美团HD(4)-二级联动效果

DJNavDropView.m

#import "DJNavDropView.h"
#import "DJCategory.h"
#import "DJNavMainCategoryCell.h"
#import "DJNavSubCategoryCell.h"

@interface DJNavDropView()<UITableViewDataSource,UITableViewDelegate>

/** 主分类 */
@property (weak, nonatomic) IBOutlet UITableView *mainTableView;
/** 子分类 */
@property (weak, nonatomic) IBOutlet UITableView *subTableView;
/** 选中的子类别集合 */
@property (nonatomic,strong) NSArray *selectedSubCategories;

@end

@implementation DJNavDropView

+ (instancetype)dropView {

   return[[[NSBundle mainBundle] loadNibNamed:@"DJNavDropView" owner:nil options:nil] lastObject];

}

- (void)setCategoryList:(NSArray *)categoryList {

    _categoryList = categoryList;

    // 刷新数据
    [self.mainTableView reloadData];

}

#pragma mark - TableView 数据源方法

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

    if (tableView == self.mainTableView) { // 主类别
        return self.categoryList.count;
    } else { // 子类别
        return self.selectedSubCategories.count;
    }
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    if (tableView == self.mainTableView) { // 主类别

        DJNavMainCategoryCell *cell = [DJNavMainCategoryCell cellWithTableView:tableView];
        // 设置当前Cell属性
        DJCategory *categoryItem = self.categoryList[indexPath.row];
        cell.textLabel.text = categoryItem.name;
        cell.imageView.image = [UIImage imageNamed:categoryItem.icon];
        // 如果当前主类别有子类别
        if (categoryItem.subcategories.count) {
            cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator; // 显示向右的箭头
        } else {
            cell.accessoryType = UITableViewCellAccessoryNone; // 隐藏箭头
        }
        return cell;

    } else { // 子类别

        DJNavSubCategoryCell *cell = [DJNavSubCategoryCell cellWithTableView:tableView];
        // 设置当前Cell属性
        cell.textLabel.text = self.selectedSubCategories[indexPath.row];
        return cell;

    }
}

#pragma mark - TableView 代理方法
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    if (tableView == self.mainTableView) { // 点击主分类上面的条目
        DJCategory *category = self.categoryList[indexPath.row];
        self.selectedSubCategories = category.subcategories;
        // 刷新子栏目列表数据
        [self.subTableView reloadData];
    } else { // 点击子分类上面的条目

    }

}

@end

DJNavMainCategoryCell.m

#import "DJNavMainCategoryCell.h"

@implementation DJNavMainCategoryCell

+ (instancetype)cellWithTableView:(UITableView *)tableView {

    static NSString *ID = @"main_category";
    DJNavMainCategoryCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];
    if (!cell) {
        cell = [[DJNavMainCategoryCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:ID];
    }
    return cell;
}

- (instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {

    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
    if (self) {

       UIImageView *bg = [[UIImageView alloc] init];
        bg.image = [UIImage imageNamed:@"bg_dropdown_leftpart"];
        self.backgroundView = bg;

        UIImageView *selectedBg = [[UIImageView alloc] init];
        selectedBg.image = [UIImage imageNamed:@"bg_dropdown_left_selected"];
        self.selectedBackgroundView = selectedBg;

    }
    return self;
}

@end

最终效果：