网易导航条渐变效果核心代码

// 滚动中调用
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGFloat offsetX = scrollView.contentOffset.x;
// 取出左右两个button的index
    NSInteger leftIndex = offsetX / ZHJScreenW;
    NSInteger rightIndex = leftIndex + 1;
// 取出左边的button
    UIButton *leftButton = self.buttons[leftIndex];

// 取出右边的button，考虑到在最右边的时候不用再滑动了，所以要判断下
    UIButton *rightButton = nil;
    if (rightIndex < self.buttons.count) {
        rightButton = self.buttons[rightIndex];
    }
 // 取出左边的缩放值
    CGFloat scaleR = offsetX / ZHJScreenW - leftIndex;
 // 取出右边的缩放值
    CGFloat scaleL = 1 - scaleR;

 // maxTitleScale ＝ 1.3 是最大缩放大小
    CGFloat transScale = maxTitleScale - 1;
    leftButton.transform = CGAffineTransformMakeScale(scaleL * transScale + 1, scaleL * transScale + 1);

    rightButton.transform = CGAffineTransformMakeScale(scaleR * transScale + 1, scaleR * transScale + 1);

  // 用rgb来实现颜色的渐变
    UIColor *rightColor = [UIColor colorWithRed:scaleR green:scaleR blue:scaleR alpha:1];
    UIColor *leftColor = [UIColor colorWithRed:scaleL green:scaleL blue:scaleL alpha:1];

    [leftButton setTitleColor:leftColor forState:UIControlStateNormal];
    [rightButton setTitleColor:rightColor forState:UIControlStateNormal];

    // 设置指示器的位置
    // 算出button的宽度
    CGFloat buttonW = (self.view.width - 100) / 3.0;
    //  设置动画
    self.indicator.transform = CGAffineTransformMakeTranslation(buttonW * (offsetX / ZHJScreenW), 0);

}