为什么这段代码中没有出现view2？ （将 UIView 2 合并到 UIView 1 中）

Question

为什么这段代码中没有出现view2？在结果中，我看到显示了本地 View1 标签，顶部有红色边框，并且在整体绿色边框内，但是我没有看到 view2 的任何内容？即带有文本“View2 Label Text”的标签不会出现。

test11ViewController.m

@implementation test11ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];
    View1 *view1 = [[[View1 alloc] initWithFrame:CGRectMake(0.0, 0.0, 400, 100) ] autorelease];
    view1.layer.borderColor = [UIColor redColor].CGColor;
    view1.layer.borderWidth = 1;
    [self.view addSubview:view1];
}
@end

View1.m

@implementation View1
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Local Label
        CGFloat width = self.frame.size.width;
        UILabel *label = [[[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, width, 30)] autorelease];
        label.text = @"View1 Label Text";
        label.layer.borderColor = [UIColor greenColor].CGColor;
        label.layer.borderWidth = 1.0;
        [self addSubview:label];

        // External - Label2
        View2 *view2 = [[[View2 alloc] initWithFrame:CGRectMake(0.0, 30, width, 30)] autorelease];
        [super addSubview:view2];   
    }
    return self;
}
@end

View2.m

@implementation View2
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        CGFloat width = self.frame.size.width;
        UILabel *label = [[[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, width, 30)] autorelease];
        label.text = @"View2 Label Text";   // Does  NOT appear in output
        label.layer.borderColor = [UIColor blueColor].CGColor;
        label.layer.borderWidth = 1.0;
    }
    return self;
}
@end

Answer 1

view2 实际上并未将标签添加到自身。你错过了这个：

[self addSubview:label];

换句话说，尝试：

@implementation View2
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        CGFloat width = self.frame.size.width;
        UILabel *label = [[[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, width, 30)] autorelease];
        label.text = @"View2 Label Text";   // Does  NOT appear in output
        label.layer.borderColor = [UIColor blueColor].CGColor;
        label.layer.borderWidth = 1.0;
        [self addSubview:label];  // NEW LINE HERE
    }
    return self;
}
@end

Answer 2

在您的测试视图控制器行中...

[self.view addSubview:view1];

...添加...

[self.view sendSubviewToBack:view1];

之后view2 现在显示吗？请注意，将两个视图的 alpha 设置为 0.5，以确保一个视图不会遮挡另一个视图。