码迷,mamicode.com
首页 > 其他好文 > 详细

AutoLayout

时间:2016-05-06 19:09:20      阅读:182      评论:0      收藏:0      [点我收藏+]

标签:

随着iPhone设备出现了不同的尺寸,iOS6.0以后storyboard和xib文件新增了一个Use Auto Layout选项,用来实现自动布局。当你勾选上这个选项,以前传统的布局方式将不能正常工作。一旦使用了自动布局,就要忘记 Frame 的概念!

要判断UIView是否可以使用自动布局,可以使用如下方法:

技术分享
if ([self.view respondsToSelector:@selector(addConstraints:)])
{
    //自动布局
}
else
{
    //传统布局
}
技术分享

可以通过-layoutIfNeeded和-setNeedsUpdateConstraints两个方法来刷新约束的改变,使UIView重新布局。layoutIfNeeded是调整布局,也就是view的位置,一般是对subviews作用。setNeedsDisplay涉及到redraw,也就是重绘,一般都是对receiver作用。

layoutIfNeeded

使用此方法强制立即进行layout,从当前view开始,此方法会遍历整个view层次(包括superviews)请求layout。因此,调用此方法会强制整个view层次布局。

setNeedsUpdateConstraints

当一个自定义view的某个属性发生改变,并且可能影响到constraint时,需要调用此方法去标记constraints需要在未来的某个点更新,系统然后调用updateConstraints.

添加约束一般要遵循下面的规则:

  • 对于两个同层级view之间的约束关系,添加到他们的父view上:
    技术分享

  • 对于两个不同层级view之间的约束关系,添加到他们最近的共同父view上:
    技术分享

  • 对于有层次关系的两个view之间的约束关系,添加到层次较高的父view上:
    技术分享

 

下面的例子演示了通过设定控件边界距离,从而确定控件尺寸:

技术分享
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:@"测试按钮" forState:UIControlStateNormal];
[button sizeToFit];
[button setBackgroundColor:[UIColor yellowColor]];
button.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:button];

NSLayoutConstraint *constraint;

//上边距
constraint = [NSLayoutConstraint
              constraintWithItem:button
              attribute:NSLayoutAttributeTop
              relatedBy:NSLayoutRelationEqual
              toItem:self.view
              attribute:NSLayoutAttributeTop
              multiplier:1.0f
              constant:50.0f];
[self.view addConstraint:constraint];

//左边距
constraint = [NSLayoutConstraint
              constraintWithItem:button
              attribute:NSLayoutAttributeLeading
              relatedBy:NSLayoutRelationEqual
              toItem:self.view
              attribute:NSLayoutAttributeLeading
              multiplier:1.0f
              constant:100.0f];
[self.view addConstraint:constraint];

//右边距
constraint = [NSLayoutConstraint
              constraintWithItem:button
              attribute:NSLayoutAttributeTrailing
              relatedBy:NSLayoutRelationEqual
              toItem:self.view
              attribute:NSLayoutAttributeTrailing
              multiplier:1.0f
              constant:-100.0f];
[self.view addConstraint:constraint];

//下边距
constraint = [NSLayoutConstraint
              constraintWithItem:button
              attribute:NSLayoutAttributeBottom
              relatedBy:NSLayoutRelationEqual
              toItem:self.view
              attribute:NSLayoutAttributeBottom
              multiplier:1.0f
              constant:-350.0f];
[self.view addConstraint:constraint];
技术分享

 

下面的例子设定了控件在父容器中水平垂直居中:

技术分享
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:@"测试按钮" forState:UIControlStateNormal];
[button sizeToFit];
[button setBackgroundColor:[UIColor yellowColor]];
button.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:button];

NSLayoutConstraint *constraint;

//水平居中
constraint = [NSLayoutConstraint
              constraintWithItem:button
              attribute:NSLayoutAttributeCenterX
              relatedBy:NSLayoutRelationEqual
              toItem:self.view
              attribute:NSLayoutAttributeCenterX
              multiplier:1.0f
              constant:0.0f];
[self.view addConstraint:constraint];

//垂直居中
constraint = [NSLayoutConstraint
              constraintWithItem:button
              attribute:NSLayoutAttributeCenterY
              relatedBy:NSLayoutRelationEqual
              toItem:self.view
              attribute:NSLayoutAttributeCenterY
              multiplier:1.0f
              constant:0.0f];
[self.view addConstraint:constraint];
技术分享

 

下面的例子直接设定了控件的尺寸:

技术分享
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:@"测试按钮" forState:UIControlStateNormal];
[button sizeToFit];
[button setBackgroundColor:[UIColor yellowColor]];
button.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:button];

NSLayoutConstraint *constraint;

//设置宽度
constraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:130.0f];
[self.view addConstraint:constraint];

//设置高度
constraint = [NSLayoutConstraint constraintWithItem:button attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:70.0f];
[self.view addConstraint:constraint];
技术分享

 

除了上面添加约束的方法,还有一种全新的方法:Visual Format Language(可视格式语言),这种语言是对视觉描述的一种抽象。基本用法如下:

技术分享
UIButton *buttonA = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[buttonA setTitle:@"AAA" forState:UIControlStateNormal];
[buttonA sizeToFit];
[buttonA setBackgroundColor:[UIColor yellowColor]];
buttonA.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:buttonA];

UIButton *buttonB = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[buttonB setTitle:@"BBB" forState:UIControlStateNormal];
[buttonB sizeToFit];
[buttonB setBackgroundColor:[UIColor yellowColor]];
buttonB.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:buttonB];


NSMutableArray *array = [NSMutableArray array];

//水平方向布局(从左向右)
[array addObjectsFromArray:[NSLayoutConstraint
                            constraintsWithVisualFormat:@"|-60-[buttonA(==90)]-30-[buttonB]"
                            options:NSLayoutFormatDirectionLeadingToTrailing
                            metrics:nil
                            views:NSDictionaryOfVariableBindings(buttonA,buttonB)]];

//垂直方向布局(从上向下)
[array addObjectsFromArray:[NSLayoutConstraint
                            constraintsWithVisualFormat:@"V:|-100-[buttonB]-50-[buttonA]"
                            options:NSLayoutFormatDirectionLeadingToTrailing
                            metrics:nil
                            views:NSDictionaryOfVariableBindings(buttonA,buttonB)]];

[self.view addConstraints:array];
技术分享

 

constraintsWithVisualFormat方法的最后一个参数views需要提供一个字典,用来指明可视化字符串里出现控件名所对应的控件:

技术分享
NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(buttonA,buttonB);

for(NSString *key in viewsDictionary)
{
    NSLog(@"key:%@, value:%@",key,viewsDictionary[key]);
}
//key:buttonA, value:<UIButton: 0x8dc5850; frame = (0 0; 30 30); opaque = NO; layer = <CALayer: 0x8dc7270>>
//key:buttonB, value:<UIButton: 0x8dc8a90; frame = (0 0; 32 30); opaque = NO; layer = <CALayer: 0x8dc8b80>>
技术分享

 

下面是两个具有代表性的语句示例:

@"|-50-[buttonA(80@100)]-[buttonB(90@200)]-50-|"

这条语句的含义是:“左右边距都为50,中间有两个按钮,相隔缺省宽度,一个控件宽度为80,约束优先级为100;另一个控件宽度为90,约束优先级为200”。实际运行后,发现buttonB的控件宽度为90,而buttonA的宽度为自适应宽度,并不是80像素;这是因为buttonB的约束优先级200大于buttonA的约束优先级,所以优先生效。可以把buttonA的优先级改的比buttonB大,就可以看到完全相反的结果。

 

@"V:[buttonA(80)]-20-[buttonB(==buttonA)]"

这条语句的含义是:“垂直方向有一个高度为80的buttonA,然后间隔20有一个和buttonA同样高度的buttonB”

P.s. NSLayoutAttributeLeft/NSLayoutAttributeRight 和 NSLayoutAttributeLeading/NSLayoutAttributeTrailing的区别是left/right永远是指左右,而leading/trailing在某些从右至左习惯的地区会变成,leading是右边,trailing是左边。

AutoLayout

标签:

原文地址:http://www.cnblogs.com/AntonyGu/p/5466621.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!