iphone - 切换 ViewControllers，但没有任何反应？

Question

我想将切换 ViewController 的代码放在一个名为 SwitchController 的类中。但是没有任何反应。

代码如下:

//AppDelegate.m

-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
        self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
        // Override point for customization after application launch.
        self.window.backgroundColor = [UIColor whiteColor];

        RootViewController *root = [[RootViewController alloc] init];
        [self.window setRootViewController:root];

        [self.window makeKeyAndVisible];
        return YES;
}

//SwitchController.h

@interface SwitchController : NSObject

@property (strong,nonatomic) RootViewController *rootViewController;

+(SwitchController *)sharedInstance;
-(void)requestToSwitchViewController:(NSInteger)tag;

@end

//SwitchController.m

#import "SwitchController.h"
#import "FirstViewController.h"
#import "SecondViewController.h"

@implementation SwitchController

@synthesize rootViewController = _rootViewController;

-(id)init
{
    self = [super init];
    if (self == nil)
    {
        _rootViewController = [[RootViewController alloc] init];
    }
    return self;
}

+(SwitchController *)sharedInstance
{
    static SwitchController *sharedSingleton = nil;
@synchronized([SwitchController class])
{
    if(sharedSingleton == nil)
    {
        sharedSingleton = [[self alloc] init];
    }
}
return sharedSingleton;
}

-(void)requestToSwitchViewController:(NSInteger)tag
{
    switch (tag)
    {
        case 1:
        {
            FirstViewController *first = [[FirstViewController alloc] init];
            [self.rootViewController presentViewController:first animated:YES completion:nil];
        }
            break;
         .........  //Do something else
        default:
            break;
    }
}

@end

//这是self.window.rootViewController------RootViewController.m

//在这个ViewController的 View 中，有一个按钮，按下它会做下面的事情

    - (IBAction)pressed:(id)sender
    {
        [[SwitchController sharedInstance] requestToSwitchViewController:[(UIButton *)sender tag]];
    }

那么，我的代码有什么问题吗？

为什么按下按钮时没有任何反应？

Answer 1

可能有几个问题..

1) 检查你的按钮 socket 是否正确连接到这个方法-(IBAction)pressed:(id)sender;

2)在SwitchController.m中的@synthesize之后添加这一行

static SwitchController *sharedSingleton = nil;

3)像这样改变你的方法

+(SwitchController *)sharedInstance
{
    if(sharedSingleton == nil)
    {
        sharedSingleton = [[self allocWithZone:NULL] init];
    }
  return sharedSingleton;
}

4) 从-id(init) 方法中删除这一行

// You do not need to re-initialize the root view controller
_rootViewController = [[RootViewController alloc] init];

5) 检查按钮是否有效。在调用此方法之前 requestToSwitchViewController: 检查它记录的内容

更新:

像这样尝试:(为此，您需要在 appDelegate 中为导航 Controller 创建一个属性并合成它)

switch (tag)
{
    case 1:
    {
        FirstViewController *first = [[FirstViewController alloc] init];
        appDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
        [appDelegate.navigationController presentViewController:first animated:YES completion:nil];
    }
    .....
  .........
 }