drawAllRoutes（）方法将侦听器附加到 $ school / routes 节点上，它将为您提供列表的 DataSnapshot 在该节点下，在 DataSnapshot＃getChildren（）中提供每个单独的子节点。你可以迭代这些子元素来分别绘制每条折线。
 
 
 
我也将路线绘制逻辑移动到 drawRoute（） code>方法，这样它就可以在地图上绘制 Route 的任何实例，而不管这个 Route  > 
 $ b 
  drawRoute（）方法使用 mMap 变量 - 这就是你的 GoogleMap 实例 - 所以你只能调用 drawAllRoutes（）方法： 
 
 
  private GoogleMap mMap; 
 
 // ... 
 
 @Override 
 public void onMapReady（final GoogleMap googleMap）{
 mMap = googleMap; 
 
 // ... 
 
 drawAllRoutes（）; 
} 
  
 
I have an application with two activities. In the first activity the user is able to set two markers on the map and a path will be drawn between the two markers. In the second activity I want to display all of the paths drawn in the first activity. To do this, I save the waypoints of the paths in a Firebase realtime database and retrieve the data in the second activity.


As of now the second activity only displays one path from the database. What I want to do is to display all paths that the user made in the first activity (saved in the database) in the second activity. I am assuming I have to do some kind of loop to do this. Any ideas on how to do this?

POJO class - Route:
public class Route {

    private ArrayList<Location> locations;

    public Route() {
    }

    public ArrayList<Location> getLocations() {
        return locations;
    }

    public void setLocations(ArrayList<Location> locations) {
        this.locations = locations;
    }
}
POJO class - Location:
public static class Location {
    private Double latitude;
    private Double longitude;

    public Location() {
    }

    public Double getLatitude() {
        return latitude;
    }

    public void setLatitude(Double latitude) {
        this.latitude = latitude;
    }

    public Double getLongitude() {
        return longitude;
    }

    public void setLongitude(Double longitude) {
        this.longitude = longitude;
    }
}
My Database:



How I retrieve data and add polyline to map:
  userRef.child(sharedPreferences.getString("school", null)).child("routes").child(sh.getString("key", null)).addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            Route route = dataSnapshot.getValue(Route.class);
            for (Location location : route.getLocations()) {
                double lat = location.getLatitude();
                double lng = location.getLongitude();
                position = new LatLng(lat, lng);
                points.add(position);
            }
        }


 PolylineOptions lineOptions = new PolylineOptions();
    for (LatLng point : points) {
        lineOptions.add(point);
    }
    lineOptions.width(12);
    lineOptions.clickable(true);
    lineOptions.color(Color.RED);
    mMap.addPolyline(lineOptions);

解决方案
In your current example, you're attaching a listener to a single node under $school/routes, so it will only retrieve that node.

If you need to retrieve all routes at once, you'll need to attach a listener to the routes node and iterate through the children individually. From the documentation on working with lists of data:

  
Attaching a ValueEventListener to a list of data will return the entire list of data as a single DataSnapshot, which you can then loop over to access individual children.
Something like this should do the job:
public void drawAllRoutes() {
    userRef.child(sharedPreferences.getString("school", null)).child("routes").addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot child : dataSnapshot.getChildren()) {
                Route route = child.getValue(Route.class);
                drawRoute(route);
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {}
    });
}

public void drawRoute(Route route) {
    PolylineOptions lineOptions = new PolylineOptions();

    for (Location location : route.getLocations()) {
        double lat = location.getLatitude();
        double lng = location.getLongitude();
        lineOptions.add(new LatLng(lat, lng));
    }

    lineOptions.width(12);
    lineOptions.clickable(true);
    lineOptions.color(Color.RED);

    mMap.addPolyline(lineOptions);
}
The drawAllRoutes() method attaches a listener to the $school/routes node instead, which will provide you with a DataSnapshot of the list under that node, with each individual child node provided in DataSnapshot#getChildren(). You can then iterate over these children to draw each polyline separately.

I have also moved your route-drawing logic into a drawRoute() method, so that it can draw any instance of Route on the map, regardless of how this Route object was created.

The drawRoute() method makes use of the mMap variable - that is your GoogleMap instance from the view - so you can only call the drawAllRoutes() method once the map is ready:
private GoogleMap mMap;

// ...

@Override
public void onMapReady(final GoogleMap googleMap) {
    mMap = googleMap;

    // ...

    drawAllRoutes();
}


                        
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