IOS开发之手写约束

最新推荐文章于 2020-02-25 13:46:48 发布

转载最新推荐文章于 2020-02-25 13:46:48 发布 · 202 阅读

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原文链接：https://my.oschina.net/luhoney/blog/670660

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#移动开发 #python

本文详细介绍了如何在iOS开发中手动添加Auto Layout约束，通过创建并添加视图，然后为这些视图定义位置和大小约束来实现精确布局。具体包括为红色视图设定左上角位置及宽高，以及为绿色视图设定相对于红色视图的位置和尺寸。

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// ViewController.m

// 02-手写约束

// Created by 鹿微微鹿 on 16/5/5.

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

//手动添加约束

//1.必须先将需要添加约束的视图创建出来

//并且添加到界面上

//2.不需要设置frame

//关闭autoresizing

//1.创建一个红色视图

UIView *redView = [[UIView alloc]init];

redView.backgroundColor = [UIColor redColor];

//关闭autoresizing

redView.translatesAutoresizingMaskIntoConstraints = NO;

//创建一个绿色视图

UIView *greenView = [[UIView alloc]init];

greenView.backgroundColor = [UIColor greenColor];

greenView.translatesAutoresizingMaskIntoConstraints = NO;

//显示在界面上

[self.view addSubview:redView];

[self.view addSubview:greenView];

//2.添加约束(红色视图一值显示在左上角

//到屏幕顶部和左边的距离为50，宽高200)

//top

//红色视图的顶部 = view顶部*1 + 50

//redView.top = self.view.top*1 + 50;

//参数1的参数2参数3参数4的参数5 * 参数6 + 参数7

NSLayoutConstraint *redtopConstraint = [NSLayoutConstraint

constraintWithItem:redView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:50];

//left

NSLayoutConstraint *redLeftConstraint = [NSLayoutConstraint

constraintWithItem:redView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeft multiplier:1 constant:50];

//width

NSLayoutConstraint *redWith = [NSLayoutConstraint

constraintWithItem:redView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:0 constant:200];

//height

NSLayoutConstraint *redHeight = [NSLayoutConstraint

constraintWithItem:redView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:0 constant:200];

//b.添加约束

[self.view addConstraints:@[ redtopConstraint,redLeftConstraint]];

[redView addConstraints:@[ redWith,redHeight]];

//=============绿色视图的约束==============

//左对齐

NSLayoutConstraint *greenAlignLeft = [NSLayoutConstraint

constraintWithItem:greenView attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual toItem:redView attribute:NSLayoutAttributeLeading multiplier:1 constant:0];

//到红色视图底部的距离

NSLayoutConstraint *greenTop = [NSLayoutConstraint

constraintWithItem:greenView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:redView attribute:NSLayoutAttributeBottom multiplier:1 constant:50];

//宽度

NSLayoutConstraint *greenWidth = [NSLayoutConstraint

constraintWithItem:greenView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:redView attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0];

//高度

NSLayoutConstraint *greenHeight = [NSLayoutConstraint

constraintWithItem:greenView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:redView attribute:NSLayoutAttributeHeight multiplier:0.5 constant:0];