android Interpolator

所有内容参考Android 6.0文档

package android.animation;public interface TimeInterpolator {    /**     * Maps a value representing the elapsed fraction of an animation to a value that represents     * the interpolated fraction. This interpolated value is then multiplied by the change in     * value of an animation to derive the animated value at the current elapsed animation time.     *     * @param input  一个0到1.0表示动画当前点的值，0表示开头。1表示结尾 A value between 0 and 1.0 indicating our current point     *        in the animation where 0 represents the start and 1.0 represents     *        the end     * @return   插值。它的值可以大于1来超出目标值，也小于0来空破底线。The interpolation value. This value can be more than 1.0 for     *         interpolators which overshoot their targets, or less than 0 for     *         interpolators that undershoot their targets.     */    float getInterpolation(float input);}

package android.view.animation;import android.animation.TimeInterpolator;/** * An interpolator defines the rate of change of an animation. This allows * the basic animation effects (alpha, scale, translate, rotate) to be  * accelerated, decelerated, repeated, etc. */public interface Interpolator extends TimeInterpolator {    // A new interface, TimeInterpolator, was introduced for the new android.animation    // package. This older Interpolator interface extends TimeInterpolator so that users of    // the new Animator-based animations can use either the old Interpolator implementations or    // new classes that implement TimeInterpolator directly.}

1.AccelerateInterpolator 加速插入器

<span style="font-size:18px;">package android.view.animation;import android.content.Context;import android.content.res.Resources;import android.content.res.Resources.Theme;import android.content.res.TypedArray;import android.util.AttributeSet;import com.android.internal.R;import com.android.internal.view.animation.HasNativeInterpolator;import com.android.internal.view.animation.NativeInterpolatorFactory;import com.android.internal.view.animation.NativeInterpolatorFactoryHelper;/** * An interpolator where the rate of change starts out slowly and * and then accelerates. * */@HasNativeInterpolatorpublic class AccelerateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {    private final float mFactor;    private final double mDoubleFactor;    public AccelerateInterpolator() {        mFactor = 1.0f;        mDoubleFactor = 2.0;    }    /**     * Constructor     *     * @param factor Degree to which the animation should be eased. Seting     *        factor to 1.0f produces a y=x^2 parabola. Increasing factor above     *        1.0f  exaggerates the ease-in effect (i.e., it starts even     *        slower and ends evens faster)     */    public AccelerateInterpolator(float factor) {        mFactor = factor;        mDoubleFactor = 2 * mFactor;    }    public AccelerateInterpolator(Context context, AttributeSet attrs) {        this(context.getResources(), context.getTheme(), attrs);    }    /** @hide */    public AccelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {        TypedArray a;        if (theme != null) {            a = theme.obtainStyledAttributes(attrs, R.styleable.AccelerateInterpolator, 0, 0);        } else {            a = res.obtainAttributes(attrs, R.styleable.AccelerateInterpolator);        }        mFactor = a.getFloat(R.styleable.AccelerateInterpolator_factor, 1.0f);        mDoubleFactor = 2 * mFactor;        setChangingConfiguration(a.getChangingConfigurations());        a.recycle();    }    public float getInterpolation(float input) {        if (mFactor == 1.0f) {            return input * input;        } else {            return (float)Math.pow(input, mDoubleFactor);        }    }    /** @hide */    @Override    public long createNativeInterpolator() {        return NativeInterpolatorFactoryHelper.createAccelerateInterpolator(mFactor);    }}</span><span style="font-size:24px;"></span>

加速的快慢度由参数fractor决定。

当fractor值为1.0f时，动画加速轨迹相当于一条y=x^2的抛物线

我们把fractor定义在[1,4]范围内，效果图如下

2.AccelerateDecelerateInterpolator加速减速插入器

直接看重点函数

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

3.DecelerateInterpolator减速插入器

 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.AnticipateOvershootInterpolator

    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);    }

5.OvershootInterpolator

 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;    }

6.BounceInterpolator

    private static float bounce(float t) {        return t * t * 8.0f;    }    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;    }

7.CycleInterpolator

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

mCycles为周期数

8.AnticipateInterpolator

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

9.LinearInterpolator

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

10.