uiscrollview的自动收费表，视图层次结构没有为约束做好准备

Question

我希望使用自动收费表向滚动视图添加滚动图像视图。

视图层次如下：

--占位符视图

-涡旋视图

守则如下：

( -(UICollectionViewCell*)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

static NSString* identifier = @"WCollectionViewCell";


WCollectionViewCell* cell =[collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
cell.imageScrollview.backgroundColor=[UIColor orangeColor];

UIImageView* imageview1 = [[UIImageView alloc]init];
imageview1.image =[UIImage imageNamed:@"1.jpg"];
imageview1.translatesAutoresizingMaskIntoConstraints=NO;
[cell.imageScrollview addSubview:imageview1];

NSDictionary* views = @{@"imageview1":imageview1,@"placeview":cell.placeHolderView,@"scrollview":cell.imageScrollview};

//set the imageview'size
NSArray *img_constraint_H = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[imageview1(placeview)]"
                                                                    options:0
                                                                    metrics:nil
                                                                      views:views];

NSArray *img_constraint_V = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[imageview1(placeview)]"
                                                                    options:0
                                                                    metrics:nil
                                                                      views:views];

[self.view addConstraints:img_constraint_H];
[self.view addConstraints:img_constraint_V];


//set the imageview's position
NSArray*  top_position = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[imageview1]"
                                                            options:0 metrics:nil views:views];

NSArray* bottom_position = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[imageview1]"
                                                              options:0 metrics:nil views:views];

[cell.imageScrollview addConstraints:top_position];
[cell.imageScrollview addConstraints:bottom_position];

return cell;

}

-错误如果需要在组装视图层次结构之前解决约束，这将导致崩溃。中断-UIView _viewHierarchyUnpreparedForConstraint:进行调试。2015-04-10 12:20:46.246 T 92361:1319616 _layoutEngine_didAddLayoutConstraint:roundingAdjustment:mutuallyExclusiveConstraints:，/SourceCache/UIKit_Sim/UIKit-3318.93/NSLayoutConstraint_UIKitAdditions.m:560 *断言失败在-UIView 2015-10 12:20:46.249 T 92361:1319616 *终止应用程序中由于“NSInternalInconsistencyException”异常，原因：“不可能设置视图层次结构未为约束做好准备的布局。”

Answer 1

您的问题是，您要将图像的高度和宽度的约束添加到self.view中，这不是图像的父视图。

您需要将约束添加到cell.imageScrollview，即单元格超级视图或图像本身。

因此，这两种方法都应该有效：

//set the imageview'size
NSArray *img_constraint_H = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[imageview1(placeview)]"
                                                                    options:0
                                                                    metrics:nil
                                                                      views:views];

NSArray *img_constraint_V = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[imageview1(placeview)]"
                                                                    options:0
                                                                    metrics:nil
                                                                      views:views];

[cell.imageScrollview addConstraints:img_constraint_H];
[cell.imageScrollview addConstraints:img_constraint_V];

或

[imageview1 addConstraints:img_constraint_H];
[imageview1 addConstraints:img_constraint_V];

这两个选项都有，因为约束不引用父程序，而只引用imageView。如果在视觉格式中有一个|，那么只有第一个选项可以工作。

还有一条建议：

您可以一次添加所有约束：

WCollectionViewCell* cell =[collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
cell.imageScrollview.backgroundColor=[UIColor orangeColor];

UIImageView* imageview1 = [[UIImageView alloc]init];
imageview1.image =[UIImage imageNamed:@"1.jpg"];
imageview1.translatesAutoresizingMaskIntoConstraints=NO;
[cell.imageScrollview addSubview:imageview1];

NSDictionary* views = @{@"imageview1":imageview1,@"placeview":cell.placeHolderView,@"scrollview":cell.imageScrollview};    
//set the imageview's position
NSArray*  horizontal_constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[imageview1(placeview)]"
                                                            options:0 metrics:nil views:views];

NSArray* vertical_constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[imageview1(placeview)]"
                                                              options:0 metrics:nil views:views];

[cell.imageScrollview addConstraints:horizontal_constraints];
[cell.imageScrollview addConstraints:vertical_constraints];

return cell;

如果你需要更多的帮助，请告诉我事情进展如何！