本文实例为大家分享了ios实现头部拉伸效果展示的具体代码，供大家参考，具体内容如下
主要涉及到导航栏透明度、图片拉伸、列表头部等。
- 导航栏透明度的实现。
- 列表拖动距离的监听，及图片放大的实现。
导航透明度的设置
添加系统导航栏的category实现
声明部分：
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@interface uinavigationbar (backgroundcolor)- (void)lt_setbackgroundcolor:(uicolor *)color;@end |
实现部分：
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#import <objc/runtime.h>@implementation uinavigationbar (backgroundcolor)static char overlaykey;- (uiview *)overlay{ return objc_getassociatedobject(self, &overlaykey);}- (void)setoverlay:(uiview *)overlay{ objc_setassociatedobject(self, &overlaykey, overlay, objc_association_retain_nonatomic);}- (void)lt_setbackgroundcolor:(uicolor *)color{ if (!self.overlay) { [self setbackgroundimage:[uiimage new] forbarmetrics:uibarmetricsdefault]; // insert an overlay into the view hierarchy self.overlay = [[uiview alloc] initwithframe:cgrectmake(0, -20, [uiscreen mainscreen].bounds.size.width, self.bounds.size.height + 20)]; self.overlay.autoresizingmask = uiviewautoresizingflexiblewidth|uiviewautoresizingflexibleheight; [self insertsubview:self.overlay atindex:0]; } self.overlay.backgroundcolor = color;}@end |
监听列表拖动及实现图片放大
主要是监听滚动的距离（scrollviewdidscroll:方法）
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#import "stretchviewcontroller.h"#import "uinavigationbar+backgroundcolor.h"// 背景图片的宽高比例#define ratio 0.8@interface stretchviewcontroller () <uitableviewdelegate, uitableviewdatasource>// 可放大的背景图片@property (nonatomic, strong) uiimageview *bgview;// 记录原始大小@property (assign) cgrect originalframe;@property (nonatomic, strong) uitableview *tableview;@end@implementation stretchviewcontroller- (void)viewwillappear:(bool)animated{ [super viewwillappear:animated]; //[self.navigationcontroller setnavigationbarhidden:yes animated:animated]; //self.navigationcontroller.navigationbar.tintcolor = [uicolor whitecolor]; //self.navigationcontroller.navigationbar.bartintcolor = [uicolor clearcolor]; //self.navigationcontroller.navigationbar.backgroundcolor = [uicolor clearcolor]; // 设置导航栏底部分割线为透明 [self.navigationcontroller.navigationbar setshadowimage:[uiimage new]];}- (void)viewdidload { [super viewdidload]; // 设置全透明 [self.navigationcontroller.navigationbar lt_setbackgroundcolor:[[uicolor greencolor] colorwithalphacomponent:0]]; // do any additional setup after loading the view. self.view.backgroundcolor = [uicolor lightgraycolor]; self.bgview = [[uiimageview alloc] initwithframe:cgrectmake(0, 0, self.view.bounds.size.width, self.view.bounds.size.width*ratio)]; self.bgview.image = [uiimage imagenamed:@"bg-mine"]; self.originalframe = self.bgview.frame; [self.view addsubview:self.bgview]; self.tableview = [[uitableview alloc] initwithframe:cgrectmake(0, 64, self.view.bounds.size.width, self.view.bounds.size.height-64) style:uitableviewstyleplain]; self.tableview.backgroundcolor = [uicolor clearcolor]; self.tableview.showsverticalscrollindicator = no; self.tableview.delegate = self; self.tableview.datasource = self; // 1. contentinset //table.contentinset = uiedgeinsetsmake(160, 0, 0, 0); // 2. heatview uiview *headview = [[uiview alloc] initwithframe:cgrectmake(0, 0, self.view.bounds.size.width, 160)]; headview.backgroundcolor = [uicolor clearcolor]; self.tableview.tableheaderview = headview; [self.view addsubview:self.tableview];}- (nonnull uitableviewcell *)tableview:(nonnull uitableview *)tableview cellforrowatindexpath:(nonnull nsindexpath *)indexpath { uitableviewcell *cell = [tableview dequeuereusablecellwithidentifier:@"cellidentifier"]; if (cell == nil) { cell = [[uitableviewcell alloc] initwithstyle:uitableviewcellstylevalue1 reuseidentifier:@"cellidentifier"]; } cell.textlabel.text = @"测试数据"; return cell;}- (nsinteger)tableview:(nonnull uitableview *)tableview numberofrowsinsection:(nsinteger)section { return 10;}- (void)scrollviewdidscroll:(uiscrollview *)scrollview{ cgfloat yoffset = scrollview.contentoffset.y; // 向上滑动，offset是增加的；向下滑动，是减少的 if (yoffset < 160) { // 当滑动到导航栏底部时 cgfloat coloralpha = yoffset/160;// self.navigationcontroller.navigationbar.backgroundcolor = [[uicolor whitecolor] colorwithalphacomponent:coloralpha]; [self.navigationcontroller.navigationbar lt_setbackgroundcolor:[[uicolor whitecolor] colorwithalphacomponent:coloralpha]]; } else { // 超过导航栏底部了 [self.navigationcontroller.navigationbar lt_setbackgroundcolor:[uicolor whitecolor]]; } // 往上滑动效果、处理放大效果 if (yoffset > 0) { self.bgview.frame = ({ cgrect frame = self.bgview.frame; frame.origin.y = self.originalframe.origin.y - yoffset; frame; }); } else { // 往下移动，放大效果 self.bgview.frame = ({ cgrect frame = self.originalframe; frame.size.height = self.originalframe.size.height - yoffset; frame.size.width = frame.size.height/ratio; // frame.origin.x = self.originalframe.origin.x - (frame.size.width - self.originalframe.size.width)/2; frame; }); }}@end |
以上是对系统原生的导航栏进行透明度设置。
也可进行自定义视图设置为导航栏
效果如下：
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服务器之家。
原文链接：https://blog.csdn.net/u010596262/article/details/78420994
