动画之Evaluator

Evaluator就是通过监听器拿到当前动画对对应的具体数值,作用在于从插值器返回的数值进行转换成对应的数值.简单来说就是转换器

Evaluator返回值的类型更加动画中值决定的,所以在使用的时候注意数据类型

     tv = (TextView)findViewById(R.id.tv);

        findViewById(R.id.start_anim).setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                ValueAnimator animator = ValueAnimator.ofInt(0,300);

                animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                    public void onAnimationUpdate(ValueAnimator animation) {
                        int curValue = (Integer)animation.getAnimatedValue();
                        tv.layout(tv.getLeft(),curValue,tv.getRight(),curValue+tv.getHeight());
                    }
                });
                animator.setDuration(1000);
                animator.setEvaluator(new ReverseEvaluator());
                animator.start();
            }
        });

import android.animation.TypeEvaluator;

public class ReverseEvaluator implements TypeEvaluator<Integer> {
    public Integer evaluate(float fraction, Integer startValue, Integer endValue) {
        int startInt = startValue;
        return (int)(endValue - fraction * (endValue - startInt));
    }
}

---

      tv = (TextView)findViewById(R.id.tv);
        findViewById(R.id.start_anim).setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                ValueAnimator animator = ValueAnimator.ofInt(0xffffff00,0xff0000ff);
                animator.setEvaluator(new ArgbEvaluator());//颜色值过滤转换
                animator.setDuration(3000);

                animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                    public void onAnimationUpdate(ValueAnimator animation) {
                        int curValue = (Integer) animation.getAnimatedValue();
                        tv.setBackgroundColor(curValue);
                    }
                });

                animator.start();
            }

---

        tv = (TextView)findViewById(R.id.tv);

        findViewById(R.id.start_anim).setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                ValueAnimator animator = ValueAnimator.ofObject(new CharEvaluator(), new Character('A'), new Character('Z'));
                animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                    public void onAnimationUpdate(ValueAnimator animation) {
                        char text = (Character) animation.getAnimatedValue();
                        tv.setText(String.valueOf(text));
                    }
                });
                animator.setDuration(10000);
                animator.setInterpolator(new AccelerateInterpolator());
                animator.start();
            }
        });

---

_抛物动画

  ballImg = (ImageView) findViewById(R.id.ball_img);

        findViewById(R.id.start_anim).setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                WindowManager wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
                int width = wm.getDefaultDisplay().getWidth();
                int height = wm.getDefaultDisplay().getHeight();

                ValueAnimator animator = ValueAnimator.ofObject(new FallingBallEvaluator(),new Point(0,0),new Point(width*2/3,height*2/3));
                animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                    public void onAnimationUpdate(ValueAnimator animation) {
                        mCurPoint = (Point) animation.getAnimatedValue();
                        ballImg.layout(mCurPoint.x, mCurPoint.y, mCurPoint.x + ballImg.getWidth(), mCurPoint.y + ballImg.getHeight());
                    }
                });
                animator.setDuration(2000);
                animator.start();
            }
        });

public class FallingBallEvaluator implements TypeEvaluator<Point> {
    private Point point = new Point();
    public Point evaluate(float fraction, Point startValue, Point endValue) {
        point.x = (int)(startValue.x + fraction *(endValue.x - startValue.x));

        if (fraction*2<=1){
          point.y = (int)(startValue.y + fraction*2*(endValue.y - startValue.y));
        }else {
            point.y = endValue.y;
        }
        return point;
    }
}

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
        android:shape="oval">
    <solid android:color="#ff0000"/>
</shape>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_gravity="center"
    tools:context="com.loaderman.customviewdemo.MainActivity">

    <ImageView
        android:id="@+id/ball_img"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:src="@drawable/cicle"/>

    <Button
        android:id="@+id/start_anim"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="开始动画"/>

</LinearLayout>