xcode 4.2 中 iPhone 的多级导航

Question

我在 xcode 4.2 中创建了一个基于视图的项目，我想实现多级导航以导航到不同的视图。我的第一个视图类是 ViewController，我在其中显示一个表格。单击一行后，我进入下一个带有选项卡栏的类。在此我有 3 个选项卡。第一个选项卡使用类 BuyerViewController。它有 4 个按钮。问题是，当我单击按钮时，它不会推送下一堂课。

ViewController.m

- (void)viewDidLoad
{
 self.title=@"Select County";
    tView = [[UITableView alloc] init];    //tView is my table view object.
    tView.frame=CGRectMake(0, 20, 320, 460);
    [tView setDelegate:self];
    [tView setDataSource:self];
    [self.view addSubview:tView];
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [countyArray count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *CellIdentifier = @"Cell";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
cell.textLabel.text = [countyArray objectAtIndex:indexPath.row];
return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { 
//This works fine and pushes to my next class to show the tabs.

ShowOptionInTab *showTabbar = [[ShowOptionInTab alloc] initWithNibName:@"ShowOptionInTab" bundle:nil];
[self.navigationController pushViewController:showTabbar animated:YES];
[showTabbar release];
}

ShowOptionInTab.m

-(void)loadView {
UIView *contentView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
contentView.backgroundColor = [UIColor whiteColor];
self.view = contentView;
[contentView release];

BuyerViewController *buyerController = [[BuyerViewController alloc] init ];

SellerViewController *sellerController = [[SellerViewController alloc] init];

LenderViewController *lenderController = [[LenderViewController alloc] init];

buyerController.title=@"Buyer";
sellerController.title = @"Seller";
lenderController.title = @"Lender";

UITabBarController *tabbarController = [[UITabBarController alloc] init];

tabbarController.view.frame = CGRectMake(0, 0, 320, 460);
[tabbarController setViewControllers:[NSArray arrayWithObjects:buyerController, sellerController,lenderController, nil]];

[buyerController release];
[sellerController release];
[lenderController release];
[self.view addSubview:tabbarController.view];    
}

BuyerViewController.m

-(void)viewWillAppear:(BOOL)animated
{
UIButton *quickEstimateButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];

    [quickEstimateButton addTarget:self action:@selector(getTagOfPressedButton:) forControlEvents:UIControlEventTouchUpInside];
[quickEstimateButton setTitle:@"QUICK ESTIMATE" forState:UIControlStateNormal];
quickEstimateButton.tag=1;
quickEstimateButton.frame = CGRectMake(10, 50, 150, 40.0);
[self.view addSubview:quickEstimateButton];

//more 3 buttons are added in same way
}
-(void) getTagOfPressedButton:(id)sender {

UIButton *getTagOfButton = (UIButton *)sender;
int buttonPressedTag = getTagOfButton.tag;
NSLog(@"TAG==========%d",buttonPressedTag);
if(buttonPressedTag==1)
{
    NSLog(@"quick estimate pressed");
    QuickEstimateViewController *q = [[QuickEstimateViewController alloc] init];
    NSLog(@"nav====%@",self.navigationController); //This returns null.
    [self.navigationController pushViewController:q animated:YES];
}
}

AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
        ViewController *overviewViewController = [[ViewController alloc] initWithNibName:@"ViewController_iPhone" bundle:nil];
    UINavigationController* navigation = [[UINavigationController alloc] initWithRootViewController:overviewViewController];
    navigation.navigationBar.tintColor = [UIColor blackColor];
    [overviewViewController release];

    [self.window addSubview:[navigation view]];
    [self.window makeKeyAndVisible];
}

为什么QuickEstimateViewController不显示？

Answer 1

因为您定义了 tabBarController 的新对象及其视图作为 ShowOptionInTab 中的子视图，然后还定义了一个新对象 BuyerViewController ，您尝试推送 QuickEstimateViewController 的 navigationController 将为零..我认为如果您的代码如下所示，它会起作用..

BuyerViewController *buyerController = [[BuyerViewController alloc] init ];
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:buyerController];

SellerViewController *sellerController = [[SellerViewController alloc] init];

LenderViewController *lenderController = [[LenderViewController alloc] init];

buyerController.title=@"Buyer";
sellerController.title = @"Seller";
lenderController.title = @"Lender";

UITabBarController *tabbarController = [[UITabBarController alloc] init];

tabbarController.view.frame = CGRectMake(0, 0, 320, 460);
[tabbarController setViewControllers:[NSArray arrayWithObjects:nav, sellerController,lenderController, nil]];