AutoLayout下CollectionView的自适应大小(三)

时间 2019-12-07

标签 autolayout collectionview 自适应大小栏目 CSS 繁體版

原文原文链接

这里上接这篇文章，通过前期的准备，这里终于开始使用AutoLayout了，有了前面的铺垫这里才显得没那么唐突，好吧，这里先说下故事的背景吧，对于一个View，咱们在布局的时候会写死它的大小，多是（320，240），可是对于不一样的屏幕尺寸，这样写显然是不合适的，对于一些简单的布局能够经过autoResizing的方式自动放大，但本例view中包含高度可变的CollectionView较为复杂，autoResizing已经不能知足咱们的需求了，因此才转向更为强大的AutoLayout,能够说AutoResizing是AutoLayout的子集，AutoLayout使用起来更为复杂，但对于简单的问题，AutoResizing可以很简单的解决。
函数

开始以前，咱们可能还须要回顾下这篇文章，这里限制条件应该加在什么地方是个问题，
布局

加在initWithFrame能够，但加在layoutSubviews中更合适，这样在addSubviews或者frame变化都会引发layoutSubviews的调用，先上一段计算当前布局高度和以前高度差值的函数spa

- (CGFloat)getRealAnimationViewHeightDt
{
    NSArray* labels = [[MFAppModel sharedObject].chatroomModelEx getFullLabels];
    
    NSInteger lineWidth = 50;
    NSUInteger rowCount = 1;
    for (int i = 1; i < labels.count; ++i) {
        NSArray* labels = [[MFAppModel sharedObject].chatroomModelEx getFullLabels];
        MFRoomLabel* currentRoomLabel = [labels objectAtIndex:i];
        NSDictionary *attribute = @{NSFontAttributeName: [UIFont systemFontOfSize:15]};
        CGSize currentLabelSize = [currentRoomLabel.name sizeWithAttributes:attribute];
        CGFloat cellWidth = MAX(50, currentLabelSize.width + 16);
        lineWidth = lineWidth + 15 + cellWidth;
        if (lineWidth > (self.frame.size.width - 65)) {
            rowCount++;
            lineWidth = cellWidth;
        }
    }

    return (rowCount - 2)*(24 + 10);
}

这里默认rowCount为2，对默认状况计算新的高度差值，来限制布局的大小。.net

这种代码写在哪里好？虽然是和UI相关的，但这里又夹杂着逻辑的数据，目前IOS开发中ViewController的使用仍是比较迷惑，这里究竟是放View仍是也能够放些和UI相关的数据呢？这种破坏MVC模式的代码到底写在Model层仍是View层？之后再讨论吧，这里先说AutoLayout的问题。code

有了这个根据数据和当前屏幕尺寸计算出来的collectionView的dt值，就能够方便的加些约束条件了，这里首先你能够参考下这篇文章，这个例子很简单，都是受到加约束条件的最简单的用法，
blog

下面上咱们的代码ip

[self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_collectionView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:nil
                         attribute:NSLayoutAttributeWidth
                         multiplier:0
                         constant:self.frame.size.width - 65]];

    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_collectionView
                         attribute:NSLayoutAttributeHeight
                         relatedBy:NSLayoutRelationEqual
                         toItem:nil
                         attribute:NSLayoutAttributeHeight
                         multiplier:0
                         constant:_collectionView.frame.size.height + [self getRealAnimationViewHeightDt]]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_mainView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_mainView
                         attribute:NSLayoutAttributeHeight
                         relatedBy:NSLayoutRelationEqual
                         toItem:nil
                         attribute:NSLayoutAttributeHeight
                         multiplier:0
                         constant:_mainView.frame.size.height + [self getRealAnimationViewHeightDt]]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_animationView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_animationView
                         attribute:NSLayoutAttributeHeight
                         relatedBy:NSLayoutRelationEqual
                         toItem:nil
                         attribute:NSLayoutAttributeHeight
                         multiplier:0
                         constant:_animationView.frame.size.height + [self getRealAnimationViewHeightDt]]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_buttonView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_cancelButton
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:0.5
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_cancelButton
                         attribute:NSLayoutAttributeLeft
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeLeft
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_okButton
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:0.5
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_okButton
                         attribute:NSLayoutAttributeRight
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeRight
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_buttonView
                         attribute:NSLayoutAttributeTop
                         relatedBy:NSLayoutRelationEqual
                         toItem:_lineView
                         attribute:NSLayoutAttributeBottom
                         multiplier:1
                         constant:0]];

    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_sortAndPositionLineView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_positionAndTagLineView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_lineView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_lineView
                         attribute:NSLayoutAttributeTop
                         relatedBy:NSLayoutRelationEqual
                         toItem:_mainView
                         attribute:NSLayoutAttributeBottom
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_buttonLineView
                         attribute:NSLayoutAttributeCenterX
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeCenterX
                         multiplier:1
                         constant:0]];
    
    [self addConstraint:[NSLayoutConstraint
                         constraintWithItem:_lineView
                         attribute:NSLayoutAttributeWidth
                         relatedBy:NSLayoutRelationEqual
                         toItem:self
                         attribute:NSLayoutAttributeWidth
                         multiplier:1
                         constant:0]];

想一想这些约束条件要是加在IB中还能看吗？这也就是说AutoLayout复杂的地方，对于屏幕尺寸变化的状况，里面的全部view都须要根据这个最外层的屏幕尺寸而发生变化，再加上View中又有高度不可控的collectionView，真是约束的不亦乐乎，但回头想一想，这也不失为一种解决问题的好办法，有没有更简单的解决问题的方法还有待挖掘，就目前对AutoLayout的理解，只能是这样的实现了开发

这个是不一样屏幕尺寸的效果，能够看到，当屏幕分辨率小的时候，collectionView的高度变化，但能够从新布局适应不一样屏幕。get