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android之interpolator的用法详解

android:interpolator

 

Interpolator 被用来修饰动画效果,定义动画的变化率,可以使存在的动画效果accelerated(加速),decelerated(减速),repeated(重复),bounced(弹跳)等。

android中的文档内容如下:

AccelerateDecelerateInterpolator 在动画开始与结束的地方速率改变比较慢,在中间的时候加速

AccelerateInterpolator  在动画开始的地方速率改变比较慢,然后开始加速

AnticipateInterpolator 开始的时候向后然后向前甩

AnticipateOvershootInterpolator 开始的时候向后然后向前甩一定值后返回最后的值

BounceInterpolator   动画结束的时候弹起

CycleInterpolator 动画循环播放特定的次数,速率改变沿着正弦曲线

DecelerateInterpolator 在动画开始的地方快然后慢

LinearInterpolator   以常量速率改变

OvershootInterpolator    向前甩一定值后再回到原来位置

如果android定义的interpolators不符合你的效果也可以自定义interpolators

 

Android中的Interpolator

nterpolator用于动画中的时间插值,其作用就是把0到1的浮点值变化映射到另一个浮点值变化。

本文列出Android API提供的Interpolator的若干种实现,列出源码,并且用一个程序绘制出其数学曲线。(项目链接附在文后)。

AccelerateDecelerateInterpolator

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/**
 * An interpolator where the rate of change starts and ends slowly but
 * accelerates through the middle.
 *
 */
public class AccelerateDecelerateInterpolator implements Interpolator {
    public AccelerateDecelerateInterpolator() {
    }
    @SuppressWarnings({"UnusedDeclaration"})
    public AccelerateDecelerateInterpolator(Context context, AttributeSet attrs) {
    }
    public float getInterpolation(float input) {
        return (float)(Math.cos((input + 1) * Math.PI) / 2.0f) + 0.5f;
    }
}
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AccelerateInterpolator

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/**
 * An interpolator where the rate of change starts out slowly and
 * and then accelerates.
 *
 */
public class AccelerateInterpolator implements Interpolator {
    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) {
        TypedArray a =
            context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.AccelerateInterpolator);
        mFactor = a.getFloat(com.android.internal.R.styleable.AccelerateInterpolator_factor, 1.0f);
        mDoubleFactor = 2 * mFactor;
        a.recycle();
    }
    public float getInterpolation(float input) {
        if (mFactor == 1.0f) {
            return input * input;
        } else {
            return (float)Math.pow(input, mDoubleFactor);
        }
    }
}
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AnticipateInterpolator

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/**
 * An interpolator where the change starts backward then flings forward.
 */
public class AnticipateInterpolator implements Interpolator {
    private final float mTension;
    public AnticipateInterpolator() {
        mTension = 2.0f;
    }
    /**
     * @param tension Amount of anticipation. When tension equals 0.0f, there is
     *                no anticipation and the interpolator becomes a simple
     *                acceleration interpolator.
     */
    public AnticipateInterpolator(float tension) {
        mTension = tension;
    }
    public AnticipateInterpolator(Context context, AttributeSet attrs) {
        TypedArray a = context.obtainStyledAttributes(attrs,
                com.android.internal.R.styleable.AnticipateInterpolator);
        mTension =
                a.getFloat(com.android.internal.R.styleable.AnticipateInterpolator_tension, 2.0f);
        a.recycle();
    }
    public float getInterpolation(float t) {
        // a(t) = t * t * ((tension + 1) * t - tension)
        return t * t * ((mTension + 1) * t - mTension);
    }
}
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AnticipateOvershootInterpolator

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/**
 * An interpolator where the change starts backward then flings forward and overshoots
 * the target value and finally goes back to the final value.
 */
public class AnticipateOvershootInterpolator implements Interpolator {
    private final float mTension;
    public AnticipateOvershootInterpolator() {
        mTension = 2.0f * 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.
     */
    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;
    }
    public AnticipateOvershootInterpolator(Context context, AttributeSet attrs) {
        TypedArray a = context.obtainStyledAttributes(attrs, AnticipateOvershootInterpolator);
        mTension = a.getFloat(AnticipateOvershootInterpolator_tension, 2.0f) *
                a.getFloat(AnticipateOvershootInterpolator_extraTension, 1.5f);
        a.recycle();
    }
    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);
    }
}
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BounceInterpolator

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/**
 * An interpolator where the change bounces at the end.
 */
public class BounceInterpolator implements Interpolator {
    public BounceInterpolator() {
    }
    @SuppressWarnings({"UnusedDeclaration"})
    public BounceInterpolator(Context context, AttributeSet attrs) {
    }
    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;
    }
}
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CycleInterpolator

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/**
 * Repeats the animation for a specified number of cycles. The
 * rate of change follows a sinusoidal pattern.
 *
 */
public class CycleInterpolator implements Interpolator {
    public CycleInterpolator(float cycles) {
        mCycles = cycles;
    }
    public CycleInterpolator(Context context, AttributeSet attrs) {
        TypedArray a =
            context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.CycleInterpolator);
        mCycles = a.getFloat(com.android.internal.R.styleable.CycleInterpolator_cycles, 1.0f);
        a.recycle();
    }
    public float getInterpolation(float input) {
        return (float)(Math.sin(2 * mCycles * Math.PI * input));
    }
    private float mCycles;
}
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参数为2时的曲线:

 

DecelerateInterpolator

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/**
 * An interpolator where the rate of change starts out quickly and
 * and then decelerates.
 *
 */
public class DecelerateInterpolator implements Interpolator {
    public DecelerateInterpolator() {
    }
    /**
     * Constructor
     *
     * @param factor Degree to which the animation should be eased. Setting factor to 1.0f produces
     *        an upside-down y=x^2 parabola. Increasing factor above 1.0f makes exaggerates the
     *        ease-out effect (i.e., it starts even faster and ends evens slower)
     */
    public DecelerateInterpolator(float factor) {
        mFactor = factor;
    }
    public DecelerateInterpolator(Context context, AttributeSet attrs) {
        TypedArray a =
            context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.DecelerateInterpolator);
        mFactor = a.getFloat(com.android.internal.R.styleable.DecelerateInterpolator_factor, 1.0f);
        a.recycle();
    }
    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;
    }
    private float mFactor = 1.0f;
}
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LinearInterpolator

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/**
 * An interpolator where the rate of change is constant
 *
 */
public class LinearInterpolator implements Interpolator {
    public LinearInterpolator() {
    }
    public LinearInterpolator(Context context, AttributeSet attrs) {
    }
    public float getInterpolation(float input) {
        return input;
    }
}
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OvershootInterpolator

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/**
 * An interpolator where the change flings forward and overshoots the last value
 * then comes back.
 */
public class OvershootInterpolator implements Interpolator {
    private final float mTension;
    public OvershootInterpolator() {
        mTension = 2.0f;
    }
    /**
     * @param tension Amount of overshoot. When tension equals 0.0f, there is
     *                no overshoot and the interpolator becomes a simple
     *                deceleration interpolator.
     */
    public OvershootInterpolator(float tension) {
        mTension = tension;
    }
    public OvershootInterpolator(Context context, AttributeSet attrs) {
        TypedArray a = context.obtainStyledAttributes(attrs,
                com.android.internal.R.styleable.OvershootInterpolator);
        mTension =
                a.getFloat(com.android.internal.R.styleable.OvershootInterpolator_tension, 2.0f);
        a.recycle();
    }
    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;
    }
}
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项目链接:

https://github.com/mengdd/HelloInterpolator.git

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