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；