android - 如何避免在每个活动中获取位置和数据的重复代码？

Question

我有 2 个活动（一个带有 listview，1 个带有 mapview）。这两个活动都有刷新按钮，用于获取位置，然后从 Internet 下载一些数据。我在这两个活动中都有重复的位置和数据获取代码。

如何将这段代码放在一个地方并能够从任何活动中调用它？我可以把它放在应用程序对象中吗？

Answer 1

创建一个类，例如 GPSGetter，它不断从 GPS 获取坐标，然后在主活动的 onCreate 方法中通过该类的 createInstance() 方法进行实例化。然后在该类中定义一个 getInstance() 方法。

例如

class GPSGetter {

GPSGetter obj;


//constructor
private GPSGetter(){

//do some stuff here 
}

public GPSGetter createInstance(){
if(obj == null)
obj = new GPSGetter();
}

public getGPSGetter(){

return obj;

}

通过这种方式，您可以从两个 Activity 类中调用 getInstance 而无需担心重复，这也将确保只创建一个类对象。

Answer 2

    package com.;


    import android.content.Context;
    import android.location.Location;
    import android.location.LocationListener;
    import android.location.LocationManager;
    import android.os.Bundle;
    import android.os.Handler;
    import android.os.Looper;
    import android.os.Message;
    import android.util.Log;


    /**
     * This class has the missionto get the current location, save it and manage it.
     * 
     * @author Aracem
     *
     */
    public class GetCurrentLocation implements Runnable {

    private Context mContext;
    private static GetCurrentLocation gcl = null;
    public static Location currentLocation = null;  
    private LocationManager mLocationManager;
    private MyLocationListener mLocationListener;
    private static Thread thread;
    private Handler handler = null;
    private static Location location = null;




    public static Location getLocation() {
        return location;
    }


    /**
     * @param Context de la aplicacion
     * 
     * Metodo que se encarga de crear la instancia de la clase de geolocalizacion
     */
    private synchronized static void createInstance(Context c) {
        if (gcl == null) gcl = new GetCurrentLocation(c);
    }//end method


    /**
     * @param Context de la aplicacion
     * @param han Handler with the handler that we want to call when the location
     * will found.
     * 
     * Metodo que se encarga de crear la instancia de la clase de geolocalizacion
     */
    private synchronized static void createInstance(Context c, Handler han) {
        if (gcl == null) gcl = new GetCurrentLocation(c, han);
    }//end method


    /**
     * @param Context context de la aplicacion
     */
    public static GetCurrentLocation getInstance(Context c) {
        if (gcl == null) createInstance(c);

        //if (currentLocation == null) getCurrentLocation();

        return gcl;
    }//end methodd

    /**
     * @param Context context de la aplicacion
     * @param han Handler with the handler that we want to call when the location
     * will found.
     */
    public static GetCurrentLocation getInstance(Context c, Handler han) {
        if (gcl == null) createInstance(c,han);

        //if (currentLocation == null) getCurrentLocation();

        return gcl;
    }//end methodd


    protected GetCurrentLocation(Context c){
        mContext = c;
        thread = new Thread(this,"Get Location");
        thread.start();

    }

    protected GetCurrentLocation(Context c, Handler han){
        mContext = c;
        handler = han;

        thread = new Thread(this,"Get Location");
        thread.start();

    }

    /**
     * Use this method to put a handler for the listener
     * this handler is activated when location is found.
     * @param han handle that you want to activate
     * when location is found.
     */
    public synchronized void setHandler(Handler han){
        handler = han;
    }

    //Location

    public static void setCurrentLocation(Location loc) {
        currentLocation = loc;
    }


    @Override
    public void run() {

        try{

            mLocationManager = (LocationManager)mContext.getSystemService(Context.LOCATION_SERVICE);

            if (mLocationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
                Looper.prepare();
                Log.i("DEBUG","Location obtain with GPS.");
                mLocationListener = new MyLocationListener();
                mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, mLocationListener);
                Looper.loop(); 
                Looper.myLooper().quit();  

            } else if (mLocationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)){
                Looper.prepare();
                Log.i("DEBUG","Location obtain with network.");
                mLocationListener = new MyLocationListener();
                mLocationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, mLocationListener);
                Looper.loop();
                Looper.myLooper().quit();
            }else{
                Looper.prepare();;
                if (handler != null) handler.sendEmptyMessage(0);

                Log.i("DEBUG","Location cant be find.");
                Looper.loop();
                Looper.myLooper().quit();
            }   
        }
        catch(SecurityException e)
        {
            Log.i("DEBUG", e.getMessage() + " Continue with network_provider");

            if (mLocationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)){
                Looper.prepare();
                Log.i("DEBUG","Location obtain with network.");
                mLocationListener = new MyLocationListener();
                mLocationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, mLocationListener);
                Looper.loop();
                Looper.myLooper().quit();
            }else{
                Looper.prepare();;
                if (handler != null) handler.sendEmptyMessage(0);

                Log.i("DEBUG","Location cant be find.");
                Looper.loop();
                Looper.myLooper().quit();
            }   
        }
    }


    /**
     * @author marcos
     * 
     * Clase de apoyo que extiende de LocationListener
     * que se utiliza para gestionar los cambios
     * en la recepción GPS tales como una nueva localizacion
     * o un cambio de Status
     */
    private class MyLocationListener implements LocationListener 
    {
        @Override
        public void onLocationChanged(Location loc) {
            if (loc != null) {
                setCurrentLocation(loc);
                //           handler.sendEmptyMessage(0);
                Log.i("DEBUG","Location: " + loc.toString());

                //Stop looking for locations
                mLocationManager.removeUpdates(mLocationListener);

                //If handler isnt null, call it 
                if (handler != null){
                    Message msg = new Message();
                    msg.obj = loc;
                    if (handler != null)
                        handler.sendMessage(msg);
                    location = loc;
                }
            }


        }

        @Override
        public void onProviderDisabled(String provider) {
        }

        @Override
        public void onProviderEnabled(String provider) {
            // TODO Auto-generated method stub
        }

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

}