Null pointer on inflated view when loading for the

I'm using a DrawerLayout and when I load for the second time a google map fragment the exception will be caught as expected; however, further in the same method when I try

Button btnShowList = (Button) ui.findViewById(R.id.btnShowList);

and I get a null pointer exception. I guess that's because ui was not assigned any value.

How can I deal with this?

Page2.java:

public class Page2 extends Fragment {

    View ui;
    final String TAG = "POPE";
    final int CODIGO_DE_RESULTADO_1 = 1; // Es para usarlo en onActivityResult();

    private GoogleMap mMap;

    public Page2(){
        // Este es el constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        if (ui != null) {
            ViewGroup parent = (ViewGroup) ui.getParent();
            if (parent != null){
                parent.removeView(ui);
            }
        }

        try {
            ui = inflater.inflate(R.layout.activity_page2,container,false);
        } catch (InflateException e) {
            Log.i(TAG,"HERE COMES THE STACK TRACE");
            e.printStackTrace();
        }

        FragmentManager fm = getFragmentManager();
        mMap = ((MapFragment) fm.findFragmentById(R.id.map)).getMap();
        mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);     
        mMap.setMyLocationEnabled(true);


        Button btnShowList = (Button) ui.findViewById(R.id.btnShowList);
        btnShowList.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                showFileslist();
            }
        });

        return ui;

    }
}

activity_page2.xml:

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

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

<Button
    android:id="@+id/btnShowList"
    style="?android:attr/buttonStyleSmall"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:text="Load points" />

Log:

07-08 22:17:44.203: I/POPE(11859): HERE COMES THE STACK TRACE
07-08 22:17:44.213: W/System.err(11859): android.view.InflateException: Binary XML file line #6: Error inflating class fragment
07-08 22:17:44.213: W/System.err(11859):    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:710)
07-08 22:17:44.213: W/System.err(11859):    at android.view.LayoutInflater.rInflate(LayoutInflater.java:752)
07-08 22:17:44.213: W/System.err(11859):    at android.view.LayoutInflater.inflate(LayoutInflater.java:495)
07-08 22:17:44.213: W/System.err(11859):    at android.view.LayoutInflater.inflate(LayoutInflater.java:397)
07-08 22:17:44.213: W/System.err(11859):    at com.jorgeandresserrano.gpstools.Page2.onCreateView(Page2.java:52)
07-08 22:17:44.213: W/System.err(11859):    at android.app.Fragment.performCreateView(Fragment.java:1695)
07-08 22:17:44.213: W/System.err(11859):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:903)
07-08 22:17:44.213: W/System.err(11859):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1075)
07-08 22:17:44.213: W/System.err(11859):    at android.app.BackStackRecord.run(BackStackRecord.java:682)
07-08 22:17:44.213: W/System.err(11859):    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1455)
07-08 22:17:44.223: W/System.err(11859):    at android.app.FragmentManagerImpl$1.run(FragmentManager.java:441)
07-08 22:17:44.223: W/System.err(11859):    at android.os.Handler.handleCallback(Handler.java:725)
07-08 22:17:44.223: W/System.err(11859):    at android.os.Handler.dispatchMessage(Handler.java:92)
07-08 22:17:44.223: W/System.err(11859):    at android.os.Looper.loop(Looper.java:137)
07-08 22:17:44.223: W/System.err(11859):    at android.app.ActivityThread.main(ActivityThread.java:5293)
07-08 22:17:44.223: W/System.err(11859):    at java.lang.reflect.Method.invokeNative(Native Method)
07-08 22:17:44.223: W/System.err(11859):    at java.lang.reflect.Method.invoke(Method.java:511)
07-08 22:17:44.223: W/System.err(11859):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
07-08 22:17:44.223: W/System.err(11859):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
07-08 22:17:44.223: W/System.err(11859):    at dalvik.system.NativeStart.main(Native Method)
07-08 22:17:44.223: W/System.err(11859): Caused by: java.lang.IllegalArgumentException: Binary XML file line #6: Duplicate id 0x7f05003f, tag null, or parent id 0xffffffff with another fragment for com.google.android.gms.maps.MapFragment
07-08 22:17:44.223: W/System.err(11859):    at android.app.Activity.onCreateView(Activity.java:4863)
07-08 22:17:44.233: W/System.err(11859):    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:686)
07-08 22:17:44.233: W/System.err(11859):    ... 19 more
07-08 22:17:44.233: D/AndroidRuntime(11859): Shutting down VM
07-08 22:17:44.233: W/dalvikvm(11859): threadid=1: thread exiting with uncaught exception (group=0x410feac8)
07-08 22:17:44.233: E/AndroidRuntime(11859): FATAL EXCEPTION: main
07-08 22:17:44.233: E/AndroidRuntime(11859): java.lang.NullPointerException
07-08 22:17:44.233: E/AndroidRuntime(11859):    at com.myname.myapp.Page2.onCreateView(Page2.java:66)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.app.Fragment.performCreateView(Fragment.java:1695)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:903)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1075)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.app.BackStackRecord.run(BackStackRecord.java:682)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1455)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.app.FragmentManagerImpl$1.run(FragmentManager.java:441)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.os.Handler.handleCallback(Handler.java:725)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.os.Handler.dispatchMessage(Handler.java:92)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.os.Looper.loop(Looper.java:137)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at android.app.ActivityThread.main(ActivityThread.java:5293)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at java.lang.reflect.Method.invokeNative(Native Method)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at java.lang.reflect.Method.invoke(Method.java:511)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
07-08 22:17:44.233: E/AndroidRuntime(11859):    at dalvik.system.NativeStart.main(Native Method)

Line 66 is:

Button btnShowList = (Button) ui.findViewById(R.id.btnShowList);

回答1:

The problem can be resolved by removing the map fragment in the onDestroyView() method just before leaving. Like this:

@Override
public void onDestroyView() {
    super.onDestroyView();
    MapFragment f = (MapFragment) getFragmentManager().findFragmentById(R.id.map);
    if (f != null){ 
        getFragmentManager().beginTransaction().remove(f).commit();
    }
}

This post explains this more in detail https://stackoverflow.com/a/14484640/2422833

回答2:

How about using OnResume for your fragment. Make a reference to your ui. And OnResume check again that ui object is null or not then inflate it again. Since it called 2nd time there possibility that it don't go through your onCreateView again.