iOS开发之|iOS开发之 storyboard自动布局 iOS开发之storyboard自动布局

一.自动布局基础知识

VFL:Visual Format Language 可视化格式语言
H:水平方向
V：水平方向
| 表示父视图
本身表示一段距离： -
表示指定距离： -距离-
注意：使用自动布局步骤：
1.使用自动布局(autolayout) frame就会失效，就不需要再去设置视图的frame
使用代码自动布局需要禁用这个属性：
translatesAutoresizingMaskIntoConstraints = NO
2.绑定视图与字符串
3.添加约束
可视化语言编译
可视化语言：
H:|-100-[view(>=100)]-100-|
V:|-150-[view(40)]
编译：
横向：距离父视图左侧100 视图本身的宽度最小是100 距离父视图右侧是100
竖向：距离父视图顶部150 视图本身的高度是40
常见的两个错误：
1.Unable to parse constraint format: Expected a view or '|' 丢了竖杠。
2.'Unable to parse constraint format: Unable to interpret '|' character, because the related view doesn't have a superview 在布局后把View放在父视图上就会报这个错要初始化view时就把它放在父视图上。

二.具体实例解析自动布局 1.先用一个简单的例子来说明（可以全部写在ViewDidLoad中）
UIView *view = [[UIView alloc]init];
view.backgroundColor = [UIColor greenColor];
[self.view addSubview:view];

//1.禁用属性 view.translatesAutoresizingMaskIntoConstraints = NO; //2.绑定视图和字符串 NSDictionary *views = NSDictionaryOfVariableBindings(view); //3.添加约束/* 第一个参数：VFL语句第二个参数：options 基于哪一个选项（基于哪个方向去计算布局）第三个参数：metrics：绑定数值(NSNumber)与字符串第四个参数：绑定视图与字符串 */ [self.view addConstraints:[NSLayoutConstraintconstraintsWithVisualFormat:@"H:|-20-[view(>=100)]-20-|" options:NSLayoutFormatAlignAllLeft metrics:nil views:views]]; [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-20-[view(40)]" options:NSLayoutFormatAlignAllLeft metrics:nil views:views]];

【iOS开发之|iOS开发之 storyboard自动布局】2.下面用一个比较复杂的例子来剖析自动布局（在viewDidLoad中调用loadDemo这个方法即可）
- (void)loadDemo{
// 1 创建三个视图红/绿/蓝/黄/橙色视图
// 红
UIView *redView = [self alive];
redView.backgroundColor = [UIColor redColor];
[self.view addSubview:redView];
// 绿
UIView *greenView = [self alive];
greenView.backgroundColor = [UIColor greenColor];
[self.view addSubview:greenView];
// 蓝
UIView *blueView = [self alive];
blueView.backgroundColor = [UIColor blueColor];
[self.view addSubview:blueView];
// 黄
UIView *yellowView = [self alive];
yellowView.backgroundColor = [UIColor yellowColor];
[self.view addSubview:yellowView];
// 橙
UIView *orangeView = [self alive];
orangeView.backgroundColor = [UIColor orangeColor];
[self.view addSubview:orangeView];

[self.view addConstraints:[self portraitConstraints:redView :greenView :blueView yellowView:yellowView orangeView:orangeView]]; }// 这样写完全是为了代码的方便使用,创建对象的同时初始化控件 - (UIView *)alive { UIView *newView = [UIView new]; newView.translatesAutoresizingMaskIntoConstraints = NO; return newView; }- (NSMutableArray *) portraitConstraints:(UIView *)redView :(UIView *)greenView :(UIView *)blueView yellowView:(UIView *)yellowView orangeView:(UIView *)orangeView{ NSMutableArray *array = [NSMutableArray array]; // 注1：红色视图的宽度大于等于10 小于30黄色视图的宽度大于40 小于120水平 [array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-20-[redView(>=10,<=30)]-20-[greenView(>=40,<=120)]-20-[yellowView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(redView, greenView, yellowView)]]; // 注2：垂直方向 red高度V:100<= <=160蓝色 V:30<= <=60橙色待定 [array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-70-[redView(>=100,<=160)]-20-[blueView(>=30,<=60)]-[orangeView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(redView, blueView, orangeView)]]; // 和注2类似 [array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-70-[greenView(>=100,<=160)]-20-[blueView(>=30,<=60)]-[orangeView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(greenView, blueView, orangeView)]]; // 和注2类似或许有人会问为什么得添加黄色和绿色，原因很简单，就是为了满足各个约束，避免造成约束不足 [array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-70-[yellowView(>=100,<=160)]-20-[blueView(>=30,<=60)]-[orangeView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(yellowView, blueView, orangeView )]]; // 注3：控制blued的宽度 [array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-20-[blueView]-120-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(blueView)]]; // 注4：为橙色高度添加约束条件 [array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[blueView]-20-[orangeView(>=blueView)]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(blueView, orangeView)]]; // 注4：为橙色添加宽度约束条件 [array addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-20-[orangeView]-20-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(blueView, orangeView)]]; return array; }