android属性动画

ObjectAnimator

ObjectAnimator继承于ValueAnimator，通常我们更多的去使用ObjectAnimator。ObjectAnimator中最常用的方法有ofInt（），ofFloat，ofObject()方法。它们都能返回一个ObjectAnimator对象。通过使用ObjectAnimator，短短几行代码就能够实现一个动画

ofFloat（）常用参数：

ofFloat(Object target, String propertyName, float... values)

这里target可以是任何对象，propertyName是属性名有rotation，alpha，translationX等，第三个参数是针对第二个属性的渐变值。

public void startAnimation(){
    ObjectAnimatior animator=ObjectAnimator.ofFloat(imageView,"rotation",0f,360f);      //让imageView沿着中心360度旋转
    animator.setDuration(1000);   //动画的执行时间
    animator.start();
}

下面列举一些常用属性：

ObjectAnimator animator=ObjectAnimator.ofFloat(imageView,"scaleY",1f,2f,1f);   //imageView沿着Y轴拉伸至俩倍再到一倍

ObjectAnimator animator=ObjectAnimator.ofFloat(imageView,"scaleX",1f,2f,1f);      imageView沿着X轴拉伸至俩倍再到一倍

ObjectAnimator animator=ObjectAnimator.ofFloat(imageView,"rotationX",0f,360f);      //imageView以X轴为轴心选择360度，rotationY同理

ObjectAnimator animator=ObjectAnimator.ofFloat(imageView,"alpha",0f,1f);     //imageView 颜色淡入由0%到100%

ObjectAnimator animator=ObjectAnimator.ofFloat(imageView,"translationX",0f,-500f,0f);   //转变imageView 的X坐标值。同理translationY。

AnimatorSet类

AnimatorSet类允许你同时编排多个动画

  public void startAnimation(){
        ObjectAnimator animator=ObjectAnimator.ofFloat(imageView,"alpha",1f,0f,1f);
        animator.setDuration(1000);

        ObjectAnimator rotation=ObjectAnimator.ofFloat(imageView,"rotation",0f,360f);

        ObjectAnimator translationX=ObjectAnimator.ofFloat(imageView,"translationX",0f,500f,0f);

        ObjectAnimator translationY=ObjectAnimator.ofFloat(imageView,"translationY",0f,500f,0f);

        AnimatorSet animatorSet=new AnimatorSet();
        animatorSet.play(animator)
                .with(rotation)
                .with(translationX)
                .with(translationY);
        animatorSet.setDuration(5000);
        animatorSet.start();
    }

如上所示，可以同时实现X，Y轴的移动并选择淡入淡出。

实现抛物线：
（水平方向100px/s，所以x=100*t*fraction，y=0.5/a*t*t a取200px/s

public void startAnimation(){
        animator=new ValueAnimator();
        animator.setDuration(5000);
        animator.setObjectValues(new PointF(0,0));
        animator.setInterpolator(new LinearInterpolator());
        animator.setEvaluator(new TypeEvaluator<PointF>() {
            @Override
            public PointF evaluate(float fraction, PointF startValue, PointF endValue) {
                PointF pointF=new PointF();
                pointF.x=100*fraction*3;
                pointF.y=0.5f*200*(3*fraction)*(3*fraction);
                return pointF;
            }
        });
        animator.start();
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                PointF pointF=(PointF) animator.getAnimatedValue();
                imageView.setX(pointF.x);
                imageView.setY(pointF.y);
            }
        });
    }