UITableViewCell 高度自适應一直是我們做動态Cell高度時遇到的最煩躁的問題,Cell動态高度計算可以去看看sunny的這篇文章介紹,今天主要和大家分享下我在使用 systemLayoutSizeFittingSize
Demo gif
先看原函數注釋
/* The size fitting most closely to targetSize in which the receiver's subtree can be laid out while optimally satisfying the constraints. If you want the smallest possible size, pass UILayoutFittingCompressedSize; for the largest possible size, pass UILayoutFittingExpandedSize.
Also see the comment for UILayoutPriorityFittingSizeLevel.
*/- (CGSize)systemLayoutSizeFittingSize:(CGSize)targetSize NS_AVAILABLE_IOS(6_0); // Equivalent to sending -systemLayoutSizeFittingSize:withHorizontalFittingPriority:verticalFittingPriority: with UILayoutPriorityFittingSizeLevel for both priorities. 從注釋中我們可以看出,當你的限制條件配置好後它可以計算出最接近目标的Size,那我們該如何下手呢?
1.首先我們需要建一個UITableViewCell
假如我們Cell的布局如下所示：
Cell所對應的Class我們取名為
ZHCalculateTableViewCell
所帶屬性我們定義為：
@interface ZHCalculateTableViewCell : UITableViewCell
@property (weak, nonatomic) IBOutlet UILabel *TitleLabel;
@property (weak, nonatomic) IBOutlet UILabel *ContentLabel;
@property (weak, nonatomic) IBOutlet UIImageView *showImgView;
@property (weak, nonatomic) IBOutlet UILabel *UseNameLabel;
@property (weak, nonatomic) IBOutlet UILabel *TimeLabel;
@property (strong, nonatomic) ZHCalculateHeightModel *model;
@end 看到這裡也許你會疑惑
ZHCalculateHeightModel
是什麼,它是我們Cell所要展示的資料來源！
2.然後我們為我們的Cell建個資料模型
Cell的模型名稱我們暫定為:
ZHCalculateHeightModel
所帶屬性：
@interface ZHCalculateHeightModel : NSObject
@property (nonatomic, strong) NSString *title;
@property (nonatomic, strong) NSString *content;
@property (nonatomic, strong) NSString *username;
@property (nonatomic, strong) NSString *time;
@property (nonatomic, strong) NSString *imageName; Ok,資料模型建立好了,展示的TableViewCell也有了, Just Show it~
3. 建一個繼承于 UITableViewController
ZHCustomLayoutTableViewController
UITableViewController
ZHCustomLayoutTableViewController
- 建一個在函數
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
@property (nonatomic, strong) ZHCalculateTableViewCell *prototypeCell; - 注冊Cell
[self.tableView registerNib:[UINib nibWithNibName:@"ZHCalculateTableViewCell" bundle:[NSBundle mainBundle]] forCellReuseIdentifier:CellIdentifier];
self.tableView.estimatedRowHeight = 100;//很重要保障滑動流暢性
self.prototypeCell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier]; - 動态計算高度
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
ZHCalculateTableViewCell *cell = self.prototypeCell;
cell.contentView.translatesAutoresizingMaskIntoConstraints = NO;
[self configureCell:cell atIndexPath:indexPath];//必須先對Cell中的資料進行配置使動态計算時能夠知道根據Cell内容計算出合适的高度
/*------------------------------重點這裡必須加上contentView的寬度限制不然計算出來的高度不準确-------------------------------------*/
CGFloat contentViewWidth = CGRectGetWidth(self.tableView.bounds);
NSLayoutConstraint *widthFenceConstraint = [NSLayoutConstraint constraintWithItem:cell.contentView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:contentViewWidth];
[cell.contentView addConstraint:widthFenceConstraint];
// Auto layout engine does its math
CGFloat fittingHeight = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
[cell.contentView removeConstraint:widthFenceConstraint];
/*-------------------------------End------------------------------------*/
return fittingHeight+2*1/[UIScreen mainScreen].scale;//必須加上上下分割線的高度
}
#pragma mark Configure Cell Data
- (void)configureCell:(ZHCalculateTableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {
cell.model = [dataArray objectAtIndex:indexPath.row];//Cell中對其進行處理
} ZHCalculateTableViewCell Model的Set函數重寫為
#pragma mark - Setters
-(void)setModel:(ZHCalculateHeightModel *)model
{
_model = model;
self.TitleLabel.text = model.title;
self.ContentLabel.text = model.content;
self.showImgView.image = model.imageName.length > 0 ? [UIImage imageNamed:model.imageName] : nil;
self.UseNameLabel.text = model.username;
self.TimeLabel.text = model.time;
} 擴充
我們可以在計算高度後對其進行緩存,下次可以直接傳回！
總結
- 在
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
ZHCalculateTableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
-
CGFloat contentViewWidth = CGRectGetWidth(self.tableView.bounds); NSLayoutConstraint *widthFenceConstraint = [NSLayoutConstraint constraintWithItem:cell.contentView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:contentViewWidth]; [cell.contentView addConstraint:widthFenceConstraint]; // Auto layout engine does its math CGFloat fittingHeight = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height; [cell.contentView removeConstraint:widthFenceConstraint];