android贝塞尔曲线实现波浪效果

public class WaveView extends View implements View.OnClickListener {
 //路径
 private Path mPath;
 //画笔
 private Paint mPaint;
 //屏幕高度
 private int screenHeight;
 //屏幕宽度
 private int screenWidth;
 //波长 自己控制
 private int waveLength = 800;
 //波长的数量
 private int waveCount;
 //贝塞尔曲线的控制点
 private int centerY;
 private ValueAnimator mValueAnimator;
 //偏移量
 private int mOffset;
 
 public WaveView(Context context) {
  this(context, null);
 }
 
 public WaveView(Context context, @Nullable AttributeSet attrs) {
  super(context, attrs);
  init();
 }
 
 private void init() {
  //初始化画笔
  mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
  mPaint.setStyle(Paint.Style.FILL);
  mPaint.setColor(Color.RED);
  
  mPath = new Path();
 }
 
 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  screenHeight = h;// 获取屏幕高度
  screenWidth = w;//获取屏幕宽度
 
  centerY = h / 2;//设置中心点
  waveCount = (int) Math.round(screenWidth / waveLength + 1.5);//波长的数量
 }
 
 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  mPath.reset();
  //首先移动到最左边 offset是偏移量
  mPath.moveTo(-waveLength + mOffset, centerY);
  for (int i = 0; i < waveCount; i++) {
   //先画底部的曲线 负的波长的3/4 第二次加一个波长的长度 以及加偏移量 曲线是向下的，控制点加60  终点则为负的波长的1/2 + 波长的长度 和偏移量 
   mPath.quadTo(-waveLength * 3 / 4 + i * waveLength + mOffset, centerY + 60, -waveLength / 2 + i * waveLength + mOffset, centerY);
   //再画顶部的曲线 负的波长的1/4         曲线是向上的，控制点减60 
   mPath.quadTo(-waveLength * 1 / 4 + i * waveLength + mOffset, centerY - 60, 0 + i * waveLength + mOffset, centerY);
  }
  //闭合路径
  mPath.lineTo(screenWidth, screenHeight);
  mPath.lineTo(0, screenHeight);
  mPath.close();
  canvas.drawPath(mPath, mPaint);
  //设置点击时间只是为了点击以后才开始循环
  setOnClickListener(this);
 }
 
 @Override
 public void onClick(View view) {
  //主要是为了获取偏移量
  mValueAnimator = ValueAnimator.ofInt(0, waveLength);
  mValueAnimator.setDuration(1000);
  mValueAnimator.setRepeatCount(ValueAnimator.INFINITE);
  mValueAnimator.setInterpolator(new LinearInterpolator());
  mValueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
   @Override
   public void onAnimationUpdate(ValueAnimator valueAnimator) {
    mOffset = (int) valueAnimator.getAnimatedValue();
    //重绘
    invalidate();
   }
  });
  mValueAnimator.start();
 }
}