android - 从 Android 中的 Activity 引用时，如何等待调用 onConnected() 方法以从通用类中获取 Lat,Long？

Question

我打算从一个通用类的活动中获得纬度经度。

    GPSResource gpsResource = new GPSResource(getApplicationContext());
    double lat = gpsResource.getLatitude();

这总是返回 null。我应该如何修改代码，以便它等待 onConnected() 被调用，然后将值返回给引用的活动？

这是我的通用类代码：

public class GPSResource implements GoogleApiClient.ConnectionCallbacks,
    GoogleApiClient.OnConnectionFailedListener,LocationSource.OnLocationChangedListener,LocationListener

{
    private Location location; // location
    private double latitude; // latitude
    private double longitude; // longitude
    private GoogleApiClient mGAC;
    private Context mContext;
    public static final String TAG = "GPSresource";
    private LocationRequest mLocationRequest;


public GPSResource(Context c)
    {
        mContext = c;
        try
        {
            buildGoogleApiClient();
        }
        catch(Exception e)
        {
            Log.d(TAG,e.toString());
        }
    }

    protected synchronized void buildGoogleApiClient()
    {
        mGAC = new GoogleApiClient.Builder(mContext)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();

        mLocationRequest = LocationRequest.create()
                .setPriority(LocationRequest.PRIORITY_LOW_POWER)
                .setInterval(10 * 1000)        // 10 seconds, in milliseconds
                .setFastestInterval(1 * 1000); // 1 second, in milliseconds

        mGAC.connect();

    }


    public double getLatitude(){

        return latitude;
    }

    /**
     * Function to get longitude
     * */
    public double getLongitude() {
        if (location != null) {
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }


    @Override
    public void onConnected(Bundle bundle) {

        Location currentLocation = LocationServices.FusedLocationApi.getLastLocation(mGAC);
        if (currentLocation == null)
        {
            LocationServices.FusedLocationApi.requestLocationUpdates(mGAC, mLocationRequest, this);
        }

        latitude = currentLocation.getLatitude();
        longitude = currentLocation.getLongitude();
    }

    @Override
    public void onConnectionSuspended(int i) {

    }


    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {

    }


private boolean checkLocServices()
{

    LocationManager manager = null;
    boolean isAvailable = false;

    try
    {
        manager = (LocationManager)mContext.getSystemService(mContext.LOCATION_SERVICE);
        if (manager.isProviderEnabled(LocationManager.GPS_PROVIDER)||manager.isProviderEnabled(LocationManager.NETWORK_PROVIDER))
        {
            isAvailable = true;
        }
        else
        {
            isAvailable = false;
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return isAvailable;

}


@Override
public void onLocationChanged(Location location) {
    // TODO Auto-generated method stub
    if(location!=null)
    {
        latitude =  location.getLatitude();
        longitude = location.getLongitude();
    }


}

}

Answer 1

1. 创建如下界面：

   public interface GPSResourceListener {
       void onLocationUpdated(Location location);
   }
   

2. 在您的活动中实现上述接口并将其实例传递给 GPSResource 构造函数，如下所示：

   class YourActivity extends AppCompatActivity implements GPSResourceListener {
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           GPSResource gpsResource = new GPSResource(getApplicationContext(), this);
       }
   }
   

3. 在 GPSResource 类中进行以下更改：

   ...
   public GPSResource(Context c, GPSResourceListener listener) {
       mContext = c;
       mListener = listener
       ...
   }
   ...
   @Override
   public void onConnected(Bundle bundle) {
       ...
       mListener.onLocationUpdated(currentLocation);
   }
   ...
   @Override
   public void onLocationChanged(Location location) {
       if(location!=null) {
           mListener.onLocationUpdated(location);
       }
   }