1.在以下情況都會(huì)調(diào)用
1.直接調(diào)用[self setNeedsLayout];（這個(gè)在上面蘋果官方文檔里有說(shuō)明）
2.addSubview的時(shí)候。
3.當(dāng)view的size發(fā)生改變的時(shí)候。
4.滑動(dòng)UIScrollView的時(shí)候。
5.旋轉(zhuǎn)Screen會(huì)觸發(fā)父UIView上的layoutSubviews事件。
注意:當(dāng)view的size的值為0的時(shí)候驻民，addSubview也不會(huì)調(diào)用layoutSubviews。當(dāng)要給這個(gè)view添加子控件的時(shí)候不管他的size有沒(méi)有值都會(huì)調(diào)用
2.先來(lái)看一下UIView的layoutSubviews在什么情況下會(huì)調(diào)用
2.1初始化,當(dāng)size不為0的時(shí)候調(diào)用一次,當(dāng)size為0的時(shí)候不會(huì)調(diào)用(在任何方法里面都不會(huì)調(diào)用)
SubView*view= [[SubView alloc]initWithFrame:CGRectMake(0,0,100,100)]; view.backgroundColor=[UIColorredColor]; [self.view addSubview:view];self.sbView= view;
2.2當(dāng)size改變的時(shí)候調(diào)用一次(size每次都不同,如果size相同就不會(huì)調(diào)用)
2.3當(dāng)添加子控件的時(shí)候,不管子控件有沒(méi)有尺寸都會(huì)調(diào)用例如:
// 添加子控件的時(shí)候都會(huì)調(diào)用CustomBtn *button = [[CustomBtn alloc] init];[self.sbView addSubview:button];
3.看UIButton什么時(shí)候調(diào)用
3.1這種情況下button的layoutSubviews調(diào)用一次,因?yàn)楫?dāng)控制器的view顯示的時(shí)候會(huì)調(diào)用控制器view的layoutSubviews(UIView除外,比較特殊)
- (void)viewDidLoad{? ? [superviewDidLoad];? ? CustomBtn*button = [[CustomBtn alloc]init];? ? [self.view addSubview:button];? }
如果放在 viewDidAppear button的layoutSubviews就不會(huì)調(diào)用
- (void)viewDidAppear:(BOOL)animated{? ? [superviewDidAppear:animated];// 因?yàn)関iew這時(shí)候已經(jīng)顯示了,父控件就不會(huì)布局了,所以代碼寫在這里最好,受干擾的因素最小CustomBtn*button = [[CustomBtn alloc]init];? ? [self.view addSubview:button]; }
3.2設(shè)置title會(huì)調(diào)用一次layoutSubviews
CustomBtn*button = [[CustomBtn alloc] init];[button setTitle:@"xxoo"forState:UIControlStateNormal]; [self.view addSubview:button];
3.2設(shè)置image的時(shí)候會(huì)調(diào)用一次layoutSubviews,注意:如果圖片的名字在工程里面沒(méi)有,就不會(huì)調(diào)用,別想騙過(guò)蘋果
CustomBtn *button = [[CustomBtn alloc] init]; [button setImage:[UIImageimageNamed:@"xoxo"] forState:UIControlStateNormal]; [self.view addSubview:button];
4.UIScrollView
4.1這種情況也會(huì)調(diào)用(比較特殊)
// scrollView比較特殊CustomScrollView *scrollView= [[CustomScrollView alloc]init];[self.view addSubview:scrollView];
4.2這種情況會(huì)調(diào)用一次layoutSubviews(代碼放在viewDidAppear,防止干擾)
// 因?yàn)閟crollView有size,所以會(huì)調(diào)用CustomScrollView *scrollView= [[CustomScrollView? alloc]initWithFrame:CGRectMake(100,100,300,200)];[self.view addSubview:scrollView]; scrollView.backgroundColor= [UIColoryellowColor]; scrollView.contentSize=CGSizeMake(0,500);
4.3當(dāng)UIScrollView滑動(dòng)的時(shí)候會(huì)掉多次layoutSubviews
