Android开发 之 属性动画（自定义ValueAnimator的TypeEvaluator）

自定义ValueAnimator的TypeEvaluator

翻译过来就是类型计算器，对，就是一个计算器，只不过这计算器的计算规则由你设定，也就是你要继承重写喽。

对于valueAnimator类中的其他ofXXx方法，其实都是有计算器，默认好像是FloatEvaluator的。

本文这次改变属性是一个点的x，y跟随要给曲线运动动画效果：

妈的，这 gif录制工具太差了，变成绿低了。但是还是能看出小蝌蚪在动。

下面看代码：

activity的布局文件就一个imageview，等会这个就是存放你的运动点的容器。

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent">    <ImageView        android:id="@+id/iv"        android:layout_width="300dp"        android:layout_height="400px"        android:layout_margin="50dp"/></LinearLayout>

activity代码

这里是根据imageview的尺寸 去设置起点和终点的。

有个iamgeview尺寸的获取，利用视图树，当iamgeview绘制好了，再去获取其宽高。

自定义了一个pointDrawable，和myself类下面有代码

package com.example.zxq.bsquxian;import android.animation.ValueAnimator;import android.os.Bundle;import android.support.annotation.Nullable;import android.support.v7.app.AppCompatActivity;import android.util.Log;import android.view.View;import android.view.ViewTreeObserver;import android.view.animation.LinearInterpolator;import android.widget.ImageView;import com.example.zxq.bsquxian.zidiyizhidonghua.MySelf;import com.example.zxq.bsquxian.zidiyizhidonghua.Point;import com.example.zxq.bsquxian.zidiyizhidonghua.PointDrawable;/** * Created by Administrator on 2017/7/26 0026. */public class ShuxingAnmationActivity extends AppCompatActivity {    private ImageView iv;    private int width;    private int height;    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_shuxingdonghua);        iv= (ImageView) findViewById(R.id.iv);        int intw=View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);        int inth=View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);        iv.measure(intw, inth);        iv.getViewTreeObserver().addOnGlobalLayoutListener(                new ViewTreeObserver.OnGlobalLayoutListener() {                    @Override                    public void onGlobalLayout() {                        height = iv.getHeight();                        width = iv.getWidth();                        iv.getViewTreeObserver().removeGlobalOnLayoutListener(this);                        final PointDrawable pointDrawable=new PointDrawable(width,height);                        iv.setBackground(pointDrawable);                        ValueAnimator valueAnimator = ValueAnimator.ofObject(new MySelf(), pointDrawable.getStartPoint(), pointDrawable.getEndPoint());                        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {                            @Override                            public void onAnimationUpdate(ValueAnimator valueAnimator) {                                Point animatedValue = (Point) valueAnimator.getAnimatedValue();                                pointDrawable.setCurrentPoint(animatedValue);                                pointDrawable.invalidateSelf();                            }                        });                        valueAnimator.setDuration(5000);                        valueAnimator.setInterpolator(new LinearInterpolator());//设置插值器                        valueAnimator.start();                    }                });    }}

pointDrawable的代码：

创建这个对象的时候，创建了两个点，起点和终点，还有画笔

在draw（）方法中去绘制图形

在setcurrentpoint（）方法中，当前运动点的位置传进来。这个方法是在activity中动画运行监听中调用的。在上面

package com.example.zxq.bsquxian.zidiyizhidonghua;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.ColorFilter;import android.graphics.Paint;import android.graphics.drawable.Drawable;import android.graphics.drawable.PictureDrawable;import android.support.annotation.IntRange;import android.support.annotation.NonNull;import android.support.annotation.Nullable;import android.util.Log;import java.util.ArrayList;import java.util.List;/** * Created by Administrator on 2017/7/26 0026. */public class PointDrawable extends Drawable {    private  Point startPoint;    private  Point endPoint;    private Point currentPoint;    private final Paint paint;    private List<Point> list=new ArrayList<Point>();    public void setCurrentPoint(Point currentPoint) {        this.currentPoint = currentPoint;    }    public void setStartPoint(Point startPoint) {        this.startPoint = startPoint;    }    public void setEndPoint(Point endPoint) {        this.endPoint = endPoint;    }    public Point getStartPoint() {        return startPoint;    }    public Point getEndPoint() {        return endPoint;    }    public PointDrawable(int width,int height){        startPoint = new Point(0,height/2);        endPoint = new Point(width,height/2);        paint = new Paint();        paint.setStyle(Paint.Style.FILL);        paint.setAntiAlias(true);        paint.setColor(Color.GREEN);    }    @Override    public void draw(@NonNull Canvas canvas) {        canvas.drawColor(Color.BLACK);        if(currentPoint!=null)        {            Log.e("jinlai",currentPoint.getX()+"???"+currentPoint.getY());            if(list.size()<20)            {                list.add(currentPoint);            }else{                list.remove(0);                list.add(currentPoint);            }            for (int i=0;i<list.size();i++)            {                Point point = list.get(i);                int r=i/2;                canvas.drawCircle(point.getX(),point.getY(),r,paint);            }        }    }    @Override    public void setAlpha(@IntRange(from = 0, to = 255) int i) {    }    @Override    public void setColorFilter(@Nullable ColorFilter colorFilter) {    }    @Override    public int getOpacity() {        return 1;    }}

MySelf类就是真个点运动位置的计算方法

实现TypeEvaluator接口

方法中的那两个点就是activity代码中的创建动画传进来的开始和结束点，x成线性变化，y成正玄曲线变化。

package com.example.zxq.bsquxian.zidiyizhidonghua;import android.animation.TypeEvaluator;import android.widget.Button;/** * Created by Administrator on 2017/7/26 0026. */public class MySelf implements TypeEvaluator<Point> {    @Override    public Point evaluate(float v, Point point, Point t1) {        int x = (int) (v*(t1.getX()-point.getX()));        int y = (int) (50 * (float) (Math.sin(0.01 * Math.PI * x)) +200);        return new Point(x,y);    }}

这就是整个过程。主要用途就是根据自己的计算规则实现动态计算，获取要的数据，然后在