1  改变NavBar颜色：选中Navigation Bar 的Tint属性。选中颜色。 

2  隐藏“back”按钮: self.navigationItem.hidesBackButton = YES; 

3 隐藏"NavBar" : self.navigationController.navigationBarHidden = YES; 

4 可以不用MainWindow.xib创建的Navigation。在每个view上自定义。 

需要把每个控制页都加上以下代码来隐藏nav： 
-(void)viewWillAppear:(BOOL)animated 
{ 
    self.navigationController.navigationBarHidden = YES;//显示"NavBar" 
} 
然后在每个控制页xib自己添加Navigation Bar。添加所需BarButtonItem按钮。 


5 页面跳转隐藏tarbar : 
HomeDetailViewController *detailview = [[HomeDetailViewController alloc] initWithNibName:@"HomeDetailView" bundle:nil]; 
detailview.hidesBottomBarWhenPushed = YES;//隐藏tarbar 
[self.navigationController pushViewController:detailview animated:YES]; 
[detailview     release]; 

6 页面返回： 
[self.navigationController popViewControllerAnimated:YES]; 

7 默认选中tabbar为第一个view: 
TabBarController.selectedIndex= 0; 


其他： 
8 已知两地经纬度 计算两地之间的距离： 
//    地图显示当前位置： 
    mapView.showsUserLocation=YES; 
    CLLocationManager *locationManager = [[CLLocationManager alloc] init];//创建位置管理器 
    locationManager.delegate=self;//设置代理 
    locationManager.desiredAccuracy=kCLLocationAccuracyBest;//指定需要的精度级别为最佳精度 
    locationManager.distanceFilter=1000.0f;//设置距离筛选器为任何移动都要发送更新 
    [locationManager startUpdatingLocation];//启动位置管理器 
    MKCoordinateSpan theSpan; 
    //地图的范围 越小越精确 
    theSpan.latitudeDelta=0.05; 
    theSpan.longitudeDelta=0.05; 
    MKCoordinateRegion theRegion; 
    theRegion.center=[[locationManager location] coordinate]; 
    theRegion.span=theSpan; 
    [mapView setRegion:theRegion]; 
    [locationManager release]; 
    
    MKUserLocation *usrLoc=mapView.userLocation; 
    CLLocationCoordinate2D usrCoordinate=usrLoc.location.coordinate; 
    NSLog(@"la==%f lo==%f",usrCoordinate.latitude,usrCoordinate.longitude); 
    
//   已知两点的经纬度，计算出两地距离： 
    CLLocation *location1 = [[[CLLocation alloc] initWithLatitude:usrCoordinate.latitude longitude:usrCoordinate.longitude] autorelease]; 
    CLLocation *location2 = [[[CLLocation alloc] initWithLatitude:36.676445 longitude:117.106793] autorelease];
    NSLog(@"JULI====%.0f km", [location1 distanceFromLocation:location2]);//4502 


9 取小数点后两位(四舍五入)，输出： 
NSLog(@"%.02f km",4478.442312); 

10 调用打电话API : 
[[UIapplication sharedApplication] openURL:[NSURL URLWithString:@"tel://10010"]]; 
使用这种方式拨打电话时，当用户结束通话后，iphone界面会停留在电话界面。 
用如下方式，可以使得用户结束通话后自动返回到应用： 
UIWebView*callWebview =[[UIWebView alloc] init]; 
    NSURL *telURL =[NSURL URLWithString:@"tel:10086"];// 貌似tel:// 或者 tel: 都行 
    [callWebview loadRequest:[NSURLRequest requestWithURL:telURL]]; 
    //记得添加到view上 
    [self.view addSubview:callWebview]; 

11 调用 SMS发短信： 
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"sms://15315310992"]]; 

12 调用自带 浏览器 safari 
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://www.baidu.com"]]; 

13 在一个程序里打开另一个程序： 
首先：plist里添加URL types   点开里边的Item0  添加URLSchemes  打开Item0 输入sinaWeibo 
然后在需要调用的地方：[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"sinaWeibo://*"]];

https://itunes.apple.com/cn/app/QQ-2012/id444934666?mt=8 

14 双引号转义： 
用 \" 表示 双引号 

15 设置按钮按下换图片 松开还是原图 
//                [danxuan setImage:[UIImage imageNamed:@"exercise_option_n.png"] forState:UIControlStateNormal]; 
                //这个是设置按下的图片，松开就是上面的图片 
//               [danxuan setImage:[UIImage imageNamed:@"exercise_option_s.png"] forState:UIControlEventTouchDragOutside]; 

16  判断数组中是否存在某元素： 
BOOL isValue=[keyArray containsObject:@"aaa"]; 

17 Nav添加button 
UIButton *btnBack = [ABUtil createNavigationCtrollerRoundedRectBtn:Localized(@"取消")]; 
    [btnBack addTarget:self 
                action:@selector(tapLeftBarButton) 
      forControlEvents:UIControlEventTouchUpInside]; 
    UIBarButtonItem *leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:btnBack]; 
    self.navigationItem.leftBarButtonItem = leftBarButtonItem; 
    [btnBack release]; 
    [leftBarButtonItem release]