我正在尝试使用此代码读取我的Android设备的位置，但它在经度和纬度上返回null，虽然我添加了正确的权限，我在启用GPS时在我的Android设备上尝试了它。我试图找出问题并发现这个if语句不正确
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
我尝试将！=更改为==它也没有工作，如果我试图删除这个if语句，它会给我错误：
调用需要用户可能拒绝的权限：代码应明确检查权限是否可用（使用checkPermission）或明确处理潜在的SecurityException
这是我的GPS代码：
public class GPSPosition extends Service implements LocationListener {
private final Context mContext;
// flag for GPS status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
// flag for GPS status
boolean canGetLocation = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 100 * 60*1; // 60 seconds
// Declaring a Location Manager
protected LocationManager locationManager;
public GPSPosition(Context context) {
this.mContext = context;
getLocation();
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
// First get location from Network Provider
if (isNetworkEnabled) {
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
Log.d("enabless1", "Network");
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return location;
}
public double getLatitude(){
if(location != null){
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
* */
public double getLongitude(){
if(location != null){
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
* */
public void showSettingsAlert(){
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS is settings");
// Setting Dialog Message
alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// Setting Icon to Dialog
//alertDialog.setIcon(R.drawable.delete);
// On pressing Settings button
alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int which) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
public void onLocationChanged(Location location) {
// Toast.makeText(mContext, "log:" + Double.toString(location.getLongitude()) + ", lat: " + Double.toString(location.getLatitude()), Toast.LENGTH_LONG).show();
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
}
这里我在MainActivity中调用它们：
public class MainActivity extends AppCompatActivity {
public static String lat="10";
public static String lang="10";
GPSPosition gps;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Toast.makeText(MainActivity.this, lat + " " + lang, Toast.LENGTH_SHORT).show();
gps = new GPSPosition(MainActivity.this);
}
public void clickingBtn(View view) {
if (gps.canGetLocation()) {
double latitude = gps.getLatitude();
lat = String.valueOf(latitude);
double longitude = gps.getLongitude();
lang = String.valueOf(longitude);
Toast.makeText(MainActivity.this, latitude + " " + longitude, Toast.LENGTH_SHORT).show();
} else {
gps.showSettingsAlert();
}
}
这是Manifest中的权限：
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
答案 0 :(得分：2)
getLastKnownLocation()将返回null。而且，即使它返回null以外的其他内容，Location也可能相当陈旧。如果getLastKnownLocation()返回不可用的内容，则必须等到onLocationChanged()被调用，然后使用传递给该方法的Location。