Question

我发送IntentService来自MainActivity的电话到MapClass的班级。 MapClass有一个名为MapClassInner的内部类，它计算用户的当前坐标。但是，外部类包含onHandleIntent方法，该方法最终将使用广播将坐标发送回MainActivity。我的问题是 - 如何访问MapClassInner的内部变量？我很确定答案很简单，但我已经连续工作了2个小时，所以我的想法变得有点不对劲。

这里是代码（MapClass.java）：

import android.app.IntentService;
import android.content.Intent;
import android.location.Location;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.model.LatLng;
import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;
import meetup.be2015.gcm_meetup.MainActivity.MyLocationReceiver;


public class MapClass extends IntentService {
    public static final String REQUEST_STRING = "myRequest";
    public static final String RESPONSE_LAT = "lat";
    public static final String RESPONSE_LNG = "lng";
    public GoogleMap map;

public MapClass() {
    super("MapClass");
}

private class MapClassInner extends AppCompatActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {

    private GoogleApiClient mGoogleApiClient;
    private GoogleMap mgoogleMap;
    private LatLng latLng;

    private GoogleApiClient client;

    public MapClassInner(GoogleMap map){
        this.mgoogleMap = map;
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        Log.d("ON_MAP_READY","In OnMapReady");
        mgoogleMap = googleMap;
        mgoogleMap.setMyLocationEnabled(true);      //Sets location to current position
        buildGoogleApiClient();
        mGoogleApiClient.connect();
    } 

    protected synchronized void buildGoogleApiClient() {
        Log.d("BUILD", "In buildClient()");
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }

    @Override
    public void onConnected(Bundle bundle) {
        Log.d("ON_CONNECTED","In onConnected()");
        Location MLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
        if (MLastLocation != null) {
            latLng = new LatLng(MLastLocation.getLatitude(), MLastLocation.getLongitude());


        } else {
            Log.d("onConnected", "Value of LatLng is NULL");
            latLng = new LatLng(0, 0);   
        }
    }

    public LatLng getLatLng(){
        return this.latLng;
    }

    @Override
    public void onConnectionSuspended(int i) {
        //Notify
        Log.d("ConnectionSuspended", "Connection Suspended. Status: " + i);
        mgoogleMap.clear();
        mGoogleApiClient.disconnect();
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        //Notify
        Log.d("ConnectionFailed", "Connection Failed. Status: " + connectionResult.toString());
        mgoogleMap.clear();
        mGoogleApiClient.disconnect();
    }
}



@Override
protected void onHandleIntent(Intent intent) {
    //Instantiating the inner class
    MapClassInner inner = new MapClassInner(map);

    //Trying to access the inner LatLng variable
    LatLng coords = inner.getLatLng();

    //Gives me a NullPointerException

    //Converting them to String values
    String lat = String.valueOf(coords.latitude);
    String lng = String.valueOf(coords.longitude);

    //Sending broadcast Intent
    Intent broadcastIntent = new Intent();
    broadcastIntent.setAction(MyLocationReceiver.PROCESS_RESPONSE);
    broadcastIntent.addCategory(Intent.CATEGORY_DEFAULT);
    broadcastIntent.putExtra(RESPONSE_LAT, lat);
    broadcastIntent.putExtra(RESPONSE_LNG, lng);
    sendBroadcast(broadcastIntent);
}
}

如何从内部类中获取LatLng？我正在为此考虑EventBus。它会起作用吗？是的，请对我有点容易;我对Android＆amp; amp; Java的。

Answer 1

我在所有代码中简化此操作所做的是创建一个静态的'AppData.java'类，并且可以从我的包中的任何类访问。然后我把这样的数据放在那里。

public class AppData
{

    private static final AppData appData = new AppData();   // Make a static instance so it is not re-inited.

    // My data
    public Location lastKnownLocation;

    /**
     * Method to return the static instance of the AppData.
     *
     * @return An AppData object that is static so you can get/set global data across the application.
     */
     public static AppData getInstance() {return appData;}
}

您可以添加getter和setter。我还给了我一个构造函数，它接受了一个Context，并且只从我的Main Activity调用了一次，它让我在类中实现了Preference Management，这对于我保留持久性的更复杂的数据很有帮助。

要在任何地方使用它，只需执行此操作：

AppData appData = AppData.getInstance();
appData.lastKnownLocation = <whatever your code does>

等等...

无法从内部类中检索LatLng

1 个答案: