android中tween动画自定义

由TranslateAnimation来看自定义动画：

  /**
     * Constructor to use when building a TranslateAnimation from code
     *
     * @param fromXDelta Change in X coordinate to apply at the start of the
     *        animation
     * @param toXDelta Change in X coordinate to apply at the end of the
     *        animation
     * @param fromYDelta Change in Y coordinate to apply at the start of the
     *        animation
     * @param toYDelta Change in Y coordinate to apply at the end of the
     *        animation
     */
    public TranslateAnimation(float fromXDelta, float toXDelta, float fromYDelta, float toYDelta) {
        mFromXValue = fromXDelta;
        mToXValue = toXDelta;
        mFromYValue = fromYDelta;
        mToYValue = toYDelta;

        mFromXType = ABSOLUTE;
        mToXType = ABSOLUTE;
        mFromYType = ABSOLUTE;
        mToYType = ABSOLUTE;
    }

构造函数中对移动信息做了初始化；

下面方法是根据interpolateTime，来计算出变换矩阵；

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        float dx = mFromXDelta;
        float dy = mFromYDelta;
        if (mFromXDelta != mToXDelta) {
            dx = mFromXDelta + ((mToXDelta - mFromXDelta) * interpolatedTime);
        }
        if (mFromYDelta != mToYDelta) {
            dy = mFromYDelta + ((mToYDelta - mFromYDelta) * interpolatedTime);
        }
        t.getMatrix().setTranslate(dx, dy);
    }

   重写的方法：   @Override    public void initialize(int width, int height, int parentWidth, int parentHeight) {        super.initialize(width, height, parentWidth, parentHeight);        mFromXDelta = resolveSize(mFromXType, mFromXValue, width, parentWidth);        mToXDelta = resolveSize(mToXType, mToXValue, width, parentWidth);        mFromYDelta = resolveSize(mFromYType, mFromYValue, height, parentHeight);        mToYDelta = resolveSize(mToYType, mToYValue, height, parentHeight);    }

initialize方法是在View的下面方法中调用：

 /**
     * Utility function, called by draw(canvas, parent, drawingTime) to handle the less common
     * case of an active Animation being run on the view.
     */
    private boolean applyLegacyAnimation(ViewGroup parent, long drawingTime,
            Animation a, boolean scalingRequired) {
        Transformation invalidationTransform;
        final int flags = parent.mGroupFlags;
        final boolean initialized = a.isInitialized();
        if (!initialized) {
            a.initialize(mRight - mLeft, mBottom - mTop, parent.getWidth(), parent.getHeight());
            a.initializeInvalidateRegion(0, 0, mRight - mLeft, mBottom - mTop);
            if (mAttachInfo != null) a.setListenerHandler(mAttachInfo.mHandler);
            onAnimationStart();
        }
................................................
}

interpolatedTime获得方式： 可以自定义插值器来 控制动画速度；

实现 Interpolator 接口；