App keeps crashing when trying to change the state of a FloatingActionButton in a reloaded Fragment

Question

I have some fragments in the app I'm working on. The default fragment is HomeFragment. I successfully set the state of a FloatingActionButton in the HomeFragment to setEnabled(true) or setEnabled(false) based on the result of a method decideDisable() when the activity is started afresh. But when I navigate to MyAccountFragment or any other fragment using navigation drawer and I try to return to the home fragment the app crashes with the following error:

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.accessopthalmics.accessophthalmics, PID: 18211
              java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.FloatingActionButton.setEnabled(boolean)' on a null object reference
                  at com.app.Main2Activity.decideDisable(Main2Activity.java:333)
                  at com.app.Main2Activity$1.onNavigationItemSelected(Main2Activity.java:132)
                  at android.support.design.widget.NavigationView$1.onMenuItemSelected(NavigationView.java:154)
                  at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:822)
                  at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:171)
                  at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:973)
                  at android.support.design.internal.NavigationMenuPresenter$1.onClick(NavigationMenuPresenter.java:342)
                  at android.view.View.performClick(View.java:5210)
                  at android.view.View$PerformClick.run(View.java:21183)
                  at android.os.Handler.handleCallback(Handler.java:739)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5452)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:762)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)

I use the following code to set HomeFragment:

            HomeFragment homeFragment = new HomeFragment();
            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            ft.replace(R.id.content_frame, homeFragment, "home");
            ft.addToBackStack(null);
            ft.commit();
            return homeFragment;

Please note that I have to do an important check with decideDisable() every time HomeFragment is loaded into view.

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Santanu Sur, Apr 02 '18 at 11:28
This error is occur because when you come again in that fragment, Your floating button is not initialized . But you can do below thing to solve your problem @Override public void setUserVisibleHint(boolean isVisibleToUser) { super.setUserVisibleHint(isVisibleToUser); if (isVisibleToUser) { do floating button find view by Id here // Do your Work } else { // Do your Work } } — Maulik Patel, Apr 02 '18 at 11:35

score 0 · Answer 1 · answered Apr 02 '18 at 11:36

0

This error is occur because when you come again in that fragment, Your floating button is not initialized . But you can do below thing to solve your problem

  @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if (isVisibleToUser) {
   do floating button find view by Id here

            // Do your Work
        } else {
            // Do your Work
        }
    }

answered Apr 02 '18 at 11:36

Maulik Patel

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should this code be in the fragment class or the activity class? – meshachviktor Apr 02 '18 at 12:10
in fragment class only – Maulik Patel Apr 02 '18 at 12:10
using the sample code you provided id did this but its not working FloatingActionButton bookFab = (FloatingActionButton) getActivity().findViewById(R.id.bookFab); bookFab.setEnabled(false); – meshachviktor Apr 02 '18 at 12:32

App keeps crashing when trying to change the state of a FloatingActionButton in a reloaded Fragment

1 Answers1