打开我的应用程序时，Android Studio Google Maps如何将相机重定向到我的当前位置

Question

打开我的应用程序时，相机动画无法正常工作，无法定向到我的位置，并且它也未添加标记

 public class MapsActivity extends FragmentActivity {

private GoogleMap mMap; // Might be null if Google Play services APK is not available.



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

}


@Override
protected void onResume() {
    super.onResume();
    setUpMapIfNeeded();
}

在这里它不会将我的相机对准我的当前位置。 当我打开应用程序时，它开始于地图中心而不是我的位置

private void setUpMapIfNeeded() {
    // Do a null check to confirm that we have not already instantiated the map.
    if (mMap == null) {
        // Try to obtain the map from the SupportMapFragment.
        mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                .getMap();
        mMap.setMyLocationEnabled(true);
        // Check if we were successful in obtaining the map.
        if (mMap != null) {
            setUpMapIfNeeded();

        }
    }

}

private void setUpMap() {
    mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker").snippet("Snippet"));
    mMap.setMyLocationEnabled(true);
    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    String provider = locationManager.getBestProvider(criteria, true);
    Location location = locationManager.getLastKnownLocation(provider);

    if (location != null) {

        LatLng target = new LatLng(location.getLatitude(), location.getLongitude());
        CameraPosition position = this.mMap.getCameraPosition();

        CameraPosition.Builder builder = new CameraPosition.Builder();
        builder.zoom(15);
        builder.target(target);

        this.mMap.animateCamera(CameraUpdateFactory.newCameraPosition(builder.build()));
        mMap.addMarker(new MarkerOptions().position(new LatLng(location.getLatitude(), location.getLongitude())).title("You are here!").snippet("Consider yourself located"));
    }
}
}

Answer 1

您有一些巨大的超级基本错误：

仅当baground中的活动进入前台时才调用first onResume 。 将setUpMapIfNeeded()放入onCreate中。

在最后一个if语句中，函数setUpMapIfNeeded()中的第二个函数不是放置setUpMap()而是放置setUpMapIfNeeded()改变它，它应该可以工作。

public class MapsActivity extends  FragmentActivity {

private GoogleMap mMap; // Might be null if Google Play services APK is not available.

这是修改后的代码：

第1部分

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

}


@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
}

第2部分

private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
    // Try to obtain the map from the SupportMapFragment.
    mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
            .getMap();
   mMap.setMyLocationEnabled(true);
    // Check if we were successful in obtaining the map.
    if (mMap != null) {
        setUpMap();

    }
    }

}

private void setUpMap() {
mMap.addMarker(new.MarkerOptions().position(new LatLng(0, 0)).title("Marker").snippet("Snippet"));
mMap.setMyLocationEnabled(true);
LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
Criteria criteria = new Criteria();
String provider = locationManager.getBestProvider(criteria, true);
Location location = locationManager.getLastKnownLocation(provider);

if (location != null) {

    LatLng target = new LatLng(location.getLatitude(), location.getLongitude());
    CameraPosition position = this.mMap.getCameraPosition();

    CameraPosition.Builder builder = new CameraPosition.Builder();
    builder.zoom(15);
    builder.target(target);

    this.mMap.animateCamera(CameraUpdateFactory.newCameraPosition(builder.build()));
    mMap.addMarker(new MarkerOptions().position(new LatLng(location.getLatitude(), location.getLongitude())).title("You are here!").snippet("Consider yourself located"));
}
}
}

Answer 2

private void setUpMapIfNeeded() {
    if (mMap == null) {
        mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
        if (mMap != null) {
            setUpMap();
        }
    }
}

private void setUpMap() {
    mMap.setMyLocationEnabled(true);
    mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
            @Override
            public void onMyLocationChange(Location location) {
                LatLng l = new LatLng(location.getLatitude(), location.getLongitude());
                mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(l, mMap.getCameraPosition().zoom));
            }
        });
}

只需更改这两种方法