Question

我通过电子邮件点击按钮发送用户的位置。下面给出了AsyncTask的doInBackground。

@Override
protected Boolean doInBackground(String... arg0) {
    // TODO Auto-generated method stub
    boolean status = false;
    try {
    double latitude=0;
    double longitude=0;
    GPSTracker gps=new GPSTracker(MainActivity.this);
    if(gps.canGetLocation()){
        latitude=gps.getLatitude();
        longitude=gps.getLongitude();
    }
    String mapUrl= "https://www.google.co.in/maps/@"+latitude+","+longitude+",17z";
    GMailSender sender = new GMailSender(
        "myemail@gmail.com", "password",
        getApplicationContext());
    status = sender.sendMail(" Subject ", "\nLocation : "+mapUrl,"myemail@gmail.com",
         "anothermail@gmail.com");
    } catch (Exception e) {
    }
    return status;
}

但总是将Location返回为0,0

GPSTracker.java

locationManager = (LocationManager) mContext
    .getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
    .isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
    // no network provider is enabled
    } else {
    this.canGetLocation = true;
    if (isNetworkEnabled) {
        locationManager.requestLocationUpdates(
            LocationManager.NETWORK_PROVIDER,
            MIN_TIME_BW_UPDATES,
            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
        Log.d("Network", "Network Enabled");
        if (locationManager != null) {
            location = locationManager
                                .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
            if (location != null) {
                latitude = location.getLatitude();
                longitude = location.getLongitude();
            }
        }
    }
    // if GPS Enabled get lat/long using GPS Services
    if (isGPSEnabled) {
        locationManager.requestLocationUpdates(
        LocationManager.GPS_PROVIDER,                    
                        MIN_TIME_BW_UPDATES,
            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
        Log.d("GPS", "GPS Enabled");
        if (locationManager != null) {
            location = locationManager
                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
            if (location != null) {
                latitude = location.getLatitude();
                longitude = location.getLongitude();
            }
        }
    }
}

日志显示

05-16 22:01:30.449: W/System.err(12459): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
05-16 22:01:30.489: W/System.err(12459): at android.os.Handler.<init>(Handler.java:121)
05-16 22:01:30.489: W/System.err(12459): at android.location.LocationManager$ListenerTransport$1.<init>(LocationManager.java:198)
05-16 22:01:30.489: W/System.err(12459): at android.location.LocationManager$ListenerTransport.<init>(LocationManager.java:198)
05-16 22:01:30.499: W/System.err(12459): at android.location.LocationManager._requestLocationUpdates(LocationManager.java:604)
05-16 22:01:30.499: W/System.err(12459): at android.location.LocationManager.requestLocationUpdates(LocationManager.java:471)
05-16 22:01:30.509: W/System.err(12459): at com.package.utils.GPSTracker.getLocation(GPSTracker.java:65)
05-16 22:02:07.309: W/System.err(12459): at com.package.utils.GPSTracker.getLocation(GPSTracker.java:65)
05-16 22:02:07.309: W/System.err(12459): at com.package.utils.GPSTracker.<init>(GPSTracker.java:44)
05-16 22:02:07.309: W/System.err(12459):    at com.webnamaste.ulrasoundindia.MainActivity$SendMailTask.doInBackground(MainActivity.java:255)
05-16 22:02:07.319: W/System.err(12459): at com.package.ulrasoundindia.MainActivity$SendMailTask.doInBackground(MainActivity.java:1)
05-16 22:02:07.319: W/System.err(12459): at android.os.AsyncTask$2.call(AsyncTask.java:264)
05-16 22:02:07.319: W/System.err(12459): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
05-16 22:02:07.319: W/System.err(12459): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
05-16 22:02:07.319: W/System.err(12459): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
05-16 22:02:07.339: W/System.err(12459): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
05-16 22:02:07.339: W/System.err(12459): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
05-16 22:02:07.349: W/System.err(12459): at java.lang.Thread.run(Thread.java:856)

Answer 1

doInBackground的方法AsyncTask在后台线程上执行，它不是主（UI）线程。在这里你可以有3个解决方案：

将获取GPS坐标程序移至onPreExecute并将结果传递至doInBackground
在runOnUiThread致电doInBackground调用GPSTracker，这是一个难看的解决方案。
使用Looper.prepare();和Looper.loop();

看看here

Answer 2

你正在尝试在gui app中显示一些数据，在doInBackgrund（）中，解决方法是把Looper.preprare（）放在doInBackgrund（）的第一行。

protected Boolean doInBackground(String... arg0) {
// TODO Auto-generated method stub
Looper.prepare();//This code
boolean status = false;
try {
double latitude=0;
double longitude=0;
GPSTracker gps=new GPSTracker(MainActivity.this);
if(gps.canGetLocation()){
    latitude=gps.getLatitude();
    longitude=gps.getLongitude();
}
String mapUrl= "https://www.google.co.in/maps/@"+latitude+","+longitude+",17z";
GMailSender sender = new GMailSender(
    "myemail@gmail.com", "password",
    getApplicationContext());
status = sender.sendMail(" Subject ", "\nLocation : "+mapUrl,"myemail@gmail.com",
     "anothermail@gmail.com");
    } catch (Exception e) {
    }
    return status;
}

GPS位置始终将位置显示为零

2 个答案: