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发布时间:2018-08-30 08:50:28   来源:本站编辑   浏览次数:

IOS自动布局


简介

自动布局在iOS 6.0中引入,仅可以支持IOS6.0 及 更高版本。它可以帮助我们创建用于多个种设备的界面。

实例步骤

1.创建一个简单的 View based application

2.修改 ViewController.m 的文件内容,如下所示

#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 NSLayoutConstraint *textFieldTopConstraint = [NSLayoutConstraint constraintWithItem:self.textfield attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:superview 
    attribute:NSLayoutAttributeTop multiplier:1.0 constant:60.0f]; NSLayoutConstraint *textFieldBottomConstraint = [NSLayoutConstraint constraintWithItem:self.textfield attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:self.rightButton 
    attribute:NSLayoutAttributeTop multiplier:0.8 constant:-60.0f]; NSLayoutConstraint *textFieldLeftConstraint = [NSLayoutConstraint constraintWithItem:self.textfield attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:superview attribute: NSLayoutAttributeLeft multiplier:1.0 constant:30.0f]; NSLayoutConstraint *textFieldRightConstraint = [NSLayoutConstraint constraintWithItem:self.textfield attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:superview attribute: NSLayoutAttributeRight multiplier:1.0 constant:-30.0f]; [superview addConstraints:@[textFieldBottomConstraint , textFieldLeftConstraint, textFieldRightConstraint, textFieldTopConstraint]]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } @end

输出

运行应用程序,在 iPhone 模拟器上会有下面的输出结果

autolayoutOutputiPhonePortrait

当我们更改模拟器为横向的方向时,输出结果如下

autolayoutOutputiPhoneLandscape

我们在 iPhone 5 模拟器上运行同一应用程序时,输出结果如下

autolayoutOutputiPhone5Portrait

当我们更改模拟器为横向的方向时,输出结果如下:

autolayoutOutputiPhone5Landscape

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