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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。
导航透明度的设置
添加系统导航栏的category实现
声明部分：
@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）
#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移动技术网。
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