Android中的Interpolator

首先介绍一个网站 https://www.desmos.com，这是一个通过函数来生成函数图像的网站，使用起来很灵活，可以 同时添加多个函数图像，分别指定他们的定义域。感谢道哥分享！

系统提供的Interpolator

LinearInterpolator 线性插值器

这里写图片描述
这里写图片描述

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
public class LinearInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {

    public LinearInterpolator() {
    }

    public LinearInterpolator(Context context, AttributeSet attrs) {
    }

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

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createLinearInterpolator();
    }
}

AccelerateInterpolator 加速插值器

这里写图片描述
这里写图片描述
源代码：
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
public class AccelerateDecelerateInterpolator extends BaseInterpolator
        implements NativeInterpolatorFactory {
    public AccelerateDecelerateInterpolator() {
    }

    @SuppressWarnings({"UnusedDeclaration"})
    public AccelerateDecelerateInterpolator(Context context, AttributeSet attrs) {
    }

    public float getInterpolation(float input) { //这里定义的函数
        return (float)(Math.cos((input + 1) * Math.PI) / 2.0f) + 0.5f;
    }

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createAccelerateDecelerateInterpolator();
    }
}

## 减速DecelerateInterpolator
这里写图片描述
这里写图片描述
源码：
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
/**
 * An interpolator where the rate of change starts out quickly and
 * and then decelerates.
 *
 */
@HasNativeInterpolator
public class DecelerateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
    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) {
        this(context.getResources(), context.getTheme(), attrs);
    }

    /** @hide */
    public DecelerateInterpolator(Resources res, Theme theme, AttributeSet attrs) {
        TypedArray a;
        if (theme != null) {
            a = theme.obtainStyledAttributes(attrs, R.styleable.DecelerateInterpolator, 0, 0);
        } else {
            a = res.obtainAttributes(attrs, R.styleable.DecelerateInterpolator);
        }

        mFactor = a.getFloat(R.styleable.DecelerateInterpolator_factor, 1.0f);
        setChangingConfiguration(a.getChangingConfigurations());
        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;

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createDecelerateInterpolator(mFactor);
    }
}

##AccelerateDecelerateInterpolator 加速减速插值器
这里写图片描述
这里写图片描述
源码：
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
@HasNativeInterpolator
public class AccelerateDecelerateInterpolator extends BaseInterpolator
        implements NativeInterpolatorFactory {
    public AccelerateDecelerateInterpolator() {
    }

    @SuppressWarnings({"UnusedDeclaration"})
    public AccelerateDecelerateInterpolator(Context context, AttributeSet attrs) {
    }

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

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createAccelerateDecelerateInterpolator();
    }
}

BounceInterpolator 弹跳插值器

这里写图片描述
这里写图片描述
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
package android.view.animation;

import android.content.Context;
import android.util.AttributeSet;

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 change bounces at the end.
 */
@HasNativeInterpolator
public class BounceInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
    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;
    }

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createBounceInterpolator();
    }
}

##AnticipateInterpolator 回荡秋千插值器
这里写图片描述
这里写图片描述
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
public class AnticipateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
    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) {
        this(context.getResources(), context.getTheme(), attrs);
    }

    /** @hide */
    public AnticipateInterpolator(Resources res, Theme theme, AttributeSet attrs) {
        TypedArray a;
        if (theme != null) {
            a = theme.obtainStyledAttributes(attrs, R.styleable.AnticipateInterpolator, 0, 0);
        } else {
            a = res.obtainAttributes(attrs, R.styleable.AnticipateInterpolator);
        }

        mTension = a.getFloat(R.styleable.AnticipateInterpolator_tension, 2.0f);
        setChangingConfiguration(a.getChangingConfigurations());
        a.recycle();
    }

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

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createAnticipateInterpolator(mTension);
    }
}

AnticipateOvershootInterpolator

这里写图片描述

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
/**
 * An interpolator where the change starts backward then flings forward and overshoots
 * the target value and finally goes back to the final value.
 */
@HasNativeInterpolator
public class AnticipateOvershootInterpolator extends BaseInterpolator
        implements NativeInterpolatorFactory {
    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) {
        this(context.getResources(), context.getTheme(), attrs);
    }

    /** @hide */
    public AnticipateOvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
        TypedArray a;
        if (theme != null) {
            a = theme.obtainStyledAttributes(attrs, AnticipateOvershootInterpolator, 0, 0);
        } else {
            a = res.obtainAttributes(attrs, AnticipateOvershootInterpolator);
        }

        mTension = a.getFloat(AnticipateOvershootInterpolator_tension, 2.0f) *
                a.getFloat(AnticipateOvershootInterpolator_extraTension, 1.5f);
        setChangingConfiguration(a.getChangingConfigurations());
        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);
    }

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createAnticipateOvershootInterpolator(mTension);
    }
}

CycleInterpolator 正弦周期变化插值器

这里写图片描述

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
 @HasNativeInterpolator
public class CycleInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
    public CycleInterpolator(float cycles) {
        mCycles = cycles;
    }

    public CycleInterpolator(Context context, AttributeSet attrs) {
        this(context.getResources(), context.getTheme(), attrs);
    }

    /** @hide */
    public CycleInterpolator(Resources resources, Theme theme, AttributeSet attrs) {
        TypedArray a;
        if (theme != null) {
            a = theme.obtainStyledAttributes(attrs, R.styleable.CycleInterpolator, 0, 0);
        } else {
            a = resources.obtainAttributes(attrs, R.styleable.CycleInterpolator);
        }

        mCycles = a.getFloat(R.styleable.CycleInterpolator_cycles, 1.0f);
        setChangingConfiguration(a.getChangingConfigurations());
        a.recycle();
    }

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

    private float mCycles;

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createCycleInterpolator(mCycles);
    }
}

##OvershootInterpolator
这里写图片描述
这里写图片描述

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
/**
 * An interpolator where the change flings forward and overshoots the last value
 * then comes back.
 */
@HasNativeInterpolator
public class OvershootInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
    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) {
        this(context.getResources(), context.getTheme(), attrs);
    }

    /** @hide */
    public OvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
        TypedArray a;
        if (theme != null) {
            a = theme.obtainStyledAttributes(attrs, R.styleable.OvershootInterpolator, 0, 0);
        } else {
            a = res.obtainAttributes(attrs, R.styleable.OvershootInterpolator);
        }

        mTension = a.getFloat(R.styleable.OvershootInterpolator_tension, 2.0f);
        setChangingConfiguration(a.getChangingConfigurations());
        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;
    }

    /** @hide */
    @Override
    public long createNativeInterpolator() {
        return NativeInterpolatorFactoryHelper.createOvershootInterpolator(mTension);
    }
}

#自定义Interpolator

Interpolator源码：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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.
}

我们来写自己的类来实现该接口

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
import android.view.animation.Interpolator;
public class MyInterpolator implements Interpolator {
	private float mFactor;
	private int i;
	public MyInterpolator(int i){
		this.i = i;
	}
	@Override
	public float getInterpolation(float input) { //定义我们的函数，input: 0 ~ 1
		switch(i){
			case 1:mFactor = input;
				break;
			case 2:mFactor = input*input*input;
				break;
		}
		return mFactor;
	}
}

来个复杂的：

用desmos画一个：
这里写图片描述

这里写图片描述

1
2
3
4
5
6
7
8
9
@Override
public float getInterpolation(float t) { //定义我们的函数，t: 0 ~ 1
	if(t<0.2094) return (float)(-34*(t-0.18)*(t-0.18)+1.08);
	else if(t <0.404) return (float)(5.9*(t-0.34)*(t-0.34)+0.95);
	else if(t < 0.6045) return (float)(-3*(t-0.53)*(t-0.53)+1.02);
	else if(t < 0.8064) return (float)((t-0.72)*(t-0.72)+0.99);
	else return (float)(-0.3*(t-0.915)*(t-0.915)+1.001);
	return mFactor;
}