ChangeScroll


public class ChangeScroll
extends Transition

java.lang.Object
   ↳ android.transition.Transition
     ↳ android.transition.ChangeScroll


This transition captures the scroll properties of targets before and after the scene change and animates any changes.

Summary

Inherited XML attributes

Inherited constants

Public constructors

ChangeScroll()
ChangeScroll(Context context, AttributeSet attrs)

Public methods

void captureEndValues(TransitionValues transitionValues)

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

void captureStartValues(TransitionValues transitionValues)

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

Animator createAnimator(ViewGroup sceneRoot, TransitionValues startValues, TransitionValues endValues)

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.

String[] getTransitionProperties()

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

Inherited methods

Public constructors

ChangeScroll

Added in API level 23
public ChangeScroll ()

ChangeScroll

Added in API level 23
public ChangeScroll (Context context, 
                AttributeSet attrs)

Parameters
context Context

attrs AttributeSet

Public methods

captureEndValues

Added in API level 23
public void captureEndValues (TransitionValues transitionValues)

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(android.view.ViewGroup, android.transition.TransitionValues, android.transition.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(android.view.ViewGroup, android.transition.TransitionValues, android.transition.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

Added in API level 23
public void captureStartValues (TransitionValues transitionValues)

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(android.view.ViewGroup, android.transition.TransitionValues, android.transition.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(android.view.ViewGroup, android.transition.TransitionValues, android.transition.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.

createAnimator

Added in API level 23
public Animator createAnimator (ViewGroup sceneRoot, 
                TransitionValues startValues, 
                TransitionValues endValues)

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: This value cannot be null.

startValues TransitionValues: This value may be null.

endValues TransitionValues: This value may be null.

Returns
Animator This value may be null.

getTransitionProperties

Added in API level 23
public String[] getTransitionProperties ()

Returns the set of property names used stored in the TransitionValues object passed into captureStartValues(android.transition.TransitionValues) 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.

Returns
String[] An array of property names as described in the class documentation for TransitionValues. The default implementation returns null.