Java/Android 重写方法

Question

我正在练习 Android 实习，我已经能够编写一个类来处理地理定位，以试图找到最佳位置，并且每当调用 onLocationChanged 时我都会不断更新内容。

现在我需要使用我的位置将标记放在 GoogleMaps 上，我显然可以从处理地理定位的类中更改 onLocationChanged 方法，但我希望提取需要在类外执行的操作，因为将来我可能会需要我当前的位置来执行很多不同的事情。

package com.example.soueuls.swipe;

import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;

public class GeoLocation {
    private final Context context;
    private final LocationManager locationManager;
    private Location currentLocation;
    private int updateLimit = 0;
    private long timeLimit = 0;

    public GeoLocation(Context context) {
        this.context = context;
        this.locationManager = (LocationManager)this.context.getSystemService(Context.LOCATION_SERVICE);
        this.currentLocation = this.locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if (this.currentLocation == null) {
            this.currentLocation = this.locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
        }
    }

    private LocationListener locationListener = new LocationListener() {

        @Override
        public void onLocationChanged(Location newLocation) {
            if (isBetterLocation(GeoLocation.this.currentLocation, newLocation)) {
                GeoLocation.this.currentLocation = newLocation;
            }

            if (--GeoLocation.this.updateLimit == 0) {
                GeoLocation.this.stopLocationUpdate();
            } else if (System.currentTimeMillis() / 1000 > GeoLocation.this.timeLimit) {
                GeoLocation.this.stopLocationUpdate();
            }
        }

        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {

        }

        @Override
        public void onProviderEnabled(String provider) {

        }

        @Override
        public void onProviderDisabled(String provider) {

        }
    };

    private boolean isBetterLocation(Location currentLocation, Location newLocation) {
        if (currentLocation == null) {
            return true;
        }

        int twoMinutes = 1000 * 60 * 2;

        long timeDelta = newLocation.getTime() - currentLocation.getTime();
        int accuracyDelta = (int) (newLocation.getAccuracy() - currentLocation.getAccuracy());

        boolean isSignificantlyNewer = timeDelta > twoMinutes;
        boolean isSignificantlyOlder = timeDelta < -twoMinutes;
        boolean isNewer = timeDelta > 0;

        if (isSignificantlyNewer) {
            return true;
        } else if (isSignificantlyOlder) {
            return false;
        }

        boolean isMoreAccurate = accuracyDelta < 0;
        boolean isLessAccurate = accuracyDelta > 0;
        boolean isSignificantlyLessAccurate = accuracyDelta > 200;
        boolean isFromSameProvider = isSameProvider(currentLocation.getProvider(), newLocation.getProvider());

        if (isMoreAccurate) {
            return true;
        } else if (isNewer && !isLessAccurate) {
            return true;
        } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
            return true;
        } else {
            return false;
        }
    }

    private boolean isSameProvider(String provider1, String provider2) {
        if (provider1 == null) {
            return provider2 == null;
        }
        return provider1.equals(provider2);
    }

    public void setUpdateLimit(int limit) {
        this.updateLimit = limit;
    }

    public void setTimeLimit(long limit) {
        this.timeLimit = System.currentTimeMillis() / 1000 + limit;
    }

    public void setLocationUpdate(String provider, int minTimeInterval, int minDistance) {
        this.locationManager.requestLocationUpdates(provider, minTimeInterval, minDistance, this.locationListener);
    }

    public void stopLocationUpdate() {
        this.locationManager.removeUpdates(this.locationListener);
    }

    public Location getCurrentLocation() {
        return this.currentLocation;
    }
}

这是 GeoLocation 类，每次调用 onLocationChanged 时我仍然需要更新 this.currentLocation。

但我希望能够检测到何时调用 onLocationChanged 以在此类之外的 Activity 内执行更新。

我该怎么做？

编辑:在 Activity 的 onResume 方法中，我正在尝试监听

GeolocationListener locationListener = new GeolocationAdapter() {
            @Override
            public void onLocationChanged(Location newLocation) {
                System.out.println("OHOHOH");
                displayWeatherInformation(weatherCache, geoLocation.getCurrentLocation());
            }
        };

Answer 1

使用监听器

将接口(interface)添加到 Geolocation 类

public class GeoLocation {

添加您的听众

   // listeners
   private List<LocationListener> listeners = new ArrayList<LocationListener>();
   public void addListener(LocationListener l){
      listeners.add(l);
   }
   public void removeListener(LocationListener l){
      listeners.remove(l);
   }

然后在您放置的private LocationListener locationListener = new LocationListener()内

    @Override
    public void onLocationChanged(Location newLocation) {
        if (isBetterLocation(GeoLocation.this.currentLocation, newLocation)) {
            GeoLocation.this.currentLocation = newLocation;
            for(LocationListener l:listeners){
                l.onLocationChanged(newLocation);
            }
        }
   ... the rest of the code

然后任何类(class)都可以注册以接收有关您的地理位置类(class)的更新

编辑:

像这样声明您的 Activity :

public class MyActivity extends Activity implements LocationListener{

    @Override
    public void onResume(){
        geoLocation.addListener(this);
    }

    @Override     
    public void onPause(){
        geoLocation.removeListener(this);
    }

    @Override
    public void onLocationChanged(Location newLocation) {

    }

}