关于awakeFromNib的学习

最新推荐文章于 2020-06-06 22:26:41 发布

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本文介绍了在iOS应用开发中，如何正确使用Nib文件加载视图组件并进行初始化的过程。重点讲解了awakeFromNib方法的作用及调用时机，以及initWithCoder方法与awakeFromNib方法之间的执行顺序。

When a nib is loaded, the nib loader allocates and initializes all objects, then hooks up all of their outlets and actions. Because of the order in which this happens, you cannot access outlets in your initializer. You can try, but they will all be nil.

After all outlets and actions are connected, the nib loader sends awakeFromNib to every object in the nib. This is where you can access outlets to set up default values or do configuration in code. Example:

http://wiresareobsolete.com/wordpress/2010/03/awakefromnib/

@implementation SecondView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}

- (void)awakeFromNib{
    [super awakeFromNib];
    NSLog(@"call %s", __FUNCTION__);
    self.backgroundColor = [UIColor redColor];
}

一般在UIView的子类重载该方法。

@implementation BlueButton

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
    }
    return self;
}
- (void)awakeFromNib{
    [super awakeFromNib];
    NSLog(@"call %s", __FUNCTION__);
    self.backgroundColor = [UIColor blueColor];
    [self setTitle:@"Blue Button" forState:UIControlStateNormal];
}
- (id)initWithCoder:(NSCoder *)aDecoder{
    NSLog(@"call %@", @"initWithCoder");
    if (self = [super initWithCoder:aDecoder]) {
        self.titleLabel.text = @"initWithCoder";
    }
    return  self;
}
@end

如果是从nib中加载BuleButton，方法 initWithCoder 会调用，并且先于 awakeFromNib 调用。