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自定义UITabBar替换系统默认的,目的是为了在UITabBar中间位置添加一个“+号按钮”,下面我们来聊聊具体的实现。
1、自定义WBTabBar,让其继承自UITabBar,代码如下:
// // WBTabBar.h // SinaWeibo // // Created by android_ls on 15/5/21. // Copyright (c) 2015年 android_ls. All rights reserved. // #import <UIKit/UIKit.h> @interface WBTabBar : UITabBar @end
2、tabBar是UITabBarController的只读成员变量(属性),是不让修改的,在UITabBarController.h文件中的声明如下:
@property(nonatomic,readonly) UITabBar *tabBar NS_AVAILABLE_IOS(3_0);
针对于这种情况,我们可以使用KVC的方式,更换系统自带的UITabBar,实现代码如下:
WBTabBar *tabBar = [[WBTabBar alloc] init]; [self setValue:tabBar forKeyPath:@"tabBar"];
3、添加一个UIButton到WBTabBar中,实现代码如下:
- (id)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if (self) { // 添加一个按钮到tabbar中 UIButton *plusBtn = [[UIButton alloc] init]; [plusBtn setBackgroundImage:[UIImage imageNamed:@"tabbar_compose_button"] forState:UIControlStateNormal]; [plusBtn setBackgroundImage:[UIImage imageNamed:@"tabbar_compose_button_highlighted"] forState:UIControlStateHighlighted]; [plusBtn setImage:[UIImage imageNamed:@"tabbar_compose_background_icon_add"] forState:UIControlStateNormal]; [plusBtn setImage:[UIImage imageNamed:@"tabbar_compose_icon_add_highlighted"] forState:UIControlStateHighlighted]; plusBtn.size = plusBtn.currentBackgroundImage.size; [plusBtn addTarget:self action:@selector(plusClick) forControlEvents:UIControlEventTouchUpInside]; [self addSubview:plusBtn]; self.plusBtn = plusBtn; } return self; }
4、设置加号按钮的位置,调整WBTabBar中各个UITabBarButton的位置和宽度,具体实现代码如下:
- (void)layoutSubviews { [super layoutSubviews]; // 1.设置加号按钮的位置 self.plusBtn.centerX = self.width * 0.5; self.plusBtn.centerY = self.height * 0.5; // 2.设置其它UITabBarButton的位置和尺寸 CGFloat tabbarButtonW = self.width / 5; CGFloat tabbarButtonIndex = 0; for (UIView *child in self.subviews) { Class class = NSClassFromString(@"UITabBarButton"); if ([child isKindOfClass:class]) { // 设置宽度 child.width = tabbarButtonW; // 设置x child.x = tabbarButtonIndex * tabbarButtonW; // 增加索引 tabbarButtonIndex++; if (tabbarButtonIndex == 2) { tabbarButtonIndex++; } } } }
5、定义WBTabBarDelegate协议,声明WBTabBar的代理,代码如下:
// // WBTabBar.h // SinaWeibo // // Created by android_ls on 15/5/21. // Copyright (c) 2015年 android_ls. All rights reserved. // #import <UIKit/UIKit.h> #pragma mark 因为在UITabBar中已经声明过一个UITabBarDelegate协议, #pragma mark 我们若想新增一个对外的代理函数,可以让我们自定义的协议继承自UITabBarDelegate,添加一个扩展函数。 @class WBTabBar; @protocol WBTabBarDelegate <UITabBarDelegate> @optional - (void)tabBarDidClickPlusButton:(WBTabBar *)tabBar; @end @interface WBTabBar : UITabBar @property (nonatomic, weak) id<WBTabBarDelegate> tabBarDelegate; @end
6、在加号按钮的点击事件处理器中,通知代理
#pragma mark 加号按钮点击事件处理器 - (void)plusClick { // 通知代理 if ([self.tabBarDelegate respondsToSelector:@selector(tabBarDidClickPlusButton:)]) { [self.tabBarDelegate tabBarDidClickPlusButton:self]; } }
7、在WBTabBarController中设置WBTabBar的代理,具体实现如下:
// 2、使用KVC的方式,更换系统自带的UITabBar WBTabBar *tabBar = [[WBTabBar alloc] init]; tabBar.tabBarDelegate = self; [self setValue:tabBar forKeyPath:@"tabBar"];
#pragma mark - HWTabBarDelegate代理方法 - (void)tabBarDidClickPlusButton:(WBTabBar *)tabBar { ComposeViewController *composeViewController= [[ComposeViewController alloc] init]; UINavigationController * navigationController = [[UINavigationController alloc]initWithRootViewController:composeViewController]; [self presentViewController:navigationController animated:YES completion:nil]; }
8、有图有真相,已实现的效果图如下:
点击加号按钮,弹出写作界面,效果图如下:
WBTabBarController.m文件完整源码如下:
// // WBTabBarController.m // SinaWeibo // // Created by android_ls on 15/5/17. // Copyright (c) 2015年 android_ls. All rights reserved. // #import "WBTabBarController.h" #import "HomeViewController.h" #import "MessageViewController.h" #import "DiscoverViewController.h" #import "ProfileViewController.h" #import "WBNavigationController.h" #import "WBTabBar.h" #import "ComposeViewController.h" @interface WBTabBarController ()<WBTabBarDelegate> { HomeViewController * _homeViewController; MessageViewController * _messageViewController; DiscoverViewController * _discoverViewController; ProfileViewController * _profileViewController; } @end @implementation WBTabBarController - (void)viewDidLoad { [super viewDidLoad]; // 初始化子控制器,并将其添加到UITabBarController中 _homeViewController = [[HomeViewController alloc]init]; [self addChildController:_homeViewController title:@"首页" image:@"tabbar_home"]; _messageViewController = [[MessageViewController alloc]init]; [self addChildController:_messageViewController title:@"消息" image:@"tabbar_message_center"]; _discoverViewController = [[DiscoverViewController alloc]init]; [self addChildController:_discoverViewController title:@"发现" image:@"tabbar_discover"]; _profileViewController = [[ProfileViewController alloc]init]; [self addChildController:_profileViewController title:@"我" image:@"tabbar_profile"]; // @property(nonatomic,readonly) UITabBar *tabBar NS_AVAILABLE_IOS(3_0); // tabBar是UITabBarController的只读成员变量(属性),是不让修改的 // 2、使用KVC的方式,更换系统自带的UITabBar WBTabBar *tabBar = [[WBTabBar alloc] init]; tabBar.tabBarDelegate = self; [self setValue:tabBar forKeyPath:@"tabBar"]; } #pragma mark - HWTabBarDelegate代理方法 - (void)tabBarDidClickPlusButton:(WBTabBar *)tabBar { ComposeViewController *composeViewController= [[ComposeViewController alloc] init]; UINavigationController * navigationController = [[UINavigationController alloc]initWithRootViewController:composeViewController]; [self presentViewController:navigationController animated:YES completion:nil]; } /** * 添加子控制器到UITabBarController中 */ - (void)addChildController:(UIViewController *)childViewController title:(NSString *)title image:(NSString *)image { // 设置子控制器,tabbar和navigationBar上的title childViewController.title = title; // 设置tabBarItem上默认的指示图片和选中时的图片 childViewController.tabBarItem.image = [UIImage imageNamed:image]; childViewController.tabBarItem.selectedImage = [[UIImage imageNamed:[NSString stringWithFormat:@"%@%@", image, @"_selected"]]imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]; // 设置tabBarItem上文字的样式(这里是设置文字在不同状态下的颜色值) [childViewController.tabBarItem setTitleTextAttributes: @{NSForegroundColorAttributeName:kColor(117, 117, 117)} forState:UIControlStateNormal]; [childViewController.tabBarItem setTitleTextAttributes: @{NSForegroundColorAttributeName:kColor(253, 109, 10)} forState:UIControlStateSelected]; // 使用系统默认的UINavigationController // [self addChildViewController:[[UINavigationController alloc] initWithRootViewController:childViewController]]; // 使用我们自定义的导航栏(WBNavigationController继承自UINavigationController) WBNavigationController * navigationController = [[WBNavigationController alloc]initWithRootViewController:childViewController]; [self addChildViewController:navigationController]; } @end
WBTabBar.h文件完整源码如下:
// // WBTabBar.h // SinaWeibo // // Created by android_ls on 15/5/21. // Copyright (c) 2015年 android_ls. All rights reserved. // #import <UIKit/UIKit.h> #pragma mark 因为在UITabBar中已经声明过一个UITabBarDelegate协议, #pragma mark 我们若想新增一个对外的代理函数,可以让我们自定义的协议继承自UITabBarDelegate,添加一个扩展函数。 @class WBTabBar; @protocol WBTabBarDelegate <UITabBarDelegate> @optional - (void)tabBarDidClickPlusButton:(WBTabBar *)tabBar; @end @interface WBTabBar : UITabBar @property (nonatomic, weak) id<WBTabBarDelegate> tabBarDelegate; @end
WBTabBar.m文件完整源码如下:
// // WBTabBar.m // SinaWeibo // // Created by android_ls on 15/5/21. // Copyright (c) 2015年 android_ls. All rights reserved. // #import "WBTabBar.h" @interface WBTabBar() @property (nonatomic, weak) UIButton *plusBtn; @end @implementation WBTabBar - (id)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if (self) { // 添加一个按钮到tabbar中 UIButton *plusBtn = [[UIButton alloc] init]; [plusBtn setBackgroundImage:[UIImage imageNamed:@"tabbar_compose_button"] forState:UIControlStateNormal]; [plusBtn setBackgroundImage:[UIImage imageNamed:@"tabbar_compose_button_highlighted"] forState:UIControlStateHighlighted]; [plusBtn setImage:[UIImage imageNamed:@"tabbar_compose_background_icon_add"] forState:UIControlStateNormal]; [plusBtn setImage:[UIImage imageNamed:@"tabbar_compose_icon_add_highlighted"] forState:UIControlStateHighlighted]; plusBtn.size = plusBtn.currentBackgroundImage.size; [plusBtn addTarget:self action:@selector(plusClick) forControlEvents:UIControlEventTouchUpInside]; [self addSubview:plusBtn]; self.plusBtn = plusBtn; } return self; } #pragma mark 加号按钮点击事件处理器 - (void)plusClick { // 通知代理 if ([self.tabBarDelegate respondsToSelector:@selector(tabBarDidClickPlusButton:)]) { [self.tabBarDelegate tabBarDidClickPlusButton:self]; } } - (void)layoutSubviews { [super layoutSubviews]; // 1.设置加号按钮的位置 self.plusBtn.centerX = self.width * 0.5; self.plusBtn.centerY = self.height * 0.5; // 2.设置其它UITabBarButton的位置和尺寸 CGFloat tabbarButtonW = self.width / 5; CGFloat tabbarButtonIndex = 0; for (UIView *child in self.subviews) { Class class = NSClassFromString(@"UITabBarButton"); if ([child isKindOfClass:class]) { // 设置宽度 child.width = tabbarButtonW; // 设置x child.x = tabbarButtonIndex * tabbarButtonW; // 增加索引 tabbarButtonIndex++; if (tabbarButtonIndex == 2) { tabbarButtonIndex++; } } } } @end
ComposeViewController继承自UIViewController,主要实现在m文件,其完整代码如下:
// // ComposeViewController.m // SinaWeibo // // Created by android_ls on 15/5/21. // Copyright (c) 2015年 android_ls. All rights reserved. // #import "ComposeViewController.h" #import "UIBarButtonItem+Category.h" @interface ComposeViewController () @end @implementation ComposeViewController - (void)viewDidLoad { [super viewDidLoad]; self.title = @"写作界面"; self.view.backgroundColor = [UIColor whiteColor]; self.navigationItem.leftBarButtonItem = [UIBarButtonItem itemWithTarget:self action:@selector(back) image:@"navigationbar_back_withtext" highImage:@"navigationbar_back_withtext_highlighted" title:@"返回"]; } - (void)back { [self.navigationController dismissViewControllerAnimated:YES completion:^{}]; } @end
作为程序员,我不善于言谈。很多时候去面试,面的有些知识点我使用过,也知道其原理,但是就是表达不清楚,老让人鄙视。
最后聊聊我的技术博客写作思路,先详细讲解每一步的实现,最后我会贴出完整代码,供想认真阅读的读者看个痛快。