https://source.android.com/ 
/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.view.animation;

import android.annotation.AnimRes;
import android.annotation.InterpolatorRes;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

import java.util.Random;


A layout animation controller is used to animated a layout's, or a view group's, children. Each child uses the same animation but for every one of them, the animation starts at a different time. A layout animation controller is used by ViewGroup to compute the delay by which each child's animation start must be offset. The delay is computed by using characteristics of each child, like its index in the view group. This standard implementation computes the delay by multiplying a fixed amount of miliseconds by the index of the child in its parent view group. Subclasses are supposed to override getDelayForView(View) to implement a different way of computing the delay. For instance, a GridLayoutAnimationController will compute the delay based on the column and row indices of the child in its parent view group. Information used to compute the animation delay of each child are stored in an instance of AnimationParameters, itself stored in the LayoutParams of the view. 
@attrref android.R.styleable#LayoutAnimation_delay
@attrref android.R.styleable#LayoutAnimation_animationOrder
@attrref android.R.styleable#LayoutAnimation_interpolator
@attrref android.R.styleable#LayoutAnimation_animation
/**
 * A layout animation controller is used to animated a layout's, or a view
 * group's, children. Each child uses the same animation but for every one of
 * them, the animation starts at a different time. A layout animation controller
 * is used by {@link android.view.ViewGroup} to compute the delay by which each
 * child's animation start must be offset. The delay is computed by using
 * characteristics of each child, like its index in the view group.
 *
 * This standard implementation computes the delay by multiplying a fixed
 * amount of miliseconds by the index of the child in its parent view group.
 * Subclasses are supposed to override
 * {@link #getDelayForView(android.view.View)} to implement a different way
 * of computing the delay. For instance, a
 * {@link android.view.animation.GridLayoutAnimationController} will compute the
 * delay based on the column and row indices of the child in its parent view
 * group.
 *
 * Information used to compute the animation delay of each child are stored
 * in an instance of
 * {@link android.view.animation.LayoutAnimationController.AnimationParameters},
 * itself stored in the {@link android.view.ViewGroup.LayoutParams} of the view.
 *
 * @attr ref android.R.styleable#LayoutAnimation_delay
 * @attr ref android.R.styleable#LayoutAnimation_animationOrder
 * @attr ref android.R.styleable#LayoutAnimation_interpolator
 * @attr ref android.R.styleable#LayoutAnimation_animation
 */
public class LayoutAnimationController {
    
Distributes the animation delays in the order in which view were added
to their view group.

/**
     * Distributes the animation delays in the order in which view were added
     * to their view group.
     */
    public static final int ORDER_NORMAL  = 0;

    
Distributes the animation delays in the reverse order in which view were
added to their view group.

/**
     * Distributes the animation delays in the reverse order in which view were
     * added to their view group.
     */
    public static final int ORDER_REVERSE = 1;

    
Randomly distributes the animation delays.

/**
     * Randomly distributes the animation delays.
     */
    public static final int ORDER_RANDOM  = 2;

    
The animation applied on each child of the view group on which this
layout animation controller is set.

/**
     * The animation applied on each child of the view group on which this
     * layout animation controller is set.
     */
    protected Animation mAnimation;

    
The randomizer used when the order is set to random. Subclasses should
use this object to avoid creating their own.

/**
     * The randomizer used when the order is set to random. Subclasses should
     * use this object to avoid creating their own.
     */
    protected Random mRandomizer;

    
The interpolator used to interpolate the delays.

/**
     * The interpolator used to interpolate the delays.
     */
    protected Interpolator mInterpolator;

    private float mDelay;
    private int mOrder;

    private long mDuration;
    private long mMaxDelay;    

    
Creates a new layout animation controller from external resources.

Params:
  • context – the Context the view  group is running in, through which
       it can access the resources
  • attrs – the attributes of the XML tag that is inflating the
       layout animation controller
/**
     * Creates a new layout animation controller from external resources.
     *
     * @param context the Context the view  group is running in, through which
     *        it can access the resources
     * @param attrs the attributes of the XML tag that is inflating the
     *        layout animation controller
     */
    public LayoutAnimationController(Context context, AttributeSet attrs) {
        TypedArray a = context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.LayoutAnimation);

        Animation.Description d = Animation.Description.parseValue(
                a.peekValue(com.android.internal.R.styleable.LayoutAnimation_delay));
        mDelay = d.value;

        mOrder = a.getInt(com.android.internal.R.styleable.LayoutAnimation_animationOrder, ORDER_NORMAL);

        int resource = a.getResourceId(com.android.internal.R.styleable.LayoutAnimation_animation, 0);
        if (resource > 0) {
            setAnimation(context, resource);
        }

        resource = a.getResourceId(com.android.internal.R.styleable.LayoutAnimation_interpolator, 0);
        if (resource > 0) {
            setInterpolator(context, resource);
        }

        a.recycle();
    }

    
Creates a new layout animation controller with a delay of 50%
and the specified animation.

Params:
  • animation – the animation to use on each child of the view group
/**
     * Creates a new layout animation controller with a delay of 50%
     * and the specified animation.
     *
     * @param animation the animation to use on each child of the view group
     */
    public LayoutAnimationController(Animation animation) {
        this(animation, 0.5f);
    }

    
Creates a new layout animation controller with the specified delay
and the specified animation.

Params:
  • animation – the animation to use on each child of the view group
  • delay – the delay by which each child's animation must be offset
/**
     * Creates a new layout animation controller with the specified delay
     * and the specified animation.
     *
     * @param animation the animation to use on each child of the view group
     * @param delay the delay by which each child's animation must be offset
     */
    public LayoutAnimationController(Animation animation, float delay) {
        mDelay = delay;
        setAnimation(animation);
    }

    
Returns the order used to compute the delay of each child's animation.

Returns:one of ORDER_NORMAL, ORDER_REVERSE or ORDER_RANDOM
@attrref android.R.styleable#LayoutAnimation_animationOrder
/**
     * Returns the order used to compute the delay of each child's animation.
     *
     * @return one of {@link #ORDER_NORMAL}, {@link #ORDER_REVERSE} or
     *         {@link #ORDER_RANDOM}
     *
     * @attr ref android.R.styleable#LayoutAnimation_animationOrder
     */
    public int getOrder() {
        return mOrder;
    }

    
Sets the order used to compute the delay of each child's animation.

Params:
@attrref android.R.styleable#LayoutAnimation_animationOrder
/**
     * Sets the order used to compute the delay of each child's animation.
     *
     * @param order one of {@link #ORDER_NORMAL}, {@link #ORDER_REVERSE} or
     *        {@link #ORDER_RANDOM}
     *
     * @attr ref android.R.styleable#LayoutAnimation_animationOrder
     */
    public void setOrder(int order) {
        mOrder = order;
    }

    
Sets the animation to be run on each child of the view group on which
this layout animation controller is .

Params:
  • context – the context from which the animation must be inflated
  • resourceID – the resource identifier of the animation
See Also:
@attrref android.R.styleable#LayoutAnimation_animation
/**
     * Sets the animation to be run on each child of the view group on which
     * this layout animation controller is .
     *
     * @param context the context from which the animation must be inflated
     * @param resourceID the resource identifier of the animation
     *
     * @see #setAnimation(Animation)
     * @see #getAnimation() 
     *
     * @attr ref android.R.styleable#LayoutAnimation_animation
     */
    public void setAnimation(Context context, @AnimRes int resourceID) {
        setAnimation(AnimationUtils.loadAnimation(context, resourceID));
    }

    
Sets the animation to be run on each child of the view group on which
this layout animation controller is .

Params:
  • animation – the animation to run on each child of the view group
See Also:
@attrref android.R.styleable#LayoutAnimation_animation
/**
     * Sets the animation to be run on each child of the view group on which
     * this layout animation controller is .
     *
     * @param animation the animation to run on each child of the view group

     * @see #setAnimation(android.content.Context, int)
     * @see #getAnimation()
     *
     * @attr ref android.R.styleable#LayoutAnimation_animation
     */
    public void setAnimation(Animation animation) {
        mAnimation = animation;
        mAnimation.setFillBefore(true);
    }

    
Returns the animation applied to each child of the view group on which
this controller is set.

See Also:
Returns:an Animation instance
/**
     * Returns the animation applied to each child of the view group on which
     * this controller is set.
     *
     * @return an {@link android.view.animation.Animation} instance
     *
     * @see #setAnimation(android.content.Context, int)
     * @see #setAnimation(Animation)
     */
    public Animation getAnimation() {
        return mAnimation;
    }

    
Sets the interpolator used to interpolate the delays between the
children.

Params:
  • context – the context from which the interpolator must be inflated
  • resourceID – the resource identifier of the interpolator
See Also:
@attrref android.R.styleable#LayoutAnimation_interpolator
/**
     * Sets the interpolator used to interpolate the delays between the
     * children.
     *
     * @param context the context from which the interpolator must be inflated
     * @param resourceID the resource identifier of the interpolator
     *
     * @see #getInterpolator()
     * @see #setInterpolator(Interpolator)
     *
     * @attr ref android.R.styleable#LayoutAnimation_interpolator
     */
    public void setInterpolator(Context context, @InterpolatorRes int resourceID) {
        setInterpolator(AnimationUtils.loadInterpolator(context, resourceID));
    }

    
Sets the interpolator used to interpolate the delays between the
children.

Params:
  • interpolator – the interpolator
See Also:
@attrref android.R.styleable#LayoutAnimation_interpolator
/**
     * Sets the interpolator used to interpolate the delays between the
     * children.
     *
     * @param interpolator the interpolator
     *
     * @see #getInterpolator()
     * @see #setInterpolator(Interpolator)
     *
     * @attr ref android.R.styleable#LayoutAnimation_interpolator
     */
    public void setInterpolator(Interpolator interpolator) {
        mInterpolator = interpolator;
    }

    
Returns the interpolator used to interpolate the delays between the
children.

Returns:an Interpolator
/**
     * Returns the interpolator used to interpolate the delays between the
     * children.
     *
     * @return an {@link android.view.animation.Interpolator}
     */
    public Interpolator getInterpolator() {
        return mInterpolator;
    }

    
Returns the delay by which the children's animation are offset. The
delay is expressed as a fraction of the animation duration.

See Also:
Returns:a fraction of the animation duration
/**
     * Returns the delay by which the children's animation are offset. The
     * delay is expressed as a fraction of the animation duration.
     *
     * @return a fraction of the animation duration
     *
     * @see #setDelay(float)
     */
    public float getDelay() {
        return mDelay;
    }

    
Sets the delay, as a fraction of the animation duration, by which the
children's animations are offset. The general formula is:

child animation delay = child index * delay * animation duration



Params:
  • delay – a fraction of the animation duration
See Also:
/**
     * Sets the delay, as a fraction of the animation duration, by which the
     * children's animations are offset. The general formula is:
     *
     * <pre>
     * child animation delay = child index * delay * animation duration
     * </pre>
     *
     * @param delay a fraction of the animation duration
     *
     * @see #getDelay()
     */
    public void setDelay(float delay) {
        mDelay = delay;
    }

    
Indicates whether two children's animations will overlap. Animations
overlap when the delay is lower than 100% (or 1.0).

Returns:true if animations will overlap, false otherwise
/**
     * Indicates whether two children's animations will overlap. Animations
     * overlap when the delay is lower than 100% (or 1.0).
     *
     * @return true if animations will overlap, false otherwise
     */
    public boolean willOverlap() {
        return mDelay < 1.0f;
    }

    
Starts the animation.

/**
     * Starts the animation.
     */
    public void start() {
        mDuration = mAnimation.getDuration();
        mMaxDelay = Long.MIN_VALUE;
        mAnimation.setStartTime(-1);
    }

    
Returns the animation to be applied to the specified view. The returned animation is delayed by an offset computed according to the information provided by AnimationParameters. This method is called by view groups to obtain the animation to set on a specific child. 
Params:
  • view – the view to animate
See Also:
Returns:an animation delayed by the number of milliseconds returned by getDelayForView(View)
/**
     * Returns the animation to be applied to the specified view. The returned
     * animation is delayed by an offset computed according to the information
     * provided by
     * {@link android.view.animation.LayoutAnimationController.AnimationParameters}.
     * This method is called by view groups to obtain the animation to set on
     * a specific child.
     *
     * @param view the view to animate
     * @return an animation delayed by the number of milliseconds returned by
     *         {@link #getDelayForView(android.view.View)}
     *
     * @see #getDelay()
     * @see #setDelay(float)
     * @see #getDelayForView(android.view.View)
     */
    public final Animation getAnimationForView(View view) {
        final long delay = getDelayForView(view) + mAnimation.getStartOffset();
        mMaxDelay = Math.max(mMaxDelay, delay);

        try {
            final Animation animation = mAnimation.clone();
            animation.setStartOffset(delay);
            return animation;
        } catch (CloneNotSupportedException e) {
            return null;
        }
    }

    
Indicates whether the layout animation is over or not. A layout animation
is considered done when the animation with the longest delay is done.

Returns:true if all of the children's animations are over, false otherwise
/**
     * Indicates whether the layout animation is over or not. A layout animation
     * is considered done when the animation with the longest delay is done.
     *
     * @return true if all of the children's animations are over, false otherwise
     */
    public boolean isDone() {
        return AnimationUtils.currentAnimationTimeMillis() >
                mAnimation.getStartTime() + mMaxDelay + mDuration;
    }

    
Returns the amount of milliseconds by which the specified view's
animation must be delayed or offset. Subclasses should override this
method to return a suitable value.
This implementation returns child animation delay
milliseconds where:

child animation delay = child index * delay

 The index is retrieved from the AnimationParameters found in the view's LayoutParams. 
Params:
  • view – the view for which to obtain the animation's delay
See Also:
Returns:a delay in milliseconds
/**
     * Returns the amount of milliseconds by which the specified view's
     * animation must be delayed or offset. Subclasses should override this
     * method to return a suitable value.
     *
     * This implementation returns <code>child animation delay</code>
     * milliseconds where:
     *
     * <pre>
     * child animation delay = child index * delay
     * </pre>
     *
     * The index is retrieved from the
     * {@link android.view.animation.LayoutAnimationController.AnimationParameters}
     * found in the view's {@link android.view.ViewGroup.LayoutParams}.
     *
     * @param view the view for which to obtain the animation's delay
     * @return a delay in milliseconds
     *
     * @see #getAnimationForView(android.view.View)
     * @see #getDelay()
     * @see #getTransformedIndex(android.view.animation.LayoutAnimationController.AnimationParameters)
     * @see android.view.ViewGroup.LayoutParams
     */
    protected long getDelayForView(View view) {
        ViewGroup.LayoutParams lp = view.getLayoutParams();
        AnimationParameters params = lp.layoutAnimationParameters;

        if (params == null) {
            return 0;
        }

        final float delay = mDelay * mAnimation.getDuration();
        final long viewDelay = (long) (getTransformedIndex(params) * delay);
        final float totalDelay = delay * params.count;

        if (mInterpolator == null) {
            mInterpolator = new LinearInterpolator();
        }

        float normalizedDelay = viewDelay / totalDelay;
        normalizedDelay = mInterpolator.getInterpolation(normalizedDelay);

        return (long) (normalizedDelay * totalDelay);
    }

    
Transforms the index stored in AnimationParameters by the order returned by getOrder(). Subclasses should override this method to provide additional support for other types of ordering. This method should be invoked by getDelayForView(View) prior to any computation. 
Params:
  • params – the animation parameters containing the index
Returns:a transformed index
/**
     * Transforms the index stored in
     * {@link android.view.animation.LayoutAnimationController.AnimationParameters}
     * by the order returned by {@link #getOrder()}. Subclasses should override
     * this method to provide additional support for other types of ordering.
     * This method should be invoked by
     * {@link #getDelayForView(android.view.View)} prior to any computation. 
     *
     * @param params the animation parameters containing the index
     * @return a transformed index
     */
    protected int getTransformedIndex(AnimationParameters params) {
        switch (getOrder()) {
            case ORDER_REVERSE:
                return params.count - 1 - params.index;
            case ORDER_RANDOM:
                if (mRandomizer == null) {
                    mRandomizer = new Random();
                }
                return (int) (params.count * mRandomizer.nextFloat());
            case ORDER_NORMAL:
            default:
                return params.index;
        }
    }

    
The set of parameters that has to be attached to each view contained in
the view group animated by the layout animation controller. These
parameters are used to compute the start time of each individual view's
animation.

/**
     * The set of parameters that has to be attached to each view contained in
     * the view group animated by the layout animation controller. These
     * parameters are used to compute the start time of each individual view's
     * animation.
     */
    public static class AnimationParameters {
        
The number of children in the view group containing the view to which
these parameters are attached.

/**
         * The number of children in the view group containing the view to which
         * these parameters are attached.
         */
        public int count;

        
The index of the view to which these parameters are attached in its
containing view group.

/**
         * The index of the view to which these parameters are attached in its
         * containing view group.
         */
        public int index;
    }
}