1.概念

缩放大小的动画，创建动画时需要指定动画开始和结束时在X轴和Y轴的缩放比，以及动画持续的时间；同时由于缩放时以不同的点作为中心会产生不同的效果，因此也需要通过pivotX 和 pivotY 指定缩放中心的坐标。

2.创建

XML：

 <?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android" android:interpolator="@android:anim/linear_interpolator">
    <scale
        android:fromXScale="0.0"
        android:toXScale="1.0"
        android:fromYScale="1.0"
        android:toYScale="1.0"
        android:pivotX="50%"
        android:duration="@android:integer/config_mediumAnimTime" />
</set>

Java：

                ScaleAnimation scaleAnimation = new ScaleAnimation(0, 2.0f,0,2.0f,ScaleAnimation.RELATIVE_TO_PARENT,0.5f,ScaleAnimation.RELATIVE_TO_PARENT,0.5f );
                //动画播放的时间间隔
                scaleAnimation.setDuration(3000);
                //动画播放的重复次数
                scaleAnimation.setRepeatCount(2);
                scaleAnimation.setRepeatMode(RESTART);
                imageView.startAnimation(scaleAnimation);

3.构造函数解析

在上面的创建示例中，Java代码的方式采用了一个有着众多参数的构造函数，其实ScaleAnimation有三个构造函数，下面就对这些参数进行解析：

    /**
     * Constructor to use when building a ScaleAnimation from code
     * 
     * @param fromX Horizontal scaling factor to apply at the start of the
     *        animation
     * @param toX Horizontal scaling factor to apply at the end of the animation
     * @param fromY Vertical scaling factor to apply at the start of the
     *        animation
     * @param toY Vertical scaling factor to apply at the end of the animation
     */
    public ScaleAnimation(float fromX, float toX, float fromY, float toY) {
        mResources = null;
        mFromX = fromX;
        mToX = toX;
        mFromY = fromY;
        mToY = toY;
        mPivotX = 0;
        mPivotY = 0;
    }

    /**
     * Constructor to use when building a ScaleAnimation from code
     * 
     * @param fromX Horizontal scaling factor to apply at the start of the
     *        animation
     * @param toX Horizontal scaling factor to apply at the end of the animation
     * @param fromY Vertical scaling factor to apply at the start of the
     *        animation
     * @param toY Vertical scaling factor to apply at the end of the animation
     * @param pivotX The X coordinate of the point about which the object is
     *        being scaled, specified as an absolute number where 0 is the left
     *        edge. (This point remains fixed while the object changes size.)
     * @param pivotY The Y coordinate of the point about which the object is
     *        being scaled, specified as an absolute number where 0 is the top
     *        edge. (This point remains fixed while the object changes size.)
     */
    public ScaleAnimation(float fromX, float toX, float fromY, float toY,
            float pivotX, float pivotY) {
        mResources = null;
        mFromX = fromX;
        mToX = toX;
        mFromY = fromY;
        mToY = toY;

        mPivotXType = ABSOLUTE;
        mPivotYType = ABSOLUTE;
        mPivotXValue = pivotX;
        mPivotYValue = pivotY;
        initializePivotPoint();
    }

    /**
     * Constructor to use when building a ScaleAnimation from code
     * 
     * @param fromX Horizontal scaling factor to apply at the start of the
     *        animation
     * @param toX Horizontal scaling factor to apply at the end of the animation
     * @param fromY Vertical scaling factor to apply at the start of the
     *        animation
     * @param toY Vertical scaling factor to apply at the end of the animation
     * @param pivotXType Specifies how pivotXValue should be interpreted. One of
     *        Animation.ABSOLUTE, Animation.RELATIVE_TO_SELF, or
     *        Animation.RELATIVE_TO_PARENT.
     * @param pivotXValue The X coordinate of the point about which the object
     *        is being scaled, specified as an absolute number where 0 is the
     *        left edge. (This point remains fixed while the object changes
     *        size.) This value can either be an absolute number if pivotXType
     *        is ABSOLUTE, or a percentage (where 1.0 is 100%) otherwise.
     * @param pivotYType Specifies how pivotYValue should be interpreted. One of
     *        Animation.ABSOLUTE, Animation.RELATIVE_TO_SELF, or
     *        Animation.RELATIVE_TO_PARENT.
     * @param pivotYValue The Y coordinate of the point about which the object
     *        is being scaled, specified as an absolute number where 0 is the
     *        top edge. (This point remains fixed while the object changes
     *        size.) This value can either be an absolute number if pivotYType
     *        is ABSOLUTE, or a percentage (where 1.0 is 100%) otherwise.
     */
    public ScaleAnimation(float fromX, float toX, float fromY, float toY,
            int pivotXType, float pivotXValue, int pivotYType, float pivotYValue) {
        mResources = null;
        mFromX = fromX;
        mToX = toX;
        mFromY = fromY;
        mToY = toY;

        mPivotXValue = pivotXValue;
        mPivotXType = pivotXType;
        mPivotYValue = pivotYValue;
        mPivotYType = pivotYType;
        initializePivotPoint();
    }

• fromX 动画开始时的X坐标的伸缩尺寸
• toX 动画结束时的X坐标的伸缩尺寸
• fromY 动画开始时的Y坐标的伸缩尺寸
• toY 动画结束时的Y坐标的伸缩尺寸
• pivotX/pivotXValue 缩放动画的中心点X坐标
• pivotY/pivotYValue 缩放动画的中心点Y坐标
• pivotXType 动画在X轴的伸缩模式，也就是中心点相对于哪个物件，取值是 Animation.ABSOLUTE、Animation.RELATIVE_TO_SELF、Animation.RELATIVE_TO_PARENT
• pivotYType 动画在Y轴的伸缩模式，也就是中心点相对于哪个物件，取值是 Animation.ABSOLUTE、Animation.RELATIVE_TO_SELF、Animation.RELATIVE_TO_PARENT