Skip to content

Latest commit

 

History

History
243 lines (161 loc) · 6.94 KB

README.md

File metadata and controls

243 lines (161 loc) · 6.94 KB
Raw

SCAutoResizeCellDemo

use autolayout on the tableview 在tableview在使用autolayout，自适应cell的高度（iOS7+）

##一、概述 ####1、声明NSDictinary *offscreenCell

a. 用来存储每种类型cell的一个对象实例 b. 此dictionary的key为每种类型cell的reuse identifier，value为该类型cell的一个对象实例


####2、cell的注册

a. 使用tableview的registerClass方法来进行cell的注册 b. 若有多种类型的cell，则要用registerClass注册多个cell


####3、初始化cell，并返回cell高度

a. 在heightForRowAtIndexPath方法里，进行cell的初始化 b. 使用systemLayoutSizeFittingSize方法获取cell的高度


####4、cell赋值

在cellForRowAtIndexPath方法里，进行cell的赋值


####5、使用autolayout对需要的控件进行布局

有两种方式：
a. 使用xib
b. 重写自定义cell类里的updateConstraints方法，手动用代码进行布局

注：本文使用Masonry进行布局


####6、通知系统进行布局

在自定义的cell类里的layoutSubviews方法，调用相关方法通知系统进行布局


##二、关键点
1、autolayout要设置正确，如果不正确，systemLayoutSizeFittingSize方法计算出来的高度是0

##三、示例代码

假设有两种类型的cell，先自定义两个cell类 分别命名为AutoResizeCell SecondResizeCell reuse identify分别为autoResizeCellId secondResizeCellId


1、在controller里的viewDidLoad

/////////////// step: 1 ///////////////
self.offscreenCell = [NSMutableDictionary dictionary];
/////////////// step: 1 ///////////////

/////////////// step: 2 ///////////////
[self.myTableView registerClass:[AutoResizeCell class] forCellReuseIdentifier:autoResizeCellId];
[self.myTableView registerClass:[SecondResizeCell class] forCellReuseIdentifier:secondResizeCellId];
// Setting the estimated row height prevents the table view from calling tableView:heightForRowAtIndexPath: for every row in the table on first load;
// it will only be called as cells are about to scroll onscreen. This is a major performance optimization.self.myTableView.estimatedRowHeight = UITableViewAutomaticDimension; // iOS7+
/////////////// step: 2 ///////////////

2、在controller里的heightForRowAtIndexPath

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    /////////////// step: 3 ///////////////
    NSDictionary *aDict = [self getRowDataDictInSection:indexPath.section row:indexPath.row];
    BOOL hasAvatar = [[aDict objectForKey:HAS_AVATAR] boolValue];
    NSString *reuseIdentifier = (hasAvatar ? secondResizeCellId : autoResizeCellId);
    UITableViewCell *cell = [self.offscreenCell objectForKey:reuseIdentifier];
    if (!cell) {
        if (hasAvatar) {
            cell = [[SecondResizeCell alloc] init];
        } else {
            cell = [[AutoResizeCell alloc] init];
        }
        [self.offscreenCell setObject:cell forKey:reuseIdentifier];
    }
    if (hasAvatar) {
        [(SecondResizeCell*)cell initModel:aDict];
    } else {
        [(AutoResizeCell*)cell initModel:aDict];
    }
    cell.bounds = CGRectMake(0.0f, 0.0f, CGRectGetWidth(tableView.bounds), CGRectGetHeight(cell.bounds));
    [cell setNeedsLayout];
    [cell layoutIfNeeded];
    
    CGFloat height = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
    height += 1;
    /////////////// step: 3 ///////////////
    
    return height;
}

3、在controller里的cellForRowAtIndexPath

- (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    /////////////// step: 4 ///////////////
    NSDictionary *aDict = [self getRowDataDictInSection:indexPath.section row:indexPath.row];
    BOOL hasAvatar = [[aDict objectForKey:HAS_AVATAR] boolValue];
    NSString *reuseIdentifier = (hasAvatar ? secondResizeCellId : autoResizeCellId);
    AutoResizeCell *cell = [tableView dequeueReusableCellWithIdentifier:reuseIdentifier];
    if (hasAvatar) {
        [(SecondResizeCell*)cell initModel:aDict];
    } else {
        [(AutoResizeCell*)cell initModel:aDict];
    }
    /////////////// step: 4 ///////////////
    return cell;
}

4、在自定义cell类的initModel

- (void)initModel:(id)model {
    
    self.titleLabel.text = [model objectForKey:@"title"];
    self.bodyLabel.text = [model objectForKey:@"content"];
    
    // Make sure the constraints have been added to this cell, since it may have just been created from scratch
    /////////////// step: 4 ///////////////
    [self setNeedsUpdateConstraints];
    [self updateConstraintsIfNeeded];
    /////////////// step: 4 ///////////////
}

5、在自定义cell类的updateConstraints

- (void)updateConstraints {
    
    /////////////// step: 5 ///////////////
    if (!self.didSetupConstraints) {
        
        // titleLabel
        [_titleLabel mas_makeConstraints:^(MASConstraintMaker *make) {
            make.top.mas_equalTo(kLabelVerticalInsets);
            make.left.mas_equalTo(kLabelHorizontalInsets);
            make.right.mas_equalTo(-kLabelHorizontalInsets); // need
        }];
        // bodyLabel
        [_bodyLabel mas_makeConstraints:^(MASConstraintMaker *make) {
            make.top.mas_equalTo(_titleLabel.mas_bottom).with.offset(kLabelVerticalInsets);
            make.left.mas_equalTo(_titleLabel.mas_left);
            make.bottom.mas_equalTo(-kLabelVerticalInsets); // need
            make.right.mas_equalTo(_titleLabel.mas_right);
        }];
        self.didSetupConstraints = YES;
    }
    [super updateConstraints];
    /////////////// step: 5 ///////////////
}

6、在自定义cell类的layoutSubviews

- (void)layoutSubviews {
    [super layoutSubviews];
    
    /////////////// step: 6 ///////////////
    [self.contentView setNeedsLayout];
    [self.contentView layoutIfNeeded];
    
    _titleLabel.preferredMaxLayoutWidth = CGRectGetWidth(_titleLabel.frame);
    _bodyLabel.preferredMaxLayoutWidth = CGRectGetWidth(_bodyLabel.frame);
    /////////////// step: 6 ///////////////
}

##四、autolayout相关资料

1）开始iOS 7中自动布局教程（上下部分）
1、http://www.cocoachina.com/industry/20131203/7462.html 2、http://www.cnblogs.com/zer0Black/p/3977288.html

2）Masonry说明： 官方：https://github.com/Masonry/Masonry 第三方：http://adad184.com/2014/09/28/use-masonry-to-quick-solve-autolayout/

3）tableview动态计算cell高度 1、 http://www.ifun.cc/blog/2014/02/21/dong-tai-ji-suan-uitableviewcellgao-du-xiang-jie/ 2、http://www.devdiv.com/autolayout_uitableviewcell_-blog-21666-52543.html 3、http://www.tuicool.com/articles/FZN3q2 4、http://stackoverflow.com/questions/18746929/using-auto-layout-in-uitableview-for-dynamic-cell-layouts-variable-row-heights