Masonry手写Autolayout专题
Masonry介绍与使用实践：快速上手Autolayout
http://www.cocoachina.com/ios/20141219/10702.html
1Masonry开发技巧
1.1简单使用技巧
1.1.1[基础]居中显示一个view
- (void)viewDidLoad
{
[superviewDidLoad];
// Do any additional setup after loading the view.
WS(ws);
UIView *sv = [UIViewnew];
[sv showPlaceHolder];
sv.backgroundColor = [UIColor blackColor];
[self.view addSubview:sv];
[sv mas_makeConstraints:^(MASConstraintMaker *make) {
make.center.equalTo(ws.view);
make.size.mas_equalTo(CGSizeMake(300, 300));
}];
}
代码效果
使用我之间写的MMPlaceHolder可以看到superview已经按照我们预期居中并且设置成了适当的大小
那么先看看这几行代码
//从此以后基本可以抛弃CGRectMake了
UIView *sv = [UIViewnew];
//在做autoLayout之前一定要先将view添加到superview上否则会报错
[self.view addSubview:sv];
//mas_makeConstraints就是Masonry的autolayout添加函数将所需的约束添加到block中行了
[sv mas_makeConstraints:^(MASConstraintMaker *make) {
//将sv居中(很容易理解吧?)
make.center.equalTo(ws.view);
//将size设置成(300,300)
make.size.mas_equalTo(CGSizeMake(300, 300));
}];
这里有两个问题要分解一下
首先在Masonry中能够添加autolayout约束有三个函数
- (NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *make))block;
- (NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *make))block;
- (NSArray *)mas_remakeConstraints:(void(^)(MASConstraintMaker *make))block;
/*
mas_makeConstraints只负责新增约束Autolayout不能同时存在两条针对于同一对象的约束否则会报错
mas_updateConstraints针对上面的情况会更新在block中出现的约束不会导致出现两个相同约束的情况
mas_remakeConstraints则会清除之前的所有约束仅保留最新的约束
三种函数善加利用就可以应对各种情况了
*/
其次equalTo和mas_equalTo的区别在哪里呢?其实mas_equalTo是一个MACRO
#define mas_equalTo(...) equalTo(MASBoxValue((__VA_ARGS__)))
#define mas_greaterThanOrEqualTo(...) greaterThanOrEqualTo(MASBoxValue((__VA_ARGS__)))
#define mas_lessThanOrEqualTo(...) lessThanOrEqualTo(MASBoxValue((__VA_ARGS__)))
#define mas_offset(...) valueOffset(MASBoxValue((__VA_ARGS__)))
可以看到mas_equalTo只是对其参数进行了一个BOX操作(装箱) MASBoxValue的定义具体可以看看源代码太长就不贴出来了
所支持的类型除了NSNumber支持的那些数值类型之外就只支持CGPoint CGSize UIEdgeInsets
介绍完这几个问题我们就继续往下了PS:刚才定义的sv会成为我们接下来所有sample的superView
1.1.2[初级]让一个view略小于其superView(边距为10)
UIView *sv1 = [UIViewnew];
[sv1 showPlaceHolder];
sv1.backgroundColor = [UIColor redColor];
[sv addSubview:sv1];
[sv1 mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10));
/*等价于
make.top.equalTo(sv).with.offset(10);
make.left.equalTo(sv).with.offset(10);
make.bottom.equalTo(sv).with.offset(-10);
make.right.equalTo(sv).with.offset(-10);
*/
/*也等价于
make.top.left.bottom.and.right.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10));
*/
}];
代码效果
可以看到edges其实就是top,left,bottom,right的一个简化分开写也可以一句话更省事
那么为什么bottom和right里的offset是负数呢?因为这里计算的是绝对的数值计算的bottom需要小鱼sv的底部高度所以要-10同理用于right
这里有意思的地方是and和with其实这两个函数什么事情都没做
- (MASConstraint *)with{
returnself;
}
- (MASConstraint *)and {
returnself;
}
但是用在这种链式语法中就非常的巧妙和易懂不得不佩服作者的心思(虽然我现在基本都会省略)
1.1.3[初级]让两个高度为150的view垂直居中且等宽且等间隔排列间隔为10(自动计算其宽度)
int padding1 = 10;
[sv2 mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.mas_equalTo(sv.mas_centerY);
make.left.equalTo(sv.mas_left).with.offset(padding1);
make.right.equalTo(sv3.mas_left).with.offset(-padding1);
make.height.mas_equalTo(@150);
make.width.equalTo(sv3);
}];
[sv3 mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.mas_equalTo(sv.mas_centerY);
make.left.equalTo(sv2.mas_right).with.offset(padding1);
make.right.equalTo(sv.mas_right).with.offset(-padding1);
make.height.mas_equalTo(@150);
make.width.equalTo(sv2);
}];
代码效果
这里我们在两个子view之间互相设置的约束可以看到他们的宽度在约束下自动的被计算出来了
1.1.4[中级]在UIScrollView顺序排列一些view并自动计算contentSize
UIScrollView *scrollView = [UIScrollViewnew];
scrollView.backgroundColor = [UIColor whiteColor];
[sv addSubview:scrollView];
[scrollView mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(sv).with.insets(UIEdgeInsetsMake(5,5,5,5));
}];
UIView *container = [UIViewnew];
[scrollView addSubview:container];
[container mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.equalTo(scrollView);
make.width.equalTo(scrollView);
}];
int count = 10;
UIView *lastView = nil;
for( int i = 1 ; i <= count ; ++i )
{
UIView *subv = [UIViewnew];
[container addSubview:subv];
subv.backgroundColor = [UIColor colorWithHue:( arc4random() % 256 / 256.0 )
saturation:( arc4random() % 128 / 256.0 ) + 0.5
brightness:( arc4random() % 128 / 256.0 ) + 0.5
alpha:1];
[subv mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.and.right.equalTo(container);
make.height.mas_equalTo(@(20*i));
if( lastView )
{
make.top.mas_equalTo(lastView.mas_bottom);
}
else
{
make.top.mas_equalTo(container.mas_top);
}
}];
lastView = subv;
}
[container mas_makeConstraints:^(MASConstraintMaker *make) {
make.bottom.equalTo(lastView.mas_bottom);
}];
头部效果
尾部效果
从scrollView的scrollIndicator可以看出scrollView的内部已如我们所想排列好了
这里的关键就在于container这个view起到了一个中间层的作用能够自动的计算uiscrollView的contentSize
1.1.5[高级]横向或者纵向等间隙的排列一组view
很遗憾autoLayout并没有直接提供等间隙排列的方法(Masonry的官方demo中也没有对应的案例)但是参考案例3我们可以通过一个小技巧来实现这个目的为此我写了一个Category
@implementation UIView(Masonry_LJC)
- (void) distributeSpacingHorizontallyWith:(NSArray*)views
{
NSMutableArray *spaces = [NSMutableArray arrayWithCapacity:views.count+1];
for( int i = 0 ; i < views.count+1 ; ++i )
{
UIView *v = [UIViewnew];
[spaces addObject:v];
[self addSubview:v];
[v mas_makeConstraints:^(MASConstraintMaker *make) {
make.width.equalTo(v.mas_height);
}];
}
UIView *v0 = spaces[0];
__weak __typeof(&*self)ws = self;
[v0 mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.equalTo(ws.mas_left);
make.centerY.equalTo(((UIView*)views[0]).mas_centerY);
}];
UIView *lastSpace = v0;
for( int i = 0 ; i < views.count; ++i )
{
UIView *obj = views[i];
UIView *space = spaces[i+1];
[obj mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.equalTo(lastSpace.mas_right);
}];
[space mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.equalTo(obj.mas_right);
make.centerY.equalTo(obj.mas_centerY);
make.width.equalTo(v0);
}];
lastSpace = space;
}
[lastSpace mas_makeConstraints:^(MASConstraintMaker *make) {
make.right.equalTo(ws.mas_right);
}];
}
- (void) distributeSpacingVerticallyWith:(NSArray*)views
{
NSMutableArray *spaces = [NSMutableArray arrayWithCapacity:views.count+1];
for( int i = 0 ; i < views.count+1 ; ++i )
{
UIView *v = [UIViewnew];
[spaces addObject:v];
[self addSubview:v];
[v mas_makeConstraints:^(MASConstraintMaker *make) {
make.width.equalTo(v.mas_height);
}];
}
UIView *v0 = spaces[0];
__weak __typeof(&*self)ws = self;
[v0 mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(ws.mas_top);
make.centerX.equalTo(((UIView*)views[0]).mas_centerX);
}];
UIView *lastSpace = v0;
for( int i = 0 ; i < views.count; ++i )
{
UIView *obj = views[i];
UIView *space = spaces[i+1];
[obj mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(lastSpace.mas_bottom);
}];
[space mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(obj.mas_bottom);
make.centerX.equalTo(obj.mas_centerX);
make.height.equalTo(v0);
}];
lastSpace = space;
}
[lastSpace mas_makeConstraints:^(MASConstraintMaker *make) {
make.bottom.equalTo(ws.mas_bottom);
}];
}
@end
简单的来测试一下
UIView *sv11 = [UIViewnew];
UIView *sv12 = [UIViewnew];
UIView *sv13 = [UIViewnew];
UIView *sv21 = [UIViewnew];
UIView *sv31 = [UIViewnew];
sv11.backgroundColor = [UIColor redColor];
sv12.backgroundColor = [UIColor redColor];
sv13.backgroundColor = [UIColor redColor];
sv21.backgroundColor = [UIColor redColor];
sv31.backgroundColor = [UIColor redColor];
[sv addSubview:sv11];
[sv addSubview:sv12];
[sv addSubview:sv13];
[sv addSubview:sv21];
[sv addSubview:sv31];
//给予不同的大小测试效果
[sv11 mas_makeConstraints:^(MASConstraintMaker *make) {
make.centerY.equalTo(@[sv12,sv13]);
make.centerX.equalTo(@[sv21,sv31]);
make.size.mas_equalTo(CGSizeMake(40, 40));
}];
[sv12 mas_makeConstraints:^(MASConstraintMaker *make) {
make.size.mas_equalTo(CGSizeMake(70, 20));
}];
[sv13 mas_makeConstraints:^(MASConstraintMaker *make) {
make.size.mas_equalTo(CGSizeMake(50, 50));
}];
[sv21 mas_makeConstraints:^(MASConstraintMaker *make) {
make.size.mas_equalTo(CGSizeMake(50, 20));
}];
[sv31 mas_makeConstraints:^(MASConstraintMaker *make) {
make.size.mas_equalTo(CGSizeMake(40, 60));
}];
[sv distributeSpacingHorizontallyWith:@[sv11,sv12,sv13]];
[sv distributeSpacingVerticallyWith:@[sv11,sv21,sv31]];
[sv showPlaceHolderWithAllSubviews];
[sv hidePlaceHolder];
代码效果
perfect!简洁明了的达到了我们所要的效果
1.2高级开发技巧
1.2.1更新layout
1.2.1.1mas_updateConstraints
使用Masonry创建constraint来定义布局的方式有三种：mas_makeConstraints，mas_updateConstraints，mas_remakeConstraints。
有时你需要更新constraint(例如，动画和调试)而不是创建固定constraint，可以使用mas_updateConstraints方法。
1.2.1.2mas_remakeConstraints
mas_remakeConstraints与mas_updateConstraints比较相似，都是更新constraint。不过，mas_remakeConstraints是删除之前constraint，然后再添加新的constraint(适用于移动动画)；而mas_updateConstraints只是更新constraint的值。
1.2.1.3代码示例
[_loginButtonmas_remakeConstraints:^(MASConstraintMaker*make) {
make.width.equalTo(weakSelf.loginNameTextField.mas_width);
make.height.equalTo(weakSelf.loginNameTextField.mas_height);
make.centerX.mas_equalTo(weakSelf.loginContainerView.mas_centerX);
if(_loginVerifyImageCodeTextField) {
make.top.equalTo(weakSelf.loginVerifyImageCodeTextField.mas_bottom).with.offset(20);
}
}];
[_loginDescLabelmas_updateConstraints:^(MASConstraintMaker*make) {
make.top.equalTo(weakSelf.loginButton.mas_bottom).with.offset(5);
}];
1.3常见问题
1.3.1在TableCell单元格中无法使用Masonry
在TableCell中增加子控件时，无法正常使用Masonry来进行布局，可能是Cell重用引起的。
1.3.2使用了Masonry布局的控件最好手动释放内存，若有APP自动释放内存，会有延迟，导致页面布局失败
//需要手动释放mas_makeConstraints的内存，若有APP自动释放内存，会有延迟，导致页面布局失败
_loginNameTextField=nil;
_loginVerifyCodeGetButton=nil;
_loginVerifyCodeTextField=nil;
1.3.3尽量直接用equalTo，而不用mas_equalTo
mas_equalTo需要等控件自身布局完成了之后才能调用，而equalTo不需要。因此进行子视图布局时，用前者容易挂机。
1.3.4使用dispatch_get_main_queue保证布局与后续处理的同步
虽然mas_updateConstraints的block回调是顺序执行的，但是布局真正起作用还是放在了main_queue的下一个runloop中执行的，所以如果要在布局完成后顺序执行某些处理（例如开始进行自定义绘制或者异步绘制），最好手动放到main_queue的下一个runloop中执行，确保布局完成后才开始执行代码。
如下是示例代码：
-(void)draw
{
[selfsetLayout];
//因为Layout库是异步的，为了保证执行顺序上的同步，需要作此处理
dispatch_async(dispatch_get_main_queue(), ^{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^{
CGRectdrawFrame =CGRectMake(0,0,SCREEN_BOUNDS.size.width,_headerHeight);
UIGraphicsBeginImageContextWithOptions(drawFrame.size,YES,0);
CGContextRefcontext =UIGraphicsGetCurrentContext();
if(!context) {
return;
}
[[UIColorwhiteColor]set];
CGContextFillRect(context,drawFrame);
[_separationLineViewdrawRect:CGRectMake(0,0,
drawFrame.size.width,_lineHeight)];
[_iconButtondrawRect:_iconButton.frame];
[_nameButtondrawRect:_nameButton.frame];
[_postDateLabeldrawRect:_postDateLabel.frame];
UIImage*tempImage =UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
dispatch_async(dispatch_get_main_queue(),^{
//_postContentTextImageView.frame= _postContentTextView.frame;//textViewRect;//
[_iconButtonsetHidden:NO];
[_nameButtonsetHidden:NO];
[_postDateLabelsetHidden:NO];
_bgImageView.image=nil;
_bgImageView.image=tempImage;
});
});
});
}
2参考链接
实时显示iOS编写UI代码效果
