Visibility

const val MODE_IN = 1: Int

Mode used in setMode to make the transition operate on targets that are appearing. Maybe be combined with MODE_OUT to target Visibility changes both in and out.

const val MODE_OUT = 2: Int

Mode used in setMode to make the transition operate on targets that are disappearing. Maybe be combined with MODE_IN to target Visibility changes both in and out.

fun captureEndValues(transitionValues: TransitionValues): Unit

Captures the values in the end scene for the properties that this transition monitors. These values are then passed as the endValues structure in a later call to createAnimator. The main concern for an implementation is what the properties are that the transition cares about and what the values are for all of those properties. The start and end values will be compared later during the createAnimator method to determine what, if any, animations, should be run.

Subclasses must implement this method. The method should only be called by the transition system; it is not intended to be called from external classes.

fun captureStartValues(transitionValues: TransitionValues): Unit

Captures the values in the start scene for the properties that this transition monitors. These values are then passed as the startValues structure in a later call to createAnimator. The main concern for an implementation is what the properties are that the transition cares about and what the values are for all of those properties. The start and end values will be compared later during the createAnimator method to determine what, if any, animations, should be run.

Subclasses must implement this method. The method should only be called by the transition system; it is not intended to be called from external classes.

fun createAnimator(
    sceneRoot: ViewGroup,
    startValues: TransitionValues?,
    endValues: TransitionValues?
): Animator?

This method creates an animation that will be run for this transition given the information in the startValues and endValues structures captured earlier for the start and end scenes. Subclasses of Transition should override this method. The method should only be called by the transition system; it is not intended to be called from external classes.

This method is called by the transition's parent (all the way up to the topmost Transition in the hierarchy) with the sceneRoot and start/end values that the transition may need to set up initial target values and construct an appropriate animation. For example, if an overall Transition is a TransitionSet consisting of several child transitions in sequence, then some of the child transitions may want to set initial values on target views prior to the overall Transition commencing, to put them in an appropriate state for the delay between that start and the child Transition start time. For example, a transition that fades an item in may wish to set the starting alpha value to 0, to avoid it blinking in prior to the transition actually starting the animation. This is necessary because the scene change that triggers the Transition will automatically set the end-scene on all target views, so a Transition that wants to animate from a different value should set that value prior to returning from this method.

Additionally, a Transition can perform logic to determine whether the transition needs to run on the given target and start/end values. For example, a transition that resizes objects on the screen may wish to avoid running for views which are not present in either the start or end scenes.

If there is an animator created and returned from this method, the transition mechanism will apply any applicable duration, startDelay, and interpolator to that animation and start it. A return value of null indicates that no animation should run. The default implementation returns null.

The method is called for every applicable target object, which is stored in the view field.

fun getMode(): Int

Returns whether appearing and/or disappearing Views are supported.

fun getTransitionProperties(): Array<String!>?

Returns the set of property names used stored in the TransitionValues object passed into captureStartValues that this transition cares about for the purposes of canceling overlapping animations. When any transition is started on a given scene root, all transitions currently running on that same scene root are checked to see whether the properties on which they based their animations agree with the end values of the same properties in the new transition. If the end values are not equal, then the old animation is canceled since the new transition will start a new animation to these new values. If the values are equal, the old animation is allowed to continue and no new animation is started for that transition.

A transition does not need to override this method. However, not doing so will mean that the cancellation logic outlined in the previous paragraph will be skipped for that transition, possibly leading to artifacts as old transitions and new transitions on the same targets run in parallel, animating views toward potentially different end values.

fun isTransitionRequired(
    startValues: TransitionValues?,
    endValues: TransitionValues?
): Boolean

Returns whether or not the transition should create an Animator, based on the values captured during captureStartValues and captureEndValues. The default implementation compares the property values returned from getTransitionProperties, or all property values if getTransitionProperties() returns null. Subclasses may override this method to provide logic more specific to the transition implementation.

fun isVisible(values: TransitionValues?): Boolean

Returns whether the view is 'visible' according to the given values object. This is determined by testing the same properties in the values object that are used to determine whether the object is appearing or disappearing in the createAnimator method. This method can be called by, for example, subclasses that want to know whether the object is visible in the same way that Visibility determines it for the actual animation.

fun onAppear(
    sceneRoot: ViewGroup,
    view: View,
    startValues: TransitionValues?,
    endValues: TransitionValues?
): Animator?

The default implementation of this method returns a null Animator. Subclasses should override this method to make targets appear with the desired transition. The method should only be called from onAppear.

fun onAppear(
    sceneRoot: ViewGroup,
    startValues: TransitionValues?,
    startVisibility: Int,
    endValues: TransitionValues?,
    endVisibility: Int
): Animator?

The default implementation of this method does nothing. Subclasses should override if they need to create an Animator when targets appear. The method should only be called by the Visibility class; it is not intended to be called from external classes.

fun onDisappear(
    sceneRoot: ViewGroup,
    view: View,
    startValues: TransitionValues?,
    endValues: TransitionValues?
): Animator?

The default implementation of this method returns a null Animator. Subclasses should override this method to make targets disappear with the desired transition. The method should only be called from onDisappear.

fun onDisappear(
    sceneRoot: ViewGroup,
    startValues: TransitionValues?,
    startVisibility: Int,
    endValues: TransitionValues?,
    endVisibility: Int
): Animator?

The default implementation of this method does nothing. Subclasses should override if they need to create an Animator when targets disappear. The method should only be called by the Visibility class; it is not intended to be called from external classes.

fun setMode(mode: Int): Unit

Changes the transition to support appearing and/or disappearing Views, depending on mode.