iOS TableView頭視圖根據(jù)偏移量下拉縮放效果

//========== 頭視圖創(chuàng)建與設(shè)置 ===========
  imageHight = 250;
  [self creatHeardView];

- (void)creatHeardView
{
  headerView = [[UIView alloc] initWithFrame:(CGRectMake(0, 0, ScreenWidth, imageHight+50))];
  //背景視圖
  heardImageView = [[UIImageView alloc] init];
  heardImageView.frame = CGRectMake(0, 0, ScreenWidth, imageHight);
  heardImageView.image = [UIImage imageNamed:@"backGround.jpg"];
  [headerView addSubview:heardImageView];
  //用戶(hù)頭像
  personImageView = [[UIImageView alloc] initWithFrame:CGRectMake(ScreenWidth-30-60, imageHight-30, 60, 60)];
  personImageView.layer.cornerRadius = CGRectGetWidth(personImageView.frame)/2;
  personImageView.layer.masksToBounds = YES;
  [headerView addSubview:personImageView];
  //用戶(hù)名
  personNameLabel = [[UILabel alloc] initWithFrame:CGRectMake(CGRectGetMinX(personImageView.frame)-200, CGRectGetMinY(personImageView.frame), 180, 30)];
  personNameLabel.font = [UIFont systemFontOfSize:15];
  personNameLabel.textColor = [UIColor whiteColor];
  personNameLabel.textAlignment = NSTextAlignmentRight;
  [headerView addSubview:personNameLabel];
  //個(gè)人簽名
  introduceLabel = [[UILabel alloc] initWithFrame:CGRectMake(30, CGRectGetMaxY(personImageView.frame), ScreenWidth-60, 20)];
  introduceLabel.font = [UIFont systemFontOfSize:10];
  introduceLabel.textColor = [UIColor grayColor];
  introduceLabel.textAlignment = NSTextAlignmentRight;
  [headerView addSubview:introduceLabel];
  
  comTableView.tableHeaderView = headerView;//設(shè)置頭視圖
}

然后在TableView的滾動(dòng)代理中有一個(gè)方法可以實(shí)時(shí)監(jiān)測(cè)滾動(dòng)偏移量，
#pragma mark - 滾動(dòng)代理
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
  CGFloat width = self.view.frame.size.width; // 圖片寬度
  CGFloat yOffset = scrollView.contentOffset.y; // 偏移的y值，還要考慮導(dǎo)航欄的64哦
  if (yOffset < 0) {//向下拉是負(fù)值，向上是正
    CGFloat totalOffset = imageHight + ABS(yOffset);
    CGFloat f = totalOffset / imageHight;//縮放比例
    //拉伸后的圖片的frame應(yīng)該是同比例縮放。
    heardImageView.frame = CGRectMake(- (width * f - width) / 2, yOffset, width * f, totalOffset); 
  }
}