java - android经纬度返回0.0

Question

我正在使用 NET_PROVIDER 检查当前的经度和纬度，并将它们打印为应用程序中的 toast 消息。但是，设置权限和连接网络后，经度和纬度总是返回0.0

我为解决此问题所做的工作:

1. 设置权限
2. 在 onLocationChanged 方法中保存了之前的位置
3. 我在模拟器和真实设备 (api22) 中都试过了。但都返回 0 给我。

这是我的代码。

TrackGps.java:

import android.Manifest;
import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;

import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;


import android.support.v4.app.ActivityCompat;
import android.util.Log;
import android.widget.Toast;

/**
 * Created by Hannah Liao on 5/7/2017
 */

public class TrackGps extends Service implements LocationListener {

    private final Context mContext;

    boolean checkNetwork = false;

    boolean canGetLocation = false;
    LocationListener locationListener;
    Location loc ;
    double latitude;
    double longitude;


    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10;


    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1;
    protected LocationManager locationManager;

    public TrackGps(Context mContext) {
        this.mContext = mContext;
        getLocation();
    }

    private Location getLocation() {

        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(LOCATION_SERVICE);

            checkNetwork = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if(!checkNetwork) {
                Toast.makeText(mContext, "No Service Provider Available", Toast.LENGTH_SHORT).show();
            } else {
                this.canGetLocation = true;
                // First get location from Network Provider
                if (checkNetwork) {
                    Toast.makeText(mContext, "Network", Toast.LENGTH_SHORT).show();

                    try {
                        locationManager.requestLocationUpdates(
                                LocationManager.NETWORK_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                        Log.d("Network", "Network");

                        if (locationManager != null) {
                            loc = locationManager
                                    .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                            this.onLocationChanged(loc);
                        }

                        if (loc != null) {
                            latitude = loc.getLatitude();
                            longitude = loc.getLongitude();
                        }
                    } catch (SecurityException e) {

                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            // otherwise just use network
           /*if (checkGPS) {
                Toast.makeText(mContext, "GPS", Toast.LENGTH_SHORT).show();
                if (loc == null) {
                    try {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, locationListener);
                        Log.d("GPS Enabled", "GPS Enabled");
                        if (locationManager != null) {
                            loc = locationManager
                                    .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                            if (loc != null) {
                                latitude = loc.getLatitude();
                                longitude = loc.getLongitude();
                            }
                        }
                    } catch (SecurityException e) {

                    }
                }
            }*/

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

        return loc;
    }

    public double getLongitude() {
        if (loc != null) {
            longitude = loc.getLongitude();
        }
        return longitude;
    }

    public double getLatitude() {
        if (loc != null) {
            latitude = loc.getLatitude();
        }
        return latitude;
    }

    public boolean canGetLocation() {
        return this.canGetLocation;
    }

    public void showSettingsAlert() {
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);


        alertDialog.setTitle("GPS Not Enabled");

        alertDialog.setMessage("Do you wants to turn On GPS");


        alertDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });


        alertDialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });


        alertDialog.show();
    }



    public void stopUsingGPS() {
        if (locationManager != null) {

            locationManager.removeUpdates(TrackGps.this);
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onLocationChanged(Location location) {
            this.loc = location;
            getLocation();
            getLongitude();
            getLatitude();
    }

    @Override
    public void onStatusChanged(String s, int i, Bundle bundle) {

    }

    @Override
    public void onProviderEnabled(String s) {

    }

    @Override
    public void onProviderDisabled(String s) {

    }

MainActivity.java

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button b_get;
    private TrackGps gps;
    double longitude;
    double latitude;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        b_get = (Button)findViewById(R.id.get);
        b_get.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                gps = new TrackGps(MainActivity.this);

                if(gps.canGetLocation()){


                    longitude = gps.getLongitude();
                    latitude = gps .getLatitude();

                        Toast.makeText(getApplicationContext(),"Longitude:"+String.valueOf(longitude)+"\nLatitude:"+Double.toString(latitude),Toast.LENGTH_SHORT).show();
                }
                else
                {

                    gps.showSettingsAlert();
                }

            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        gps.stopUsingGPS();
    }
}

list :

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.map.hannah.location3">

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-feature android:name="android.hardware.location.gps" />
    <application


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

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <service android:name=".TrackGps" android:enabled="true" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

gradle:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.3"
    defaultConfig {
        applicationId "com.map.hannah.location3"
        minSdkVersion 17
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.3.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
}

Answer 1

 For Api marshmallow and above use run time permission as:
 if (ContextCompat.checkSelfPermission(this, 
 Manifest.permission.ACCESS_FINE_LOCATION)
        == PackageManager.PERMISSION_GRANTED) {
 // do your work
 } else {
 //  request permission.
        ActivityCompat.requestPermissions(this, new String[]
 {
 Manifest.permission.ACCESS_FINE_LOCATION}, MY_LOCATION_REQUEST_CODE);
 }

 public void onRequestPermissionsResult(int requestCode, String[] 
 permissions, int[] grantResults) {
 if (requestCode == MY_LOCATION_REQUEST_CODE) {
 if (permissions.length == 1 &&
  permissions[0] == Manifest.permission.ACCESS_FINE_LOCATION &&
  grantResults[0] == PackageManager.PERMISSION_GRANTED) {
/// granted do your work
 }  else {
  // Permission was denied. Display an error message.
  }
 }