iOS 仿知乎/途家导航栏渐变文字动画效果

效果图如上,简单分析下

• 1.导航栏一开始是隐藏的,随着scrollView滚动而渐变
• 2.导航栏左右两边的navigationItem是一直显示的
• 3.导航栏参考了途家app,使用了毛玻璃效果,背景是一张图片
• 4.下拉放大图片效果
• 5.title文字动画效果

通过简单分析,系统的导航栏实现以上效果有点困难,直接自定义一个假的导航栏更容易点

分布拆解实现以上效果

一.下拉放大header图片

- (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);
    }];
}

二.导航栏左右两边的navigationItem是一直显示的

- (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];
}

三.自定义导航栏及毛玻璃效果及title文字动画效果

// 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;
}

由于是直接写项目中,没有demo可供下载,抱歉,如果有更好的方法实现,希望不吝赐教,共勉!!!