ios - Making beautiful transitions at PageViewController -

i want make custom transition in pageviewcontroller: while user moves next slide (scroll) background image dissolves image.

such effect have apple weather (except there background video).

what i've done:

• i've made uiviewcontoller background image (that image need change).
• i've placed containerview in uiviewcontroller, containerview have embed pageviewcontroller. uiviewcontroller -> containerview -> pageviewcontroller

at point i'm stuck, have working pageviewcontroller shared background image (from top uiviewcontroller), have no idea go next.

now can catch page changing delegate (main viewcontoller):

func pagechanged(currentpage: int) {} 

and default delegate method (pageviewcontoller) (i have 2 slides, don't know how better):

func pageviewcontroller(pageviewcontroller: uipageviewcontroller, didfinishanimating finished: bool, previousviewcontrollers: [anyobject], transitioncompleted completed: bool) {     let prevcontroller = previousviewcontrollers [contentviewcontroller]     if completed {         if prevcontroller[0].index == 0 {             delegate.pagechanged(1)         } else {             delegate.pagechanged(2)         }     } } 

but instant function, can't here animation in dependency of user swipes :).

i totally agree vasily. need use uicollectionview , use self.collectionview.pagingenabled = yes;. can control scrollview contentoffset via uiscrollviewdelegate.

optional func scrollviewdidscroll(_ scrollview: uiscrollview) 

the code:

func scrollviewdidscroll(scrollview: uiscrollview) {      var currentx = scrollview.contentoffset.x     var ratio = currentx / uiscreen.mainscreen().bounds.size.width     var previouspageindex = floor(ratio)     var nextpageindex = ceil(ratio)     ratio = ratio - previouspageindex  } 

for instance, if ratio 0.33, transition 33% between page previouspageindex , page nextpageindex. can use values set alpha values in uiimageviews:

func scrollviewdidscroll(scrollview: uiscrollview) {      var currentx = scrollview.contentoffset.x     var ratio = currentx / uiscreen.mainscreen().bounds.size.width     var previouspageindex = floor(ratio)     var nextpageindex = ceil(ratio)     ratio = ratio - previouspageindex      fromimageview.alpha = 1.0 - ratio;     toimageview.alpha = ratio;  } 

the pageviewcontroller doesn't allow control scrolling itself. transition discrete event here. swipe gesture discrete event , can add smooth effect it. pan gesture can code more complex , dirty.