摘要:Android 動畫
有關詳細的interpolator可參考此連結:
http://cogitolearning.co.uk/?p=1078
測試範例是從Android demo sample來了解各種interpolator變化
Android所提供的各種interpolator:
AccelerateDecelerateInterolator
先加速後減速，開始結束時慢，中間加速
public float getInterpolation(float input) {
return (float)(Math.cos((input + 1) * Math.PI) / 2.0f) + 0.5f;
// y = cos((t + 1)Math.PI)/2 + 0.5
}
AccelerateInterpolator
加速，開始時慢中間加速
public float getInterpolation(float input) {
if (mFactor == 1.0f) {
return input * input;
} else {
return (float)Math.pow(input, mDoubleFactor);
}
}
DecelerateInterpolator
減速，開始時快然後減速
public float getInterpolation(float input) {
float result;
if (mFactor == 1.0f) {
result = (float)(1.0f - (1.0f - input) * (1.0f - input));
} else {
result = (float)(1.0f - Math.pow((1.0f - input), 2 * mFactor));
// y = (1 - (1 - t)^2f)
}
return result;
}
AnticipateInterpolator
反向 ，先向相反方向改變一段再加速播放
public float getInterpolation(float t) {
// a(t) = t * t * ((tension + 1) * t - tension)
return t * t * ((mTension + 1) * t - mTension);
// y = (T+1)*t^3 - T*t^2
}
AnticipateOvershootInterpolator
反向加超越，先向相反方向改變，再加速播放，會超出目的值然後緩慢移動至目的值
public float getInterpolation(float t) {
// a(t, s) = t * t * ((s + 1) * t - s)
// o(t, s) = t * t * ((s + 1) * t + s)
// f(t) = 0.5 * a(t * 2, tension * extraTension), when t < 0.5
// f(t) = 0.5 * (o(t * 2 - 2, tension * extraTension) + 2), when t <= 1.0
if (t < 0.5f) return 0.5f * a(t * 2.0f, mTension);
else return 0.5f * (o(t * 2.0f - 2.0f, mTension) + 2.0f);
}
BounceInterpolator
跳躍，快到目的值時值會跳躍，如目的值100，後面的值可能依次為85，77，70，80，90，100
public float getInterpolation(float t) {
// _b(t) = t * t * 8
// bs(t) = _b(t) for t < 0.3535
// bs(t) = _b(t - 0.54719) + 0.7 for t < 0.7408
// bs(t) = _b(t - 0.8526) + 0.9 for t < 0.9644
// bs(t) = _b(t - 1.0435) + 0.95 for t <= 1.0
// b(t) = bs(t * 1.1226)
t *= 1.1226f;
if (t < 0.3535f) return bounce(t);
else if (t < 0.7408f) return bounce(t - 0.54719f) + 0.7f;
else if (t < 0.9644f) return bounce(t - 0.8526f) + 0.9f;
else return bounce(t - 1.0435f) + 0.95f;
}
CycleIinterpolator
迴圈，動畫迴圈一定次數，值的改變為一正弦函數
public float getInterpolation(float input) {
return (float)(Math.sin(2 * mCycles * Math.PI * input));
}
LinearInterpolator
線性，線性均勻改變
public float getInterpolation(float input) {
return input; // y = t
}
OvershottInterpolator
超越，最後超出目的值然後緩慢改變到目的值
public float getInterpolation(float t) {
// _o(t) = t * t * ((tension + 1) * t + tension)
// o(t) = _o(t - 1) + 1
t -= 1.0f;
return t * t * ((mTension + 1) * t + mTension) + 1.0f;
}
TimeInterpolator
一個介面，允許你自訂interpolator，以上幾個都是實現了這個介面
修改google api-demo的animation部分:
測試一:
(1) No Interpolator, (2) LinearInterpolator, (3) AccelerateInterpolator, (4) DecelerateInterpolator, (5) AccelerateDecelerateInterolator
測試二:
(1) No Interpolator, (2) AnticipateInterpolator, (3) AnticipateOvershootInterpolator, (4) BounceInterpolator, (5) CycleIinterpolator
