UISegmentedControl結(jié)合UIScrollView，實現(xiàn)點擊及側(cè)滑切換控制器視圖，使用addChildViewController方法以及addSubview方法，將視圖添加到UIScrollView上，發(fā)現(xiàn)每個控制器內(nèi)部的viewWillAppear方法不會走，這是因為沒有把controller和它控制的view remove掉 ?？梢愿鶕?jù)UIScrollView滑動時的偏移量進(jìn)行手動調(diào)用viewWillAppear等方法，實現(xiàn)自己想要的效果。

#pragma mark - **************** UIScrollViewDelegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    kLog(@"%f",scrollView.contentOffset.x);
    self.segmentedControl.selectedSegmentIndex =  (NSInteger)(scrollView.contentOffset.x / kScreenWidth);
    if (self.segmentedControl.selectedSegmentIndex == 0) {
        [_OptionalViewController viewWillAppear:YES];
    }else if (self.segmentedControl.selectedSegmentIndex == 1) {
        [_CurrencyViewController viewWillAppear:YES];
    }else if (self.segmentedControl.selectedSegmentIndex == 2) {
        [_CoinHomeViewController viewWillAppear:YES];
    }
    
}