Why does my app crash when trying to get latitude and longitude values Android

Question

I'm working on an app where users need to give their latitude and longitude location in order to post any information. The problem is when I use the following code:

/********************************************************************
* GET LATITUDE                                                      *
********************************************************************/
public String getLatitude(){
    LocationManager lm = (LocationManager) ACTIVITY.getSystemService(Context.LOCATION_SERVICE); 

    if( lm.isProviderEnabled( LocationManager.GPS_PROVIDER )){
        Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if(location != null){
            return Double.toString( location.getLatitude() );
        }
    }
    return null;
}


/********************************************************************
* GET LONGITUDE                                                     *
********************************************************************/
public String getLongitude(){
    LocationManager lm = (LocationManager) ACTIVITY.getSystemService(Context.LOCATION_SERVICE); 

    if( lm.isProviderEnabled( LocationManager.GPS_PROVIDER )){
        Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if(location != null){
            return Double.toString( location.getLongitude() );
        }
    }
    return null;
}

I get to see the following error messages:

12-06 22:31:46.791: W/dalvikvm(1173): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
12-06 22:31:46.811: E/AndroidRuntime(1173): FATAL EXCEPTION: main
12-06 22:31:46.811: E/AndroidRuntime(1173): java.lang.IllegalStateException: Could not execute method of the activity
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.view.View$1.onClick(View.java:3044)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.view.View.performClick(View.java:3511)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.view.View$PerformClick.run(View.java:14105)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.os.Handler.handleCallback(Handler.java:605)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.os.Looper.loop(Looper.java:137)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.app.ActivityThread.main(ActivityThread.java:4424)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at java.lang.reflect.Method.invokeNative(Native Method)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at java.lang.reflect.Method.invoke(Method.java:511)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at dalvik.system.NativeStart.main(Native Method)
12-06 22:31:46.811: E/AndroidRuntime(1173): Caused by: java.lang.reflect.InvocationTargetException
12-06 22:31:46.811: E/AndroidRuntime(1173):     at java.lang.reflect.Method.invokeNative(Native Method)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at java.lang.reflect.Method.invoke(Method.java:511)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at android.view.View$1.onClick(View.java:3039)
12-06 22:31:46.811: E/AndroidRuntime(1173):     ... 11 more
12-06 22:31:46.811: E/AndroidRuntime(1173): Caused by: java.lang.NullPointerException
12-06 22:31:46.811: E/AndroidRuntime(1173):     at com.example.cay.saati.Helper.getLatitude(Helper.java:100)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at com.example.cay.saati.MenuPage.prepareLoginInformation(MenuPage.java:230)
12-06 22:31:46.811: E/AndroidRuntime(1173):     at  com.example.cay.saati.MenuPage.onClick(MenuPage.java:267)
12-06 22:31:46.811: E/AndroidRuntime(1173):     ... 14 more

I use the following permissions to use LocationManager:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

And also library:

<uses-library android:name="com.google.android.maps" />

Can someone tell me what the exact problem is? What does cause java.lang.reflect.invocationTargetException? I don't get it. Thanks!

Answer 1

lastKnownLocation can return null.

gps works using an observer design pattern - you request it to give you a location , and using a listener , it will call the relevant function by itself , giving you the location it has found .