Transitions in Android help users navigate from one screen to another with a smooth animation.

There are mainly 2 ways you can create and attach a transition.

1. Create a res/anim resource and attach it to fragment transaction via setCustomAnimations

2. Create a res/transition resource and attach it to fragment via setEnterTransition and setExitTransition

via setCustomAnimations

Simplest way to set custom transition animation is via setCustomAnimations which accepts 4 animation files, one for each transition.

val fragment = FragmentB()
supportFragmentManager.commit {
    setCustomAnimations(
        enter = R.anim.slide_in,
        exit = R.anim.fade_out,
        popEnter = R.anim.fade_in,
        popExit = R.anim.slide_out
    )
    replace(R.id.fragment_container, fragment)
    addToBackStack(null)
}

All transitions will be part of your res/anim folder.

Pros:

• Simplest way to add a transition.

• Supports all build-in animations such as scale, Fade, translate etc.

• Handles most common scenarios.

Cons:

• Cannot fine-tune transitions based of Views. Transition will be applied to whole view.

To overcome the above limitation, android has another method to attach a transition.

Via setEnterTransition Or setExitTransition

setEnterTransition and setExitTransition work differently than setCustomAnimations as they accept Transition Object instead of animation, we need to create transitions in res/transition folder.

Pros:

• Instead of running animation on complete view, a transition will run transition on all the child view's and their child views if they have any background.

• We can exclude a view from transition with excludeTarget(R.id.view_to_exclude, true) . Transition will run on all views except this view and its children.

• Similarly, you can add a view to transition using addTarget(R.id.rv_bottom_widget_list) . Transition will only run on this view and exclude all other views in the fragment.

Now we can come to the part where we run multiple transitions on same fragment.

Running Multiple Transitions At Once

We can use TransitionSet to create a set of all the transitions that we want to run together. The only caveat is:

You can only run one type of transition only once per view

Q. What does it mean?

A. For example, if you are running Fade transition on a layout then that it's child, a imageView cannot have another Fade transition which goes on for a longer duration. You have only one choice, remove imageVIew from 1st transition and add only imageView in the second Fade Transition.

// Remove imageView from parent transition, this will remove Fade transition only from imageView
val firstTransition = new Fade().excludeTarget(R.id.imageView, true)
// add second fade transition to imageView so second transition will only run on imageView
val secondTransition = new Fade().addTarge(R.id.imageVIew)

Add delay to transition

• With setStarteDelay : You can add delay with setStartDelay(long delay). It will ask the transition to run after a specified delay.

    new Fade().setStartDelay(1000)
  

• with setOrdering : You can also create a TransitionSet and make it execute sequentially so each transition will execute one after another.

    TransitionSet()
        .setOrdering(TransitionSet.ORDERING_SEQUENTIAL)
  

• With Interpolator : interpolator allows you to return different time value instead of a linear time. With this, you can return time value as zero until you want to start your animation.

    public class SlideInterpolator implements TimeInterpolator {
        public SlideInterpolator() {
        }
  
        @Override
        public float getInterpolation(float input) {
            float out;
            if (input < 0.5f) {
                out = 0;
            } else {
                out = input;
            }
            return out;
        }
    }