Masonry手寫Autolayout專題
Masonry介紹與使用實踐：快速上手Autolayout
http://www.cocoachina.com/ios/20141219/10702.html
1Masonry開發技巧
1.1簡單使用技巧
1.1.1[基礎]居中顯示一個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));
}];
}
代碼效果
使用我之間寫的MMPlaceHolder可以看到superview已經按照我們預期居中并且設置成了適當的大小
那么先看看這幾行代碼
//從此以后基本可以拋棄CGRectMake了
UIView *sv = [UIViewnew];
//在做autoLayout之前一定要先將view添加到superview上否則會報錯
[self.view addSubview:sv];
//mas_makeConstraints就是Masonry的autolayout添加函數將所需的約束添加到block中行了
[sv mas_makeConstraints:^(MASConstraintMaker *make) {
//將sv居中(很容易理解吧?)
make.center.equalTo(ws.view);
//將size設置成(300,300)
make.size.mas_equalTo(CGSizeMake(300, 300));
}];
這里有兩個問題要分解一下
首先在Masonry中能夠添加autolayout約束有三個函數
- (NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *make))block;
- (NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *make))block;
- (NSArray *)mas_remakeConstraints:(void(^)(MASConstraintMaker *make))block;
/*
mas_makeConstraints只負責新增約束Autolayout不能同時存在兩條針對于同一對象的約束否則會報錯
mas_updateConstraints針對上面的情況會更新在block中出現的約束不會導致出現兩個相同約束的情況
mas_remakeConstraints則會清除之前的所有約束僅保留最新的約束
三種函數善加利用就可以應對各種情況了
*/
其次equalTo和mas_equalTo的區別在哪里呢?其實mas_equalTo是一個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只是對其參數進行了一個BOX操作(裝箱) MASBoxValue的定義具體可以看看源代碼太長就不貼出來了
所支持的類型除了NSNumber支持的那些數值類型之外就只支持CGPoint CGSize UIEdgeInsets
介紹完這幾個問題我們就繼續往下了PS:剛才定義的sv會成為我們接下來所有sample的superView
1.1.2[初級]讓一個view略小于其superView(邊距為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));
/*等價于
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);
*/
/*也等價于
make.top.left.bottom.and.right.equalTo(sv).with.insets(UIEdgeInsetsMake(10, 10, 10, 10));
*/
}];
代碼效果
可以看到edges其實就是top,left,bottom,right的一個簡化分開寫也可以一句話更省事
那么為什么bottom和right里的offset是負數呢?因為這里計算的是絕對的數值計算的bottom需要小魚sv的底部高度所以要-10同理用于right
這里有意思的地方是and和with其實這兩個函數什么事情都沒做
- (MASConstraint *)with{
returnself;
}
- (MASConstraint *)and {
returnself;
}
但是用在這種鏈式語法中就非常的巧妙和易懂不得不佩服作者的心思(雖然我現在基本都會省略)
1.1.3[初級]讓兩個高度為150的view垂直居中且等寬且等間隔排列間隔為10(自動計算其寬度)
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);
}];
代碼效果
這里我們在兩個子view之間互相設置的約束可以看到他們的寬度在約束下自動的被計算出來了
1.1.4[中級]在UIScrollView順序排列一些view并自動計算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);
}];
頭部效果
尾部效果
從scrollView的scrollIndicator可以看出scrollView的內部已如我們所想排列好了
這里的關鍵就在于container這個view起到了一個中間層的作用能夠自動的計算uiscrollView的contentSize
1.1.5[高級]橫向或者縱向等間隙的排列一組view
很遺憾autoLayout并沒有直接提供等間隙排列的方法(Masonry的官方demo中也沒有對應的案例)但是參考案例3我們可以通過一個小技巧來實現這個目的為此我寫了一個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
簡單的來測試一下
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];
//給予不同的大小測試效果
[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];
代碼效果
perfect!簡潔明了的達到了我們所要的效果
1.2高級開發技巧
1.2.1更新layout
1.2.1.1mas_updateConstraints
使用Masonry創建constraint來定義布局的方式有三種：mas_makeConstraints，mas_updateConstraints，mas_remakeConstraints。
有時你需要更新constraint(例如，動畫和調試)而不是創建固定constraint，可以使用mas_updateConstraints方法。
1.2.1.2mas_remakeConstraints
mas_remakeConstraints與mas_updateConstraints比較相似，都是更新constraint。不過，mas_remakeConstraints是刪除之前constraint，然后再添加新的constraint(適用于移動動畫)；而mas_updateConstraints只是更新constraint的值。
1.2.1.3代碼示例
[_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常見問題
1.3.1在TableCell單元格中無法使用Masonry
在TableCell中增加子控件時，無法正常使用Masonry來進行布局，可能是Cell重用引起的。
1.3.2使用了Masonry布局的控件最好手動釋放內存，若有APP自動釋放內存，會有延遲，導致頁面布局失敗
//需要手動釋放mas_makeConstraints的內存，若有APP自動釋放內存，會有延遲，導致頁面布局失敗
_loginNameTextField=nil;
_loginVerifyCodeGetButton=nil;
_loginVerifyCodeTextField=nil;
1.3.3盡量直接用equalTo，而不用mas_equalTo
mas_equalTo需要等控件自身布局完成了之后才能調用，而equalTo不需要。因此進行子視圖布局時，用前者容易掛機。
1.3.4使用dispatch_get_main_queue保證布局與后續處理的同步
雖然mas_updateConstraints的block回調是順序執行的，但是布局真正起作用還是放在了main_queue的下一個runloop中執行的，所以如果要在布局完成后順序執行某些處理（例如開始進行自定義繪制或者異步繪制），最好手動放到main_queue的下一個runloop中執行，確保布局完成后才開始執行代碼。
如下是示例代碼：
-(void)draw
{
[selfsetLayout];
//因為Layout庫是異步的，為了保證執行順序上的同步，需要作此處理
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;
});
});
});
}
2參考鏈接
實時顯示iOS編寫UI代碼效果
