iOS开发——UI基础-自定义构造方法，layoutSubviews，Xib文件，利用Xib自定义View

一、自定义构造方法

---

有时候需要快速创建对象，可以自定义构造方法

+ (instancetype)shopView
{
    return [[self alloc] init];
}
 
- (instancetype)initWithShop:(NJShop *)shop
{
    if (self = [super init]) {
        self.shop = shop;
    }
    return self;
}
 
+ (instancetype)shopViewWithShop:(NJShop *)shop
{
 
    return [[self alloc] initWithShop:shop];
}

一般情况下自定义一个控件会重写控件的initWithFrame方法, , 因为用户可能通过init方法创建也可能通过initWithFrame方法创建, 为了保证无论用户通过哪一个方法创建都能添加子控件, 所以重写initWithFrame

init方法内部会调用initWithFrame

- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
 
        NSLog(@"%s", __func__);
        // 1.创建一张图片
        UIImageView *iv = [[UIImageView alloc] init];
        iv.backgroundColor = [UIColor yellowColor];
        [self addSubview:iv];
        self.iv = iv;
 
        // 2.创建一个文本
        UILabel *lable = [[UILabel alloc] init];
        lable.backgroundColor = [UIColor purpleColor];
        lable.textAlignment = NSTextAlignmentCenter;
        [self addSubview:lable];
        self.lable = lable;
    }
    return self;
}

NJShopView *shopView = [[NJShopView alloc] initWithFrame:CGRectMake(shopX, shopY, , )];
 
NJShopView *shopView = [NJShopView shopView];
 
NJShopView *shopView = [[NJShopView alloc] initWithShop:self.shops[index]];
 
NJShopView *shopView = [NJShopView shopViewWithShop: self.shops[index]];

二、layoutSubviews

---

layoutSubviews方法是专门用于布局子控件的位置的

注意: 重写layoutSubviews方法, 一定要调用[super layoutSubviews]方法 \

如果不调用, 会出现一些奇葩的错误

/*

layoutSubviews方法什么时候调用

1.只要创建一个控件, 那么就会调用

2.只要修改控件的尺寸就会调用(bounds/frame)

3.修改位置不会调用

4.如果当前修改的尺寸和上一次的尺寸没有变化, 不会调用

*/

- (void)layoutSubviews
 
{
 
    [super layoutSubviews];
 
    NSLog(@"%s", __func__);
 
    CGFloat shopViewWidth = self.frame.size.width;
 
    CGFloat shopViewHeight = self.frame.size.height;
 
    // 1.布局图片的位置
 
     self.iv.frame = CGRectMake(, , shopViewWidth, shopViewWidth);
 
    // 2.布局文本的位置
 
    self.lable.frame = CGRectMake(, shopViewWidth, shopViewWidth, shopViewHeight - self.iv.frame.size.height);
 
}

三、Xib文件

---

什么是Xib?

Xib和Storyboard一样都是用来描述界面的

Xib是Storyboard的前身

Xib是用于描述一个简单的界面或者一个局部的界面

Storyboard是用于描述整体

四、利用Xib自定义View

---

#import <UIKit/UIKit.h>
 
@class NJShop;
@interface XMGShopView : UIView
 
@property(nonatomic, strong)NJShop *shop;
 
+ (instancetype)shopView;
@end
 
#import "XMGShopView.h"
#import "NJShop.h"
 
@interface XMGShopView ()
@property (weak, nonatomic) IBOutlet UIImageView *iconView;
@property (weak, nonatomic) IBOutlet UILabel *nameLabel;
@end
 
@implementation XMGShopView
 
+ (instancetype)shopView
{
    return [[[NSBundle mainBundle] loadNibNamed:@"XMGShopView" owner:nil options:nil] firstObject];
}
 
- (void)setShop:(NJShop *)shop
{
    _shop = shop;
 
    self.iconView.image = [UIImage imageNamed:_shop.icon];
    self.nameLabel.text = _shop.name;
}
 
@end

xib加载原理:

    // 1. 根据custom class创建对象
 
     XMGShopView *shopView = [XMGShopView alloc] init];
 
     // 2. 根据xib中的设置, 设置控件的相关属性
 
     shopView.backgroundColor = [UIColor redColor];
 
     shopView.frame = CGRectMake(, , , );
 
     // 3. 创建所有子控件, 并且设置子控件的属性
 
     UIImageView *iv = [[UIImageView alloc] init];
 
     iv.frame = CGRectMake(, , , );
 
     UILabel *label = [[UILabel alloc] init];
 
     label.frame = CGRectMake(, , , );
 
     // 4. 检查子控件是否有连线, 如果有就进行关联
 
     self.iconView = iv;
 
     self.nameLabel = label;
 
     // 5.将所有子控件添加到父控件中
 
     [shopView addSubview:iv];
 
     [shopView addSubview:label];