Android动画之小球拟合动画实例

package com.example.administrator.animationworkdemo.views;

import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.util.AttributeSet;
import android.view.View;

import java.util.concurrent.CyclicBarrier;

/**
 * 这个例子中，大家可以发现作者的拟合做的并不是很好，连接的地方比较生硬，大家可以思考下如何改善
 * 贝塞尔曲线绘制比较复杂，大家在学习过程中，可以仿照示例中的，将辅助点和线绘制出来，这样会看的更清楚一点
 */
public class BallShapeChangeView extends View {

  // 使用贝塞尔曲线来拟合圆的magic number
  //C 是三阶贝塞尔曲线拟合 圆的 误差最小  获得控制点的参数.
  private static final float C = 0.551915024494f;
  private Paint mPaint;
  private int mRadiusBig = 120, mRadiusSmall = (int) (mRadiusBig / 2f), mWidth, mHeight, mMimWidth = (int) (mRadiusSmall * 2 * 3)/*fill view mim width*/;
  private float mFraction = 0, mFractiOnDegree= 0, /*degree*/
      mLength, mDistanceBezier;
  private Path mPathCircle, mPathBezier;
  private ValueAnimator mValueAnimator;
  private float[] mPointData = new float[8];// 4个数据点 顺时针排序，从左边开始
  private float[] mPointCtrl = new float[16];// 8个控制点
  private float[] mPos = new float[2];
  private PathMeasure mPathMeasure;
  private Path mPathBezier2;

  public BallShapeChangeView(Context context, AttributeSet attrs) {
    super(context, attrs);
    mPaint = new Paint();
    mPaint.setStyle(Paint.Style.FILL);
    mPaint.setColor(0xFF7C191E);
    mPaint.setAntiAlias(true);
    mPathCircle = new Path();
    mPathBezier = new Path();
    mPathBezier2 = new Path();
    mPathMeasure = new PathMeasure();
    mValueAnimator = ValueAnimator.ofFloat(0, 1, 0);
    mValueAnimator.setDuration(3000);
    mValueAnimator.setRepeatCount(Integer.MAX_VALUE);
    mValueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
      @Override
      public void onAnimationUpdate(ValueAnimator animation) {
        mFraction = (float) animation.getAnimatedValue();
        mFractiOnDegree= animation.getAnimatedFraction();
        invalidate();
      }
    });
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    // 为了能够更好的控制绘制的大小和位置，当然，初学者写死也是可以的
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    mWidth = MeasureSpec.getSize(widthMeasureSpec);
    mHeight = MeasureSpec.getSize(heightMeasureSpec);
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    if (widthMode != MeasureSpec.AT_MOST && heightMode != MeasureSpec.AT_MOST) {
      if (mWidth