ios - UITabBarControllerDelegate's method is not called -

i create programmatically uitabbarcontroller more 5 tabs (exactly 8 child view controllers).

my purpose custom transition animation tab changing. setup delegate uitabbarcontroller , implement method:

- (nullable id <uiviewcontrolleranimatedtransitioning>)tabbarcontroller:(uitabbarcontroller *)tabbarcontroller             animationcontrollerfortransitionfromviewcontroller:(uiviewcontroller *)fromvc                                               toviewcontroller:(uiviewcontroller *)tovc   

when select tab sending:

[tabbarcontroller setselectedindex: 6]; 

delegate's method not called.

delegate's method called when send

[tabbarcontroller setselectedindex: 3];  

for example, i.e. visible tab.

one more remark: if selected view controller in visible range 0..3 , next view out of visible range 0..3 delegate's method still called. in case when selected view controller out of visible range 0..3 , next view out of visible range 0..3 delegate's method not called. , lose custom transition animation. problem.

i tried send

[tabbarcontroller setselectedviewcontroller: someviewcontroller]; 

instead of

[tabbarcontroller setselectedindex: 6]; 

it doesn't work.

you have many tabs use selectedindex, other tabs in morenavigationcontroller if morenavigationcontroller not displayed on screen - meaning should return nsnotfound when using selectedindex.

you should use selectedviewcontroller instead, per ios docs

[tabbarcontroller setselectedviewcontroller: yourindexsixviewcontroller]; 

wiki