使用谷歌位置API获取Android中onMapReady的当前位置

Question

我正试图在我的应用程序内的谷歌地图上显示用户的当前位置,但我不想在用户移动时不断更新位置.他的初始位置应该被记录并显示,直到他关闭应用程序.我为此编写了以下代码:

private GoogleMap mMap;
protected GoogleApiClient mGoogleApiClient;
Location mLastLocation;
double lat =0, lng=0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_map);
    buildGoogleApiClient();

    // Obtain the SupportMapFragment and get notified when the map is ready to be used.
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);


}

private void buildGoogleApiClient() {
    mGoogleApiClient = new GoogleApiClient.Builder(this)
            .addConnectionCallbacks(this)
            .addOnConnectionFailedListener(this)
            .addApi(LocationServices.API)
            .build();
}


/**
 * Manipulates the map once available.
 * This callback is triggered when the map is ready to be used.
 * This is where we can add markers or lines, add listeners or move the camera. In this case,
 * we just add a marker near Sydney, Australia.
 * If Google Play services is not installed on the device, the user will be prompted to install
 * it inside the SupportMapFragment. This method will only be triggered once the user has
 * installed Google Play services and returned to the app.
 */
@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    // Add a marker in Sydney and move the camera
    mMap.setMyLocationEnabled(true);

    LatLng loc = new LatLng(lat, lng);
    mMap.addMarker(new MarkerOptions().position(loc).title("New Marker"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(loc));
}

@Override
public void onConnected(Bundle bundle) {
    mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
            mGoogleApiClient);
    if (mLastLocation != null) {
        lat = mLastLocation.getLatitude();
        lng = mLastLocation.getLongitude();
    }
}

@Override
protected void onStart() {
    super.onStart();

    mGoogleApiClient.connect();
}

这段代码的问题是我lat, lng在onMapReady函数已经完成执行后得到了.我认为纠正这种情况的方法之一是创建一个AsyncTask以确保在地图之前检索位置数据.但是,我试图以一种不会使用的方式实现它AsyncTask.

Answer 1

只是移动,从创建标记的代码onMapReady()来onConnected(),和移动电话buildGoogleApiClient(),从电话onCreate()到onMapReady():

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_map);
    //buildGoogleApiClient();

    // Obtain the SupportMapFragment and get notified when the map is ready to be used.
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);

}


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

    // Add a marker in Sydney and move the camera
    mMap.setMyLocationEnabled(true);

    //add this here:
    buildGoogleApiClient();

    //LatLng loc = new LatLng(lat, lng);
    //mMap.addMarker(new MarkerOptions().position(loc).title("New Marker"));
    //mMap.moveCamera(CameraUpdateFactory.newLatLng(loc));
}

@Override
public void onConnected(Bundle bundle) {
    mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
            mGoogleApiClient);
    if (mLastLocation != null) {
        lat = mLastLocation.getLatitude();
        lng = mLastLocation.getLongitude();

        LatLng loc = new LatLng(lat, lng);
        mMap.addMarker(new MarkerOptions().position(loc).title("New Marker"));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(loc));
    }
}

虽然,请注意,您将经常从调用中获取null getLastLocation().您可以使用requestLocationUpdates(),并removeLocationUpdates()在第一个位置进入时拨打电话.看看这个答案,它有一个完整的例子,说明您正在尝试做什么.