ios - 自定义 UIView 在 addSubview 上不可见

Question

我创建了一个简单的 ProgressView 类，我希望在执行一些长任务时显示它。但是，当我将它添加到父 View 时，它永远不会变得可见，并且永远不会调用 layoutSubviews。

类实现如下:

@implementation ProgressView

@synthesize title;
@synthesize cancel;
@synthesize progress;
@synthesize delegate;

- (id)initWithFrame:(CGRect)frame
{
    //frame = CGRectMake( 0, 0, 240, 112 );
    self = [super initWithFrame:frame];
    if ( self )
    {
        self.title      = [[UILabel alloc] init];
        self.cancel     = [UIButton buttonWithType: UIButtonTypeCustom];
        self.progress   = [[UIProgressView alloc] init];

        self.backgroundColor    = [UIColor darkGrayColor];

        [self addSubview: self.title];
        [self addSubview: self.cancel];
        [self addSubview: self.progress];
    }
    return self;
}

+ (id) createWithTitle: (NSString*) pTitle
{
    ProgressView* pRet  = [[ProgressView alloc] initWithTitle: pTitle];
    return pRet;
}

- (id) initWithTitle: (NSString*) pTitle
{
    self = [super initWithFrame: CGRectMake( 0, 0, 240, 112 )];
    if ( self )
    {
        self.title.text = pTitle;
    }
    return self;
}

- (void) layoutSubviews
{
    CGSize superFrameSize       = self.superview.frame.size;
    CGSize halfSuperFrameSize   = CGSizeMake( superFrameSize.width / 2, superFrameSize.height / 2 );

    CGSize frameSize            = self.frame.size;
    CGSize halfFrameSize        = CGSizeMake( frameSize.width / 2, frameSize.height / 2 );

    // Center the window on its parent.
    [self setFrame: CGRectMake( halfSuperFrameSize.width - halfFrameSize.width, halfSuperFrameSize.height - halfFrameSize.height, frameSize.width, frameSize.height )];

    [self.title     setFrame: CGRectMake( 4,  4, frameSize.width - 8, 24 )];
    [self.progress  setFrame: CGRectMake( 4, 32, frameSize.width - 8, 24 )];
    [self.cancel    setFrame: CGRectMake( 4, 64, frameSize.width - 8, 44 )];

    [self setNeedsDisplay];
}

然后我添加如下 View :

pProgressView   = [[ProgressView alloc] initWithTitle: @"Downloading..."];
[pProgressView setDelegate: self];
[self.view addSubview: pProgressView];

但它永远不会显示。我已经检查过删除肯定会在稍后发生，并且有足够的时间让 View 可见。但是我很茫然。无论我做什么，ProgressView 都不会显示。

有人可以指出我正在犯的最有可能是愚蠢的错误吗？

Answer 1

需要在-initWithTitle中调用指定的初始化器，而不是[super init]:

self = [self initWithFrame: CGRectMake( 0, 0, 240, 112 )];

指定的初始化器是调用父类(super class)初始化器的那个，参见here了解更多信息。