java.lang.IllegalStateException: Can't change tag of fragment

Question

Hi i am getting this error while using a pageViwer and Adapter to slide across 3 fragments.

here is my pageAdapter

public class FreedomPageAdapter extends FragmentPagerAdapter {

    private List<Fragment> listFragment;


    public FreedomPageAdapter(FragmentManager fm, List<Fragment> listFragment) {

        super(fm);
        this.listFragment = listFragment;
    }

    /*
     * (non-Javadoc)
     * 
     * @see android.support.v4.app.FragmentPagerAdapter#getItem(int)
     */
    @Override
    public Fragment getItem(int position) {
        // TODO Auto-generated method stub
        return listFragment.get(position);
    }

    /*
     * (non-Javadoc)
     * 
     * @see android.support.v4.view.PagerAdapter#getCount()
     */
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return listFragment.size();
    }

here is how i define the pageview

viewPager = (ViewPager) findViewById(R.id.pager);

        viewPager.setOnPageChangeListener(this);

        savedListFragment = new SubscribedFragment();

        fragmentList.add(savedListFragment);

        fragmentList.add(savedListFragment);

        fragmentList.add(savedListFragment);

        viewPager.setAdapter(new FreedomPageAdapter(fragmentManager(),
                fragmentList));



    private FragmentManager fragmentManager() {
        return getSupportFragmentManager();
    }

    private FragmentTransaction getFragmentTransaction() {
        return fragmentManager().beginTransaction();
    }

page view listener

/*
     * (non-Javadoc)
     * 
     * @see android.support.v4.view.ViewPager.OnPageChangeListener#
     * onPageScrollStateChanged(int)
     */
    @Override
    public void onPageScrollStateChanged(int arg0) {

    }

    /*
     * (non-Javadoc)
     * 
     * @see
     * android.support.v4.view.ViewPager.OnPageChangeListener#onPageScrolled
     * (int, float, int)
     */
    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {

    }

    /*
     * (non-Javadoc)
     * 
     * @see
     * android.support.v4.view.ViewPager.OnPageChangeListener#onPageSelected
     * (int)
     */
    @Override
    public void onPageSelected(int position) {
        actionBar.setSelectedNavigationItem(position);

    }

Custom fragment object

   public class SubscribedFragment extends Fragment{

    /* (non-Javadoc)
     * @see android.app.Fragment#onCreate(android.os.Bundle)
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

    }

    /* (non-Javadoc)
     * @see android.app.Fragment#onCreateView(android.view.LayoutInflater, android.view.ViewGroup, android.os.Bundle)
     */
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        return inflater.inflate(R.layout.discussion_list_layout, container);
    }

}

Full stack trace of error:

    05-02 19:15:44.599: E/AndroidRuntime(19839): FATAL EXCEPTION: main
05-02 19:15:44.599: E/AndroidRuntime(19839): java.lang.IllegalStateException: Can't change tag of fragment SubscribedFragment{41157420 id=0x7f070005 android:switcher:2131165189:0}: was android:switcher:2131165189:0 now android:switcher:2131165189:1
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:398)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:389)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:99)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:800)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.support.v4.view.ViewPager.populate(ViewPager.java:991)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.support.v4.view.ViewPager.populate(ViewPager.java:880)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1374)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:847)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4825)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2434)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.View.measure(View.java:15518)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1874)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1089)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1265)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.Choreographer.doCallbacks(Choreographer.java:562)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.Choreographer.doFrame(Choreographer.java:532)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.os.Handler.handleCallback(Handler.java:725)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.os.Handler.dispatchMessage(Handler.java:92)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.os.Looper.loop(Looper.java:137)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at android.app.ActivityThread.main(ActivityThread.java:5226)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at java.lang.reflect.Method.invokeNative(Native Method)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at java.lang.reflect.Method.invoke(Method.java:511)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
05-02 19:15:44.599: E/AndroidRuntime(19839):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

It's probably because you're adding the same fragment instance three times to the list. You should create a new instance for each page.

Also, I suggest looking into FragmentStatePagerAdapter if you're not too far into development. It may be a better choice if you want to refresh the content of the fragments from the main activity.

Answer 2

The following method should return one fragment for each tab:

@Override
public Fragment getItem(int position) {
    //Add some code
    //to verify that it will not return null
    return listFragment.get(position);
}

The code is fine, but make sure that the listFragment contains three different Fragment's, and the fragment is not null.

Answer 3

It is probably, you are sending the fragment instance null. Never ever send the fragment instance null.

    public static MyFragment getInstance() {
    MyFragment myFragment = new MyFragment();
    return myFragment;
}

And In pager adapter always use the @Override public Fragment getItem(int position) { return fragments[position]; }

or

  @Override
public Fragment getItem(int position) {
    return fragments.get(position);
}

as per your list of fragment. Also please prefer the link FragmentPagerAdapter

Notes :- Never ever use context memory as a static

Answer 4

In my case It was due to returning some null fragment, which was not handled in the getItem(position) function. Hope it helps someone.