As the questioner said, if it was just the interaction between Toolbar and Fragment, it would be relatively simple:

1. Activity#setActionBar(android.widget.Toolbar) 或者 AppCompatActivity#setSupportActionBar(android.support.v7.widget.Toolbar)

2. Fragment#setHasOptionsMenu(boolean)

3. FragmentThe internal ActionBar is processed the same as Activity, see the picture below:
   

p.s. Below the dividing line is the relevant information about the interaction between Fragments.

The simplest way is EventBus, optional libraries:

1. greenrobot/EventBus

2. AndroidKnife/RxBus

3. square/otto

The second is LocalBroadcastManager, reference:

• Android Developer Reference # android.support.v4.content.LocalBroadcastManager

Once again, Fragment uses Activity to interact, reference:

1. Android Developer Guide # Communicating with Other Fragments

2. Android Developer Guide # Fragment

Finally, it is implemented directly through TargetFragment, related functions:

1. Fragment#setTargetFragment(android.app.Fragment, int)

2. Fragment#getTargetFragment()

3. Fragment#getTargetRequestCode()

After selecting the method, the last thing you need to pay attention to is:

FragmentPagerAdapter and FragmentStatePagerAdapter have differences in managing FragmentPagerAdapter和FragmentStatePagerAdapter在管理Fragment时是有差别: 回收Fragment的处理是不同的. 因此, 需要考虑的是, 当Fragment: the processing of recycling

is different. Therefore, what needs to be considered is when

If you want to exchange data between two Fragments, you can use EventBus

If you are just operating the toolbar to switch fragments, load the fragment and pass in the data directly