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Transition

abstract class Transition : Cloneable
kotlin.Any
   ↳ androidx.transition.Transition

A Transition holds information about animations that will be run on its targets during a scene change. Subclasses of this abstract class may choreograph several child transitions (TransitionSet or they may perform custom animations themselves. Any Transition has two main jobs: (1) capture property values, and (2) play animations based on changes to captured property values. A custom transition knows what property values on View objects are of interest to it, and also knows how to animate changes to those values. For example, the Fade transition tracks changes to visibility-related properties and is able to construct and run animations that fade items in or out based on changes to those properties.

Note: Transitions may not work correctly with either SurfaceView or TextureView, due to the way that these views are displayed on the screen. For SurfaceView, the problem is that the view is updated from a non-UI thread, so changes to the view due to transitions (such as moving and resizing the view) may be out of sync with the display inside those bounds. TextureView is more compatible with transitions in general, but some specific transitions (such as Fade) may not be compatible with TextureView because they rely on android.view.ViewOverlay functionality, which does not currently work with TextureView.

Transitions can be declared in XML resource files inside the res/transition directory. Transition resources consist of a tag name for one of the Transition subclasses along with attributes to define some of the attributes of that transition. For example, here is a minimal resource file that declares a ChangeBounds transition:

<changeBounds/>
  

Note that attributes for the transition are not required, just as they are optional when declared in code; Transitions created from XML resources will use the same defaults as their code-created equivalents. Here is a slightly more elaborate example which declares a TransitionSet transition with ChangeBounds and Fade child transitions:

<transitionSet xmlns:android="http://schemas.android.com/apk/res/android"
           android:transitionOrdering="sequential">
          <changeBounds/>
          <fade android:fadingMode="fade_out">
              <targets>
                  <target android:targetId="@id/grayscaleContainer"/>
              </targets>
          </fade>
      </transitionSet>
  

In this example, the transitionOrdering attribute is used on the TransitionSet object to change from the default TransitionSet#ORDERING_TOGETHER behavior to be TransitionSet#ORDERING_SEQUENTIAL instead. Also, the Fade transition uses a fadingMode of Fade#OUT instead of the default out-in behavior. Finally, note the use of the targets sub-tag, which takes a set of {code target} tags, each of which lists a specific targetId which this transition acts upon. Use of targets is optional, but can be used to either limit the time spent checking attributes on unchanging views, or limiting the types of animations run on specific views. In this case, we know that only the grayscaleContainer will be disappearing, so we choose to limit the Fade transition to only that view.

Summary

Nested classes
abstract

Class to get the epicenter of Transition.

abstract

A transition listener receives notifications from a transition.

Constants
static Int

With setMatchOrder(int...), chooses to match by android.view.View#getId().

static Int

With setMatchOrder(int...), chooses to match by View instance.

static Int

With setMatchOrder(int...), chooses to match by the android.widget.Adapter item id.

static Int

With setMatchOrder(int...), chooses to match by android.view.View#getTransitionName().

Public constructors

Constructs a Transition object with no target objects.

<init>(@NonNull context: Context, @NonNull attrs: AttributeSet)

Perform inflation from XML and apply a class-specific base style from a theme attribute or style resource.

Public methods
open Transition

Adds a listener to the set of listeners that are sent events through the life of an animation, such as start, repeat, and end.

open Transition
addTarget(@NonNull target: View)

Sets the target view instances that this Transition is interested in animating.

open Transition
addTarget(@IdRes targetId: Int)

Adds the id of a target view that this Transition is interested in animating.

open Transition
addTarget(@NonNull targetName: String)

Adds the transitionName of a target view that this Transition is interested in animating.

open Transition
addTarget(@NonNull targetType: Class<*>)

Adds the Class of a target view that this Transition is interested in animating.

abstract Unit
captureEndValues(@NonNull transitionValues: TransitionValues)

Captures the values in the end scene for the properties that this transition monitors.

abstract Unit
captureStartValues(@NonNull transitionValues: TransitionValues)

Captures the values in the start scene for the properties that this transition monitors.

open Transition

open Animator?
createAnimator(@NonNull sceneRoot: ViewGroup, @Nullable startValues: TransitionValues?, @Nullable endValues: TransitionValues?)

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.

open Transition
excludeChildren(@NonNull target: View, exclude: Boolean)

Whether to add the children of given target to the list of target children to exclude from this transition.

open Transition
excludeChildren(@IdRes targetId: Int, exclude: Boolean)

Whether to add the children of the given id to the list of targets to exclude from this transition.

open Transition
excludeChildren(@NonNull type: Class<*>, exclude: Boolean)

Whether to add the given type to the list of types whose children should be excluded from this transition.

open Transition
excludeTarget(@NonNull target: View, exclude: Boolean)

Whether to add the given target to the list of targets to exclude from this transition.

open Transition
excludeTarget(@IdRes targetId: Int, exclude: Boolean)

Whether to add the given id to the list of target ids to exclude from this transition.

open Transition
excludeTarget(@NonNull targetName: String, exclude: Boolean)

Whether to add the given transitionName to the list of target transitionNames to exclude from this transition.

open Transition
excludeTarget(@NonNull type: Class<*>, exclude: Boolean)

Whether to add the given type to the list of types to exclude from this transition.

open Long

Returns the duration set on this transition.

open Rect?

Returns the epicenter as specified by the android.transition.Transition.EpicenterCallback or null if no callback exists.

open Transition.EpicenterCallback?

Returns the callback used to find the epicenter of the Transition.

open TimeInterpolator?

Returns the interpolator set on this transition.

open String

Returns the name of this Transition.

open PathMotion

Returns the algorithm object used to interpolate along two dimensions.

open TransitionPropagation?

Returns the android.transition.TransitionPropagation used to calculate Animator start delays.

open Long

Returns the startDelay set on this transition.

open MutableList<Int!>

Returns the array of target IDs that this transition limits itself to tracking and animating.

open MutableList<String!>?

Returns the list of target transitionNames that this transition limits itself to tracking and animating.

open MutableList<Class<*>!>?

Returns the list of target transitionNames that this transition limits itself to tracking and animating.

open MutableList<View!>

Returns the array of target views that this transition limits itself to tracking and animating.

open Array<String!>?

Returns the set of property names used stored in the TransitionValues object passed into captureStartValues(TransitionValues) that this transition cares about for the purposes of canceling overlapping animations.

open TransitionValues?
getTransitionValues(@NonNull view: View, start: Boolean)

This method can be called by transitions to get the TransitionValues for any particular view during the transition-playing process.

open Boolean
isTransitionRequired(@Nullable startValues: TransitionValues?, @Nullable endValues: TransitionValues?)

Returns whether or not the transition should create an Animator, based on the values captured during captureStartValues(TransitionValues) and captureEndValues(TransitionValues).

open Transition

Removes a listener from the set listening to this animation.

open Transition
removeTarget(@NonNull target: View)

Removes the given target from the list of targets that this Transition is interested in animating.

open Transition
removeTarget(@IdRes targetId: Int)

Removes the given targetId from the list of ids that this Transition is interested in animating.

open Transition
removeTarget(@NonNull targetName: String)

Removes the given targetName from the list of transitionNames that this Transition is interested in animating.

open Transition
removeTarget(@NonNull target: Class<*>)

Removes the given target from the list of targets that this Transition is interested in animating.

open Transition
setDuration(duration: Long)

Sets the duration of this transition.

open Unit
setEpicenterCallback(@Nullable epicenterCallback: Transition.EpicenterCallback?)

Sets the callback to use to find the epicenter of a Transition.

open Transition
setInterpolator(@Nullable interpolator: TimeInterpolator?)

Sets the interpolator of this transition.

open Unit
setMatchOrder(vararg matches: Int)

Sets the order in which Transition matches View start and end values.

open Unit
setPathMotion(@Nullable pathMotion: PathMotion?)

Sets the algorithm used to calculate two-dimensional interpolation.

open Unit
setPropagation(@Nullable transitionPropagation: TransitionPropagation?)

Sets the method for determining Animator start delays.

open Transition
setStartDelay(startDelay: Long)

Sets the startDelay of this transition.

open String

Constants

MATCH_ID

static val MATCH_ID: Int

With setMatchOrder(int...), chooses to match by android.view.View#getId(). Negative IDs will not be matched.

Value: 0x3

MATCH_INSTANCE

static val MATCH_INSTANCE: Int

With setMatchOrder(int...), chooses to match by View instance.

Value: 0x1

MATCH_ITEM_ID

static val MATCH_ITEM_ID: Int

With setMatchOrder(int...), chooses to match by the android.widget.Adapter item id. When android.widget.Adapter#hasStableIds() returns false, no match will be made for items.

Value: 0x4

MATCH_NAME

static val MATCH_NAME: Int

With setMatchOrder(int...), chooses to match by android.view.View#getTransitionName(). Null names will not be matched.

Value: 0x2

Public constructors

<init>

Transition()

Constructs a Transition object with no target objects. A transition with no targets defaults to running on all target objects in the scene hierarchy (if the transition is not contained in a TransitionSet), or all target objects passed down from its parent (if it is in a TransitionSet).

<init>

Transition(
    @NonNull context: Context,
    @NonNull attrs: AttributeSet)

Perform inflation from XML and apply a class-specific base style from a theme attribute or style resource. This constructor of Transition allows subclasses to use their own base style when they are inflating.

Parameters
context Context: The Context the transition is running in, through which it can access the current theme, resources, etc.
attrs AttributeSet: The attributes of the XML tag that is inflating the transition.

Public methods

addListener

@NonNull open fun addListener(@NonNull listener: Transition.TransitionListener): Transition

Adds a listener to the set of listeners that are sent events through the life of an animation, such as start, repeat, and end.

Parameters
listener Transition.TransitionListener: the listener to be added to the current set of listeners for this animation.
Return
Transition This transition object.

addTarget

@NonNull open fun addTarget(@NonNull target: View): Transition

Sets the target view instances that this Transition is interested in animating. By default, there are no targets, and a Transition will listen for changes on every view in the hierarchy below the sceneRoot of the Scene being transitioned into. Setting targets constrains the Transition to only listen for, and act on, these views. All other views will be ignored.

The target list is like the targetId list except this list specifies the actual View instances, not the ids of the views. This is an important distinction when scene changes involve view hierarchies which have been inflated separately; different views may share the same id but not actually be the same instance. If the transition should treat those views as the same, then addTarget(int) should be used instead of addTarget(View). If, on the other hand, scene changes involve changes all within the same view hierarchy, among views which do not necessarily have ids set on them, then the target list of views may be more convenient.

Parameters
target View: A View on which the Transition will act, must be non-null.
Return
Transition The Transition to which the target is added. Returning the same object makes it easier to chain calls during construction, such as transitionSet.addTransitions(new Fade()).addTarget(someView);

See Also

addTarget

@NonNull open fun addTarget(@IdRes targetId: Int): Transition

Adds the id of a target view that this Transition is interested in animating. By default, there are no targetIds, and a Transition will listen for changes on every view in the hierarchy below the sceneRoot of the Scene being transitioned into. Setting targetIds constrains the Transition to only listen for, and act on, views with these IDs. Views with different IDs, or no IDs whatsoever, will be ignored.

Note that using ids to specify targets implies that ids should be unique within the view hierarchy underneath the scene root.

Parameters
targetId Int: The id of a target view, must be a positive number.
Return
Transition The Transition to which the targetId is added. Returning the same object makes it easier to chain calls during construction, such as transitionSet.addTransitions(new Fade()).addTarget(someId);

See Also

addTarget

@NonNull open fun addTarget(@NonNull targetName: String): Transition

Adds the transitionName of a target view that this Transition is interested in animating. By default, there are no targetNames, and a Transition will listen for changes on every view in the hierarchy below the sceneRoot of the Scene being transitioned into. Setting targetNames constrains the Transition to only listen for, and act on, views with these transitionNames. Views with different transitionNames, or no transitionName whatsoever, will be ignored.

Note that transitionNames should be unique within the view hierarchy.

Parameters
targetName String: The transitionName of a target view, must be non-null.
Return
Transition The Transition to which the target transitionName is added. Returning the same object makes it easier to chain calls during construction, such as transitionSet.addTransitions(new Fade()).addTarget(someName);

addTarget

@NonNull open fun addTarget(@NonNull targetType: Class<*>): Transition

Adds the Class of a target view that this Transition is interested in animating. By default, there are no targetTypes, and a Transition will listen for changes on every view in the hierarchy below the sceneRoot of the Scene being transitioned into. Setting targetTypes constrains the Transition to only listen for, and act on, views with these classes. Views with different classes will be ignored.

Note that any View that can be cast to targetType will be included, so if targetType is View.class, all Views will be included.

Parameters
targetType Class<*>: The type to include when running this transition.
Return
Transition The Transition to which the target class was added. Returning the same object makes it easier to chain calls during construction, such as transitionSet.addTransitions(new Fade()).addTarget(ImageView.class);

captureEndValues

abstract fun captureEndValues(@NonNull 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(ViewGroup, TransitionValues, TransitionValues). 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(ViewGroup, TransitionValues, TransitionValues) 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.

Parameters
transitionValues TransitionValues: The holder for any values that the Transition wishes to store. Values are stored in the values field of this TransitionValues object and are keyed from a String value. For example, to store a view's rotation value, a transition might call transitionValues.values.put("appname:transitionname:rotation", view.getRotation()). The target view will already be stored in the transitionValues structure when this method is called.

captureStartValues

abstract fun captureStartValues(@NonNull 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(ViewGroup, TransitionValues, TransitionValues). 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(ViewGroup, TransitionValues, TransitionValues) 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.

Parameters
transitionValues TransitionValues: The holder for any values that the Transition wishes to store. Values are stored in the values field of this TransitionValues object and are keyed from a String value. For example, to store a view's rotation value, a transition might call transitionValues.values.put("appname:transitionname:rotation", view.getRotation()). The target view will already be stored in the transitionValues structure when this method is called.

clone

open fun clone(): Transition

createAnimator

@Nullable open fun createAnimator(
    @NonNull sceneRoot: ViewGroup,
    @Nullable startValues: TransitionValues?,
    @Nullable 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 TransitionValues#view field.

Parameters
sceneRoot ViewGroup: The root of the transition hierarchy.
startValues TransitionValues?: The values for a specific target in the start scene.
endValues TransitionValues?: The values for the target in the end scene.
Return
Animator? A Animator to be started at the appropriate time in the overall transition for this scene change. A null value means no animation should be run.

excludeChildren

@NonNull open fun excludeChildren(
    @NonNull target: View,