iOS实现知乎和途家导航栏渐变的文字动画效果

- (void)viewDidLoad { [super viewDidLoad]; [self.view addSubview:self.scaleImageView]; // 设置展示图片的约束 [_scaleImageView mas_makeConstraints:^(MASConstraintMaker *make) {  make.top.mas_equalTo(0);  make.left.equalTo(self.view.mas_left);  make.right.equalTo(self.view.mas_right);  make.height.mas_equalTo(kHeardH); }];}// tableView懒加载-(UITableView *)tableView{ if(_tableView == nil){  _tableView = [[UITableView alloc]initWithFrame:self.view.bounds style:UITableViewStylePlain];  _tableView.contentInset = UIEdgeInsetsMake(kHeardH-35, 0, 0, 0);  _tableView.delegate = self;  _tableView.dataSource = self;  _tableView.separatorStyle = UITableViewCellSeparatorStyleNone; } return _tableView;}// 图片的懒加载- (UIImageView *)scaleImageView{ if (!_scaleImageView) {  _scaleImageView = [[UIImageView alloc] init];  _scaleImageView.contentMode = UIViewContentModeScaleAspectFill;  _scaleImageView.clipsToBounds = YES;  _scaleImageView.image = [UIImage imageNamed:@"666"]; } return _scaleImageView;}// 导航栏高度#define kNavBarH 64.0f// 头部图片的高度#define kHeardH 260#pragma mark - UIScrollViewDelegate- (void)scrollViewDidScroll:(UIScrollView *)scrollView { // 计算当前偏移位置 CGFloat offsetY = scrollView.contentOffset.y; CGFloat delta = offsetY - _lastOffsetY; DLog(@"delta=%f",delta); DLog(@"offsetY=%f",offsetY); CGFloat height = kHeardH - delta; if (height < kNavBarH) {  height = kNavBarH; } [_scaleImageView mas_updateConstraints:^(MASConstraintMaker *make) {  make.height.mas_equalTo(height); }];}

- (void)viewDidLoad { [super viewDidLoad]; // 直接添加到控制器的View上面,注意添加顺序,在添加导航栏之后,否则会被遮盖住 [self configNavigationBar];}- (void)configNavigationBar{ //左边返回按钮 UIButton *backBtn = [[UIButton alloc]init]; backBtn.frame = CGRectMake(0, 20, 44, 44); [backBtn setImage:[UIImage imageNamed:@"special_back"] forState:UIControlStateNormal]; [backBtn addTarget:self action:@selector(back) forControlEvents:UIControlEventTouchUpInside]; //右边分享按钮 UIButton *shartBtn = [[UIButton alloc]init]; shartBtn.frame = CGRectMake(SCREENWIDTH-44, 20, 44, 44); [shartBtn setImage:[UIImage imageNamed:@"special_share"] forState:UIControlStateNormal]; [shartBtn addTarget:self action:@selector(shareBtnClick) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:backBtn]; [self.view addSubview:shartBtn];}// 返回-(void)back{ [self.navigationController popViewControllerAnimated:YES];}

// 隐藏系统导航栏- (void)viewWillAppear:(BOOL)animated{ [super viewWillAppear:animated]; self.navigationController.navigationBar.hidden = YES;}- (void)viewDidLoad { [super viewDidLoad]; self.navigationController.navigationBar.hidden = YES; self.lastOffsetY = - kHeardH+35; [self.view addSubview:self.tableView]; self.tableView.backgroundColor = [UIColor clearColor]; [self.view addSubview:self.navigationView]; self.navigationController.navigationBar.barStyle = UIBarStyleBlack;}// 自定义导航栏-(UIView *)navigationView{ if(_navigationView == nil){  _navigationView = [[UIView alloc]init];  _navigationView.frame = CGRectMake(0, 0, SCREENWIDTH, kNavBarH);  _navigationView.backgroundColor = [UIColor clearColor];  _navigationView.alpha = 0.0;  //添加子控件  [self setNavigationSubView]; } return _navigationView;}// 注意:毛玻璃效果API是iOS8的,适配iOS8以下的请用其他方法-(void)setNavigationSubView{ // 毛玻璃背景 UIImageView *bgImgView = [[UIImageView alloc] initWithFrame:_navigationView.bounds]; bgImgView.image = [UIImage imageNamed:@"666"]; [_navigationView addSubview:bgImgView]; /** 毛玻璃特效类型  * UIBlurEffectStyleExtraLight,  * UIBlurEffectStyleLight,  * UIBlurEffectStyleDark  */ UIBlurEffect * blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark]; // 毛玻璃视图 UIVisualEffectView * effectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect]; //添加到要有毛玻璃特效的控件中 effectView.frame = bgImgView.bounds; [bgImgView addSubview:effectView]; //设置模糊透明度 effectView.alpha = 0.9f; //中间文本框 UIView *centerTextView = [[UIView alloc]init]; self.centerTextView = centerTextView; CGFloat centerTextViewX = 0; CGFloat centerTextViewY = 64; CGFloat centerTextViewW = 0; CGFloat centerTextViewH = 0; //文字大小 NSString *title = @"Pg.lostk开启后摇滚的新图景"; NSString *desc = @"摇滚清心坊8套"; CGSize titleSize = [title sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:12]}]; CGSize descSize = [desc sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:11]}]; centerTextViewW = titleSize.width > descSize.width ? titleSize.width : descSize.width; centerTextViewH = titleSize.height + descSize.height +10; centerTextViewX = (SCREENWIDTH - centerTextViewW) / 2; centerTextView.frame = CGRectMake(centerTextViewX, centerTextViewY, centerTextViewW, centerTextViewH); //文字label UILabel *titleLabel = [[UILabel alloc]init]; titleLabel.text = title; titleLabel.font = [UIFont systemFontOfSize:12]; titleLabel.textColor = [UIColor whiteColor]; titleLabel.frame = CGRectMake(0,5, centerTextViewW, titleSize.height); UILabel *descLabel = [[UILabel alloc]init]; descLabel.textAlignment = NSTextAlignmentCenter; descLabel.text = desc; descLabel.font = [UIFont systemFontOfSize:11]; descLabel.textColor = [UIColor whiteColor]; descLabel.frame = CGRectMake(0, titleSize.height + 5, centerTextViewW, descSize.height); [centerTextView addSubview:titleLabel]; [centerTextView addSubview:descLabel]; [_navigationView addSubview:centerTextView];}声明控件@property(nonatomic,strong) UIView *navigationView;  // 导航栏@property(nonatomic,strong) UIView *centerTextView;  // title文字@property (assign, nonatomic) CGFloat lastOffsetY;  // 记录上一次位置@property (nonatomic,strong) UIImageView *scaleImageView; // 顶部图片核心代码#pragma mark - ScrollViewDelegate- (void)scrollViewDidScroll:(UIScrollView *)scrollView { // 计算当前偏移位置 CGFloat offsetY = scrollView.contentOffset.y; CGFloat delta = offsetY - _lastOffsetY; DLog(@"delta=%f",delta); DLog(@"offsetY=%f",offsetY); CGFloat height = kHeardH - delta; if (height < kNavBarH) {  height = kNavBarH; } CGFloat margin = 205; if (delta>margin && delta<margin+39) {  self.centerTextView.y = 64 - (delta-margin);  self.centerTextView.alpha = 1.0; } if (delta>margin+39) {  self.centerTextView.y = 25;  self.centerTextView.alpha = 1.0; } if (delta<=margin) {  self.centerTextView.alpha = 0; } if (delta<= 0) {  self.centerTextView.y =64;  self.centerTextView.alpha = 0.0; } [_scaleImageView mas_updateConstraints:^(MASConstraintMaker *make) {  make.height.mas_equalTo(height); }]; CGFloat alpha = delta / (kHeardH - kNavBarH); if (alpha >= 1.0) {  alpha = 1.0; } self.navigationView.alpha = alpha;}