width = w;
    height = h;
    left = top = 0;
    right = width;
    bottom = height * 0.8f;
    cx = (right + left) / 2;
    cy = (bottom + top) / 2;
    RectF rectF = new RectF(left, top, bottom, bottom);
    path.arcTo(rectF, 90, 180);
    rectF.left = right - bottom;
    rectF.right = right;
    path.arcTo(rectF, 270, 180);
    path.close();
    circle_left = 0;
    circle_right = bottom;
    circle_width = circle_right - circle_left;
    float circle_height = (bottom - top) / 2;
    radius = circle_height * 0.9f;
    borderwidth = (int) (2 * (circle_height - radius));
    circle_cx = width - circle_height;

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    paint.setStyle(Style.FILL);
    paint.setAntiAlias(true);
    canvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG));
    if (isChoose) {
      paint.setColor(onColor);
    } else {
      paint.setColor(offColor);
    }
    canvas.drawPath(path, paint);
    isAnimation = isAnimation - 0.1f > 0 ? isAnimation - 0.1f : 0;
    //缩放大小参数随isAnimation变化而变化
    final float scale = 0.98f * (isChoose ? isAnimation : 1 - isAnimation);
    //保存canvas状态
    canvas.save();
    canvas.scale(scale, scale, circle_cx, cy);
    paint.setColor(offColor);
    canvas.drawPath(path, paint);
    canvas.restore();
    paint.reset();
    float bTranslateX = width - circle_width;
    final float translate = bTranslateX * (isChoose ? 1 - isAnimation : isAnimation);
    canvas.translate(translate, 0);
    if (isAnimation > 0) {
      invalidate();
    }
    canvas.save();
    paint.setStyle(Style.FILL);
    paint.setColor(offColor);
    canvas.drawCircle(circle_width / 2, circle_width / 2, radius, paint); // 按钮白底
    paint.setStyle(Style.STROKE);
    paint.setColor(borderColor);
    paint.setStrokeWidth(borderwidth);
    canvas.drawCircle(circle_width / 2, circle_width / 2, radius, paint); // 按钮灰边
    canvas.restore();
  }

  public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction()) {
      case MotionEvent.ACTION_DOWN:
        return true;
      case MotionEvent.ACTION_CANCEL:
        return true;
      case MotionEvent.ACTION_UP:
          isAnimation = 1;
          isChoose = !isChoose;
          listener.onStateChanged(isChoose);
          invalidate();
        break;
    }
    return super.onTouchEvent(event);

  }