Question

你好我试图在开车时画一条简单的线。我想在后台收集位置数据，这就是我使用服务的原因。服务端的代码如下所示：

  // THIS IS FOR GPS

private class LocationListener implements android.location.LocationListener{

    Location mLastLocation;

    public LocationListener(String provider){

        Log.e(TAG, "LocationListener " + provider);
        mLastLocation = new Location(provider);
    }

    @Override
    public void onLocationChanged(Location location) {

        Intent mapIntent = new Intent();

        Log.e(TAG, "onLocationChanged: " + location);
        mLastLocation.set(location);

        double latitude = location.getLatitude();
        double longitude = location.getLongitude();

        mapIntent.putExtra("Latitude", latitude);
        mapIntent.putExtra("Longitude", longitude);

        mapIntent.setAction(MAP_ACTION);
        sendBroadcast(mapIntent);

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

        Log.e(TAG, "onStatusChanged: " + provider);
    }

    @Override
    public void onProviderEnabled(String provider) {

        Log.e(TAG, "onProviderEnabled: " + provider);

    }

    @Override
    public void onProviderDisabled(String provider) {

        Log.e(TAG, "onProviderDisabled: " + provider);
    }
}

LocationListener[] mLocationListeners = new LocationListener[] {
        new LocationListener(LocationManager.GPS_PROVIDER),
        new LocationListener(LocationManager.NETWORK_PROVIDER)
};

private void initializeLocationManager() {
    Log.e(TAG, "initializeLocationManager");
    if (mLocationManager == null) {
        mLocationManager = (LocationManager) getApplicationContext().getSystemService(Context.LOCATION_SERVICE);
    }
}

我使用putExtra发送纬度和经度，我在FragmentActivity中读取此内容。

   class MapBroadcast extends BroadcastReceiver{

    @Override
    public void onReceive(Context context, Intent intent) {

        Bundle extras = intent.getExtras();
        LatLng temp = new LatLng(extras.getDouble("Latitude"),extras.getDouble("Longitude"));


        points.add(temp);

        try {

            googleMap.clear();  

            PolylineOptions options = new PolylineOptions().width(5).color(Color.BLUE).geodesic(true);
            for (int i = 0; i < points.size(); i++) {
                LatLng point = points.get(i);
                options.add(point);

                Log.d("LATLONG", String.valueOf(options));
            }

            if (options != null)
            {
               line = googleMap.addPolyline(options);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

我能够在片段一侧读取纬度和经度，所以看起来一切正常但它不会划线。但是期权价值如下：

D / LATLANG：com.google.android.gms.maps.model.PolylineOptions@21ea8168

它给我一个错误：

W / System.err：java.lang.NullPointerException

ArrayList<LatLng> points;初始化onCreateView

我在这几个小时内挣扎，我无法找到解决方案。我会非常感谢你的帮助。

错误消息是：

12-02 23:19:35.079 5423-5423/com.example.mattkopacz.obdmenu E/AndroidRuntime: FATAL EXCEPTION: main
                                                                          Process: com.example.mattkopacz.obdmenu, PID: 5423
                                                                          java.lang.RuntimeException: Error receiving broadcast Intent { act=MAP_ACTION flg=0x10 (has extras) } in com.example.mattkopacz.obdmenu.Menu1$MapBroadcast@21f0fb18
                                                                              at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:782)
                                                                              at android.os.Handler.handleCallback(Handler.java:733)
                                                                              at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                              at android.os.Looper.loop(Looper.java:146)
                                                                              at android.app.ActivityThread.main(ActivityThread.java:5653)
                                                                              at java.lang.reflect.Method.invokeNative(Native Method)
                                                                              at java.lang.reflect.Method.invoke(Method.java:515)
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
                                                                              at dalvik.system.NativeStart.main(Native Method)
                                                                           Caused by: java.lang.NullPointerException
                                                                              at com.example.mattkopacz.obdmenu.Menu1$MapBroadcast.onReceive(Menu1.java:260)
                                                                              at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:772)
                                                                              at android.os.Handler.handleCallback(Handler.java:733) 
                                                                              at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                              at android.os.Looper.loop(Looper.java:146) 
                                                                              at android.app.ActivityThread.main(ActivityThread.java:5653) 
                                                                              at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                              at java.lang.reflect.Method.invoke(Method.java:515) 
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291) 
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107) 
                                                                              at dalvik.system.NativeStart.main(Native Method)

Answer 1

您无需单独添加每个LatLng，而是可以使用polyOptions.addAll(points)将整个列表添加到一起。

  final PolylineOptions polyOptions = new PolylineOptions();
        polyOptions.color(Color.BLUE);
        polyOptions.width(5);
        polyOptions.geodesic(true);
        polyOptions.jointType(ROUND);
        polyOptions.addAll(points);
        googleMap.addPolyline(polyOptions);

使用googleMaps和服务绘制PolyLine

1 个答案: