iOS構建視圖以編程方式取決於對象ivar

Question

我有一個非常有趣的問題，涉及loadView,viewDidLoad,viewWillAppear和伊娃的狀態。我有一個基於導航的應用程序。從我的第一層次看，我有一個表格列表，然後點擊其中一個單元格，它會將我帶到二級視圖（細節視圖）。當我點擊一個單元格時，我還向被推入的視圖控制器添加了一個「Office」對象（其中包含像streetAddress和boxAddress這樣的字符串）。然後，我使用Office對象的內容填充詳細視圖，如[box setText:[self.office boxAddress]];（框是UILabel）。現在我想在這裏實現的是，有時boxAddress的stringValue是空的，在這種情況下，我不想向UILabel添加空字符串，而是要將下一個UILabel向上移動（並取代boxAddress）。因此，我已經做了一個有條件檢查，看看boxAddress是否爲空，如果它應該設置爲UILabel s與特定的座標，如果它不是空的，它應該設置UILabel s與其他特定的座標。

我知道你應該使用viewWillAppear如果你希望每次加載視圖時運行代碼。但由於某種原因，viewWillAppear似乎只在boxAddress字符串爲空時纔會運行。如果我點擊一個空格爲boxAddress的單元格，它將使用我點擊的最後一個單元格的值爲boxAddress，該單元格的空格爲非空的boxAddress。

我會在這裏粘貼我的代碼，看看你是否可以給我一個指針，說明我在這裏做錯了什麼。

// Implement loadView to create a view hierarchy programmatically, 
// without using a nib. 
- (void)loadView { 

    //allocate the view 
    self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; 

    //set the view's background color 
    self.view.backgroundColor = [UIColor whiteColor]; 
} 

- (void)viewDidLoad 
{ 

    //add the labels 
    name = [[UILabel alloc] initWithFrame:CGRectMake(10.0,10.0,320.0,20.0)]; 
    [name setBackgroundColor:[UIColor clearColor]]; 
    [name setTextColor:[UIColor blackColor]]; 

    street = [[UILabel alloc] initWithFrame:CGRectMake(10.0,30.0,320.0,20.0)]; 
    [street setBackgroundColor:[UIColor clearColor]]; 
    [street setTextColor:[UIColor blackColor]]; 

    //if no box address, move up the rest of the addresses 
    if ([[self.office boxAddress] length] == 0) { 

     zip = [[UILabel alloc] initWithFrame:CGRectMake(10.0,50.0,320.0,20.0)]; 
     [zip setBackgroundColor:[UIColor clearColor]]; 
     [zip setTextColor:[UIColor blackColor]]; 

     phone = [[UILabel alloc] initWithFrame:CGRectMake(10.0,70.0,320.0,20.0)]; 
     [phone setBackgroundColor:[UIColor clearColor]]; 
     [phone setTextColor:[UIColor blackColor]]; 

     fax = [[UILabel alloc] initWithFrame:CGRectMake(10.0,90.0,320.0,20.0)]; 
     [fax setBackgroundColor:[UIColor clearColor]]; 
     [fax setTextColor:[UIColor blackColor]]; 

     [self.view addSubview:name]; 
     [self.view addSubview:street]; 
     [self.view addSubview:zip]; 
     [self.view addSubview:phone]; 
     [self.view addSubview:fax]; 

    } else { 

     box = [[UILabel alloc] initWithFrame:CGRectMake(10.0,50.0,320.0,20.0)]; 
     [box setBackgroundColor:[UIColor clearColor]]; 
     [box setTextColor:[UIColor blackColor]]; 

     zip = [[UILabel alloc] initWithFrame:CGRectMake(10.0,70.0,320.0,20.0)]; 
     [zip setBackgroundColor:[UIColor clearColor]]; 
     [zip setTextColor:[UIColor blackColor]]; 

     phone = [[UILabel alloc] initWithFrame:CGRectMake(10.0,90.0,320.0,20.0)]; 
     [phone setBackgroundColor:[UIColor clearColor]]; 
     [phone setTextColor:[UIColor blackColor]]; 

     fax = [[UILabel alloc] initWithFrame:CGRectMake(10.0,110.0,320.0,20.0)]; 
     [fax setBackgroundColor:[UIColor clearColor]]; 
     [fax setTextColor:[UIColor blackColor]]; 

     [self.view addSubview:name]; 
     [self.view addSubview:street]; 
     [self.view addSubview:box]; 
     [self.view addSubview:zip]; 
     [self.view addSubview:phone]; 
     [self.view addSubview:fax]; 
    } 

    [super viewDidLoad]; 
    // Do any additional setup after loading the view from its nib. 
} 

// viewWillAppear method is run every time the view is loaded as opposite to the viewDidLoad method which only is run once 
// in this program DisclosureDetail view needs to be loaded for each detail view with different content each time 
- (void)viewWillAppear:(BOOL)animated { 

    NSLog(@"%@", [self.office boxAddress]); 

    [name setText:[self.office name]]; 
    [street setText:[self.office streetAddress]]; 
    if ([[self.office boxAddress] length] > 0) { 
     [box setText:[self.office boxAddress]]; 
    } 
    [zip setText:[NSString stringWithFormat:@"%@ %@", [self.office zipCode], [self.office city]]]; 
    [phone setText:[self.office phoneNo]]; 
    [fax setText:[self.office faxNo]]; 

    [super viewWillAppear:animated]; 
} 

Answer 1

if ([[self.office boxAddress] length] > 0) { 
    [box setText:[self.office boxAddress]]; 
} 

如果boxAddress的長度爲0，那麼box將繼續包含任何文本你在它設定的最後一次視圖中顯示。

每次出現視圖時，您都需要隱藏並顯示box，而不僅僅是當視圖加載時，因爲視圖可能已加載，然後用於顯示多個不同的office s。