OC 版本
CGFloat needScrollowOffsetX = CGRectGetMaxX(button.frame) - SCREEN_WIDTH / 2;
if (needScrollowOffsetX < 0) {
needScrollowOffsetX = 0;
}
CGFloat maxScrollowOffsetX = _scrollView.contentSize.width - _scrollView.width;
if (needScrollowOffsetX > maxScrollowOffsetX) {
needScrollowOffsetX = (maxScrollowOffsetX <= 0) ? 0 : maxScrollowOffsetX;
}
if (needScrollowOffsetX != _scrollView.contentOffset.x) {
[_scrollView setContentOffset:CGPointMake(needScrollowOffsetX, 0) animated:NO];
}
Swift 版本
func selectLabelCenter() {
//計算選中label的centerX
let centerX = CGFloat(self.segmentControl.selectedSegmentIndex)*itemWidth + itemWidth/2
//計算出應該偏移的offsetX
var needScrollowOffsetX = centerX - slidingView.width/2
//最小值不能小於0
if needScrollowOffsetX < 0{
needScrollowOffsetX = 0
}
//不能大於最大值(滑動至最右側)
let maxScrollowOffsetX = slidingView.contentSize.width-slidingView.width
if needScrollowOffsetX > maxScrollowOffsetX {
needScrollowOffsetX = maxScrollowOffsetX
}
//不需要滑動時不用滑動
if needScrollowOffsetX != slidingView.contentOffset.x {
slidingView.isUserInteractionEnabled = false
UIView.animate(withDuration: 1.0, animations: {
self.slidingView.contentOffset = CGPoint(x: needScrollowOffsetX, y: 0)
}, completion: { (_) in
self.slidingView.isUserInteractionEnabled = true
})
}
}
出處