属性动画-插值器

TimeInterpolator
时间插值器，一个接口类
float getInterpolation(float input);
系统会根据动画当前时间和动画总时长，计算时间进度fraction，fraction为float类型，值范围为0f~1f，该值是随着时间流逝匀速变化的。我们将 fraction 作为参数input传入getInterpolation(float input)方法：

float getInterpolation(float input);
interface Interpolator 继承 TimeInterpolator
BaseInterpolator implements Interpolator
形成了BaseInterpolator
BaseInterpolator 这里面会有
private @Config int mChangingConfiguration;
这个干嘛的呢？不清楚

然后我们会拿getInterpolation（float input）的input做插值器处理

1，以下是系统提供的插值器
1,LinearInterpolator 线性插值器

 public float getInterpolation(float input) {
        return input;
    }

2,AccelerateInterpolator 加速插值器
y = t^2f

  public AccelerateInterpolator(float factor) {
        mFactor = factor;
        mDoubleFactor = 2 * mFactor;
    }

public float getInterpolation(float input) {
        if (mFactor == 1.0f) {
            return input * input;
        } else {
            return (float)Math.pow(input, mDoubleFactor);
        }
    }

3,DecelerateInterpolator 减速插值器
y = 1 - (1 - t)^2f

 public DecelerateInterpolator(float factor) {
        mFactor = factor;
    }

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));
        }
        return result;
    }

4,AccelerateDecelerateInterpolator 加速减速插值器
y = cos((t + 1)π)/2 + 0.5

 public AccelerateDecelerateInterpolator() {
    }

public float getInterpolation(float input) {
        return (float)(Math.cos((input + 1) * Math.PI) / 2.0f) + 0.5f;
    }

5,BounceInterpolator 弹跳插值器

 public BounceInterpolator(Context context, AttributeSet attrs) {
    }

 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;
    }

6,AnticipateInterpolator 回荡秋千插值器
y = (T + 1) * t^3 - T * t^2

 public AnticipateInterpolator(float tension) {
        mTension = tension;
    }

 public float getInterpolation(float t) {
        // a(t) = t * t * ((tension + 1) * t - tension)
        return t * t * ((mTension + 1) * t - mTension);
    }

7,AnticipateOvershootInterpolator 回荡秋千加超过末尾插值器

 public AnticipateOvershootInterpolator(float tension) {
        mTension = tension * 1.5f;
    }

    /**
     * @param tension Amount of anticipation/overshoot. When tension equals 0.0f,
     *                there is no anticipation/overshoot and the interpolator becomes
     *                a simple acceleration/deceleration interpolator.
     * @param extraTension Amount by which to multiply the tension. For instance,
     *                     to get the same overshoot as an OvershootInterpolator with
     *                     a tension of 2.0f, you would use an extraTension of 1.5f.
     */
    public AnticipateOvershootInterpolator(float tension, float extraTension) {
        mTension = tension * extraTension;
    }

    private static float a(float t, float s) {
        return t * t * ((s + 1) * t - s);
    }

    private static float o(float t, float s) {
        return t * t * ((s + 1) * t + s);
    }

    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);
     }

8,CycleInterpolator 正弦周期变化插值器
y = sin(2π * c)

 public CycleInterpolator(float cycles) {
        mCycles = cycles;
    }

 public float getInterpolation(float input) {
        return (float)(Math.sin(2 * mCycles * Math.PI * input));
    }

9,OvershootInterpolator 超过末尾拦截器

public OvershootInterpolator(float tension) {
        mTension = tension;
    }

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;
    }

2，自定义插值器

 private class CusInterInterpolator implements Interpolator{

        @Override
        public float getInterpolation(float input) {
            //你想要的处理
            if (input <= 0.5) {
                return (float) (Math.sin(Math.PI * input)) / 2;
            } else {
                return (float) (2 - Math.sin(Math.PI * input)) / 2;
            }
        }
    }

3，使用插值器

objectAnimator.setInterpolator()