iOS开发: 仿京东导航控制器push和pop时, 导航条效果

• 在开发过程中, 需要做一个类似于京东手机app里面, 导航控制器push和pop的效果, 在网上找了很久, 都没有找到类似的方法
  当然也不是一无所获, 倒也发现了一种实现push和pop都带层次的效果, 但并不是我想要的。

• 我需要的是push过程为普通样式, pop的时候才有层次结构
  最后, 在朋友的帮助下, 完成了下面的效果:

• 慢动作:

  
  

• 正常速度:

  
  

实现思路

1. push的效果必须是普通的, 所以在push过程中, 不能做任何操作
2. pop的效果是导航条跟着控制器走
3. 所以在push过程中, 导航条一直显示, 而在pop过程中使用动画的方式隐藏导航条

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    // 动画效果隐藏导航条
    [self.navigationController setNavigationBarHidden:YES animated:YES];
}

就会出现如下效果:

• 结果: push的效果和pop的效果已经实现了, 但是有一个问题, 那就是pop过程中, 前一个界面的导航条被隐藏了

• 所以我们还需要一个操作, 那就是要在pop过程中, 前一个界面中显示导航条才行, 这个问题想了很久, 最后决定使用截屏的方式实现效果

• 过程:

  • 在整个push的时候, 控制器将要消失的方法里截取屏幕, 并添加到根视图上, 这里需要显示在根视图的最上面

UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, NO, 0.0);
[self.navigationController.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.screenshots.hidden = NO;
self.screenshots.image = image;
[self.view bringSubviewToFront:self.screenshots];

• 这里的screenshots, 是一个UIImageView对象, 用来显示截取的图片
• 当添加完截图后, 就有了这样的现象

• 效果看起来已经实现了, 但是却有一个问题, 那就是第一个界面上显示的只是一张截图, 并没有导航条, 并且截图是无法操作业务的
• 所以在截图完成后, 我们需要将导航条显示出来, 由于截取的图片上的导航条和实际导航条是一样的, 所以这里直接显示导航条而不通过动画, 并且隐藏掉截图

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    [self.navigationController setNavigationBarHidden:NO animated:NO];
    self.screenshots.hidden = YES;
}

最后

通过这种方式, 就实现了模仿京东导航条的效果

下面是我写的一个UIViewController分类, 可以直接使用, 如果有什么地方质量不够好请留言, 我会修改

.h文件

#import <UIKit/UIKit.h>

/**
 导航控制器的状态

 - LTNavigationControllerStatusNone: 无导航控制器, 或则是 导航控制器的跟控制器
 - LTNavigationControllerStatusPush: 正在push
 - LTNavigationControllerStatusPop: 正在pop
 LTNavigationControllerStatusNotApply: 不使用
 */
typedef NS_ENUM(NSInteger, LTNavigationControllerStatus) {
    LTNavigationControllerStatusNone,
    LTNavigationControllerStatusPush,
    LTNavigationControllerStatusPop,
    LTNavigationControllerStatusNotApply
};

@interface UIViewController (LTExchangeMethod)

/** 截图 */
@property (nonatomic, strong) UIImageView *screenshots;

/** 当前控制器的导航控制器状态 */
@property (nonatomic, assign) LTNavigationControllerStatus navigationControllerStatus;

@end

.m文件

#import "UIViewController+LTExchangeMethod.h"
#import <objc/runtime.h>

static const NSString *screenshotsKey = @"screenshots";
static const NSString *navigationControllerStatusKey = @"navigationControllerStatus";
@implementation UIViewController (LTExchangeMethod)

+ (void)load
{
    // 加载过程中, 交换方法
    
    //控制器已经出现
    Method viewDidAppear = class_getInstanceMethod(self, @selector(viewDidAppear:));
    Method lt_viewDidAppear = class_getInstanceMethod(self, @selector(lt_viewDidAppear:));
    method_exchangeImplementations(viewDidAppear, lt_viewDidAppear);
    
    //控制器即将消失
    Method viewWillDisappear = class_getInstanceMethod(self, @selector(viewWillDisappear:));
    Method lt_viewWillDisappear = class_getInstanceMethod(self, @selector(lt_viewWillDisappear:));
    method_exchangeImplementations(viewWillDisappear, lt_viewWillDisappear);
    
    //控制器已经消失
    Method viewDidDisappear = class_getInstanceMethod(self, @selector(viewDidDisappear:));
    Method lt_viewDidDisappear = class_getInstanceMethod(self, @selector(lt_viewDidDisappear:));
    method_exchangeImplementations(viewDidDisappear, lt_viewDidDisappear);
}

/**
 控制器即将消失
 */
- (void)lt_viewWillDisappear:(BOOL)animation
{
    UIViewController *viewController = self.navigationController.childViewControllers.lastObject;
    if (viewController.navigationControllerStatus == LTNavigationControllerStatusPop) {
        [self.navigationController setNavigationBarHidden:YES animated:YES];
    }else if (viewController.navigationControllerStatus == LTNavigationControllerStatusPush) {
        if (self.screenshots.hidden == NO) return;
        UIGraphicsBeginImageContextWithOptions([UIScreen mainScreen].bounds.size, NO, 0.0);
        [self.navigationController.view.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        self.screenshots.image = image;
        [self.view bringSubviewToFront:self.screenshots];
        self.screenshots.hidden = NO;
    }
    [self lt_viewWillDisappear:animation];
}

/**
 控制器已经消失
 */
- (void)lt_viewDidDisappear:(BOOL)animation
{
    if (self.navigationControllerStatus == LTNavigationControllerStatusPop) {
        self.screenshots.hidden = NO;
    }
    [self lt_viewDidDisappear:animation];
}

/**
 控制器已经出现
 */
- (void)lt_viewDidAppear:(BOOL)animation
{
    if (self.navigationControllerStatus == LTNavigationControllerStatusPop) {
        [self.navigationController setNavigationBarHidden:NO animated:NO];
        self.screenshots.hidden = YES;
    }
    [self lt_viewDidAppear:animation];
}

#pragma mark - < 截图 >

- (void)setScreenshots:(UIImageView *)screenshots
{
    objc_setAssociatedObject(self, (__bridge const void *)(screenshotsKey), screenshots, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UIImageView *)screenshots
{
    UIImageView *screenshots = objc_getAssociatedObject(self, (__bridge const void *)(screenshotsKey));
    if (!screenshots) {
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:[UIScreen mainScreen].bounds];
        imageView.hidden = YES;
        [self.view addSubview:imageView];
        self.screenshots = imageView;
        screenshots = imageView;
    }
    return screenshots;
}

#pragma mark - < 当前控制器的导航控制器状态 >

- (void)setNavigationControllerStatus:(LTNavigationControllerStatus)navigationControllerStatus
{
    objc_setAssociatedObject(self, (__bridge const void *)(navigationControllerStatusKey), @(navigationControllerStatus), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (LTNavigationControllerStatus)navigationControllerStatus
{
    NSNumber *navigationControllerStatus = objc_getAssociatedObject(self, (__bridge const void *)(navigationControllerStatusKey));
    return navigationControllerStatus.integerValue;
}

@end

@interface UINavigationController (LTExchangeMethod)

@end

@implementation UINavigationController (LTExchangeMethod)

+ (void)load
{
    //控制器已经出现
    Method pushViewController = class_getInstanceMethod(self, @selector(pushViewController:animated:));
    Method lt_pushViewController = class_getInstanceMethod(self, @selector(lt_pushViewController:animated:));
    method_exchangeImplementations(pushViewController, lt_pushViewController);
}

- (void)lt_pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (self.childViewControllers.count > 0) {
        if (viewController.navigationControllerStatus != LTNavigationControllerStatusNotApply) {
            viewController.navigationControllerStatus = LTNavigationControllerStatusPush;
            self.childViewControllers.lastObject.navigationControllerStatus = LTNavigationControllerStatusPop;
        }
    }
    [self lt_pushViewController:viewController animated:animated];
}

@end;

使用方法: 写一个分类保存, 直接拖入工程中即可, 不需引用自动生效

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