IOS - 自動(dòng)布局

簡(jiǎn)介

在 iOS 6.0中引入的自動(dòng)布局，我們只能支持6.0和更高的部署目標(biāo)。它可以幫助我們創(chuàng)建接口，可用于多個(gè)方向和多個(gè)設(shè)備。

我們例子的目標(biāo)

我們將添加兩個(gè)按鈕，將屏幕的中心一定距離放置。我們也將嘗試將放置有一定距離，從上面的按鈕，添加一個(gè)可調(diào)整大小的文本字段。

我們的方案

我們將添加文本字段和兩個(gè)按鈕的代碼，隨著它們的約束。每個(gè)UI元素的約束將被創(chuàng)建并添加超級(jí)視圖，并為我們添加的每一個(gè)UI元素，以獲得所需的結(jié)果，我們將關(guān)閉自動(dòng)調(diào)整大小。

涉及的步驟

1. 創(chuàng)建一個(gè)簡(jiǎn)單的應(yīng)用程序。

2.我們將只修改 ViewController.m 的文件內(nèi)容，它是如下：

#import "ViewController.h"
@interface ViewController ()
@property (nonatomic, strong) UIButton *leftButton;
@property (nonatomic, strong) UIButton *rightButton;
@property (nonatomic, strong) UITextField *textfield;

@end
@implementation ViewController

- (void)viewDidLoad{
    [super viewDidLoad];
    UIView *superview = self.view;
    /*1. Create leftButton and add to our view*/
    self.leftButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    self.leftButton.translatesAutoresizingMaskIntoConstraints = NO;
    [self.leftButton setTitle:@"LeftButton" forState:UIControlStateNormal];
    [self.view addSubview:self.leftButton];    
    /* 2. Constraint to position LeftButton's X*/
    NSLayoutConstraint *leftButtonXConstraint = [NSLayoutConstraint 
    constraintWithItem:self.leftButton attribute:NSLayoutAttributeCenterX 
    relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:superview attribute:
    NSLayoutAttributeCenterX multiplier:1.0 constant:-60.0f];
    /* 3. Constraint to position LeftButton's Y*/
    NSLayoutConstraint *leftButtonYConstraint = [NSLayoutConstraint 
    constraintWithItem:self.leftButton attribute:NSLayoutAttributeCenterY 
    relatedBy:NSLayoutRelationEqual toItem:superview attribute:
    NSLayoutAttributeCenterY multiplier:1.0f constant:0.0f];   
    /* 4. Add the constraints to button's superview*/
    [superview addConstraints:@[ leftButtonXConstraint,
    leftButtonYConstraint]];    
    /*5. Create rightButton and add to our view*/
    self.rightButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    self.rightButton.translatesAutoresizingMaskIntoConstraints = NO;
    [self.rightButton setTitle:@"RightButton" forState:UIControlStateNormal];
    [self.view addSubview:self.rightButton];    
    /*6. Constraint to position RightButton's X*/
    NSLayoutConstraint *rightButtonXConstraint = [NSLayoutConstraint 
    constraintWithItem:self.rightButton attribute:NSLayoutAttributeCenterX 
    relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:superview attribute:
    NSLayoutAttributeCenterX multiplier:1.0 constant:60.0f];
    /*7. Constraint to position RightButton's Y*/
    rightButtonXConstraint.priority = UILayoutPriorityDefaultHigh;
    NSLayoutConstraint *centerYMyConstraint = [NSLayoutConstraint 
    constraintWithItem:self.rightButton attribute:NSLayoutAttributeCenterY 
    relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:superview attribute:
    NSLayoutAttributeCenterY multiplier:1.0f constant:0.0f];
    [superview addConstraints:@[centerYMyConstraint,
    rightButtonXConstraint]];
   //8. Add Text field
    self.textfield = [[UITextField alloc]initWithFrame:
    CGRectMake(0, 100, 100, 30)];
    self.textfield.borderStyle = UITextBorderStyleRoundedRect;
    self.textfield.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:self.textfield];
    //9. Text field Constraints
    NSLayoutConstrai