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java - 除了 onMapReady 之外，如何在 Google 地图中添加自定义标记

问题描述

我正在努力解决一个问题。如何在 Google Maps Activity 中实现方法来添加标记。

我想创建带有两个参数（纬度，经度）的方法，并在每次我的 restfull 客户端给我新数据时添加标记。

我的问题实际上是我想遵守 MVC 约定。当我将改造控制器包含到 MapsActivity 中时，一切正常。

当我将数据从 Controller 发送到 MapsActivity（以 NullPointerException 结尾）时，问题就开始了。

地图活动：

public class MapsActivity extends FragmentActivity implements 
OnMapReadyCallback {

private GoogleMap mMap;

private Handler mHandler = new Handler();



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);

    mapFragment.getMapAsync(this);


}

public void onCarChangeLocation(Double lat, Double lon) {


    LatLng carLatLng = new LatLng(lat, lon);
    mMap.addMarker(new MarkerOptions().position(carLatLng).title("Integra Location"));
    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(carLatLng, 15.5f));


}




public Runnable getDataRunnable = new Runnable() {
    @Override
    public void run() {
        Controller controller = new Controller();
        controller.getData();
        mHandler.postDelayed(this,1000);
    }
};

@Override
public void onMapReady(GoogleMap googleMap) {

     mMap = googleMap;
     getDataRunnable.run();


}



}

控制器：

public class Controller {

public static final String BASE_URL = "server_ip";
private static Retrofit retrofit = null;
 public Double lat;
public Double lon;
public void getData() {

    if (retrofit == null) {
        retrofit = new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

    }

    JsonPlaceHolderApi jsonPlaceHolderApi = retrofit.create(JsonPlaceHolderApi.class);
    Call<OutputModel> call = jsonPlaceHolderApi.getCords();

    call.enqueue(new Callback<OutputModel>() {
        @Override
        public void onResponse(Call<OutputModel> call, retrofit2.Response<OutputModel> response) {

            if (!response.isSuccessful()) {
                // onFailTV.setText("Code: " + response.code());
                return;
            }


           // mMap.clear();
            lat = response.body().getLatitude();
            lon = response.body().getLongitude();
            MapsActivity mapsActivity = new MapsActivity();
            mapsActivity.onCarChangeLocation(lat, lon);




        }


        @Override
        public void onFailure(Call<OutputModel> call, Throwable t) {

        }
    });
}
}

感谢您的回复。

标签： javaandroidgoogle-maps

解决方案

如下更新您的 MapsActivity 代码

public class MapsActivity extends FragmentActivity implements
        OnMapReadyCallback {
    private GoogleMap mMap;
    private Handler mHandler = new Handler();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
        getDataRunnable.run();
    }
    LatLng carLatLng;
    public void onCarChangeLocation(Double lat, Double lon) {
        if (mMap != null) {//Check here map is not initialized 
            carLatLng = new LatLng(lat, lon);
            mMap.addMarker(new MarkerOptions().position(carLatLng).title("Integra Location"));
            mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(carLatLng, 15.5f));
        } else {
            carLatLng = new LatLng(lat, lon);
        }

    }
    public Runnable getDataRunnable = new Runnable() {
        @Override
        public void run() {
            Controller controller = new Controller();
            controller.getData();
            mHandler.postDelayed(this, 1000);
        }
    };
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        if (carLatLng != null) { //recall for setup pin
            onCarChangeLocation(carLatLng.latitude, carLatLng.longitude);
        }
    }
}

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