当视图控制器的View将要出现时触发

- (void)viewWillAppear:(BOOL)animated

当视图控制器的View已经出现时触发

- (void)viewDidAppear:(BOOL)animated

当视图控制器的View将要消失时触发

- (void)viewWillDisappear:(BOOL)animated

当视图控制器的View已经消失时触发

- (void)viewDidDisappear:(BOOL)animated

当由前一个界面,push下一个界面时,如A push B,四个方法执行顺序A(ViewWillDisappear)>B(viewWillAppear)>A(viewDidDisappear)>B(viewDidAppear)

当由后一个界面pop前一个界面时,如B pop A,四个方法执行顺序B(viewWillDisappear)>A(viewWillAppear)>B(viewDidDisappear)>A(viewDidAppear)

navigationBar常用属性
一. 对navigationBar直接配置,所以该操作对每一界面navigationBar上显示的内容都会有影响(效果是一样的)
1.修改navigationBar颜色  

self.navigationController.navigationBar.barTintColor = [UIColor redColor];

2.关闭navigationBar的毛玻璃效果   

self.navigationController.navigationBar.translucent = NO;   

3.将navigationBar隐藏掉

self.navigationController.navigationBarHidden = YES;

4.给navigationBar设置图片   

不同尺寸的图片效果不同:
1.320 * 44,只会给navigationBar附上图片

2.高度小于44,以及大于44且小于64:会平铺navigationBar以及状态条上显示 

3.高度等于64:整个图片在navigationBar以及状态条上显示

[self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"32050"] forBarMetrics:UIBarMetricsDefault];

二.为每一个界面的navigationBar上显示的内容单独定制(每个界面显示内容不一样)
单独定制,修改视图控制器的navigationItem  

    1.设置界面的title
self.navigationItem.title = @"远东大开发”;
    2.修改titleView(中间显示视图)
UISegmentedControl *segment = [[UISegmentedControlalloc]initWithItems:@[@"分组",@"好友"]]; self.navigationItem.titleView = segment;[segment release];
    3.修改navigationBar的颜色self.navigationController.navigationBar.barTintColor = [UIColor whiteColor];

    4.修改navigationBar,右边显示内容
UIBarButtonItem *right = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(add:)]; 

self.navigationItem.rightBarButtonItem = right;

[right release];
    5.修改navigationBar,左侧显示内容
UIBarButtonItem *left = [[UIBarButtonItemalloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAddtarget:selfaction:@selector(add:)];

    self.navigationItem.leftBarButtonItem = left;   

[left release];

iOS导航控制器常用函数与navigationBar常用属性