CODEWITHSUNDEEP
androidnavigation
omerjerk
omerjerk

Reputation: 4279

app crashing while implementing lateral navigation

I created a new activity with navigation type "tabs + swipe". I made these changes in the getItem() method :

@Override
    public Fragment getItem(int i) {
        Fragment fragment ; 

        switch(i){
        case 0:
             fragment = new Fragment1();

             break;
        case 1:
             fragment = new Fragment2();
             break;
        case 3:
             fragment = new Fragment3();
             break;
             //
        default : return null;
        }

        //set args if necessary


        //return fragment
        return fragment;
    }

so for each tab I've defined a separate class. One of the class is this :

public static class Fragment1 extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */

    public Fragment1() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // Create a new TextView and set its text to the fragment's section
        // number argument value.
        View v = inflater.inflate(R.layout.center, null);
        return v;
    }
}

when I run the app the new activity starts successfully but when I swipe the screen to the second tab then the app crashes... this is the logcat :

02-16 08:48:43.328: E/AndroidRuntime(21541): FATAL EXCEPTION: main
02-16 08:48:43.328: E/AndroidRuntime(21541): java.lang.NullPointerException
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:394)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:389)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:99)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:801)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.support.v4.view.ViewPager.populate(ViewPager.java:992)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.support.v4.view.ViewPager.populate(ViewPager.java:881)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.support.v4.view.ViewPager$3.run(ViewPager.java:237)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.os.Handler.handleCallback(Handler.java:605)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.os.Looper.loop(Looper.java:137)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at android.app.ActivityThread.main(ActivityThread.java:4575)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at java.lang.reflect.Method.invokeNative(Native Method)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at java.lang.reflect.Method.invoke(Method.java:511)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
02-16 08:48:43.328: E/AndroidRuntime(21541):    at dalvik.system.NativeStart.main(Native Method)

Please solve my problem.

Upvotes: 1

Views: 2765

Answers (1)

chuthan20
chuthan20

Reputation: 5409

Most likely, your default statement returning null and it tries to add a null fragment.. and fails... do you know that you are missing case 2 for your switch statement.. is it on purpose?
If I were you, I would put a break 

    switch(i){

and check the value of i... and see if its either, 0, 1 or 3... otherwise your app will crash becuz it is returning null.

Upvotes: 6

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