用Maonry如何实现UIScrollView

一，使用UIScrollView 与其他View 布局不同的地方在于，

ScrollView的高度/宽度不固定；

ScrollView的高度和宽度由其内容决定（即 Scroll View 的 contentSize 所决定）；

内容的大小不能依赖于Scrollview；

二，网上使用Xib/StoryBoard的做法太多，自行百度就是。

如何使用Masonry实现UIScrollView，参考见：

Masonry介绍与使用实践：快速上手Autolayout

做法：1，新建一个container View，其他子View都添加到container View上。

    _bottomChannelsView = [[UIScrollView  alloc]init];
    [_bottomChannelsView setScrollEnabled:YES];
    //_bottomChannelsView.scrollEnabled = YES;
    [self  addSubview:_bottomChannelsView];
    
     container = [UIView new];
    [_bottomChannelsView addSubview:container];

2，设置布局方法：

需要注意的是，container View的subView的constraints都必须依赖container，依赖scrollview和其他的view都不能达到想要的效果。

-(void)setBottomLayout
{
    if (self.bottomView.count<=0) {
        return;
    }

    
    WS(ws);

    [_bottomChannelsView   mas_remakeConstraints:^(MASConstraintMaker *make) {
        make.left.and.right.and.bottom.mas_equalTo(ws);
        make.top.mas_equalTo(_topChannelsView.mas_bottom);
     //   make.left.and.right.mas_equalTo(ws);
    }];
    
    [container mas_remakeConstraints:^(MASConstraintMaker *make) {
        make.edges.equalTo(_bottomChannelsView);
        make.width.equalTo(_bottomChannelsView);
    }];
    
    [moreText  mas_remakeConstraints:^(MASConstraintMaker *make) {
        make.right.equalTo(container);
        make.left.equalTo(container).with.offset(15);
        make.top.equalTo(container.mas_top).with.offset(10);
        make.height.mas_equalTo(@15);
    }];
    
    
    //排底部channelItem
    
    CGFloat itemWidth =((kScreenWidth - 20)-3*14/2)/4;
    
    ChannelListItem *firstItem = (ChannelListItem *)self.bottomView[0];
    firstItem.hidden = NO;
    [firstItem mas_remakeConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(moreText.mas_bottom).with.offset(12);
        make.left.equalTo(container.mas_left).with.offset(10);
        make.width.equalTo(@(itemWidth));
        make.height.equalTo(@24);
          //第一排离superview是15 vpadding
    }];
    
    
    
    ChannelListItem *lastItem = firstItem;
    ChannelListItem *item ;
    for (int i = 1 ; i<self.bottomView.count; i++) {
       item = (ChannelListItem *)self.bottomView[i];
        
        [item mas_remakeConstraints:^(MASConstraintMaker *make) {
            make.height.and.width.equalTo(firstItem);
            
        }];
        
        if (i%4==0) {
            [item mas_updateConstraints:^(MASConstraintMaker *make) {
                make.left.equalTo(container.mas_left).offset(10);
                
            }];
            
            firstItem = item;
        }else
        {
            [item mas_updateConstraints:^(MASConstraintMaker *make) {
                make.left.equalTo(lastItem.mas_right).offset(7);   //约束冲突
                make.top.mas_equalTo(firstItem);
            }];
            
        }
        if(i<4)
        {
            [item mas_updateConstraints:^(MASConstraintMaker *make) {
                // make.top.equalTo(_topChannelsView.mas_top).offset(15);  //第一排离superview是15 vpadding
                make.top.equalTo(firstItem);
            }];
        }else  if(i%4==0) {
            [item mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.equalTo(lastItem.mas_bottom).offset(16);  //非第一排
                //  make.top.equalTo(firstItem.mas_top);
            }];
            
        }
        else {
            [item mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.equalTo(firstItem);
            }];
        }
        lastItem = item;
    }
    
    [container mas_makeConstraints:^(MASConstraintMaker *make) {
        make.bottom.equalTo(item.mas_bottom).with.offset(20);
    }];

}