AutoLayout 代码实现约束

话说今天没事，拿来AutoLayout开发秘籍书看起来。书中描述了AutoLayout的内容还是挺深奥一点。特写了个小例子玩玩。
工欲善其事，比有利器。还是第三方的开源库使用起来爽啊！做个记录。权当复习了。

//
//  ViewController.m
//  AutoLayoutDemo1
//
//  Created by jason-lu on 16/1/29.
//  Copyright © 2016年 Jason. All rights reserved.
//

#import "ViewController.h"
#import 

@interface ViewController ()

@end

@implementation ViewController

@synthesize userLabel;
@synthesize userName;
@synthesize pwdLabel;
@synthesize pwd;
@synthesize login;
@synthesize reset;

- (void)viewDidLoad {
    [super viewDidLoad];
    [self dract];
}
//初始化界面
- (void)dract {
    self.view.backgroundColor =[UIColor whiteColor];
    userLabel = [[UILabel alloc]initWithFrame:CGRectZero];
    userLabel.text = @"用户名:";
    userLabel.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:userLabel];

    userName =[[UITextField alloc]initWithFrame:CGRectZero];
    userName.translatesAutoresizingMaskIntoConstraints = NO;
    userName.placeholder = @"请输入用户名";
    userName.borderStyle = UITextBorderStyleRoundedRect;
    userName.delegate = self;
    [self.view addSubview:userName];

    pwdLabel = [[UILabel alloc]initWithFrame:CGRectZero];
    pwdLabel.text = @"密  码:";
    pwdLabel.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:pwdLabel];

    pwd =[[UITextField alloc]initWithFrame:CGRectZero];
    pwd.translatesAutoresizingMaskIntoConstraints = NO;
    pwd.secureTextEntry = YES;
    pwd.placeholder = @"请输入密码";
    pwd.delegate = self;
    pwd.borderStyle = UITextBorderStyleRoundedRect;
    [self.view addSubview:pwd];

    //init login button
    login = [[UIButton alloc]initWithFrame:CGRectZero];
    [login setTitle:@"登陆" forState:UIControlStateNormal];
    login.backgroundColor =[UIColor redColor];
    [self.view addSubview:login];
    login.translatesAutoresizingMaskIntoConstraints = NO;
    [login addTarget:self action:@selector(loginAction:) forControlEvents:UIControlEventTouchUpInside];
    //init reset button
    reset = [[UIButton alloc]initWithFrame:CGRectZero];
    [reset setTitle:@"重置" forState:UIControlStateNormal];
    reset.backgroundColor = [UIColor redColor];
    [self.view addSubview:reset];
    reset.translatesAutoresizingMaskIntoConstraints = NO;
    [reset addTarget:self action:@selector(resetAction:) forControlEvents:UIControlEventTouchUpInside];
    //设置userLabel的约束条件
    NSLayoutConstraint *constraintUserLabel;
    constraintUserLabel = [NSLayoutConstraint constraintWithItem:userLabel attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:60];
    [self.view addConstraint:constraintUserLabel];

    constraintUserLabel = [NSLayoutConstraint constraintWithItem:userLabel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:80];
    [self.view addConstraint:constraintUserLabel];

    constraintUserLabel =[NSLayoutConstraint constraintWithItem:userLabel attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeading multiplier:1 constant:30 ];
    [self.view addConstraint:constraintUserLabel];

    constraintUserLabel = [NSLayoutConstraint constraintWithItem:userLabel attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:30];
    [self.view addConstraint:constraintUserLabel];

    //设置用户名输入框的约束条件
    NSLayoutConstraint *constraintUserAccount;
    constraintUserAccount = [NSLayoutConstraint constraintWithItem:userName attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:150];
    [self.view addConstraint:constraintUserAccount];

    constraintUserAccount = [NSLayoutConstraint constraintWithItem:userName attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:30];
    [self.view addConstraint:constraintUserAccount];

    constraintUserAccount =[NSLayoutConstraint constraintWithItem:userName attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeading multiplier:1 constant:90];
    [self.view addConstraint:constraintUserAccount];

    constraintUserAccount = [NSLayoutConstraint constraintWithItem:userName attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:55];
    [self.view addConstraint:constraintUserAccount];

    //设置密码的label的约束条件

    NSLayoutConstraint *constraintPwdLabel;
    constraintPwdLabel = [NSLayoutConstraint constraintWithItem:pwdLabel attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:60];
    [self.view addConstraint:constraintPwdLabel];

    constraintPwdLabel = [NSLayoutConstraint constraintWithItem:pwdLabel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:80];
    [self.view addConstraint:constraintPwdLabel];

    constraintPwdLabel =[NSLayoutConstraint constraintWithItem:pwdLabel attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeading multiplier:1 constant:30 ];
    [self.view addConstraint:constraintPwdLabel];

    constraintPwdLabel = [NSLayoutConstraint constraintWithItem:pwdLabel attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:60];
    [self.view addConstraint:constraintPwdLabel];

    //设置密码输入框的约束条件
    NSLayoutConstraint *constraintPwd;
    constraintPwd = [NSLayoutConstraint constraintWithItem:pwd attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:150];
    [self.view addConstraint:constraintPwd];

    constraintPwd = [NSLayoutConstraint constraintWithItem:pwd attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:30];
    [self.view addConstraint:constraintPwd];

    constraintPwd =[NSLayoutConstraint constraintWithItem:pwd attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeading multiplier:1 constant:90];
    [self.view addConstraint:constraintPwd];

    constraintPwd = [NSLayoutConstraint constraintWithItem:pwd attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:90];
    [self.view addConstraint:constraintPwd];

    //设置登陆按钮的约束条件
    NSLayoutConstraint *constraintLogin ;
    constraintLogin = [NSLayoutConstraint constraintWithItem:login attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:130];
    [self.view addConstraint:constraintLogin];

    constraintLogin =[NSLayoutConstraint constraintWithItem:login attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:30];
    [self.view addConstraint:constraintLogin];

    constraintLogin = [NSLayoutConstraint constraintWithItem:login attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeading multiplier:1 constant:30];
    [self.view addConstraint:constraintLogin];

    constraintLogin = [NSLayoutConstraint constraintWithItem:login attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:150];
    [self.view addConstraint:constraintLogin];


    //设置重置按钮的约束条件
    NSLayoutConstraint *constraintReset ;
    constraintReset = [NSLayoutConstraint constraintWithItem:reset attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:130];
    [self.view addConstraint:constraintReset];

    constraintReset =[NSLayoutConstraint constraintWithItem:reset attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1 constant:30];
    [self.view addConstraint:constraintReset];

    constraintReset = [NSLayoutConstraint constraintWithItem:reset attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeading multiplier:1 constant:170];
    [self.view addConstraint:constraintReset];

    constraintReset = [NSLayoutConstraint constraintWithItem:reset attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:150];
    [self.view addConstraint:constraintReset];

}

- (void)loginAction:(UIButton *)btn {
    UIAlertController *alert =[UIAlertController alertControllerWithTitle:@"系统提示:" message:@"是否确认登陆系统" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"检测账号" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
        NSString *user = userName.text;
        NSString*password = pwd.text;
        if ([user isEqualToString:@"jason"] && [password isEqualToString:@"123456"]) {
            //弹出加载页面
            _hud = [[MBProgressHUD alloc] initWithView:self.view];
            _hud.mode = MBProgressHUDModeIndeterminate;
            _hud.dimBackground = YES;
            [self.view addSubview:_hud];
            _hud.labelText = @"正在登陆...";
            [_hud showAnimated:YES whileExecutingBlock:^{
                NSLog(@"%@",@"do somethings....");
                [self doTask];
            } completionBlock:^{
                [_hud removeFromSuperview];
            }];
        }
    }];
    UIAlertAction *defaultAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {

    }];
    [alert addAction:okAction];
    [alert addAction:defaultAction];
    [self presentViewController:alert animated:YES completion:nil];
}

-(void) doTask{
    //你要进行的一些逻辑操作
    sleep(10);
}

- (void)resetAction:(UIButton *)btn {
    UIAlertController *alert =[UIAlertController alertControllerWithTitle:@"系统提示:" message:@"清楚你输入的内容" preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *action =[UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:nil];
    UIAlertAction *defaultAction =[UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:nil];
    [alert addAction:action];
    [alert addAction:defaultAction];
    [self presentViewController:alert animated:YES completion:nil];
}

- (BOOL)textFieldShouldReturn:(UITextField *)textField {
    [userName becomeFirstResponder];
    [pwd becomeFirstResponder];
    return YES;
}
@end