UIScrollView沒有顯示在UIViewController上

Question

我正在為我的應用程序制作一個簡單的“注冊”屏幕。 我不使用Storyboards ，而是通過代碼來完成所有事情。 因此，為了促進視圖的動態滾動以為鍵盤留出空間，我使用了標准的Apple做法，即將UITextFields嵌入UIScrollView ，但它們根本沒有顯示！

代碼：

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    [self registerForKeyboardNotifications];

    self.title = NSLocalizedString(@"Register", nil);
    [self.navigationController setNavigationBarHidden:NO];

    // Because Rendering Bug in iOS 7
    self.view.backgroundColor = [UIColor whiteColor];


    UIScrollView *scrollView = [[UIScrollView alloc] init];
    _scrollView.frame = self.view.frame;
    _scrollView.scrollEnabled = YES;
    _scrollView.showsVerticalScrollIndicator = YES;
    _scrollView.contentSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height * 2);
    [self.view addSubview:scrollView];

    // Personal Image View
    UIButton *profileImageButton = [UIButton buttonWithType:UIButtonTypeSystem];
    profileImageButton.frame = CGRectMake(0, 0, 80, 80);
    profileImageButton.center = CGPointMake(self.view.center.x, 80);
    [profileImageButton setBackgroundImage:[UIImage imageNamed:@"DefaultAvatar"] forState:UIControlStateNormal];
    [profileImageButton addTarget:self action:@selector(uploadImage) forControlEvents:UIControlEventTouchUpInside];
    [_scrollView addSubview:profileImageButton];

    // Username Text Field
    _usernameTextField = [[UITextField alloc] init];
    _usernameTextField.frame = CGRectMake(0, 0, self.view.frame.size.width, 64);
    _usernameTextField.center = CGPointMake(self.view.center.x, 225);
    _usernameTextField.placeholder = @"\tUsername";
    _usernameTextField.layer.backgroundColor = [UIColor colorWithRed:244.0f/255.0f green:244.0f/255.0f blue:244.0f/255.0f alpha:1.0].CGColor;
    _usernameTextField.font = [UIFont fontWithName:@"HelveticaNeue-Thin" size:20.0];
    _usernameTextField.autocorrectionType = UITextAutocorrectionTypeNo;
    [_scrollView addSubview:_usernameTextField];

    // Password Text Field
    _passwordTextField = [[UITextField alloc] init];
    _passwordTextField.frame = CGRectMake(0, 0, self.view.frame.size.width, 64);
    _passwordTextField.center = CGPointMake(self.view.center.x, 320);
    _passwordTextField.placeholder = @"\tPassword";
    _passwordTextField.layer.backgroundColor = [UIColor colorWithRed:244.0f/255.0f green:244.0f/255.0f blue:244.0f/255.0f alpha:1.0].CGColor;
    _passwordTextField.font = [UIFont fontWithName:@"HelveticaNeue-Thin" size:20.0];
    _passwordTextField.autocorrectionType = UITextAutocorrectionTypeNo;
    [_scrollView addSubview:_passwordTextField];
}

Answer 1

以此替換滾動視圖聲明，

UIScrollView *scrollView = [[UIScrollView alloc] init];
scrollView.frame = self.view.frame;
scrollView.scrollEnabled = YES;
scrollView.showsVerticalScrollIndicator = YES;
scrollView.contentSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height * 2);
[self.view addSubview:scrollView];

或者像這樣

 _scrollView = [[UIScrollView alloc] init];
_scrollView.frame = self.view.frame;
_scrollView.scrollEnabled = YES;
_scrollView.showsVerticalScrollIndicator = YES;
_scrollView.contentSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height * 2);
[self.view addSubview:scrollView];

這是因為您初始化了“ scrollView”並添加了“ _scrollView”進行查看。 還要在scrollView中相應地添加所有子視圖。

Answer 2

UIScrollView *scrollView = [[UIScrollView alloc] init];
    _scrollView.frame = self.view.frame;
    _scrollView.scrollEnabled = YES;
    _scrollView.showsVerticalScrollIndicator = YES;
    _scrollView.contentSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height * 2);
    [self.view addSubview:scrollView]; //making mistake here

在這里，您犯錯了，您正在為實例obj分配動態屬性並將本地obj添加為子視圖...

將此行更改為[self.view addSubview：scrollView]; 到[self.view addSubview：_scrollView];

並且做一件事還要分配init _scrollview。