如何在 GoogleApiClient onConnected() 上 return 值？

Question

我正在使用 GoogleApiClient 获取用户位置。我创建了一个单例 class 来获取用户位置。这是 class:

public class LocationUtils {

    private static LocationUtils locationUtils;
    private GoogleApiClient googleApiClient;

    public static LocationUtils getInstance() {

        if(locationUtils == null)
            locationUtils = new LocationUtils();
        return locationUtils;
    }

    private LocationUtils() {}

    public Location getLocation(Context context){

        final Location[] location = {null};

        googleApiClient = new GoogleApiClient.Builder(App.getContext())
                .addConnectionCallbacks(new GoogleApiClient.ConnectionCallbacks() {
                    @Override
                    public void onConnected(Bundle bundle) {
                        if(ContextCompat.checkSelfPermission(App.getContext(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
                            location[0] =  LocationServices.FusedLocationApi.getLastLocation(googleApiClient );

                        googleApiClient.disconnect();
                    }

                    @Override
                    public void onConnectionSuspended(int i) {

                    }
                })
                .addOnConnectionFailedListener(new GoogleApiClient.OnConnectionFailedListener() {
                    @Override
                    public void onConnectionFailed(ConnectionResult connectionResult) {

                    }
                })
                .addApi( LocationServices.API )
                .build();

        googleApiClient.connect();

        return location[0];

    }



}

我想使用 LocationUtils.getInstance().getLocation(context) 获取用户位置。当我调用 getLocation() 方法时，它应该连接到 GoogleApiClient，return 用户位置，并在每次调用时断开与 GoogleApiClient 的连接。但是当我调用该方法时，它 return 为空。主线程不等待 onConnected() 方法和 returns 位置对象为空。它如何等待 onConnect() 方法？或者我如何 return onConnected() 中的 Location 对象？

已解决 根据 Tim Castelijns 的回答

首先我创建了一个界面：

public interface LocationCallbackInterface {
    void onComplete(Location location);
}

然后在 getLocationMethod() 中使用它：

public void getLocation（上下文上下文，最终 LocationCallbackInterface 回调）{

final Location[] location = {null};

googleApiClient = new GoogleApiClient.Builder(App.getContext())
        .addConnectionCallbacks(new GoogleApiClient.ConnectionCallbacks() {
            @Override
            public void onConnected(Bundle bundle) {
                if(ContextCompat.checkSelfPermission(App.getContext(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
                    location[0] = LocationServices.FusedLocationApi.getLastLocation(googleApiClient);
                    //Toast.makeText(App.getContext(), "location came :" + location[0].toString(), Toast.LENGTH_LONG).show();
                    callback.onComplete(location[0]);
                }

                googleApiClient.disconnect();
            }

            @Override
            public void onConnectionSuspended(int i) {

            }
        })
        .addOnConnectionFailedListener(new GoogleApiClient.OnConnectionFailedListener() {
            @Override
            public void onConnectionFailed(ConnectionResult connectionResult) {

            }
        })
        .addApi( LocationServices.API )
        .build();

googleApiClient.connect();

}

然后在 activity:

中调用该方法

 LocationUtils.getInstance().getLocation(getActivity(), new LocationCallbackInterface() {

            @Override
            public void onComplete(Location location) {
                if (location != null) {
                    Toast.makeText(getActivity(), "location :" + location.toString(), Toast.LENGTH_SHORT).show();
                    initCamera(location);
                } else
                    Toast.makeText(getActivity(), "location is null", Toast.LENGTH_SHORT).show();
            }
        });

Answer 1

由于位置是异步获取的，您应该使用回调到 return 位置，否则您的 return 值将始终为 null，因为 googleApiClient 尚未完成。

像这样定义一个接口

public interface LocationCallback {
    void onComplete(Location location);
}

改变

public Location getLocation(Context context)

到

public Location getLocation(Context context, LocationCallback callback)

然后这样称呼它

LocationUtils.getLocation(context, new LocationCallback() {
    @Override
    onComplete(Location location) {
        // when this is called, you will have a location.
    }
});

如何在 GoogleApiClient onConnected() 上 return 值？

How to return value on GoogleApiClient onConnected()?

multithreading

android

google-maps

android-location

google-api-client