如何使用相对点以编程方式定位视图？

Question

当超视图的界限尚未知晓时,相对于其超视图大小定位视图的最佳方法是什么？

如果可能的话,我试图避免硬编码坐标.也许这很愚蠢,如果是这样,这是一个完全可以接受的答案.

在使用自定义UI时,我遇到过很多次.最近的例子是我试图UINavigationItem用自定义视图替换纯文本标题.我希望该视图填充超视图,但另外,我想UIActivityIndicatorView在右侧,插入约2个像素并垂直居中.这是代码:

- (void) viewDidLoad
{
    [super viewDidLoad];

    customTitleView = [[UIView alloc] initWithFrame:CGRectZero];
    customTitleView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;

    titleLabel = [[UILabel alloc] initWithFrame:CGRectZero];
    titleLabel.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
    titleLabel.lineBreakMode = UILineBreakModeWordWrap;
    titleLabel.numberOfLines = 2;
    titleLabel.minimumFontSize = 11.0;
    titleLabel.font = [UIFont systemFontOfSize:17.0];
    titleLabel.adjustsFontSizeToFitWidth = YES;
    [customTitleView addSubview:titleLabel];

    spinnerView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    spinnerView.center = CGPointMake(customTitleView.bounds.size.width - (spinnerView.bounds.size.width / 2) - 2,
                                     customTitleView.bounds.size.height / 2);
    spinnerView.hidesWhenStopped = YES;
    [customTitleView addSubview:spinnerView];

    self.navigationItem.titleView = customTitleView;
    [customTitleView release];
}

这是我的问题:在这段代码运行的时候,customTitleView.bounds仍然是零.自动调整大小的掩码还没有机会做它的事情,但我非常想要这些值,以便我可以计算其他子视图的相对位置(这里是活动指示符).

这可能不丑吗？

Answer 1

customTitleView.bounds 宽度和高度为零的唯一原因是您已使用 CGRectZero 以这种方式初始化它。您可以使用任何非零大小初始化视图，然后根据该任意大小定义其子视图。只要您正确定义了子视图的自动调整大小行为，当超级视图的框架在运行时发生变化时，它们的布局就会适当调整。

例如：

- (void) viewDidLoad
{
    [super viewDidLoad];

    customTitleView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 100.0f, 100.0f)];
    customTitleView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;

    titleLabel = [[UILabel alloc] initWithFrame:customTitleView.bounds];
    titleLabel.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
    titleLabel.lineBreakMode = UILineBreakModeWordWrap;
    titleLabel.numberOfLines = 2;
    titleLabel.minimumFontSize = 11.0;
    titleLabel.font = [UIFont systemFontOfSize:17.0];
    titleLabel.adjustsFontSizeToFitWidth = YES;
    [customTitleView addSubview:titleLabel];
    [titleLabel release];

    spinnerView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    spinnerView.center = CGPointMake(customTitleView.bounds.size.width - (spinnerView.bounds.size.width / 2) - 2,
                                     customTitleView.bounds.size.height / 2);
    spinnerView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin;
    spinnerView.hidesWhenStopped = YES;
    [customTitleView addSubview:spinnerView];
    [spinnerView release];

    self.navigationItem.titleView = customTitleView;
    [customTitleView release];
}