ValueAnimator和TypeEvaluator 的使用

属性值=f( g(a) ,b ,c )f(...)：代表TypeEvaluator：插值g(a)：代表TimeInterpolator：插值的时间点b: 起始属性值c:  结束属性值

TimeInterpolator：获取动画的进度时间(时间可以不均匀变化)：

比如：一个动画执行100秒，属性值相对应0到100（随进度均匀），
TimeInterpolator可以控制现实中度过一秒时，动画就执行了十秒；
也可以控制现实中度过80秒时属性值已经到达100，然后回属性值再回退到90。

TypeEvaluator：获取动画的属性值（属性值随当前的进度而变化，可以不均匀变化）

比如：一个动画执行100秒，属性值可以正弦sin(t)变化，也可以线性变化。

参考：ViewPropertyAnimator的使用

一、相关API：

获取ValueAnimator

public static ValueAnimator ofArgb(int... values)public static ValueAnimator ofFloat(float... values)public static ValueAnimator ofInt(int... values)public static ValueAnimator ofPropertyValuesHolder(PropertyValuesHolder... values)public static ValueAnimator ofObject(TypeEvaluator evaluator, Object... values) {    ValueAnimator anim = new ValueAnimator();    anim.setObjectValues(values);    anim.setEvaluator(evaluator);    return anim;}

设置ValueAnimator

public ValueAnimator setDuration(long duration)public void setTarget(Object target)public void setRepeatCount(int value)public void setRepeatMode(@RepeatMode int value)public void setStartDelay(long startDelay) public void setInterpolator(TimeInterpolator value)public void setEvaluator(TypeEvaluator value)public void setIntValues(int... values)public void setFloatValues(float... values) public void setObjectValues(Object... values)public void setValues(PropertyValuesHolder... values)//获取当前进度值public Object getAnimatedValue()//启动public void start() 

监听ValueAnimator

public void addListener(AnimatorListener listener) //可选择实现public void addPauseListener(AnimatorPauseListener listener)public void addUpdateListener(AnimatorUpdateListener listener)//AnimatorListenerAdapter包含AnimatorListener，AnimatorPauseListener//抽象类可以选择实现public abstract class AnimatorListenerAdapter implements                                                 Animator.AnimatorListener,                                                 Animator.AnimatorPauseListener{...}public static interface AnimatorListener {    void onAnimationStart(Animator animation);    void onAnimationEnd(Animator animation);    void onAnimationCancel(Animator animation);    void onAnimationRepeat(Animator animation);}public static interface AnimatorPauseListener {    void onAnimationPause(Animator animation);    void onAnimationResume(Animator animation);}public static interface AnimatorUpdateListener {    void onAnimationUpdate(ValueAnimator animation);}

二、示例：

示例效果：

小圆沿着正弦曲线不断运动

PointSinView

public class PointSinView extends View {    private static final int RADIUS = 20;    private Point currentPoint;    private Paint paint;    private Point startP;    private Point endP;    public PointSinView(Context context) {        this(context, null);    }    public PointSinView(Context context, @Nullable AttributeSet attrs) {        this(context, attrs, 0);    }    public PointSinView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        paint = new Paint();        paint.setAntiAlias(true);        paint.setColor(Color.RED);        paint.setStrokeWidth(10);        paint.setStyle(Paint.Style.FILL);        paint.setDither(true);    }    @Override    protected void onSizeChanged(int w, int h, int oldw, int oldh) {        super.onSizeChanged(w, h, oldw, oldh);        startP = new Point(RADIUS, getHeight() / 2);//初始值（起点）        endP = new Point(getWidth() - RADIUS, getHeight() / 2);//结束值（终点）        currentPoint = startP;    }    Handler handler = new Handler();    public void start() {        handler.postDelayed(runnable, 100);    }    Runnable runnable = new Runnable() {        @Override        public void run() {            final ValueAnimator valueAnimator = ValueAnimator.ofObject(new PointSinEvaluator(), startP, endP);            valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {                @Override                public void onAnimationUpdate(ValueAnimator animation) {                    currentPoint = (Point) animation.getAnimatedValue();                    postInvalidate();                }            });            valueAnimator.setDuration(5000);            valueAnimator.start();            handler.postDelayed(this, 5000);        }    };    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        canvas.drawPoint(currentPoint.x, currentPoint.y, paint);    }}

PointSinEvaluator ：决定值

public class PointSinEvaluator implements TypeEvaluator {    @Override    public Object evaluate(float fraction, Object startValue, Object endValue) {        Point startPoint = (Point) startValue;        Point endPoint = (Point) endValue;        int x = (int) (startPoint.x + fraction * (endPoint.x - startPoint.x));        int y = (int) ((float) (Math.sin(x * Math.PI / 180) * 100) + endPoint.y / 2);        return new Point(x, y);    }}

布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <Button        android:id="@+id/btn"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="启动动画" />    <com.joanzapata.android.PointSinView        android:id="@+id/pointsin"        android:layout_width="match_parent"        android:layout_height="300dp"        android:background="#e5e5e5" /></LinearLayout>

MyActivityI

public class MyActivityI extends AppCompatActivity {    private PointSinView pointSin;    private Button btn;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_anim);        btn = ((Button) this.findViewById(R.id.btn));        pointSin = ((PointSinView) this.findViewById(R.id.pointsin));        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                pointSin.start();            }        });    }}