iOS实现头部拉伸效果

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:

@interface UINavigationBar (BackgroundColor)

- (void)lt_setBackgroundColor:(UIColor *)color;

@end

实现部分:

#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, span) UIImageView *bgView;

// 记录原始大小

@property (assign) CGRect originalFrame;

@property (nonatomic, span) 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:

以上是 iOS实现头部拉伸效果 的全部内容, 来源链接: utcz.com/z/348234.html

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