Use setSupportActionBar on Fragment

Question

I have an app that uses NavigationDrawer, I need to change the name of toolbar for each fragment.

My MainActivity extension of AppCompatActivity then I can change the fragment name using:

toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
toolbar.setTitle("Nome Fragmento");

Except in my main fragment I have buttons that also calls fragmentos, and I need their names changed, but I can’t use the setSupportActionBar(toolbar); I saw somewhere people using ((AppCompatActivity) getActivity()).setSupportActionBar(toolbar); but also can’t, it opens the application and when I click the app closes and gives the following error in Logcat:

05-03 15:16:30.305 14847-14847/com.example.expres E/AndroidRuntime: FATAL EXCEPTION: main
    java.lang.NullPointerException
        at com.example.expres.fragmentos.principal$1.onClick(principal.java:95)
        at android.view.View.performClick(View.java:4476)
        at android.view.View$PerformClick.run(View.java:18795)
        at android.os.Handler.handleCallback(Handler.java:730)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:176)
        at android.app.ActivityThread.main(ActivityThread.java:5493)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1225)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1041)
        at dalvik.system.NativeStart.main(Native Method)

I really need help.

Answer 1

I didn’t really understand the business logic, normally I would advise to use a central Toolbar on Activity and use Fragment only for the content, but following its logic, it would be like this:

v = inflater.inflate (R.layout.layout, container, false);

    Toolbar toolbar = v.findViewById(R.id.toolbar);
    ((AppCompatActivity)getActivity()).setSupportActionBar (toolbar);
    if(((AppCompatActivity)getActivity()).getSupportActionBar () != null) {
        ((AppCompatActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(false); //Mostrar o botão
        ((AppCompatActivity) getActivity()).getSupportActionBar().setHomeButtonEnabled(false);
        ((AppCompatActivity) getActivity()).setTitle ("TITULO");
    }

And if you want to use events in this same context:

toolbar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
        toolbar.setOnMenuItemClickListener(new Toolbar.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem item) {
                return false;
            }
        });