Keyframe

public abstract class Keyframe
extends Object implements Cloneable

java.lang.Object
   ↳ androidx.core.animation.Keyframe<T>


This class holds a time/value pair for an animation. The Keyframe class is used by ValueAnimator to define the values that the animation target will have over the course of the animation. As the time proceeds from one keyframe to the other, the value of the target object will animate between the value at the previous keyframe and the value at the next keyframe. Each keyframe also holds an optional Interpolator object, which defines the time interpolation over the intervalue preceding the keyframe.

The Keyframe class itself is abstract. The type-specific factory methods will return a subclass of Keyframe specific to the type of value being stored. This is done to improve performance when dealing with the most common cases (e.g., float and int values). Other types will fall into a more general Keyframe class that treats its values as Objects. Unless your animation requires dealing with a custom type or a data structure that needs to be animated directly (and evaluated using an implementation of TypeEvaluator), you should stick to using float and int as animations using those types have lower runtime overhead than other types.

Summary

Public constructors

Keyframe()

Public methods

abstract Keyframe<T> clone()
float getFraction()

Gets the time for this keyframe, as a fraction of the overall animation duration.

Interpolator getInterpolator()

Gets the optional interpolator for this Keyframe.

Class<?> getType()

Gets the type of keyframe.

abstract T getValue()

Gets the value for this Keyframe.

boolean hasValue()

Indicates whether this keyframe has a valid value.

static Keyframe<Float> ofFloat(float fraction)

Constructs a Keyframe object with the given time.

static Keyframe<Float> ofFloat(float fraction, float value)

Constructs a Keyframe object with the given time and value.

static Keyframe<Integer> ofInt(float fraction, int value)

Constructs a Keyframe object with the given time and value.

static Keyframe<Integer> ofInt(float fraction)

Constructs a Keyframe object with the given time.

static <T> Keyframe<T> ofObject(float fraction, T value)

Constructs a Keyframe object with the given time and value.

static <T> Keyframe<T> ofObject(float fraction)

Constructs a Keyframe object with the given time.

void setFraction(float fraction)

Sets the time for this keyframe, as a fraction of the overall animation duration.

void setInterpolator(Interpolator interpolator)

Sets the optional interpolator for this Keyframe.

abstract void setValue(T value)

Sets the value for this Keyframe.

Inherited methods

Public constructors

Keyframe

public Keyframe ()

Public methods

clone

public abstract Keyframe<T> clone ()

Returns
Keyframe<T>

getFraction

public float getFraction ()

Gets the time for this keyframe, as a fraction of the overall animation duration.

Returns
float The time associated with this keyframe, as a fraction of the overall animation duration. This should be a value between 0 and 1.

Value is between 0.0 and 1.0 inclusive.

getInterpolator

public Interpolator getInterpolator ()

Gets the optional interpolator for this Keyframe. A value of null indicates that there is no interpolation, which is the same as linear interpolation.

Returns
Interpolator The optional interpolator for this Keyframe.

getType

public Class<?> getType ()

Gets the type of keyframe. This information is used by ValueAnimator to determine the type of TypeEvaluator to use when calculating values between keyframes. The type is based on the type of Keyframe created.

Returns
Class<?> The type of the value stored in the Keyframe.

getValue

public abstract T getValue ()

Gets the value for this Keyframe.

Returns
T The value for this Keyframe.

hasValue

public boolean hasValue ()

Indicates whether this keyframe has a valid value. This method is called internally when an ObjectAnimator first starts; keyframes without values are assigned values at that time by deriving the value for the property from the target object.

Returns
boolean boolean Whether this object has a value assigned.

ofFloat

public static Keyframe<Float> ofFloat (float fraction)

Constructs a Keyframe object with the given time. The value at this time will be derived from the target object when the animation first starts (note that this implies that keyframes with no initial value must be used as part of an ObjectAnimator). The time defines the time, as a proportion of an overall animation's duration, at which the value will hold true for the animation. The value for the animation between keyframes will be calculated as an interpolation between the values at those keyframes.

Parameters
fraction float: The time, expressed as a value between 0 and 1, representing the fraction of time elapsed of the overall animation duration.

Value is between 0.0 and 1.0 inclusive.

Returns
Keyframe<Float>

ofFloat

public static Keyframe<Float> ofFloat (float fraction, 
                float value)

Constructs a Keyframe object with the given time and value. The time defines the time, as a proportion of an overall animation's duration, at which the value will hold true for the animation. The value for the animation between keyframes will be calculated as an interpolation between the values at those keyframes.

Parameters
fraction float: The time, expressed as a value between 0 and 1, representing the fraction of time elapsed of the overall animation duration.

Value is between 0.0 and 1.0 inclusive.

value float: The value that the object will animate to as the animation time approaches the time in this keyframe, and the the value animated from as the time passes the time in this keyframe.

Returns
Keyframe<Float>

ofInt

public static Keyframe<Integer> ofInt (float fraction, 
                int value)

Constructs a Keyframe object with the given time and value. The time defines the time, as a proportion of an overall animation's duration, at which the value will hold true for the animation. The value for the animation between keyframes will be calculated as an interpolation between the values at those keyframes.

Parameters
fraction float: The time, expressed as a value between 0 and 1, representing the fraction of time elapsed of the overall animation duration.

Value is between 0.0 and 1.0 inclusive.

value int: The value that the object will animate to as the animation time approaches the time in this keyframe, and the the value animated from as the time passes the time in this keyframe.

Returns
Keyframe<Integer>

ofInt

public static Keyframe<Integer> ofInt (float fraction)

Constructs a Keyframe object with the given time. The value at this time will be derived from the target object when the animation first starts (note that this implies that keyframes with no initial value must be used as part of an ObjectAnimator). The time defines the time, as a proportion of an overall animation's duration, at which the value will hold true for the animation. The value for the animation between keyframes will be calculated as an interpolation between the values at those keyframes.

Parameters
fraction float: The time, expressed as a value between 0 and 1, representing the fraction of time elapsed of the overall animation duration.

Value is between 0.0 and 1.0 inclusive.

Returns
Keyframe<Integer>

ofObject

public static Keyframe<T> ofObject (float fraction, 
                T value)

Constructs a Keyframe object with the given time and value. The time defines the time, as a proportion of an overall animation's duration, at which the value will hold true for the animation. The value for the animation between keyframes will be calculated as an interpolation between the values at those keyframes.

Parameters
fraction float: The time, expressed as a value between 0 and 1, representing the fraction of time elapsed of the overall animation duration.

Value is between 0.0 and 1.0 inclusive.

value T: The value that the object will animate to as the animation time approaches the time in this keyframe, and the the value animated from as the time passes the time in this keyframe.

Returns
Keyframe<T>

ofObject

public static Keyframe<T> ofObject (float fraction)

Constructs a Keyframe object with the given time. The value at this time will be derived from the target object when the animation first starts (note that this implies that keyframes with no initial value must be used as part of an ObjectAnimator). The time defines the time, as a proportion of an overall animation's duration, at which the value will hold true for the animation. The value for the animation between keyframes will be calculated as an interpolation between the values at those keyframes.

Parameters
fraction float: The time, expressed as a value between 0 and 1, representing the fraction of time elapsed of the overall animation duration.

Value is between 0.0 and 1.0 inclusive.

Returns
Keyframe<T>

setFraction

public void setFraction (float fraction)

Sets the time for this keyframe, as a fraction of the overall animation duration.

Parameters
fraction float: time associated with this keyframe, as a fraction of the overall animation duration. This should be a value between 0 and 1.

Value is between 0.0 and 1.0 inclusive.

setInterpolator

public void setInterpolator (Interpolator interpolator)

Sets the optional interpolator for this Keyframe. A value of null indicates that there is no interpolation, which is the same as linear interpolation.

Parameters
interpolator Interpolator

setValue

public abstract void setValue (T value)

Sets the value for this Keyframe.

Parameters
value T: value for this Keyframe.