修改系统自带的东西

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修改系统UITabBarController.tabBar

//
//  HWTabBar.h
#import <UIKit/UIKit.h>
@class HWTabBar;

#warning 因为HWTabBar继承自UITabBar，所以称为HWTabBar的代理，也必须实现UITabBar的代理协议
@protocol HWTabBarDelegate <UITabBarDelegate>
@optional
- (void)tabBarDidClickPlusButton:(HWTabBar *)tabBar;
@end

@interface HWTabBar : UITabBar
@property (nonatomic, weak) id<HWTabBarDelegate> delegate;
@end

 

//
//  HWTabBar.m

#import "HWTabBar.h"

@interface HWTabBar()
@property (nonatomic, weak) UIButton *plusBtn;
@end

@implementation HWTabBar

- (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_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;
}

/**
 *  加号按钮点击
 */
- (void)plusClick
{
    // 通知代理
    if ([self.delegate respondsToSelector:@selector(tabBarDidClickPlusButton:)]) {
        [self.delegate tabBarDidClickPlusButton:self];
    }
}

- (void)layoutSubviews
{
#warning [super layoutSubviews] 一定要调用
    [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.设置其他tabbarButton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

 

 

修改UITabBarController.tabBar只读的   不希望程序员对其修改    也不希望  tabBar.delegate被修改