Question

我正在尝试放大用户在地图上的当前位置。该位置绝对可以访问，因为它在地图上显示为蓝点

但是，GoogleMap.getMyLocation(）返回null。

为了启用位置数据，我遵循Google documentation并在清单中添加了适当的权限，此外还添加了必要的API密钥。

如果它对MyActivity.java有用：

package com.example.beckah.helloworld;

import android.support.v4.app.FragmentActivity;
import android.os.Bundle;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import android.location.Location;
import android.location.LocationListener;
import android.content.Context;
import android.location.LocationManager;

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {

    private GoogleMap mMap;
    private LatLng location;
    Location mLocation;
    LocationManager locationManager;

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


    /**
     * 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;

        mMap.setMyLocationEnabled(true);
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        mLocation = googleMap.getMyLocation();


        if(mLocation != null) location = new LatLng(mLocation.getLatitude(), mLocation.getLongitude());
        else location = new LatLng(31, 31);

        mMap.addMarker(new MarkerOptions().position(location).title("Marker in Sydney"));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(location));


    }
}

我的清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.beckah.helloworld">

    <!--
         The ACCESS_COARSE/FINE_LOCATION permissions are not required to use
         Google Maps Android API v2, but you must specify either coarse or fine
         location permissions for the 'MyLocation' functionality. 
    -->
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_GPS" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <permission android:name="com.example.beckah.helloworld.permission.MAPS_RECEIVE"
        android:protectionLevel="signature"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <!--
             The API key for Google Maps-based APIs is defined as a string resource.
             (See the file "res/values/google_maps_api.xml").
             Note that the API key is linked to the encryption key used to sign the APK.
             You need a different API key for each encryption key, including the release key that is used to
             sign the APK for publishing.
             You can define the keys for the debug and release targets in src/debug/ and src/release/. 
        -->
        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_maps_key" />

        <activity
            android:name=".MapsActivity"
            android:label="@string/title_activity_maps">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

如何确保GoogleMap.getMyLocation（）不返回null并且能够获取位置数据？

Answer 1

以下代码应适用于用户的最后已知位置

LocationManager service = (LocationManager) 

getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria();
String provider = service.getBestProvider(criteria, false);
Location location = service.getLastKnownLocation(provider);
LatLng userLocation = new LatLng(location.getLatitude(),location.getLongitude());

Answer 2

尝试将此方法添加到代码中以查找上一个已知位置：

private Location getMyLocation() {
    LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
    Location myLocation = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    if (myLocation == null) {
        Criteria criteria = new Criteria();
        criteria.setAccuracy(Criteria.ACCURACY_COARSE);
        String provider = lm.getBestProvider(criteria, true);
        myLocation = lm.getLastKnownLocation(provider);
    }
    return myLocation;
}

然后替换

mLocation = googleMap.getMyLocation();

与

mLocation = getMyLocation();

GoogleMap.getMyLocation（）返回null

2 个答案: