PropertyValuesHolder与Keyframe 笔记

PropertyValuesHolder

ValueAnimator和ObjectAnimator都有对应的ofPorpertyValuesHolder方法

PorpertyValuesHolde创建实例的方法

public static PropertyValuesHolder ofFloat(String PropertyName,float... values)
public static PropertyValuesHolder ofInt(String PropertyName,int... values)
public static PropertyValuesHolder ofObject(String PropertyName,TypeEvaluator evaluator,Object... values)
public static PropertyValuesHolder ofKeyFrame(String PropertyName,KeyFrame... values)

ofFloat,ofInt使用示例

PropertyValuesHolder holder = PropertyValuesHolder.ofFLoat("alpha",0.1f,0.3f,0.7f,1f);
ObjectAnimator animator = ObjectAnimator.ofPorpertyValuesHolder(view,holder);
animator.setDuration(2000);
animator.start();

ofObject方法参数，可以实现一个自定义的插值器，使用实例：

    public class CharEvaLuator implements TypeEvaluator<Character>{
        @Override
        public Character evaluate(float fraction, Character startValue, Character endValue) {
            int startInt = startValue;
            int endInt = endValue;
            int curInt = startInt + fraction * (endInt- startInt);
            char result = (Char)curInt;
            return result;
        }
    }
    
    PropertyValuesHolder holder = PropertyValuesHolder.ofObject("CharText",new CharEvaluator,
    new Character('A'),new Character('Z'));
    ObjectAnimator animator = ObjectAnimator.ofPorpertyValuesHolder(tv,holder);
    animator.setDuration(2000);
    animator.start();
    
    //注意因为TextView 中setText(CharSequence text)参数，需要内部自定义setCharText(Charactor text)结合ofObject使用

Keyframe

keyframe 我个人感觉可以理解为好比做动画时绘制的帧。

public static KeyFrame ofFloat(float fraction,float duration)
//fraction 当前显示的进度，value 当前动画所在数值位置

ofFloat,ofInt使用实例：

KeyFrame frame0 = KeyFrame.ofFloat(0f,0);
KeyFrame frame1 = KeyFrame.ofFloat(0.5f,50);
KeyFrame frame2 = KeyFrame.ofFloat(1f,100);
PropertyValuesHolder holder = PropertyValuesHolder.ofKeyframe("alpha",frame0,frame1,frame2);
ObjetAnimator animator = ObjetAnimator.ofPropertyValuesHolder(view,holder);
animator.setDuration(2000);
animator.start();

//也可以给除第一帧以外的设置插值器
frame1.setInterpolator(new BounceInterpolator());

ofObject()同样也可以实现一些自定义的属性参数，例如

KeyFrame frame0 = KeyFrame.ofObject(0,new Character('A'));
KeyFrame frame1 = KeyFrame.ofObject(0,new Character('B'));
KeyFrame frame2 = KeyFrame.ofObject(0,new Character('C'));

//结合上面的CharEvaLuator自定义插值器使用
PropertyValuesHolder holder = PropertyValuesHolder.ofKeyframe("CharText",frame0,frame1,frame2);
holder.setEvalutar(new CharEvaLuator());
ObjetAnimator animator = ObjetAnimator.ofPropertyValuesHolder(view,holder);
animator.setDuration(2000);
animator.start();

注意

1. 多个KeyFrame，都会默认把第一个frame设为首帧，最后一个设为尾帧，不管是不是你期望的效果

2. 必须存在2个或2个以上的frame，不然会报数组越界