Android应用程式只能在模拟器中使用

Question

I have a basic android app that gets current location and time of last fix. It is divided into 3 tabs (fragments). First 2 works good on emulator and also on phone but when I try to switch to 3rd one on phone the app crashes. Here is a part of code of tab3 fragment but I think this isnt causing the problem:

public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    TextView Latitude = (TextView) getView().findViewById(R.id.txtLat);
    TextView Longitude = (TextView) getView().findViewById(R.id.txtLong);
    TextView Status = (TextView) getView().findViewById(R.id.txtStatus);
    gpsHandler gpsHandler = new gpsHandler((LocationManager) getActivity().getSystemService(Context.LOCATION_SERVICE), Longitude ,Latitude, Status);
    gpsHandler.lastFix();
}

and here is the code of gpsHandler class (I think the problem is somewhere here but I dont know where):

package hzs.sk.hzs;

import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.TextView;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.List;
import java.util.TimeZone;

/**
 * Created by Daniel on 19.10.2014.
 */
public class gpsHandler implements LocationListener {
    protected LocationManager locationManager;
    protected LocationListener locationListener;
    TextView TWlongitude, TWlatitude, TWstatus;
    public gpsHandler(LocationManager locationManager, TextView TWlongitude, TextView TWlatitude, TextView TWstatus){
        this.locationManager = locationManager;
        this.TWlongitude = TWlongitude;
        this.TWlatitude = TWlatitude;
        this.TWstatus = TWstatus;
        //GPS provider, minRefreshTime, minRefreshDistance, locationListener
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000, 5, this);
    }
    public void lastFix(){
        List<String> providers = locationManager.getAllProviders();
        String latestFixProvider  = new String();
        long time = 0;
        for(int i = 0; i < providers.size(); i++){
            Location lastKnown = locationManager.getLastKnownLocation(providers.get(i));
            if(lastKnown != null && lastKnown.getTime() > time){
                latestFixProvider = providers.get(i);
                time = lastKnown.getTime();
            }
        }
        String lastFixDate = getDate(time, "dd/MM/yyyy hh:mm:ss.SSS");

        TWlongitude.setText(Double.toString(locationManager.getLastKnownLocation(latestFixProvider).getLongitude()));
        TWlatitude.setText(Double.toString(locationManager.getLastKnownLocation(latestFixProvider).getLatitude()));
        TWstatus.setText(lastFixDate);
    }
    private static String getDate(long milliSeconds, String dateFormat)
    {
        // Create a DateFormatter object for displaying date in specified format.
        SimpleDateFormat formatter = new SimpleDateFormat(dateFormat);

        // Create a calendar object that will convert the date and time value in milliseconds to date.
        Calendar calendar = Calendar.getInstance();
        TimeZone tz = calendar.getTimeZone();
        formatter.setTimeZone(tz);
        calendar.setTimeInMillis(milliSeconds);
        return formatter.format(calendar.getTime());
    }
    @Override
    public void onLocationChanged(Location location) {
        TWlongitude.setText(Double.toString(location.getLongitude()));
        TWlatitude.setText(Double.toString(location.getLatitude()));
        long time= System.currentTimeMillis();
        TWstatus.setText(getDate(time, "dd/MM/yyyy hh:mm:ss.SSS"));
    }

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

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
}

here is logcat:

10-20 08:11:08.007 I/ActivityManager(2044): Force stopping package hzs.sk.hzs uid=10036
10-20 08:11:23.292 E/AndroidRuntime(25044):     at hzs.sk.hzs.gpsHandler.lastFix(gpsHandler.java:42)
10-20 08:11:23.292 E/AndroidRuntime(25044):     at hzs.sk.hzs.tab3.onActivityCreated(tab3.java:55)
10-20 08:11:31.349 E/ActivityManager(2044): App already has crash dialog: ProcessRecord{44487f30 25044:hzs.sk.hzs/u0a36}
10-20 08:11:34.773 I/ActivityManager(2044): Process hzs.sk.hzs (pid 25044) has died.
10-20 08:12:17.065 I/ConfigFetchService(21453): PackageReceiver: Intent { act=android.intent.action.PACKAGE_ADDED dat=package:hzs.sk.hzs flg=0x8000010 cmp=com.google.android.gms/.config.ConfigFetchService$PackageReceiver (has extras) }
10-20 08:12:17.075 I/ConfigFetchService(21453): onStartCommand Intent { act=android.intent.action.PACKAGE_ADDED dat=package:hzs.sk.hzs cmp=com.google.android.gms/.config.ConfigFetchService (has extras) }
10-20 08:12:17.616 D/PackageBroadcastService(21453): Received broadcast action=android.intent.action.PACKAGE_ADDED and uri=hzs.sk.hzs
10-20 08:13:37.455 E/AndroidRuntime(26655):     at hzs.sk.hzs.gpsHandler.lastFix(gpsHandler.java:42)
10-20 08:13:37.455 E/AndroidRuntime(26655):     at hzs.sk.hzs.tab3.onActivityCreated(tab3.java:55)
10-20 08:13:37.455 E/AndroidRuntime(26655):     at hzs.sk.hzs.MainActivity.onTabSelected(MainActivity.java:103)
10-20 08:13:44.993 E/ActivityManager(2044): App already has crash dialog: ProcessRecord{44658fc0 26655:hzs.sk.hzs/u0a36}
10-20 08:13:46.835 I/ActivityManager(2044): Process hzs.sk.hzs (pid 26655) has died.

It looks like it has some problems with setting text of textview. Thanks in forward for your help.

Answer 1

As you see in logcat, the error happens in line 42:

TWlongitude.setText(Double.toString(locationManager.getLastKnownLocation(latestFixProvider).getLongitude()));

So there are 2 possible exceptions that can occur in this line:

• NullpointerException because locationManager.getLastKnownLocation(latestFixProvider) returns null. You should catch this

• the locationManager.getLastKnownLocation() call could be the reason for the force close, because you specified an invalid parameter.

Most likely: See line 31, bad style: String latestFixProvider = new String();

If the for-loop in line 33 doesn't find a latestFixProvider, you will call the method with an empty String. This could be the reason for the force close.

Better:

    String latestFixProvider  = null;
    long time = 0;
    for(int i = 0; i < providers.size(); i++){
        Location lastKnown = locationManager.getLastKnownLocation(providers.get(i));
        if(lastKnown != null && lastKnown.getTime() > time){
            latestFixProvider = providers.get(i);
            time = lastKnown.getTime();
        }
    }
    String lastFixDate = getDate(time, "dd/MM/yyyy hh:mm:ss.SSS");

    if (latestFixProvider != null) {
        Location loc = locationManager.getLastKnownLocation(latestFixProvider);
        if (loc != null) {
           TWlongitude.setText(Double.toString(loc.getLongitude()));
           TWlatitude.setText(Double.toString(loc.getLatitude()));
        }
    }

PS: instead of String foobar = new String(); you should use String foobar = "";