Yet Another View Animation ( a simple and elegant view animation helper library for Android)
This library helps you convert any curve into ready-to-use Interpolator or TypeEvaluator for ValueAnimator, and thirty Rovert Penner's Easing Functions are already included.
关于本项目的创建缘由以及实现思路，欢迎阅读我写的这三篇文章，详细介绍了Android动画中的三个重要类：ValueAnimator、TypeEvaluator和TimeInterpolator，我保证您会有所收获的 😜
当数学遇上动画：讲述ValueAnimator、TypeEvaluator和TimeInterpolator之间的恩恩怨怨(1)
当数学遇上动画：讲述ValueAnimator、TypeEvaluator和TimeInterpolator之间的恩恩怨怨(2)
当数学遇上动画：讲述ValueAnimator、TypeEvaluator和TimeInterpolator之间的恩恩怨怨(3)
该项目实现的功能就是将抽象的函数曲线轻松转换成立即可用的Interpolator和TypeEvaluator，然后应用在Android动画中。这个项目还提供了常见的30个缓动函数(Easing Functions)的实现，它们既可以当做Interpolator来用，又可以当做TypeEvaluator来用，真的非常方便。
举个例子，以弹跳动画效果为例，可以直接使用EasingFunction.BOUNCE_OUT作为Interpolator或者TypeEvaluator来使用：
第一种方式：使用线性插值器和自定义的TypeEvaluator
ObjectAnimator animator1 = new ObjectAnimator();
animator1.setTarget(textView1);
animator1.setPropertyName("translationY");
animator1.setFloatValues(0f, -100f);
animator1.setDuration(1000);
animator1.setInterpolator(new LinearInterpolator());
animator1.setEvaluator(EasingFunction.BOUNCE_OUT); //这里将EasingFunction.BOUNCE_OUT作为TypeEvaluator来使用
animator1.start();第二种方式：使用自定义的Interpolator和"线性估值器"
ObjectAnimator animator2 = new ObjectAnimator();
animator2.setTarget(textView2);
animator2.setPropertyName("translationY");
animator2.setFloatValues(0f, -100f);
animator2.setDuration(1000);
animator2.setInterpolator(EasingFunction.BOUNCE_OUT); //这里将EasingFunction.BOUNCE_OUT作为Interpolator来使用
animator2.setEvaluator(new FloatEvaluator());
animator2.start();如果你想使用自己定义的函数来制作动画，可以使用Functions的with方法，传入一个实现了IFunction接口的类就行，返回值你既可以当做Interpolator，也可以当做TypeEvaluator来使用
代码示例：
ObjectAnimator animator1 = new ObjectAnimator();
animator1.setTarget(textView1);
animator1.setPropertyName("translationY");
animator1.setFloatValues(0f, -100f);
animator1.setDuration(1000);
animator1.setInterpolator(new LinearInterpolator());
animator1.setEvaluator(Functions.with(new IFunction() { //自定义为TypeEvaluator
@Override
public float getValue(float input) {
return input * 2 + 3;
}
}));
animator1.start();或者这样：
ObjectAnimator animator2 = new ObjectAnimator();
animator2.setTarget(textView2);
animator2.setPropertyName("translationY");
animator2.setFloatValues(0f, -100f);
animator2.setDuration(1000);
animator2.setInterpolator(Functions.with(new IFunction() { //自定义为Interpolator
@Override
public float getValue(float input) {
return input * 2 + 3;
}
}));
animator2.setEvaluator(new FloatEvaluator());
animator2.start();你只需要拷贝library中的4个重要类到你的项目中就行了！
或者
1.在项目根目录的build.gradle文件中加入
allprojects {
repositories {
...
maven { url "https://www.jitpack.io" }
}
}
2.然后在需要的build.gradle文件中加入依赖
dependencies {
compile 'com.github.hujiaweibujidao:yava:1.0.0'
}
项目只有4个核心类，放在library中
(1) IFunction接口
/**
* 函数接口：给定输入，得到输出
*/
public interface IFunction {
float getValue(float input);
}(2)AbstractFunction抽象类
/**
* 抽象函数实现，既可以当做简单函数使用，也可以当做Interpolator或者TypeEvaluator去用于制作动画
*/
public abstract class AbstractFunction implements IFunction, Interpolator, TypeEvaluator<Float> {
@Override
public float getInterpolation(float input) {
return getValue(input);
}
@Override
public Float evaluate(float fraction, Float startValue, Float endValue) {
return startValue + getValue(fraction) * (endValue - startValue);
}
}(3)Functions类
/**
* 工具类，将自定义的函数快速封装成AbstractFunction
*/
class Functions {
public static AbstractFunction with(final IFunction function) {
return new AbstractFunction() {
@Override
public float getValue(float input) {
return function.getValue(input);
}
};
}
}(4)EasingFunction枚举：包含了30个常见的缓动函数
/**
* 常见的30个缓动函数的实现
*/
public enum EasingFunction implements IFunction, Interpolator, TypeEvaluator<Float> {
/* ------------------------------------------------------------------------------------------- */
/* BACK
/* ------------------------------------------------------------------------------------------- */
BACK_IN {
@Override
public float getValue(float input) {
return input * input * ((1.70158f + 1) * input - 1.70158f);
}
},
BACK_OUT {
@Override
public float getValue(float input) {
return ((input = input - 1) * input * ((1.70158f + 1) * input + 1.70158f) + 1);
}
},
BACK_INOUT {
@Override
public float getValue(float input) {
float s = 1.70158f;
if ((input *= 2) < 1) {
return 0.5f * (input * input * (((s *= (1.525f)) + 1) * input - s));
}
return 0.5f * ((input -= 2) * input * (((s *= (1.525f)) + 1) * input + s) + 2);
}
},
//other easing functions ......
//如果这个function在求值的时候需要duration作为参数的话，那么可以通过setDuration来设置，否则使用默认值
private float duration = 1000f;
public float getDuration() {
return duration;
}
public EasingFunction setDuration(float duration) {
this.duration = duration;
return this;
}
//将Function当做Interpolator使用，默认的实现，不需要枚举元素去重新实现
@Override
public float getInterpolation(float input) {
return getValue(input);
}
//将Function当做TypeEvaluator使用，默认的实现，不需要枚举元素去重新实现
@Override
public Float evaluate(float fraction, Float startValue, Float endValue) {
return startValue + getValue(fraction) * (endValue - startValue);
}
//几个数学常量
public static final float PI = (float) Math.PI;
public static float TWO_PI = PI * 2.0f;
public static float HALF_PI = PI * 0.5f;
}本项目主要参考了以下项目和内容
1.EaseInterpolator
2.AnimationEasingFunctions
3.easings.net
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