android - 为什么位置为空？

Question

我正在尝试使用以下代码在我的应用程序中获取我的当前位置：

    List<Address> adds = null;
    double lat;
    double lng;
    private Geocoder geocoder;
    String bestProvider;

    LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

    Criteria criteria = new Criteria();
    bestProvider = lm.getBestProvider(criteria, false);
    Location location = lm.getLastKnownLocation(bestProvider);


    if (location == null)
    {
         Toast.makeText(this,"Location Not found",Toast.LENGTH_LONG).show();
    }
    else
    {
        geocoder = new Geocoder(this);
        try 
        {
            users = geocoder.getFromLocation(location.getLatitude(), location.getLongitude(), 1);
            lat=(double)users.get(0).getLatitude();
            lng=(double)users.get(0).getLongitude();
            System.out.println(" DDD lat: " +lat+",  longitude: "+lng);

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

}

但是位置一直显示为空，因此找不到位置消息出现在应用程序上。我错过了什么吗？

清单权限：

 <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
 <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

任何帮助，将不胜感激。

Answer 1

使用此网站以正确的方式获取位置： 获取最后一个已知位置

而这个权限： 权限

如果您仍然需要我的代码：

public class MainActivity extends AppCompatActivity implements GoogleApiClient.ConnectionCallbacks, OnConnectionFailedListener {

GoogleApiClient mGoogleApiClient;
Location mLastLocation;
TextView mLatitudeText, mLongitudeText;
final int MY_PERMISSIONS_REQUEST_MAPS = 1;

protected void onStart() {
    mGoogleApiClient.connect();
    super.onStart();
}

protected void onStop() {
    mGoogleApiClient.disconnect();
    super.onStop();
}

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

    mLatitudeText = (TextView) findViewById(R.id.textView);
    mLongitudeText = (TextView) findViewById(R.id.textView2);

    if (mGoogleApiClient == null) {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }
    Log.i("permit Fine", ""+ ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION));
    Log.i("permit coarse", ""+ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION));
}

@Override
public void onConnected(@Nullable Bundle bundle) {
    if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        // TODO: Consider calling
        //    ActivityCompat#requestPermissions
        // here to request the missing permissions, and then overriding
        //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
        //                                          int[] grantResults)
        // to handle the case where the user grants the permission. See the documentation
        // for ActivityCompat#requestPermissions for more details.
        if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                Manifest.permission.READ_CONTACTS)) {

            // Show an explanation to the user *asynchronously* -- don't block
            // this thread waiting for the user's response! After the user
            // sees the explanation, try again to request the permission.
            Log.i("in","Explaination");

        } else {

            // No explanation needed, we can request the permission.

            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION},
                    MY_PERMISSIONS_REQUEST_MAPS);
            Log.i("in","Else");

            // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
            // app-defined int constant. The callback method gets the
            // result of the request.
        }
        return;
    }
    mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
            mGoogleApiClient);
    if (mLastLocation != null) {
        mLatitudeText.setText(String.valueOf(mLastLocation.getLatitude()));
        mLongitudeText.setText(String.valueOf(mLastLocation.getLongitude()));
    }
}

@Override
public void onRequestPermissionsResult(int requestCode,
                                       String permissions[], int[] grantResults) {
    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_MAPS: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! Do the
                // contacts-related task you need to do.
                Log.i("permit Fine", ""+ ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION));
                Log.i("permit coarse", ""+ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION));

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.
            }
            return;
        }

        // other 'case' lines to check for other
        // permissions this app might request
    }
}

@Override
public void onConnectionSuspended(int i) {

}

@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {

}

}