//懒加载，创建搜索结果控制器。当在搜索框里里输入内容时，显示搜索结果控制器。结束在搜索结果控制器输入内容时，隐藏搜索控制器，为了避免多次创建搜索结果控制器，使用懒加载。
- (MTCitySearchResultViewController *)citySearchResult
{
    if (!_citySearchResult) {
        MTCitySearchResultViewController *citySearchResult = [[MTCitySearchResultViewController alloc] init];
        [self addChildViewController:citySearchResult];
        self.citySearchResult = citySearchResult;
        [self.view addSubview:self.citySearchResult.view];
        //用第三方框架设置创建搜索结果控制器的view和父view的位置关系。
        [self.citySearchResult.view autoPinEdgesToSuperviewEdgesWithInsets:UIEdgeInsetsZero excludingEdge:ALEdgeTop];
        [self.citySearchResult.view autoPinEdge:ALEdgeTop toEdge:ALEdgeBottom ofView:self.searchBar withOffset:15];
    }
    return _citySearchResult;
}
#pragma mark - 搜索框代理方法
/**
 *  键盘弹出:搜索框开始编辑文字
 */
- (void)searchBarTextDidBeginEditing:(UISearchBar *)searchBar
{
    // 1.隐藏导航栏
    [self.navigationController setNavigationBarHidden:YES animated:YES];
    
    // 2.修改搜索框的背景图片
    [searchBar setBackgroundImage:[UIImage imageNamed:@"bg_login_textfield_hl"]];
    
    // 3.显示搜索框右边的取消按钮
    [searchBar setShowsCancelButton:YES animated:YES];
    
    // 4.显示遮盖
    [UIView animateWithDuration:0.5 animations:^{
        self.cover.alpha = 0.5;
    }];
}

/**
 *  键盘退下:搜索框结束编辑文字
 */
- (void)searchBarTextDidEndEditing:(UISearchBar *)searchBar
{
    // 1.显示导航栏
    [self.navigationController setNavigationBarHidden:NO animated:YES];
    
    // 2.修改搜索框的背景图片
    [searchBar setBackgroundImage:[UIImage imageNamed:@"bg_login_textfield"]];
    
    // 3.隐藏搜索框右边的取消按钮
    [searchBar setShowsCancelButton:NO animated:YES];
    
    // 4.隐藏遮盖
    [UIView animateWithDuration:0.5 animations:^{
        self.cover.alpha = 0.0;
    }];
    
    // 5.移除搜索结果
    self.citySearchResult.view.hidden = YES;
    searchBar.text = nil;
}

/**
 *  点击搜索框里的取消时调用
 */
- (void)searchBarCancelButtonClicked:(UISearchBar *)searchBar
{
    [searchBar resignFirstResponder];
}

/**
 *  搜索框里面的文字变化的时候调用
 */
- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
    if (searchText.length) {
        self.citySearchResult.view.hidden = NO;
        self.citySearchResult.searchText = searchText;
    } else {
        self.citySearchResult.view.hidden = YES;
    }
}