ios的tabbar问题求详细解答，这个tabbar下面的图标突出一块怎么做的

自己自定义一个标签视图控制器吧：
自定义一个类继承自UITabBarController；
然后在该类的.m文件中自己写button和其点击事件间的切换

#import "MyTabBarController.h"
#define WIDTH (myView.frame.size.width / 4)
#define HEIGHT (myView.frame.size.height)
@interface MyTabBarController ()

//之前选中的按钮
@property(nonatomic, retain) UIButton *selectedBtn;
@end
@implementation MyTabBarController
(void)viewDidLoad {
[super viewDidLoad];
//删除现有的tabBar
CGRect rect = self.tabBar.frame;
[self.tabBar removeFromSuperview];
//添加自己的视图

UIView *myView = [[BaseView alloc] init];
myView.backgroundColor = [UIColor whiteColor];
myView.frame = rect;
[self.view addSubview:myView];

//主页发现按钮

UIButton *findBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[findBtn setImage:[UIImage imageNamed:@"icon_home_n"] forState:UIControlStateNormal];
[findBtn setImage:[UIImage imageNamed:@"icon_home_h"] forState:UIControlStateSelected];
findBtn.tag = 1;
findBtn.frame = CGRectMake(0, -20, WIDTH, HEIGHT); //y设成负值，高再设高一点就好了!!!

//默认选中是发现按钮

findBtn.selected = YES;
[findBtn setTintColor:[UIColor colorWithRed:0.886 green:0.365 blue:0.247 alpha:1.000]];
self.selectedBtn = findBtn;
[myView addSubview:findBtn];
UILabel *findLabel = [[UILabel alloc] initWithFrame:CGRectMake(WIDTH/2 -10, HEIGHT - 20, WIDTH, 20)];
findLabel.text = @"发现";
findLabel.textColor = [UIColor colorWithRed:0.804 green:0.325 blue:0.227 alpha:1.000];
findLabel.font = [UIFont systemFontOfSize:10];
findLabel.tag = 101;
[myView addSubview:findLabel];
[findLabel release];

//搜索页

UIButton *searchBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[searchBtn setImage:[UIImage imageNamed:@"icon_search_n"] forState:UIControlStateNormal];
[searchBtn setImage:[UIImage imageNamed:@"icon_search_h"] forState:UIControlStateSelected];
searchBtn.tag = 2;
searchBtn.frame = CGRectMake(WIDTH, -20, WIDTH, HEIGHT);
[myView addSubview:searchBtn];
UILabel *searchLabel = [[UILabel alloc] initWithFrame:CGRectMake(WIDTH + WIDTH/2 -10, HEIGHT - 20, WIDTH, 20)];
searchLabel.text = @"搜索";
searchLabel.textColor = [UIColor grayColor];
searchLabel.font = [UIFont systemFontOfSize:10];
searchLabel.tag = 102;
[myView addSubview:searchLabel];
[searchLabel release];

//收藏页

UIButton *costBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[costBtn setImage:[UIImage imageNamed:@"iconfont-like"] forState:UIControlStateNormal];
[costBtn setImage:[UIImage imageNamed:@"iconfont-like-selected"] forState:UIControlStateSelected];
costBtn.tag = 3;
costBtn.frame = CGRectMake(2 * WIDTH, -20, WIDTH, HEIGHT);
[myView addSubview:costBtn];
UILabel *collectLabel = [[UILabel alloc] initWithFrame:CGRectMake(2 * WIDTH + WIDTH/2 -10, HEIGHT - 20, WIDTH, 20)];
collectLabel.text = @"收藏";
collectLabel.textColor = [UIColor grayColor];
collectLabel.font = [UIFont systemFontOfSize:10];
collectLabel.tag = 103;
[myView addSubview:collectLabel];
[collectLabel release];

//设置页

UIButton *setUpBtn = [UIButton buttonWithType:UIButtonTypeCustom];
[setUpBtn setImage:[UIImage imageNamed:@"icon_setting_n"] forState:UIControlStateNormal];
[setUpBtn setImage:[UIImage imageNamed:@"icon_setting_h"] forState:UIControlStateSelected];
setUpBtn.tag = 4;
setUpBtn.frame = CGRectMake(3 * WIDTH, -20, WIDTH, HEIGHT);
[myView addSubview:setUpBtn];

UILabel *setUpLabel = [[UILabel alloc] initWithFrame:CGRectMake(3 * WIDTH + WIDTH/2 -10, HEIGHT - 20, WIDTH, 20)];
setUpLabel.text = @"设置";
setUpLabel.textColor = [UIColor grayColor];
setUpLabel.font = [UIFont systemFontOfSize:10];
setUpLabel.tag = 104;
[myView addSubview:setUpLabel];
[setUpLabel release];

for (int i = 1; i <4; i++) {
UIButton *btn = [self.view viewWithTag:i];
[btn addTarget:self action:@selector(clickBtn:) forControlEvents:UIControlEventTouchUpInside];
}
}

#pragma mark -- 自定义tabBar按钮的点击事件
-(void)clickBtn:(UIButton *)sender {
//设置上一个按钮

self.selectedBtn.selected = NO;
UILabel *titleFormer = [self.view viewWithTag:self.selectedBtn.tag + 100];
titleFormer.textColor = [UIColor grayColor];

//设置选中状态
sender.selected = YES;
self.selectedBtn = sender;
UILabel *titleNow = [self.view viewWithTag:self.selectedBtn.tag + 100];
titleNow.textColor = [UIColor colorWithRed:0.804 green:0.325 blue:0.227 alpha:1.000];

//跳转相应的视图控制器
self.selectedIndex = sender.tag - 1;
}