IOS布局笔记一（代码实现自己主动布局）

//
// WildCatViewController.h
// AutoLayoutDemo
//
// Created by wildcat on 14-4-20.
// Copyright (c) 2014年 com.wildcat. All rights reserved.
//
#import <UIKit/UIKit.h>
@interface WildCatViewController : UIViewController
@property(nonatomic,strong) UIButton*button;
@end

//
// WildCatViewController.m
// AutoLayoutDemo
//
// Created by wildcat on 14-4-20.
// Copyright (c) 2014年 com.wildcat. All rights reserved.
//
#import "WildCatViewController.h"@interface WildCatViewController ()
@end

@implementation WildCatViewController
@synthesize button=_button;
- (void)viewDidLoad
{
[super viewDidLoad];
_button=[UIButton buttonWithType:UIButtonTypeRoundedRect];
_button.translatesAutoresizingMaskIntoConstraints=NO;
[_button setTitle:@"WildCat" forState:UIControlStateNormal];
[self.view addSubview:_button];

UIView *superView=_button.superview;
//加入约束，使按钮在屏幕水平方向的中央
NSLayoutConstraint *centerXContraint=[NSLayoutConstraint
constraintWithItem:_button
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:superView
attribute:NSLayoutAttributeCenterX
multiplier:1.0f
constant:0.0];
//加入约束。使按钮在屏幕垂直方向的中央
NSLayoutConstraint *centerYContraint=[NSLayoutConstraint
constraintWithItem:_button
attribute:NSLayoutAttributeCenterY
relatedBy:NSLayoutRelationEqual
toItem:superView
attribute:NSLayoutAttributeCenterY
multiplier:1.0f
constant:0.0];
//给button的父节点加入约束
[superView addConstraints:@[centerXContraint,centerYContraint]];

}

-(NSUInteger)supportedInterfaceOrientations{
return UIInterfaceOrientationMaskAll; //屏幕能够旋转
}

- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end

不要忘记更改设备能够旋转方向。
执行结果例如以下图：

本文转自：http://1.wildcat.sinaapp.com/?p=42

限制条件和他们要加入到的视图的关系图例如以下：

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接下来学什么：IOS布局笔记二（ Visual Format Language 定义水平和垂直约束）