One of the core concepts of these transition animations is that there are two types of * changes that cause the transition and four different animations that run because of * those changes. The changes that trigger the transition are items being added to a container * (referred to as an "appearing" transition) or removed from a container (also known as * "disappearing"). Setting the visibility of views (between GONE and VISIBLE) will trigger * the same add/remove logic. The animations that run due to those events are one that animates * items being added, one that animates items being removed, and two that animate the other * items in the container that change due to the add/remove occurrence. Users of * the transition may want different animations for the changing items depending on whether * they are changing due to an appearing or disappearing event, so there is one animation for * each of these variations of the changing event. Most of the API of this class is concerned * with setting up the basic properties of the animations used in these four situations, * or with setting up custom animations for any or all of the four.
* *By default, the DISAPPEARING animation begins immediately, as does the CHANGE_APPEARING * animation. The other animations begin after a delay that is set to the default duration * of the animations. This behavior facilitates a sequence of animations in transitions as * follows: when an item is being added to a layout, the other children of that container will * move first (thus creating space for the new item), then the appearing animation will run to * animate the item being added. Conversely, when an item is removed from a container, the * animation to remove it will run first, then the animations of the other children in the * layout will run (closing the gap created in the layout when the item was removed). If this * default choreography behavior is not desired, the {@link #setDuration(int, long)} and * {@link #setStartDelay(int, long)} of any or all of the animations can be changed as * appropriate.
* *The animations specified for the transition, both the defaults and any custom animations
* set on the transition object, are templates only. That is, these animations exist to hold the
* basic animation properties, such as the duration, start delay, and properties being animated.
* But the actual target object, as well as the start and end values for those properties, are
* set automatically in the process of setting up the transition each time it runs. Each of the
* animations is cloned from the original copy and the clone is then populated with the dynamic
* values of the target being animated (such as one of the items in a layout container that is
* moving as a result of the layout event) as well as the values that are changing (such as the
* position and size of that object). The actual values that are pushed to each animation
* depends on what properties are specified for the animation. For example, the default
* CHANGE_APPEARING animation animates the left, top, right,
* bottom, scrollX, and scrollY properties.
* Values for these properties are updated with the pre- and post-layout
* values when the transition begins. Custom animations will be similarly populated with
* the target and values being animated, assuming they use ObjectAnimator objects with
* property names that are known on the target object.
This class, and the associated XML flag for containers, animateLayoutChanges="true", * provides a simple utility meant for automating changes in straightforward situations. * Using LayoutTransition at multiple levels of a nested view hierarchy may not work due to the * interrelationship of the various levels of layout. Also, a container that is being scrolled * at the same time as items are being added or removed is probably not a good candidate for * this utility, because the before/after locations calculated by LayoutTransition * may not match the actual locations when the animations finish due to the container * being scrolled as the animations are running. You can work around that * particular issue by disabling the 'changing' animations by setting the CHANGE_APPEARING * and CHANGE_DISAPPEARING animations to null, and setting the startDelay of the * other animations appropriately.
*/ public class LayoutTransition { /** * A flag indicating the animation that runs on those items that are changing * due to a new item appearing in the container. */ public static final int CHANGE_APPEARING = 0; /** * A flag indicating the animation that runs on those items that are changing * due to an item disappearing from the container. */ public static final int CHANGE_DISAPPEARING = 1; /** * A flag indicating the animation that runs on those items that are appearing * in the container. */ public static final int APPEARING = 2; /** * A flag indicating the animation that runs on those items that are disappearing * from the container. */ public static final int DISAPPEARING = 3; /** * A flag indicating the animation that runs on those items that are changing * due to a layout change not caused by items being added to or removed * from the container. This transition type is not enabled by default; it can be * enabled via {@link #enableTransitionType(int)}. */ public static final int CHANGING = 4; /** * Private bit fields used to set the collection of enabled transition types for * mTransitionTypes. */ private static final int FLAG_APPEARING = 0x01; private static final int FLAG_DISAPPEARING = 0x02; private static final int FLAG_CHANGE_APPEARING = 0x04; private static final int FLAG_CHANGE_DISAPPEARING = 0x08; private static final int FLAG_CHANGING = 0x10; /** * These variables hold the animations that are currently used to run the transition effects. * These animations are set to defaults, but can be changed to custom animations by * calls to setAnimator(). */ private Animator mDisappearingAnim = null; private Animator mAppearingAnim = null; private Animator mChangingAppearingAnim = null; private Animator mChangingDisappearingAnim = null; private Animator mChangingAnim = null; /** * These are the default animations, defined in the constructor, that will be used * unless the user specifies custom animations. */ private static ObjectAnimator defaultChange; private static ObjectAnimator defaultChangeIn; private static ObjectAnimator defaultChangeOut; private static ObjectAnimator defaultFadeIn; private static ObjectAnimator defaultFadeOut; /** * The default duration used by all animations. */ private static long DEFAULT_DURATION = 300; /** * The durations of the different animations */ private long mChangingAppearingDuration = DEFAULT_DURATION; private long mChangingDisappearingDuration = DEFAULT_DURATION; private long mChangingDuration = DEFAULT_DURATION; private long mAppearingDuration = DEFAULT_DURATION; private long mDisappearingDuration = DEFAULT_DURATION; /** * The start delays of the different animations. Note that the default behavior of * the appearing item is the default duration, since it should wait for the items to move * before fading it. Same for the changing animation when disappearing; it waits for the item * to fade out before moving the other items. */ private long mAppearingDelay = DEFAULT_DURATION; private long mDisappearingDelay = 0; private long mChangingAppearingDelay = 0; private long mChangingDisappearingDelay = DEFAULT_DURATION; private long mChangingDelay = 0; /** * The inter-animation delays used on the changing animations */ private long mChangingAppearingStagger = 0; private long mChangingDisappearingStagger = 0; private long mChangingStagger = 0; /** * The default interpolators used for the animations */ private TimeInterpolator mAppearingInterpolator = new AccelerateDecelerateInterpolator(); private TimeInterpolator mDisappearingInterpolator = new AccelerateDecelerateInterpolator(); private TimeInterpolator mChangingAppearingInterpolator = new DecelerateInterpolator(); private TimeInterpolator mChangingDisappearingInterpolator = new DecelerateInterpolator(); private TimeInterpolator mChangingInterpolator = new DecelerateInterpolator(); /** * These hashmaps are used to store the animations that are currently running as part of * the transition. The reason for this is that a further layout event should cause * existing animations to stop where they are prior to starting new animations. So * we cache all of the current animations in this map for possible cancellation on * another layout event. LinkedHashMaps are used to preserve the order in which animations * are inserted, so that we process events (such as setting up start values) in the same order. */ private final HashMaptransitionType parameter determines the animation whose start delay
* is being set.
*
* @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING},
* {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines
* the animation whose start delay is being set.
* @param delay The length of time, in milliseconds, to delay before starting the animation.
* @see Animator#setStartDelay(long)
*/
public void setStartDelay(int transitionType, long delay) {
switch (transitionType) {
case CHANGE_APPEARING:
mChangingAppearingDelay = delay;
break;
case CHANGE_DISAPPEARING:
mChangingDisappearingDelay = delay;
break;
case CHANGING:
mChangingDelay = delay;
break;
case APPEARING:
mAppearingDelay = delay;
break;
case DISAPPEARING:
mDisappearingDelay = delay;
break;
}
}
/**
* Gets the start delay on one of the animation objects used by this transition. The
* transitionType parameter determines the animation whose start delay
* is returned.
*
* @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING},
* {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines
* the animation whose start delay is returned.
* @return long The start delay of the specified animation.
* @see Animator#getStartDelay()
*/
public long getStartDelay(int transitionType) {
switch (transitionType) {
case CHANGE_APPEARING:
return mChangingAppearingDelay;
case CHANGE_DISAPPEARING:
return mChangingDisappearingDelay;
case CHANGING:
return mChangingDelay;
case APPEARING:
return mAppearingDelay;
case DISAPPEARING:
return mDisappearingDelay;
}
// shouldn't reach here
return 0;
}
/**
* Sets the duration on one of the animation objects used by this transition. The
* transitionType parameter determines the animation whose duration
* is being set.
*
* @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING},
* {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines
* the animation whose duration is being set.
* @param duration The length of time, in milliseconds, that the specified animation should run.
* @see Animator#setDuration(long)
*/
public void setDuration(int transitionType, long duration) {
switch (transitionType) {
case CHANGE_APPEARING:
mChangingAppearingDuration = duration;
break;
case CHANGE_DISAPPEARING:
mChangingDisappearingDuration = duration;
break;
case CHANGING:
mChangingDuration = duration;
break;
case APPEARING:
mAppearingDuration = duration;
break;
case DISAPPEARING:
mDisappearingDuration = duration;
break;
}
}
/**
* Gets the duration on one of the animation objects used by this transition. The
* transitionType parameter determines the animation whose duration
* is returned.
*
* @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING},
* {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines
* the animation whose duration is returned.
* @return long The duration of the specified animation.
* @see Animator#getDuration()
*/
public long getDuration(int transitionType) {
switch (transitionType) {
case CHANGE_APPEARING:
return mChangingAppearingDuration;
case CHANGE_DISAPPEARING:
return mChangingDisappearingDuration;
case CHANGING:
return mChangingDuration;
case APPEARING:
return mAppearingDuration;
case DISAPPEARING:
return mDisappearingDuration;
}
// shouldn't reach here
return 0;
}
/**
* Sets the length of time to delay between starting each animation during one of the
* change animations.
*
* @param transitionType A value of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING}, or
* {@link #CHANGING}.
* @param duration The length of time, in milliseconds, to delay before launching the next
* animation in the sequence.
*/
public void setStagger(int transitionType, long duration) {
switch (transitionType) {
case CHANGE_APPEARING:
mChangingAppearingStagger = duration;
break;
case CHANGE_DISAPPEARING:
mChangingDisappearingStagger = duration;
break;
case CHANGING:
mChangingStagger = duration;
break;
// noop other cases
}
}
/**
* Gets the length of time to delay between starting each animation during one of the
* change animations.
*
* @param transitionType A value of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING}, or
* {@link #CHANGING}.
* @return long The length of time, in milliseconds, to delay before launching the next
* animation in the sequence.
*/
public long getStagger(int transitionType) {
switch (transitionType) {
case CHANGE_APPEARING:
return mChangingAppearingStagger;
case CHANGE_DISAPPEARING:
return mChangingDisappearingStagger;
case CHANGING:
return mChangingStagger;
}
// shouldn't reach here
return 0;
}
/**
* Sets the interpolator on one of the animation objects used by this transition. The
* transitionType parameter determines the animation whose interpolator
* is being set.
*
* @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING},
* {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines
* the animation whose interpolator is being set.
* @param interpolator The interpolator that the specified animation should use.
* @see Animator#setInterpolator(TimeInterpolator)
*/
public void setInterpolator(int transitionType, TimeInterpolator interpolator) {
switch (transitionType) {
case CHANGE_APPEARING:
mChangingAppearingInterpolator = interpolator;
break;
case CHANGE_DISAPPEARING:
mChangingDisappearingInterpolator = interpolator;
break;
case CHANGING:
mChangingInterpolator = interpolator;
break;
case APPEARING:
mAppearingInterpolator = interpolator;
break;
case DISAPPEARING:
mDisappearingInterpolator = interpolator;
break;
}
}
/**
* Gets the interpolator on one of the animation objects used by this transition. The
* transitionType parameter determines the animation whose interpolator
* is returned.
*
* @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING},
* {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines
* the animation whose interpolator is being returned.
* @return TimeInterpolator The interpolator that the specified animation uses.
* @see Animator#setInterpolator(TimeInterpolator)
*/
public TimeInterpolator getInterpolator(int transitionType) {
switch (transitionType) {
case CHANGE_APPEARING:
return mChangingAppearingInterpolator;
case CHANGE_DISAPPEARING:
return mChangingDisappearingInterpolator;
case CHANGING:
return mChangingInterpolator;
case APPEARING:
return mAppearingInterpolator;
case DISAPPEARING:
return mDisappearingInterpolator;
}
// shouldn't reach here
return null;
}
/**
* Sets the animation used during one of the transition types that may run. Any
* Animator object can be used, but to be most useful in the context of layout
* transitions, the animation should either be a ObjectAnimator or a AnimatorSet
* of animations including PropertyAnimators. Also, these ObjectAnimator objects
* should be able to get and set values on their target objects automatically. For
* example, a ObjectAnimator that animates the property "left" is able to set and get the
* left property from the View objects being animated by the layout
* transition. The transition works by setting target objects and properties
* dynamically, according to the pre- and post-layoout values of those objects, so
* having animations that can handle those properties appropriately will work best
* for custom animation. The dynamic setting of values is only the case for the
* CHANGE animations; the APPEARING and DISAPPEARING animations are simply run with
* the values they have.
*
* It is also worth noting that any and all animations (and their underlying * PropertyValuesHolder objects) will have their start and end values set according * to the pre- and post-layout values. So, for example, a custom animation on "alpha" * as the CHANGE_APPEARING animation will inherit the real value of alpha on the target * object (presumably 1) as its starting and ending value when the animation begins. * Animations which need to use values at the beginning and end that may not match the * values queried when the transition begins may need to use a different mechanism * than a standard ObjectAnimator object.
* * @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING}, * {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines the * animation whose animator is being set. * @param animator The animation being assigned. A value ofnull means that no
* animation will be run for the specified transitionType.
*/
public void setAnimator(int transitionType, Animator animator) {
switch (transitionType) {
case CHANGE_APPEARING:
mChangingAppearingAnim = animator;
break;
case CHANGE_DISAPPEARING:
mChangingDisappearingAnim = animator;
break;
case CHANGING:
mChangingAnim = animator;
break;
case APPEARING:
mAppearingAnim = animator;
break;
case DISAPPEARING:
mDisappearingAnim = animator;
break;
}
}
/**
* Gets the animation used during one of the transition types that may run.
*
* @param transitionType One of {@link #CHANGE_APPEARING}, {@link #CHANGE_DISAPPEARING},
* {@link #CHANGING}, {@link #APPEARING}, or {@link #DISAPPEARING}, which determines
* the animation whose animator is being returned.
* @return Animator The animation being used for the given transition type.
* @see #setAnimator(int, Animator)
*/
public Animator getAnimator(int transitionType) {
switch (transitionType) {
case CHANGE_APPEARING:
return mChangingAppearingAnim;
case CHANGE_DISAPPEARING:
return mChangingDisappearingAnim;
case CHANGING:
return mChangingAnim;
case APPEARING:
return mAppearingAnim;
case DISAPPEARING:
return mDisappearingAnim;
}
// shouldn't reach here
return null;
}
/**
* This function sets up animations on all of the views that change during layout.
* For every child in the parent, we create a change animation of the appropriate
* type (appearing, disappearing, or changing) and ask it to populate its start values from its
* target view. We add layout listeners to all child views and listen for changes. For
* those views that change, we populate the end values for those animations and start them.
* Animations are not run on unchanging views.
*
* @param parent The container which is undergoing a change.
* @param newView The view being added to or removed from the parent. May be null if the
* changeReason is CHANGING.
* @param changeReason A value of APPEARING, DISAPPEARING, or CHANGING, indicating whether the
* transition is occurring because an item is being added to or removed from the parent, or
* if it is running in response to a layout operation (that is, if the value is CHANGING).
*/
private void runChangeTransition(final ViewGroup parent, View newView, final int changeReason) {
Animator baseAnimator = null;
Animator parentAnimator = null;
final long duration;
switch (changeReason) {
case APPEARING:
baseAnimator = mChangingAppearingAnim;
duration = mChangingAppearingDuration;
parentAnimator = defaultChangeIn;
break;
case DISAPPEARING:
baseAnimator = mChangingDisappearingAnim;
duration = mChangingDisappearingDuration;
parentAnimator = defaultChangeOut;
break;
case CHANGING:
baseAnimator = mChangingAnim;
duration = mChangingDuration;
parentAnimator = defaultChange;
break;
default:
// Shouldn't reach here
duration = 0;
break;
}
// If the animation is null, there's nothing to do
if (baseAnimator == null) {
return;
}
// reset the inter-animation delay, in case we use it later
staggerDelay = 0;
final ViewTreeObserver observer = parent.getViewTreeObserver(); // used for later cleanup
if (!observer.isAlive()) {
// If the observer's not in a good state, skip the transition
return;
}
int numChildren = parent.getChildCount();
for (int i = 0; i < numChildren; ++i) {
final View child = parent.getChildAt(i);
// only animate the views not being added or removed
if (child != newView) {
setupChangeAnimation(parent, changeReason, baseAnimator, duration, child);
}
}
if (mAnimateParentHierarchy) {
ViewGroup tempParent = parent;
while (tempParent != null) {
ViewParent parentParent = tempParent.getParent();
if (parentParent instanceof ViewGroup) {
setupChangeAnimation((ViewGroup)parentParent, changeReason, parentAnimator,
duration, tempParent);
tempParent = (ViewGroup) parentParent;
} else {
tempParent = null;
}
}
}
// This is the cleanup step. When we get this rendering event, we know that all of
// the appropriate animations have been set up and run. Now we can clear out the
// layout listeners.
observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
public boolean onPreDraw() {
parent.getViewTreeObserver().removeOnPreDrawListener(this);
int count = layoutChangeListenerMap.size();
if (count > 0) {
CollectionThe default changing transitions animate the bounds and scroll positions of the
* target views. These are the animations that will run on the parent hierarchy, not
* the custom animations that happen to be set on the transition. This allows custom
* behavior for the children of the transitioning container, but uses standard behavior
* of resizing/rescrolling on any changing parents.
*
* @param animateParentHierarchy A boolean value indicating whether the parents of
* transitioning views should also be animated during the transition. Default value is true.
*/
public void setAnimateParentHierarchy(boolean animateParentHierarchy) {
mAnimateParentHierarchy = animateParentHierarchy;
}
/**
* Utility function called by runChangingTransition for both the children and the parent
* hierarchy.
*/
private void setupChangeAnimation(final ViewGroup parent, final int changeReason,
Animator baseAnimator, final long duration, final View child) {
// If we already have a listener for this child, then we've already set up the
// changing animation we need. Multiple calls for a child may occur when several
// add/remove operations are run at once on a container; each one will trigger
// changes for the existing children in the container.
if (layoutChangeListenerMap.get(child) != null) {
return;
}
// Don't animate items up from size(0,0); this is likely because the objects
// were offscreen/invisible or otherwise measured to be infinitely small. We don't
// want to see them animate into their real size; just ignore animation requests
// on these views
if (child.getWidth() == 0 && child.getHeight() == 0) {
return;
}
// Make a copy of the appropriate animation
final Animator anim = baseAnimator.clone();
// Set the target object for the animation
anim.setTarget(child);
// A ObjectAnimator (or AnimatorSet of them) can extract start values from
// its target object
anim.setupStartValues();
// If there's an animation running on this view already, cancel it
Animator currentAnimation = pendingAnimations.get(child);
if (currentAnimation != null) {
currentAnimation.cancel();
pendingAnimations.remove(child);
}
// Cache the animation in case we need to cancel it later
pendingAnimations.put(child, anim);
// For the animations which don't get started, we have to have a means of
// removing them from the cache, lest we leak them and their target objects.
// We run an animator for the default duration+100 (an arbitrary time, but one
// which should far surpass the delay between setting them up here and
// handling layout events which start them.
ValueAnimator pendingAnimRemover = ValueAnimator.ofFloat(0f, 1f).
setDuration(duration + 100);
pendingAnimRemover.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
pendingAnimations.remove(child);
}
});
pendingAnimRemover.start();
// Add a listener to track layout changes on this view. If we don't get a callback,
// then there's nothing to animate.
final View.OnLayoutChangeListener listener = new View.OnLayoutChangeListener() {
public void onLayoutChange(View v, int left, int top, int right, int bottom,
int oldLeft, int oldTop, int oldRight, int oldBottom) {
// Tell the animation to extract end values from the changed object
anim.setupEndValues();
if (anim instanceof ValueAnimator) {
boolean valuesDiffer = false;
ValueAnimator valueAnim = (ValueAnimator)anim;
PropertyValuesHolder[] oldValues = valueAnim.getValues();
for (int i = 0; i < oldValues.length; ++i) {
PropertyValuesHolder pvh = oldValues[i];
KeyframeSet keyframeSet = pvh.mKeyframeSet;
if (keyframeSet.mFirstKeyframe == null ||
keyframeSet.mLastKeyframe == null ||
!keyframeSet.mFirstKeyframe.getValue().equals(
keyframeSet.mLastKeyframe.getValue())) {
valuesDiffer = true;
}
}
if (!valuesDiffer) {
return;
}
}
long startDelay = 0;
switch (changeReason) {
case APPEARING:
startDelay = mChangingAppearingDelay + staggerDelay;
staggerDelay += mChangingAppearingStagger;
break;
case DISAPPEARING:
startDelay = mChangingDisappearingDelay + staggerDelay;
staggerDelay += mChangingDisappearingStagger;
break;
case CHANGING:
startDelay = mChangingDelay + staggerDelay;
staggerDelay += mChangingStagger;
break;
}
anim.setStartDelay(startDelay);
anim.setDuration(duration);
Animator prevAnimation = currentChangingAnimations.get(child);
if (prevAnimation != null) {
prevAnimation.cancel();
}
Animator pendingAnimation = pendingAnimations.get(child);
if (pendingAnimation != null) {
pendingAnimations.remove(child);
}
// Cache the animation in case we need to cancel it later
currentChangingAnimations.put(child, anim);
parent.requestTransitionStart(LayoutTransition.this);
// this only removes listeners whose views changed - must clear the
// other listeners later
child.removeOnLayoutChangeListener(this);
layoutChangeListenerMap.remove(child);
}
};
// Remove the animation from the cache when it ends
anim.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationStart(Animator animator) {
if (hasListeners()) {
ArrayList