Parallax

<init>

Parallax()

Parallax tracks a list of dynamic Propertys typically representing foreground UI element positions on screen. Parallax keeps a list of ParallaxEffect objects which define rules to mapping property values to ParallaxTarget.

Example: // when Property "var1" changes from 15 to max value, perform parallax effect to // change myView's translationY from 0 to 100. Parallax parallax = new Parallax() {...}; p1 = parallax.addProperty("var1"); parallax.addEffect(p1.at(15), p1.atMax()) .target(myView, PropertyValuesHolder.ofFloat("translationY", 0, 100));

To create a ParallaxEffect, user calls addEffect(PropertyMarkerValue[]) with a list of PropertyMarkerValue which defines the range of Parallax.IntProperty or Parallax.FloatProperty. Then user adds ParallaxTarget into ParallaxEffect.

App may subclass Parallax.IntProperty or Parallax.FloatProperty to supply additional information about how to retrieve Property value. RecyclerViewParallax is a great example of Parallax implementation tracking child view positions on screen.

Restrictions of properties
• FloatProperty and IntProperty cannot be mixed in one Parallax
• Values must be in ascending order.
• If the UI element is unknown above screen, use UNKNOWN_BEFORE.
• if the UI element is unknown below screen, use UNKNOWN_AFTER.
• UNKNOWN_BEFORE and UNKNOWN_AFTER are not allowed to be next to each other.

Subclass must override updateValues() to update property values and perform ParallaxEffects. Subclass may call updateValues() automatically e.g. RecyclerViewParallax calls updateValues() in RecyclerView scrolling. App might call updateValues() manually when Parallax is unaware of the value change. For example, when a slide transition is running, RecyclerViewParallax is unaware of translation value changes; it's the app's responsibility to call updateValues() in every frame of animation.

addEffect

open fun addEffect(vararg ranges: Parallax.PropertyMarkerValue<Any!>!): ParallaxEffect!

Create a ParallaxEffect object that will track source variable changes within a provided set of ranges.

addProperty

fun addProperty(name: String!): PropertyT

Add a new IntProperty in the Parallax object. App may override createProperty(String, int).

createProperty

abstract fun createProperty(name: String!, index: Int): PropertyT

Create a new Property object. App does not directly call this method. See addProperty(String).

getEffects

open fun getEffects(): MutableList<ParallaxEffect!>!

Returns a list of ParallaxEffect object which defines rules to perform mapping to multiple ParallaxTargets.

getMaxValue

abstract fun getMaxValue(): Float

Return the max value which is typically size of parent visible area, e.g. RecyclerView's height if we are tracking Y position of a child. The size can be used to calculate marker value using the provided fraction of FloatPropertyMarkerValue.

getProperties

fun getProperties(): MutableList<PropertyT>!

removeAllEffects

open fun removeAllEffects(): Unit

Remove all ParallaxEffect objects.

removeEffect

open fun removeEffect(effect: ParallaxEffect!): Unit

Remove the ParallaxEffect object.

updateValues

@CallSuper open fun updateValues(): Unit

Update property values and perform ParallaxEffects. Subclass may override and call super.updateValues() after updated properties values.