如何在表视图中的UITableViewCells中使用“自动布局”,让每个单元格的内容和子视图确定行高度(自身/自动),同时保持平滑的滚动性能?
当前回答
我只是对rowHeight和estimatedRowHeight的两个值进行了一些愚蠢的尝试和错误,并认为它可能会提供一些调试细节:
如果同时设置它们,或者仅设置估计的RowHeight,则将获得所需的行为:
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 1.00001 // MUST be greater than 1
建议您尽最大努力得到正确的估计,但最终结果并无不同。这只会影响你的表现。
如果只设置rowHeight,即只执行以下操作:
tableView.rowHeight = UITableViewAutomaticDimension
您的最终结果不会如预期:
如果将estimatedRowHeight设置为1或更小,则无论rowHeight如何,都会崩溃。
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 1
我崩溃了,出现以下错误消息:
Terminating app due to uncaught exception
'NSInternalInconsistencyException', reason: 'table view row height
must not be negative - provided height for index path (<NSIndexPath:
0xc000000000000016> {length = 2, path = 0 - 0}) is -1.000000'
...some other lines...
libc++abi.dylib: terminating with uncaught exception of type
NSException
其他回答
swift 4
@IBOutlet weak var tableViewHeightConstraint: NSLayoutConstraint!
@IBOutlet weak var tableView: UITableView!
private var context = 1
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.addObserver(self, forKeyPath: "contentSize", options: [.new,.prior], context: &context)
}
// Added observer to adjust tableview height based on the content
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if context == &self.context{
if let size = change?[NSKeyValueChangeKey.newKey] as? CGSize{
print("-----")
print(size.height)
tableViewHeightConstraint.constant = size.height + 50
}
}
}
//Remove observer
deinit {
NotificationCenter.default.removeObserver(self)
}
我只是对rowHeight和estimatedRowHeight的两个值进行了一些愚蠢的尝试和错误,并认为它可能会提供一些调试细节:
如果同时设置它们,或者仅设置估计的RowHeight,则将获得所需的行为:
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 1.00001 // MUST be greater than 1
建议您尽最大努力得到正确的估计,但最终结果并无不同。这只会影响你的表现。
如果只设置rowHeight,即只执行以下操作:
tableView.rowHeight = UITableViewAutomaticDimension
您的最终结果不会如预期:
如果将estimatedRowHeight设置为1或更小,则无论rowHeight如何,都会崩溃。
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 1
我崩溃了,出现以下错误消息:
Terminating app due to uncaught exception
'NSInternalInconsistencyException', reason: 'table view row height
must not be negative - provided height for index path (<NSIndexPath:
0xc000000000000016> {length = 2, path = 0 - 0}) is -1.000000'
...some other lines...
libc++abi.dylib: terminating with uncaught exception of type
NSException
我将@smileyborg的iOS7解决方案归入一个类别
我决定用@smileyborg将这个聪明的解决方案包装成UICollectionViewCell+AutoLayoutDynamicHeightCalculation类别。
该类别还纠正了@wildsmonkey的回答中概述的问题(从笔尖和systemLayoutSizeFittingSize加载单元格:返回CGRectZero)
它不考虑任何缓存,但现在适合我的需要。随意复制、粘贴和破解。
UI集合视图单元格+自动布局动态高度计算.h
#import <UIKit/UIKit.h>
typedef void (^UICollectionViewCellAutoLayoutRenderBlock)(void);
/**
* A category on UICollectionViewCell to aid calculating dynamic heights based on AutoLayout contraints.
*
* Many thanks to @smileyborg and @wildmonkey
*
* @see stackoverflow.com/questions/18746929/using-auto-layout-in-uitableview-for-dynamic-cell-layouts-variable-row-heights
*/
@interface UICollectionViewCell (AutoLayoutDynamicHeightCalculation)
/**
* Grab an instance of the receiving type to use in order to calculate AutoLayout contraint driven dynamic height. The method pulls the cell from a nib file and moves any Interface Builder defined contrainsts to the content view.
*
* @param name Name of the nib file.
*
* @return collection view cell for using to calculate content based height
*/
+ (instancetype)heightCalculationCellFromNibWithName:(NSString *)name;
/**
* Returns the height of the receiver after rendering with your model data and applying an AutoLayout pass
*
* @param block Render the model data to your UI elements in this block
*
* @return Calculated constraint derived height
*/
- (CGFloat)heightAfterAutoLayoutPassAndRenderingWithBlock:(UICollectionViewCellAutoLayoutRenderBlock)block collectionViewWidth:(CGFloat)width;
/**
* Directly calls `heightAfterAutoLayoutPassAndRenderingWithBlock:collectionViewWidth` assuming a collection view width spanning the [UIScreen mainScreen] bounds
*/
- (CGFloat)heightAfterAutoLayoutPassAndRenderingWithBlock:(UICollectionViewCellAutoLayoutRenderBlock)block;
@end
UI集合视图单元格+自动布局动态高度计算.m
#import "UICollectionViewCell+AutoLayout.h"
@implementation UICollectionViewCell (AutoLayout)
#pragma mark Dummy Cell Generator
+ (instancetype)heightCalculationCellFromNibWithName:(NSString *)name
{
UICollectionViewCell *heightCalculationCell = [[[NSBundle mainBundle] loadNibNamed:name owner:self options:nil] lastObject];
[heightCalculationCell moveInterfaceBuilderLayoutConstraintsToContentView];
return heightCalculationCell;
}
#pragma mark Moving Constraints
- (void)moveInterfaceBuilderLayoutConstraintsToContentView
{
[self.constraints enumerateObjectsUsingBlock:^(NSLayoutConstraint *constraint, NSUInteger idx, BOOL *stop) {
[self removeConstraint:constraint];
id firstItem = constraint.firstItem == self ? self.contentView : constraint.firstItem;
id secondItem = constraint.secondItem == self ? self.contentView : constraint.secondItem;
[self.contentView addConstraint:[NSLayoutConstraint constraintWithItem:firstItem
attribute:constraint.firstAttribute
relatedBy:constraint.relation
toItem:secondItem
attribute:constraint.secondAttribute
multiplier:constraint.multiplier
constant:constraint.constant]];
}];
}
#pragma mark Height
- (CGFloat)heightAfterAutoLayoutPassAndRenderingWithBlock:(UICollectionViewCellAutoLayoutRenderBlock)block
{
return [self heightAfterAutoLayoutPassAndRenderingWithBlock:block
collectionViewWidth:CGRectGetWidth([[UIScreen mainScreen] bounds])];
}
- (CGFloat)heightAfterAutoLayoutPassAndRenderingWithBlock:(UICollectionViewCellAutoLayoutRenderBlock)block collectionViewWidth:(CGFloat)width
{
NSParameterAssert(block);
block();
[self setNeedsUpdateConstraints];
[self updateConstraintsIfNeeded];
self.bounds = CGRectMake(0.0f, 0.0f, width, CGRectGetHeight(self.bounds));
[self setNeedsLayout];
[self layoutIfNeeded];
CGSize calculatedSize = [self.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
return calculatedSize.height;
}
@end
用法示例:
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
MYSweetCell *cell = [MYSweetCell heightCalculationCellFromNibWithName:NSStringFromClass([MYSweetCell class])];
CGFloat height = [cell heightAfterAutoLayoutPassAndRenderingWithBlock:^{
[(id<MYSweetCellRenderProtocol>)cell renderWithModel:someModel];
}];
return CGSizeMake(CGRectGetWidth(self.collectionView.bounds), height);
}
谢天谢地,我们不必在iOS8中演奏爵士乐,但现在就可以了!
只要你的单元格布局良好。
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [self tableView:tableView cellForRowAtIndexPath:indexPath];
return [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
}
更新:您应该使用iOS 8中引入的动态调整大小。
动态表视图单元格高度和自动布局
解决故事板自动布局问题的好方法:
- (CGFloat)heightForImageCellAtIndexPath:(NSIndexPath *)indexPath {
static RWImageCell *sizingCell = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sizingCell = [self.tableView dequeueReusableCellWithIdentifier:RWImageCellIdentifier];
});
[sizingCell setNeedsLayout];
[sizingCell layoutIfNeeded];
CGSize size = [sizingCell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
return size.height;
}
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