IOS頁面自動佈局之 NSLayoutConstraint基礎篇

時間 2019-12-12

標籤 ios 頁面自動佈局 nslayoutconstraint 基礎欄目 iOS 简体版

原文原文鏈接

使用AutoLayout以前須要知道如下兩點：ios

1.必須設置 translatesAutoresizingMaskIntoConstraints爲NO。ide

2.若是是viewControl則AutoLayout適配寫在[- updateViewConstraints]中；this

若是是view則AutoLayout適配寫在[- updateConstraints]中。spa

1、要講解的方法:code

 1 /* Create constraints explicitly.  Constraints are of the form "view1.attr1 = view2.attr2 * multiplier + constant" 
 2  If your equation does not have a second view and attribute, use nil and NSLayoutAttributeNotAnAttribute.
 3  */
 4 +(instancetype)constraintWithItem:(id)view1 
 5                         attribute:(NSLayoutAttribute)attr1 
 6                         relatedBy:(NSLayoutRelation)relation 
 7                            toItem:(id)view2
 8                         attribute:(NSLayoutAttribute)attr2 
 9                        multiplier:(CGFloat)multiplier 
10                          constant:(CGFloat)c;

參數說明：orm

第一個參數 view1: 要設置的視圖；blog

第二個參數 attr1: view1要設置的屬性，稍後詳解；ip

第三個參數 relation: 視圖view1和view2的指定屬性之間的關係，稍後詳解；ci

第四個參數 view2: 參照的視圖；rem

第五個參數 attr2: 參照視圖view2的屬性，稍後詳解；

第六個參數 multiplier: 視圖view1的指定屬性是參照視圖view2制定屬性的多少倍；

第七個參數 c: 視圖view1的指定屬性須要加的浮點數。

根據參數的講解，得出計算公式以下：

view1.attr1 [= , >= , <=] view2.attr2 * multiplier + c;

參數詳解：

一、NSLayoutAttribute

 1 typedef NS_ENUM(NSInteger, NSLayoutAttribute) {
 2     NSLayoutAttributeLeft = 1, 
 3     NSLayoutAttributeRight,
 4     NSLayoutAttributeTop,
 5     NSLayoutAttributeBottom,
 6     NSLayoutAttributeLeading,
 7     NSLayoutAttributeTrailing,
 8     NSLayoutAttributeWidth,
 9     NSLayoutAttributeHeight,
10     NSLayoutAttributeCenterX,
11     NSLayoutAttributeCenterY,
12     NSLayoutAttributeBaseline,
13     NSLayoutAttributeLastBaseline = NSLayoutAttributeBaseline,
14     NSLayoutAttributeFirstBaseline NS_ENUM_AVAILABLE_IOS(8_0),
15     
16     
17     NSLayoutAttributeLeftMargin NS_ENUM_AVAILABLE_IOS(8_0),
18     NSLayoutAttributeRightMargin NS_ENUM_AVAILABLE_IOS(8_0),
19     NSLayoutAttributeTopMargin NS_ENUM_AVAILABLE_IOS(8_0),
20     NSLayoutAttributeBottomMargin NS_ENUM_AVAILABLE_IOS(8_0),
21     NSLayoutAttributeLeadingMargin NS_ENUM_AVAILABLE_IOS(8_0),
22     NSLayoutAttributeTrailingMargin NS_ENUM_AVAILABLE_IOS(8_0),
23     NSLayoutAttributeCenterXWithinMargins NS_ENUM_AVAILABLE_IOS(8_0),
24     NSLayoutAttributeCenterYWithinMargins NS_ENUM_AVAILABLE_IOS(8_0),
25     
26     NSLayoutAttributeNotAnAttribute = 0
27 };

分三部分解釋 NSLayoutAttribute

第一部分：經常使用的

NSLayoutAttributeLeft: CGRectGetMinX(view.frame);

NSLayoutAttributeRight: CGRectGetMaxX(view.frame);

NSLayoutAttributeTop: CGRectGetMinY(view.frame);

NSLayoutAttributeBottom: CGRectGetMinY(view.frame);

NSLayoutAttributeWidth: CGRectGetWidth(view.frame);

NSLayoutAttributeHeight: CGRectGetHeight(view.frame);

NSLayoutAttributeCenterX: view.center.x;

NSLayoutAttributeCenterY:view.center.y ;

NSLayoutAttributeBaseline: 文本底標線，在大多數視圖中等同於NSLayoutAttributeBottom；在少數視圖，如UILabel，是指字母的底部出現的位置;

NSLayoutAttributeLastBaseline: 至關於NSLayoutAttributeBaseline;

NSLayoutAttributeFirstBaseline: 文本上標線;

NSLayoutAttributeNotAnAttribute: None;

第二部分：根據國家使用習慣不一樣表示的意思不一樣

NSLayoutAttributeLeading: 在習慣由左向右看的地區，至關於NSLayoutAttributeLeft；在習慣從右至左看的地區，至關於NSLayoutAttributeRight;

NSLayoutAttributeTrailing: 在習慣由左向右看的地區，至關於NSLayoutAttributeRight；在習慣從右至左看的地區，至關於NSLayoutAttributeLeft;

第三部分：ios8新增屬性，各類間距，具體用法下節介紹

NSLayoutAttributeLeftMargin，

NSLayoutAttributeRightMargin，

NSLayoutAttributeTopMargin，

NSLayoutAttributeBottomMargin，

NSLayoutAttributeLeadingMargin，

NSLayoutAttributeTrailingMargin，

NSLayoutAttributeCenterXWithinMargins，

NSLayoutAttributeCenterYWithinMargins，

從網上找了一張圖，標註以上屬性

二、NSLayoutRelation

1 typedef NS_ENUM(NSInteger, NSLayoutRelation) {
2     NSLayoutRelationLessThanOrEqual = -1,
3     NSLayoutRelationEqual = 0,
4     NSLayoutRelationGreaterThanOrEqual = 1,
5 };

NSLayoutRelationLessThanOrEqual: <=;

NSLayoutRelationEqual: =;

NSLayoutRelationGreaterThanOrEqual: >=;

2、要講解的方法

一、獲取當前view中全部的 NSLayoutConstraint

1 - (NSArray *)constraints NS_AVAILABLE_IOS(6_0);

二、舊版方法，將指定的NSLayoutConstraint添加到頁面或者從頁面中移除

1 1 - (void)addConstraint:(NSLayoutConstraint *)constraint NS_AVAILABLE_IOS(6_0); // This method will be deprecated in a future release and should be avoided.  Instead, set NSLayoutConstraint's active property to YES.
2 2 - (void)addConstraints:(NSArray *)constraints NS_AVAILABLE_IOS(6_0); // This method will be deprecated in a future release and should be avoided.  Instead use +[NSLayoutConstraint activateConstraints:].
3 3 - (void)removeConstraint:(NSLayoutConstraint *)constraint NS_AVAILABLE_IOS(6_0); // This method will be deprecated in a future release and should be avoided.  Instead set NSLayoutConstraint's active property to NO.
4 4 - (void)removeConstraints:(NSArray *)constraints NS_AVAILABLE_IOS(6_0); // This method will be deprecated in a future release and should be avoided.  Instead use +[NSLayoutConstraint deactivateConstraints:].

三、ios8新加方法，激活或者停用指定約束

1 /* The receiver may be activated or deactivated by manipulating this property.  Only active constraints affect the calculated layout.  Attempting to activate a constraint whose items have no common ancestor will cause an exception to be thrown.  Defaults to NO for newly created constraints. */
2 @property (getter=isActive) BOOL active NS_AVAILABLE(10_10, 8_0);
3 
4 /* Convenience method that activates each constraint in the contained array, in the same manner as setting active=YES. This is often more efficient than activating each constraint individually. */
5 + (void)activateConstraints:(NSArray *)constraints NS_AVAILABLE(10_10, 8_0);
6 
7 /* Convenience method that deactivates each constraint in the contained array, in the same manner as setting active=NO. This is often more efficient than deactivating each constraint individually. */
8 + (void)deactivateConstraints:(NSArray *)constraints NS_AVAILABLE(10_10, 8_0);

3、Coding Time

a> 設置視圖view1爲寬度=20的正方形

兩種寫法，第一種寬度=20，高度=20

1     [self addConstraint:[NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:20]];
2     [self addConstraint:[NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:20]];

第二種寬度=20，高度=寬度

1     [self addConstraint:[NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:20]];
2     [self addConstraint:[NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:view1 attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0]];

第二種方法的優點是，若是想修改view1的大小，只須要修改一處。

b>設置視圖view1.frame.origin.x = 視圖view2.frame.origin.x

NSLayoutConstraint *leftConstraint = [NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:view2 attribute:NSLayoutAttributeLeft multiplier:1.0 constant:0]；

//舊版方法
//[self addConstraint:leftConstraint];

//新版方法1
[NSLayoutConstraint activateConstraints:@[leftConstraint]]; 
//新版方法2
leftConstraint.active = YES;