iOS tableView实现头部拉伸并改变导航条渐变色

本文实例为大家分享了ios tableview实现头部拉伸改变，导航条渐变色的具体代码，供大家参考，具体内容如下

#import "tableviewcontroller.h"

static nsstring *ident = @"cell";

#define rgba(r,g,b,a) [uicolor colorwithred:r/255.0f green:g/255.0f blue:b/255.0f alpha:a]
#define rgb(r,g,b) rgba(r,g,b,1.0f)
#define zhuticolor rgb(76,16,198)
#define zhuticoloralpha(alpha) rgba(76, 16, 198, alpha)

// 判断是否是iphone x
#define iphonex ([uiscreen instancesrespondtoselector:@selector(currentmode)] ? cgsizeequaltosize(cgsizemake(1125, 2436), [[uiscreen mainscreen] currentmode].size) : no)
// 状态栏高度
#define status_bar_height (iphonex ? 44.f : 20.f)
// 导航栏高度
#define navigation_bar_height (iphonex ? 88.f : 64.f)
// tabbar高度
#define tab_bar_height (iphonex ? (49.f + 34.f) : 49.f)
// home indicator
#define home_indicator_height (iphonex ? 34.f : 0.f)

#define screenwidth ([uiscreen mainscreen].bounds.size.width)
#define screenheight ([uiscreen mainscreen].bounds.size.height)

#define imagehight 200


@interface tableviewcontroller ()

@property (nonatomic,strong) uiimageview *headimage;
@property (nonatomic, strong) uiview *headerbackview;
@property (nonatomic, strong) uiview *mengview;

@end

@implementation tableviewcontroller

- (void)viewdidload {
  [super viewdidload];
  [self.tableview registerclass:[uitableviewcell class] forcellreuseidentifier:ident];
  self.view.backgroundcolor = [uicolor redcolor];
  self.tableview.tableheaderview = self.headerbackview;
  [self.headerbackview addsubview:self.headimage];
  [self.headimage addsubview:self.mengview];
  [self navcleanfromalpha:0];
  
}

-(void)navcleanfromalpha:(cgfloat)alpha
{
  [self.navigationcontroller.navigationbar setbackgroundimage:[self createimagewithcolor:zhuticoloralpha(alpha)] forbarmetrics:uibarmetricsdefault];
  self.navigationcontroller.navigationbar.shadowimage = [uiimage new];
}

-(uiimage*) createimagewithcolor:(uicolor*) color
{
  cgrect rect=cgrectmake(0.0f, 0.0f, 1.0f, 1.0f);
  uigraphicsbeginimagecontext(rect.size);
  cgcontextref context = uigraphicsgetcurrentcontext();
  cgcontextsetfillcolorwithcolor(context, [color cgcolor]);
  cgcontextfillrect(context, rect);
  uiimage *theimage = uigraphicsgetimagefromcurrentimagecontext();
  uigraphicsendimagecontext();
  return theimage;
}

-(uiimageview *)headimage
{
  if(!_headimage)
  {
    _headimage= [[uiimageview alloc]initwithframe: self.headerbackview.bounds];
    _headimage.image = [uiimage imagenamed:@"1024"];
  }
  return _headimage;
}

-(uiview *)mengview
{
  if (!_mengview)
  {
    _mengview = [[uiview alloc]initwithframe:self.headerbackview.bounds];
    _mengview.backgroundcolor = rgba(1, 1, 1, 0.1);
  }
  return _mengview;
}

-(uiview *)headerbackview
{
  if (!_headerbackview)
  {
    _headerbackview = [[uiview alloc] initwithframe:cgrectmake(0, 0, screenwidth, imagehight)];
    [_headerbackview setbackgroundcolor:[uicolor lightgraycolor]];
  }
  return _headerbackview;
}

- (void)didreceivememorywarning {
  [super didreceivememorywarning];
  // dispose of any resources that can be recreated.
}

- (void)scrollviewdidscroll:(uiscrollview *)scrollview
{
  //---------------------- 图片拉升 -------------------------
  //图片高度
  cgfloat imageheight = self.headerbackview.frame.size.height;
  //图片宽度
  cgfloat imagewidth = screenwidth;
  //图片上下偏移量
  cgfloat imageoffsety = scrollview.contentoffset.y;
  
//  nslog(@"图片上下偏移量 imageoffsety:%f ->",imageoffsety);
  
  //上移
  if (imageoffsety < 0)
  {
    cgfloat totaloffset = imageheight + abs(imageoffsety);
    cgfloat f = totaloffset / imageheight;
    
    self.headimage.frame = cgrectmake(-(imagewidth * f - imagewidth) * 0.5, imageoffsety, imagewidth * f, totaloffset);
    self.mengview.frame = self.headimage.bounds;
  }
  
  //------------------- 导航条颜色渐变 ----------------------------
  
  cgfloat tableviewoffsety = [self.tableview rectforsection:0].origin.y - navigation_bar_height;
  cgfloat contentoffsety = scrollview.contentoffset.y;

  if (contentoffsety >= tableviewoffsety)
  {
//    scrollview.contentoffset = cgpointmake(0, tableviewoffsety); //定位
    [self navcleanfromalpha:1];

  }
  else
  {
    cgfloat alpha = scrollview.contentoffset.y/imagehight;
    
    if (alpha >= 1) { alpha = 1; }
    if (alpha <= 0) { alpha = 0; }
    nslog(@"%.2f",alpha);
    [self navcleanfromalpha:alpha];
  }
  
  
}

- (nsinteger)tableview:(uitableview *)tableview numberofrowsinsection:(nsinteger)section {
  return 20;
}


- (uitableviewcell *)tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath {
  uitableviewcell *cell = [tableview dequeuereusablecellwithidentifier:ident forindexpath:indexpath];
  
  // configure the cell...
  
  cell.textlabel.text = [nsstring stringwithformat:@"asdada = %zd",indexpath.row];
  
  return cell;
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。