运行时异常无法启动MainActivity

Question

I'm trying to test my Android app on a new phone I've just purchased with Android 4.2. It runs every other app I test, and this particular app also works on other devices. When I try to run the code it's giving me the following errors:

> 02-23 12:15:08.532: E/AndroidRuntime(5431): FATAL EXCEPTION: main
02-23 12:15:08.532: E/AndroidRuntime(5431): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.antiquity/com.example.antiquity.MainActivity}: java.lang.NullPointerException
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.ActivityThread.access$600(ActivityThread.java:162)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.os.Handler.dispatchMessage(Handler.java:107)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.os.Looper.loop(Looper.java:194)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.ActivityThread.main(ActivityThread.java:5371)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at java.lang.reflect.Method.invokeNative(Native Method)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at java.lang.reflect.Method.invoke(Method.java:525)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at dalvik.system.NativeStart.main(Native Method)
02-23 12:15:08.532: E/AndroidRuntime(5431): Caused by: java.lang.NullPointerException
02-23 12:15:08.532: E/AndroidRuntime(5431):     at com.example.antiquity.MainActivity.setUpLocation(MainActivity.java:127)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at com.example.antiquity.MainActivity.onCreate(MainActivity.java:96)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.Activity.performCreate(Activity.java:5139)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1084)
02-23 12:15:08.532: E/AndroidRuntime(5431):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)
02-23 12:15:08.532: E/AndroidRuntime(5431):     ... 11 more

Now I've checked line 127 and even removing that and leaving an empty line will still cause this error relating to line 127.

My MainActivity.class code:

public class MainActivity extends Activity {

    private GoogleMap map;
    Intent data;    
    MonumentsDatabase monDatabase;
    int _id;
    int _lat;
    int _lng;
    String _title;
    LatLng MARKERS;
    LocationManager locationManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

        map.setOnInfoWindowClickListener(new OnInfoWindowClickListener() {
            @Override
            public void onInfoWindowClick(Marker marker) {
               Intent data = new Intent(MainActivity.this, DisplayData.class);
               startActivity(data);

            }
        });

        setUpLocation();

        locationManager = (LocationManager) getSystemService( Context.LOCATION_SERVICE );

        if ( !locationManager.isProviderEnabled( LocationManager.GPS_PROVIDER ) ) {
            disabledGPS();
        }       

        map.setMyLocationEnabled(true);
    }


    public void setUpLocation() {
        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);     
        Criteria criteria = new Criteria();      
        String provider = locationManager.getBestProvider(criteria, true);
        Location myLocation = locationManager.getLastKnownLocation(provider);
        double latitude = myLocation.getLatitude();
        double longitude = myLocation.getLongitude();
        LatLng latLng = new LatLng(latitude, longitude);      
        map.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        map.animateCamera(CameraUpdateFactory.zoomTo(40));      
    }


    private void disabledGPS() {
        final AlertDialog.Builder gpsDisabled = new AlertDialog.Builder(this);
        gpsDisabled.setMessage("This app requires GPS to be enabled. Do you wish to continue?")
            .setCancelable(false)
            .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    startActivity(new Intent(android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS));
                }
            })
            .setNegativeButton("No", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    dialog.cancel();
                }
            });
        AlertDialog mainAlert = gpsDisabled.create();
        mainAlert.show();
    }

    /**
    public boolean onMarkerClick(Marker marker) {
        //Intent data = new Intent(this, DisplayData.class);
        // TODO Auto-generated method stub
        startActivity(data);
        return true;
    }
    */

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    public void createDatabase() {
        monDatabase = new MonumentsDatabase(this);
        try {   
            monDatabase.createDatabase();
        } catch (IOException ioe) {
            throw new Error("Unable to create database");
        }
        try {
            monDatabase.openDatabase();
        }catch(SQLException sqle){ 
            throw sqle;
        }
    }

}

I find it strange how it works on one device and then crashes on another.

Thanks for any help! :)

EDIT:

activity_layout.xml file:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="fill_parent"

tools:context=".MainActivity" >

<fragment
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.MapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

AndroidManifest.xml file:

Not sure why, but it isn't liking the indents.

So sorry for the link but:

http://pastebin.com/kd4EpP4W

Answer 1

I think your

 Location myLocation = locationManager.getLastKnownLocation(provider); 

line returning null.

Please check this answer. It might be helpful

Answer 2

Here, If you are targeting your minimum SDK version < 12 in your manifest file then you can't use MapFragment . So must be sure that your minimum SDK version is above or equals to 12. And if it is not then change in your xml file from

android:name="com.google.android.gms.maps.MapFragment"

to

android:name="com.google.android.gms.maps.SupportMapFragment"

And also in your activity change from

 map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

to

 map=((SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map)).getMap();

And also If you're using fragments on older devices (pre Honeycomb) you should always extend your Activity from FragmentActivity .

Also import android.support.v4.app.FragmentActivity and for more information on this go to my this answer

Answer 3

If I don't mistake, fragments should be used in Activity which extends either Fragment or FragmentActivity . Probably something is wrong with map