關于iOS布局自動iPhone6之后就是AutoLayOut，AutoLayOut固然非常好用，不過有時候我們需要在頁面手動進行頁面布局，VFL算是一種選擇，而且VFL不復雜，理解起來很容易，實際開發中用的特別熟還好，要是第一次看估計要花點功夫才能搞定。Masonry算是VFL的簡化版，用的人比較多，之前項目中用過一次，對手動寫頁面的開發來說算是福利。
基礎知識
首先我們看一個常見的問題將一個子View放在的UIViewController的某個位置，通過設置邊距來實現，效果如下:
如果通過VFL我們代碼會是這樣的:
UIView *superview = self.view; UIView *view1 = [[UIView alloc] init];view1.translatesAutoresizingMaskIntoConstraints = NO;view1.backgroundColor = [UIColor redColor];[superview addSubview:view1]; UIEdgeInsets padding = UIEdgeInsetsMake(200, 50, 200, 50); [superview addConstraints:@[ //約束 [NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeTop multiplier:1.0 constant:padding.top], [NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeLeft multiplier:1.0 constant:padding.left], [NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeBottom multiplier:1.0 constant:-padding.bottom], [NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:superview attribute:NSLayoutAttributeRight multiplier:1 constant:-padding.right], ]];
只是簡單的設置了一個邊距，如果視圖的關系比較復雜，維護起來會是一個很痛苦的事情，我們看一下Masonry是如何實現的，導入Masonry.h頭文件，約束的代碼:
UIView *childView=[UIView new];[childView setBackgroundColor:[UIColor redColor]];//先將子View加入在父視圖中[self.view addSubview:childView];__weak typeof(self) weakSelf = self;UIEdgeInsets padding = UIEdgeInsetsMake(200, 50, 200, 50);[childView mas_makeConstraints:^(MASConstraintMaker *make) { make.edges.equalTo(weakSelf.view).with.insets(padding);}];通過mas_makeConstraints設置邊距有種鳥槍換炮的感覺，我們即將開啟一段新的旅程，可以緊接著看下面比較實用的功能~
實用知識
1.View設置大小
UIView *childView=[UIView new];[childView setBackgroundColor:[UIColor redColor]];//先將子View加入在父視圖中[self.view addSubview:childView];__weak typeof(self) weakSelf = self;[childView mas_makeConstraints:^(MASConstraintMaker *make) { //設置大小 make.size.mas_equalTo(CGSizeMake(100, 100)); //居中 make.center.equalTo(weakSelf.view);}];效果如下:
這里友情其實一個小內容，目前我們設置約束都是通過mas_makeConstraints用來創建約束,mas_updateConstraints用來更新約束，mas_remakeConstraints重置約束，清除之前的約束，保留最新的約束,如果想深入解釋下，可以閱讀下面的英文解釋~
/** * Creates a MASConstraintMaker with the callee view. * Any constraints defined are added to the view or the appropriate superview once the block has finished executing * * @param block scope within which you can build up the constraints which you wish to apply to the view. * * @return Array of created MASConstraints */- (NSArray *)mas_makeConstraints:(void(^)(MASConstraintMaker *make))block; /** * Creates a MASConstraintMaker with the callee view. * Any constraints defined are added to the view or the appropriate superview once the block has finished executing. * If an existing constraint exists then it will be updated instead. * * @param block scope within which you can build up the constraints which you wish to apply to the view. * * @return Array of created/updated MASConstraints */- (NSArray *)mas_updateConstraints:(void(^)(MASConstraintMaker *make))block; /** * Creates a MASConstraintMaker with the callee view. * Any constraints defined are added to the view or the appropriate superview once the block has finished executing. * All constraints previously installed for the view will be removed. * * @param block scope within which you can build up the constraints which you wish to apply to the view. * * @return Array of created/updated MASConstraints */- (NSArray *)mas_remakeConstraints:(void(^)(MASConstraintMaker *make))block;
2.設置高度，這里設置左右邊距，因此不設置寬度，如果想單獨設置width可參考高度的設置方式:
UIView *childView=[UIView new];[childView setBackgroundColor:[UIColor greenColor]];//先將子View加入在父視圖中[self.view addSubview:childView];__weak typeof(self) weakSelf = self;[childView mas_makeConstraints:^(MASConstraintMaker *make) { //距離頂部44 make.top.equalTo(weakSelf.view.mas_top).with.offset(44); //距離左邊30 make.left.equalTo(weakSelf.view.mas_left).with.offset(30); //距離右邊30，注意是負數 make.right.equalTo(weakSelf.view.mas_right).with.offset(-30); //高度150 make.height.mas_equalTo(@150);}];
3.子視圖之間的位置設置:
UIView *childView=[UIView new];[childView setBackgroundColor:[UIColor greenColor]];//先將子View加入在父視圖中[self.view addSubview:childView];__weak typeof(self) weakSelf = self;[childView mas_makeConstraints:^(MASConstraintMaker *make) { //距離頂部44 make.top.equalTo(weakSelf.view.mas_top).with.offset(44); //距離左邊30 make.left.equalTo(weakSelf.view.mas_left).with.offset(30); //距離右邊30，注意是負數 make.right.equalTo(weakSelf.view.mas_right).with.offset(-30); //高度150 make.height.mas_equalTo(@150);}];//地址:http://www.cnblogs.com/xiaofeixiang/UIView *nextView=[UIView new];[nextView setBackgroundColor:[UIColor redColor]];[self.view addSubview:nextView];[nextView mas_makeConstraints:^(MASConstraintMaker *make) { make.top.equalTo(childView.mas_bottom).with.offset(30); make.right.equalTo(childView.mas_right).with.offset(-30); make.width.mas_equalTo(@100); make.height.mas_equalTo(@100);}];
4.鏈式寫法，算是一個便利的寫法:
UIView *childView=[UIView new]; [childView setBackgroundColor:[UIColor greenColor]]; //先將子View加入在父視圖中 [self.view addSubview:childView]; __weak typeof(self) weakSelf = self; [childView mas_makeConstraints:^(MASConstraintMaker *make) { make.top.and.left.mas_equalTo(weakSelf.view).with.offset(100); make.bottom.and.right.mas_equalTo(weakSelf.view).with.offset(-100); //第二種寫法更簡單，相對于就是父視圖// make.top.and.left.mas_equalTo(100);// make.bottom.and.right.mas_equalTo(-100); }]; UILabel *label=[UILabel new]; [label setText:@"博客園-FlyElephant"]; [label setTextColor:[UIColor redColor]]; [label setTextAlignment:NSTextAlignmentCenter]; [self.view addSubview:label]; [label mas_makeConstraints:^(MASConstraintMaker *make) { make.left.mas_equalTo(weakSelf.view).with.offset(10); make.height.mas_equalTo(20); make.right.mas_equalTo(weakSelf.view).with.offset(-10); make.bottom.mas_equalTo(weakSelf.view).with.offset(-50); }];
網上關于Masonry的教程很多，給的例子的也很多，這幾種情況基本上滿足了開發中的需求，不會有太多的出入，算是一個簡易版的教程，Masonry的中屬性和iOS中的屬性是有對應的關系，不過因為很簡單，基本上沒怎么看，下圖是一個對照關系:
總結：
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疑難解答
