android - intentservice详解 - 启动intentservice




从IntentService获取位置时,在死线程上向Handler发送消息 (2)

即使手机没有醒来,我的应用也需要定期修复定位。 为此,我使用IntentService和Commonsware慷慨提供的模式。 https://github.com/commonsguy/cwac-wakeful

为了获得位置修复,我依赖于一个名为Fedor的成员提供的以下代码。 在Android上获取用户当前位置的最简单,最强大的方法是什么? 。 我稍微修改它以返回null而不是获取最后的已知位置

它们在没有组合时都能很好地工作:我可以在一个Activity中从Fedor的类中获得一个位置修复,我可以使用Commonsware类做一些基本的东西(比如记录一些东西)。

当我试图从Commonsware的WakefulIntentService子类获取位置修复时,会出现问题。 LocationListeners没有对locationUpdates作出反应,我得到了这些警告(我还没有得到线程,处理程序......的细微之处)。 有人可以帮我理解问题所在吗? 谢谢,祝大家新年快乐:)

12-31 14:09:33.664: W/MessageQueue(3264): Handler (android.location.LocationManager$ListenerTransport$1) {41403330} sending message to a      Handler on a dead thread
12-31 14:09:33.664: W/MessageQueue(3264): java.lang.RuntimeException: Handler (android.location.LocationManager$ListenerTransport$1) {41403330} sending message to a Handler on a dead thread
12-31 14:09:33.664: W/MessageQueue(3264): at android.os.MessageQueue.enqueueMessage(MessageQueue.java:196)
12-31 14:09:33.664: W/MessageQueue(3264): at android.os.Handler.sendMessageAtTime(Handler.java:473)
12-31 14:09:33.664: W/MessageQueue(3264): at android.os.Handler.sendMessageDelayed(Handler.java:446)
12-31 14:09:33.664: W/MessageQueue(3264): at android.os.Handler.sendMessage(Handler.java:383)
12-31 14:09:33.664: W/MessageQueue(3264): at android.location.LocationManager$ListenerTransport.onLocationChanged(LocationManager.java:193)
12-31 14:09:33.664: W/MessageQueue(3264): at android.location.ILocationListener$Stub.onTransact(ILocationListener.java:58)
12-31 14:09:33.664: W/MessageQueue(3264): at android.os.Binder.execTransact(Binder.java:338)
12-31 14:09:33.664: W/MessageQueue(3264): at dalvik.system.NativeStart.run(Native Method)

这是我的WakefulIntentService子类:

public class AppService extends WakefulIntentService {
public static final String TAG = "AppService";
public AppService() {
    super("AppService");
}

public LocationResult locationResult = new LocationResult() {
    @Override
    public void gotLocation(final Location location) {
        if (location == null)
            Log.d(TAG, "location could not be retrieved");
        else
            sendMessage(location);
    }
};

@Override
protected void doWakefulWork(Intent intent) {
    PhoneLocation myLocation;
    myLocation = new PhoneLocation();
    myLocation.getLocation(getApplicationContext(), locationResult);
}

这里有Fedor级别的副本(略有修改:不需要GPS也不需要上次知道位置)

public class PhoneLocation {
public static String TAG = "MyLocation";
Timer timer1;
LocationManager lm;
LocationResult locationResult;
boolean gps_enabled=false;
boolean network_enabled=false;

public boolean getLocation(Context context, LocationResult result)
{
    //I use LocationResult callback class to pass location value from MyLocation to user code.
    locationResult=result;
    if(lm==null) lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

    //exceptions will be thrown if provider is not permitted.
    try{gps_enabled=lm.isProviderEnabled(LocationManager.GPS_PROVIDER);}catch(Exception ex){}
    try{network_enabled=lm.isProviderEnabled(LocationManager.NETWORK_PROVIDER);}catch(Exception ex){}

    //don't start listeners if no provider is enabled
    if(!gps_enabled && !network_enabled)
        return false;

     if(network_enabled)  lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListenerNetwork);

    timer1=new Timer();
    timer1.schedule(new ReturnNullLocation(), 20000);
    return true;
}

 LocationListener locationListenerNetwork = new LocationListener() {
     public void onLocationChanged(Location location) {
        timer1.cancel();
        locationResult.gotLocation(location);
        lm.removeUpdates(this);
    }
    public void onProviderDisabled(String provider) {}
    public void onProviderEnabled(String provider) {}
    public void onStatusChanged(String provider, int status, Bundle extras) {}
};

class ReturnNullLocation extends TimerTask {
    @Override
    public void run() { 
          lm.removeUpdates(locationListenerNetwork);
          locationResult.gotLocation(null);
    }
}

public static abstract class LocationResult{
    public abstract void gotLocation(Location location);

}

}


对于像我这样的人:我遇到了与AsyncTask相关的类似问题。 据我所知,该类假定它是在UI(主)线程上初始化的。

解决方法(可能的几种方法之一)是将以下内容放在MyApplication类中:

@Override
public void onCreate() {
    // workaround for http://code.google.com/p/android/issues/detail?id=20915
    try {
        Class.forName("android.os.AsyncTask");
    } catch (ClassNotFoundException e) {}
    super.onCreate();
}

(别忘了在AndroidManifest.xml提及它:

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:name="MyApplication"
    >


您无法安全地从IntentService注册侦听IntentService ,因为只要onHandleIntent() (aka, doWakefulWork() )完成, doWakefulWork()就会消失。 相反,您将需要使用常规服务,以及超时等处理细节(例如,用户在地下室并且无法获得GPS信号)。