masonry 在UIScrollview上布局

问题：

直接在scrollview上addSubview，往往出偏差

解决办法：

是加一层容器containerView做间隔，containerView add到scrollview上，自定义的子view add到containerView上

然后重点是：在containerView的mas设置block中

需要竖向滑动时设置 width
make.width.equalTo(scrollView);
需要横向滑动时设置 height
make.height.equalTo(scrollView);

示例

- (void)setupUI {
    //scrollview加到controller的self.view上[self.view addSubview:self.backgroundScrollView];//容器containerView加到scrollview上[self.backgroundScrollView addSubview:self.containerView];//子view加到容器containerView上[self.containerView addSubview:self.subViewA];[self.containerView addSubview:self.subViewB];
}- (void)addConstraints {
        [self.backgroundScrollView mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.left.right.equalTo(self.view);make.bottom.equalTo(self.view).offset(-TAB_BAR_HEIGHT);}];[self.containerView mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.left.bottom.right.equalTo(self.backgroundScrollView);//主要是这里，如下是竖向滑动，就设置width同scrollviewmake.width.equalTo(self.backgroundScrollView);}];[self.subViewA mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.left.right.equalTo(self.containerView);}];[self.subViewB mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.equalTo(self.subViewA.mas_bottom).offset(16);make.left.right.bottom.equalTo(self.containerView);}];
}