final float distanceCoef = d_inf + (t - t_inf) / (t_sup - t_inf) * (d_sup - d_inf);
mCurrX = mStartX + Math.round(distanceCoef * (mFinalX - mStartX));
// Pin to mMinX <= mCurrX <= mMaxX
mCurrX = Math.min(mCurrX, mMaxX);
mCurrX = Math.max(mCurrX, mMinX);
mCurrY = mStartY + Math.round(distanceCoef * (mFinalY - mStartY));
// Pin to mMinY <= mCurrY <= mMaxY
mCurrY = Math.min(mCurrY, mMaxY);
mCurrY = Math.max(mCurrY, mMinY);
if (mCurrX == mFinalX && mCurrY == mFinalY) {
mFinished = true;
}
break;
}
}
else {
mCurrX = mFinalX;
mCurrY = mFinalY;
mFinished = true;
}
return true;
}

看代码主要当平滑没有完成的情况下，计算出当前滑动的坐标位置，如果平滑完成了，就不需要计算了；这里有一个SCROLL_MODE和FLING_MODEL两种滑动模式，这里是SCROLL_MODE手动拖动平滑模式，FLING_MODEL是由于手指滑动速率来判断惯性滑动。一般这个方法执行完成之后，根据返回值判断是否需要invalidate/postinvalidate，再根据Scroller计算好的坐标值，View将scrollTo/scrollBy到新的坐标位置；

3、fling（）方法：

public void fling(int startX, int startY, int velocityX, int velocityY,
int minX, int maxX, int minY, int maxY) {
// Continue a scroll or fling in progress
if (mFlywheel && !mFinished) {
float oldVel = getCurrVelocity();
float dx = (float) (mFinalX - mStartX);
float dy = (float) (mFinalY - mStartY);
float hyp = FloatMath.sqrt(dx * dx + dy * dy);
float ndx = dx / hyp;
float ndy = dy / hyp;
float oldVelocityX = ndx * oldVel;
float oldVelocityY = ndy * oldVel;
if (Math.signum(velocityX) == Math.signum(oldVelocityX) &&
Math.signum(velocityY) == Math.signum(oldVelocityY)) {
velocityX += oldVelocityX;
velocityY += oldVelocityY;
}
}
mMode = FLING_MODE;
mFinished = false;
float velocity = FloatMath.sqrt(velocityX * velocityX + velocityY * velocityY);
mVelocity = velocity;
final double l = Math.log(START_TENSION * velocity / ALPHA);
mDuration = (int) (1000.0 * Math.exp(l / (DECELERATION_RATE - 1.0)));
mStartTime = AnimationUtils.currentAnimationTimeMillis();
mStartX = startX;
mStartY = startY;
float coeffX = velocity == 0 ? 1.0f : velocityX / velocity;
float coeffY = velocity == 0 ? 1.0f : velocityY / velocity;
int totalDistance =
(int) (ALPHA * Math.exp(DECELERATION_RATE / (DECELERATION_RATE - 1.0) * l));
mMinX = minX;
mMaxX = maxX;
mMinY = minY;
mMaxY = maxY;
mFinalX = startX + Math.round(totalDistance * coeffX);
// Pin to mMinX <= mFinalX <= mMaxX
mFinalX = Math.min(mFinalX, mMaxX);
mFinalX = Math.max(mFinalX, mMinX);
mFinalY = startY + Math.round(totalDistance * coeffY);
// Pin to mMinY <= mFinalY <= mMaxY
mFinalY = Math.min(mFinalY, mMaxY);
mFinalY = Math.max(mFinalY, mMinY);
}

滑动，这个滑就跟GestureDetector.OnGestureListener这个接口中的onFling事件一样，根据滑动速率来判断一些事件。主要处理一些一些惯性坐标变化（惯性行为）。用得比较少；

4、abortAnimation（）方法：

public void abortAnimation() {
mCurrX = mFinalX;
mCurrY = mFinalY;
mFinished = true;
}

看源码，停止动画（就是设置一个标记而已，不再计算坐标的变化值）

在代码的开始外看到这样一段静态代码块：

static {
float x_min = 0.0f;
for (int i = 0; i <= NB_SAMPLES; i++) {
final float t = (float) i / NB_SAMPLES;
float x_max = 1.0f;
float x, tx, coef;
while (true) {
x = x_min + (x_max - x_min) / 2.0f;
coef = 3.0f * x * (1.0f - x);
tx = coef * ((1.0f - x) * START_TENSION + x * END_TENSION) + x * x * x;
if (Math.abs(tx - t) < 1E-5) break;
if (tx > t) x_max = x;
else x_min = x;
}
final float d = coef + x * x * x;
SPLINE[i] = d;
}
SPLINE[NB_SAMPLES] = 1.0f;
// This controls the viscous fluid effect (how much of it)
sViscousFluidScale = 8.0f;
// must be set to 1.0 (used in viscousFluid())
sViscousFluidNormalize = 1.0f;
sViscousFluidNormalize = 1.0f / viscousFluid(1.0f);
}

这一段代码让我纠结了好久，照我的理解应该是把惯性滑动模式中的滑动距离比率（不好描述）分成100份，精确到0.00001，在惯性滑动的时候根据当前时间比率来计算当前坐标处于的位置；

其实说到这里，感觉Android里面的动画，其实就是对于坐标的精确计算，这里只是简单的平滑滑动，有能力者我们也可以根据自己的需求写出自己的坐标计算类来达到我们的需求；