iOS仿新闻tab标题栏效果

- (void)viewDidLoad{ [super viewDidLoad]; // Do any additional setup after loading the view. [self createTitleScrollView]; [self createButtonLine]; [self createContentScrollview];} #pragma mark - 初始化UI- (void)createTitleScrollView{ // 根据是否有导航栏调整坐标 CGFloat marginY = self.navigationController ? self.navigationController.view.frame.size.height : kUpMargin;  // 标题栏,包括小横线的位置 _titleScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, marginY, kFrameWidth, kTitleHeight + kButtonLineHeight)]; _titleScrollView.showsHorizontalScrollIndicator = NO; _titleScrollView.bounces = NO; _titleScrollView.delegate = self; [self.view addSubview:_titleScrollView];  // 添加button NSArray *titleArray = @[@"头条", @"社会", @"财经", @"科技", @"体育", @"娱乐", @"时尚", @"军事", @"教育", @"游戏"]; _pageCount = titleArray.count; _titleScrollView.contentSize = CGSizeMake(kButtonWidth * _pageCount, kTitleHeight); for (int i = 0; i < _pageCount; i++) {  UIButton *titleBtn = [[UIButton alloc] initWithFrame:CGRectMake(kButtonWidth * i, 0, kButtonWidth, kTitleHeight)];  [titleBtn setTitle:titleArray[i] forState:UIControlStateNormal];  [titleBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];  titleBtn.titleLabel.font = [UIFont systemFontOfSize:16];  [titleBtn addTarget:self action:@selector(titleButtonClicked:) forControlEvents:UIControlEventTouchDown];  titleBtn.tag = 1000 + i; // button做标记，方便后面索引，为了不出冲突，就把这个数值设得大一些  [_titleScrollView addSubview:titleBtn]; };} - (void)createButtonLine{ // 初始时刻停在最左边与按钮对齐 _buttonLine = [[UIView alloc] initWithFrame:CGRectMake(0, kTitleHeight, kButtonWidth, kButtonLineHeight)]; _buttonLine.backgroundColor = [UIColor redColor]; // 小横线加载scrollview上才能跟随button联动 [_titleScrollView addSubview:_buttonLine];} - (void)createContentScrollview{ CGFloat marginY = self.navigationController ? self.navigationController.view.frame.size.height : kUpMargin;  // 添加内容页面 _contentScrollview = [[UIScrollView alloc] initWithFrame:CGRectMake(0, marginY + kTitleHeight + kButtonLineHeight, kFrameWidth, kFrameHeight - marginY - kTitleHeight - kButtonLineHeight)]; _contentScrollview.pagingEnabled = YES; _contentScrollview.bounces = NO; _contentScrollview.contentSize = CGSizeMake(kFrameWidth * _pageCount, kFrameHeight - marginY - kTitleHeight); _contentScrollview.showsHorizontalScrollIndicator = NO; _contentScrollview.delegate = self; [self.view addSubview:_contentScrollview];  // 添加分页面 for (int i = 0; i < _pageCount; i++) {  PageViewController *pageViewController = [[PageViewController alloc] init];  UIButton *button = [_titleScrollView viewWithTag:1000 + i];  pageViewController.title = button.currentTitle;  pageViewController.view.frame = CGRectMake(kFrameWidth * i, 0, kFrameWidth, kFrameHeight - marginY - kTitleHeight);  [_contentScrollview addSubview:pageViewController.view]; }  // 初始化后选中某个栏目 [self titleButtonClicked:[_titleScrollView viewWithTag:1000 + 0]];} #pragma mark - 标题button点击事件- (void)titleButtonClicked:(UIButton *)sender{ // 根据点击的button切换页面和偏移 printf("%s clicked/n", sender.currentTitle.UTF8String);  // 以下不用了，因为scroll切换会自动处理好尺寸和颜色了// for (int i = 0; i < _pageCount; i++)// {//  UIButton *button = [_titleScrollView viewWithTag:1000 + i];//  // 重置button尺寸颜色//  button.transform = CGAffineTransformMakeScale(1, 1);//  [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];// }  // 强调被选中的button // 放大聚焦 sender.transform = CGAffineTransformMakeScale(kMaxTitleScale, kMaxTitleScale); // 变色 [sender setTitleColor:[UIColor greenColor] forState:UIControlStateNormal];  // 居中title [self settleTitleButton:sender];  // 带动画切换到对应的内容,会触发scrollViewDidScroll NSInteger pageIndex = sender.tag - 1000; [_contentScrollview setContentOffset:CGPointMake(kFrameWidth * pageIndex, 0) animated:YES];} #pragma mark - scrollview滑动事件- (void)scrollViewDidScroll:(UIScrollView *)scrollView{ // 根据content内容偏移调整标题栏 if (scrollView == _titleScrollView) {  printf("title moved/n");     } else if (scrollView == _contentScrollview) {  printf("content moved/n");    // 获得左右两个button的索引, 注意最后取整  CGFloat offsetX = scrollView.contentOffset.x;  NSInteger leftTitleIndex = offsetX / kFrameWidth;  NSInteger rightTitleIndex = leftTitleIndex + 1;  // 因为设置了到边不能滑动，所以不考虑边界  UIButton *leftTitleButton = [_titleScrollView viewWithTag:1000 + leftTitleIndex];  UIButton *rightTitleButton = [_titleScrollView viewWithTag:1000 + rightTitleIndex];    // 设置大小和颜色渐变以及小横线的联动  // 权重因子 0~1 小数, 左边和右边互补  CGFloat rightTitleFactor = offsetX / kFrameWidth - leftTitleIndex;  CGFloat leftTitleFactor = 1 - rightTitleFactor;    // 尺寸  CGFloat maxExtraScale = kMaxTitleScale - 1;  leftTitleButton.transform = CGAffineTransformMakeScale(1 + leftTitleFactor * maxExtraScale, 1 + leftTitleFactor * maxExtraScale);  rightTitleButton.transform = CGAffineTransformMakeScale(1 + rightTitleFactor * maxExtraScale, 1 + rightTitleFactor * maxExtraScale);  // 颜色  UIColor *leftTitleColor = [UIColor colorWithRed:0 green:leftTitleFactor blue:0 alpha:1];  UIColor *rightTitleColor = [UIColor colorWithRed:0 green:rightTitleFactor blue:0 alpha:1];  [leftTitleButton setTitleColor:leftTitleColor forState:UIControlStateNormal];  [rightTitleButton setTitleColor:rightTitleColor forState:UIControlStateNormal];  // 小横线位移  _buttonLine.frame = CGRectMake(kButtonWidth * (leftTitleIndex + rightTitleFactor), _buttonLine.frame.origin.y, kButtonWidth, kButtonLineHeight); }} - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{ // 内容区块滑动结束调整标题栏居中 if (scrollView == _contentScrollview) {  // 取得索引值  NSInteger titleIndex = scrollView.contentOffset.x / kFrameWidth;  // title居中  [self settleTitleButton:[_titleScrollView viewWithTag:1000 + titleIndex]]; }} #pragma mark - 标题按钮和横线居中偏移- (void)settleTitleButton:(UIButton *)button{ // 标题 // 这个偏移量是相对于scrollview的content frame原点的相对对标 CGFloat deltaX = button.center.x - kFrameWidth / 2; // 设置偏移量，记住这段算法 if (deltaX < 0) {  // 最左边  deltaX = 0; } CGFloat maxDeltaX = _titleScrollView.contentSize.width - kFrameWidth; if (deltaX > maxDeltaX) {  // 最右边不能超范围  deltaX = maxDeltaX; } [_titleScrollView setContentOffset:CGPointMake(deltaX, 0) animated:YES]; }