float normalizedTime;
if (duration != 0) {
normalizedTime = ((float) (currentTime - (mStartTime + startOffset))) /
(float) duration;
} else {
// time is a step-change with a zero duration
normalizedTime = currentTime < mStartTime 0.0f : 1.0f;
}
final boolean expired = normalizedTime >= 1.0f;
mMore = !expired;
if (!mFillEnabled) normalizedTime = Math.max(Math.min(normalizedTime, 1.0f), 0.0f);
// 前面的部分是计算normalizedTime,这里开始才是调用执行
if ((normalizedTime >= 0.0f || mFillBefore) && (normalizedTime <= 1.0f || mFillAfter)) {
if (!mStarted) {
if (mListener != null) {
mListener.onAnimationStart(this);
}
mStarted = true;
if (USE_CLOSEGUARD) {
guard.open("cancel or detach or getTransformation");
}
}
if (mFillEnabled) normalizedTime = Math.max(Math.min(normalizedTime, 1.0f), 0.0f);
if (mCycleFlip) {
normalizedTime = 1.0f - normalizedTime;
}
final float interpolatedTime = mInterpolator.getInterpolation(normalizedTime);
applyTransformation(interpolatedTime, outTransformation);
}
// 完成了applyTransformation的调用，后面计算动画是否循环
if (expired) {
if (mRepeatCount == mRepeated) {
if (!mEnded) {
mEnded = true;
guard.close();
if (mListener != null) {
mListener.onAnimationEnd(this);
}
}
} else {
if (mRepeatCount > 0) {
mRepeated++;
}
if (mRepeatMode == REVERSE) {
mCycleFlip = !mCycleFlip;
}
mStartTime = -1;
mMore = true;
if (mListener != null) {
mListener.onAnimationRepeat(this);
}
}
}
if (!mMore && mOneMoreTime) {
mOneMoreTime = false;
return true;
}
return mMore;
}这个方法中，还有一个成员是mListener，它的类型是AnimationListener，在这个Animation类的末尾，定义了AnimationListener接口，继承Animation类的子类可以使用此接口，来监听比如动画开始时要做保存工作，动画结束时要做清除及恢复工作等。
[java]
/**
*
An animation listener receives notifications from an animation.
* Notifications indicate animation related events, such as the end or the
* repetition of the animation.
*/
public static interface AnimationListener {
/**
*
Notifies the start of the animation.
*
* @param animation The started animation.
*/
void onAnimationStart(Animation animation);
/**
*
Notifies the end of the animation. This callback is not invoked
* for animations with repeat count set to INFINITE.
*
* @param animation The animation which reached its end.
*/
void onAnimationEnd(Animation animation);
/**
*
Notifies the repetition of the animation.
*
* @param animation The animation which was repeated.
*/
void onAnimationRepeat(Animation animation);
}
/**
*
An animation listener receives notifications from an animation.
* Notifications indicate animation related events, such as the end or the
* repetitio