下拉放大, 上推渐变

2016-08-20 13_11_15.gif

属性

@property (nonatomic, strong)UITableView *tableView;
@property (nonatomic, strong)UIView *backGroundView;
@property (nonatomic, strong)UIImageView *imageView;
@property (nonatomic, strong)UIImageView *barImageView;```
######要在导航栏上显示图片

[self.navigationController.navigationBar setBackgroundImage:[UIImage alloc] forBarMetrics:UIBarMetricsDefault];
[self.navigationController.navigationBar setShadowImage:[[UIImage alloc] init]];

######创建TableView

• (void)creatTableView {
  self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, -64, self.view.bounds.size.width, self.view.bounds.size.height + 64)];
  _tableView.delegate = self;
  _tableView.dataSource = self;
  [self.view addSubview:_tableView];
  [_tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"cell"];
  _tableView.tableHeaderView = [self creatTableViewHeaderView];
  self.barImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, -20, WIDTH, 64)];
  _barImageView.image = [UIImage imageNamed:@"tts-navbar"];
  [self.navigationController.navigationBar addSubview:_barImageView];
  self.navigationItem.title = @"导航栏";
  }
• (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
  return 20;
  }
• (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
  cell.textLabel.text = [NSString stringWithFormat:@"cell = %ld", (long)indexPath.row];
  return cell;
  }

######将图片放在头视图上

• (UIView *)creatTableViewHeaderView {
  self.backGroundView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, WIDTH, 200)];
  self.imageView = [[UIImageView alloc] initWithFrame:self.backGroundView.bounds];
  _imageView.image = [UIImage imageNamed:@"1.jpg"];
  [self.backGroundView addSubview:_imageView];
  return _backGroundView;
  }

#####上推渐变, 下拉放大的设置

• (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  // 上推渐变
  CGFloat offset_Y = scrollView.contentOffset.y;
  CGFloat alpha = (offset_Y + 64) / 200.0f;
  self.barImageView.alpha = alpha;
  // 下拉放大
  if (offset_Y < -64) {
  CGFloat add_height = -(offset_Y + 64);
  CGFloat scale = (200 + add_height) / 200.0f;
  self.imageView.frame = CGRectMake(-(WIDTH * scale - WIDTH) / 2.0f, -add_height, WIDTH * scale, 200 + add_height);
  NSLog(@"%f", scale);
  }
  }