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();
  }
}