dropList下拉框，可微调控制在ScrollView上的位置，通过设置下拉框的X、Y值为ScrollView的偏移量即可

//.h

@protocol LJBDropListViewDelegate <NSObject>

/**

 数据源行数

 */

- (NSInteger)ljbDropListView:(UIView *)dropListView;

/**

 数据源内容

 */

- (NSString *)ljbDropListView:(UIView *)dropListView cellForRow:(NSInteger)row;

/**

 选中内容

 */

- (void)ljbDropListView:(UIView *)dropListView didSelectRow:(NSInteger)row;

/**

 默认选中行

 */

@optional

- (NSInteger)defaultShowRowLjbDropListView:(UIView *)dropListView;

@end

@interface LJBDropListView : UIImageView

@property(assign)id<LJBDropListViewDelegate> delegate;

@property(nonatomic,strong)UIView *superMainView;//主控制器

@property(assign)CGFloat edgeX;

@property(assign)CGFloat edgeY;

@property(nonatomic,strong)UITableView *tableView;

- (instancetype)initWithFrame:(CGRect)frame delegate:(id)delegate;

@property(nonatomic,weak)UILabel *resultLab;

//.m

- (instancetype)initWithFrame:(CGRect)frame delegate:(id)delegate {

    if (self = [superinitWithFrame:frame]) {

        self.delegate = delegate;

        self.userInteractionEnabled =YES;

        self.backgroundColor = [UIColorwhiteColor];

        //

        UILabel *resultLab = [[UILabelalloc]initWithFrame:self.bounds];

        self.resultLab = resultLab;

        resultLab.textAlignment =NSTextAlignmentCenter;

        [selfaddSubview:resultLab];

        //

        UITapGestureRecognizer *tap = [[UITapGestureRecognizeralloc]initWithTarget:selfaction:@selector(showTableView:)];

        [selfaddGestureRecognizer:tap];

    }

    returnself;

}

- (void)showTableView:(UITapGestureRecognizer *)tap {

    if (self.tableView.isHidden) {

        [selftapHiddenTableView:nil];

    } else {

        self.bgView = [[UIViewalloc]initWithFrame:self.superMainView.bounds];

        UITapGestureRecognizer *tap = [[UITapGestureRecognizeralloc]initWithTarget:selfaction:@selector(tapHiddenTableView:)];

        [self.bgViewaddGestureRecognizer:tap];

        [self.superMainViewaddSubview:self.bgView];

        [self.bgViewaddSubview:self.tableView];

        [self.tableViewreloadData];

    }

}

- (void)tapHiddenTableView:(UITapGestureRecognizer *)tap {

    [self.bgViewremoveFromSuperview];

    [self.tableViewremoveFromSuperview];

}

- (UITableView *)tableView {

    if (!_tableView) {

        _tableView = [[UITableViewalloc]initWithFrame:CGRectZerostyle:UITableViewStyleGrouped];

        _tableView.delegate =self;

        _tableView.dataSource =self;

    }

    //

    NSInteger count = [self.delegateljbDropListView:self];

    CGFloat tbX =self.frame.origin.x+self.edgeX;

    CGFloat tbY =CGRectGetMaxY(self.frame)+self.edgeY;

    CGFloat tbW =self.frame.size.width;

    CGFloat tbH =0;

    if (count <4) {

        tbH = count * cellHeight;

    } else {

        tbH = 4 *cellHeight;

    }

    _tableView.frame =CGRectMake(tbX, tbY, tbW, tbH);

    

    return_tableView;

}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {

    return [self.delegateljbDropListView:self];

}

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

    return0;

}

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

    returnnil;

}

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {

    UIView *view = [[UIViewalloc]init];

    view.tag = section;

    UITapGestureRecognizer *tap = [[UITapGestureRecognizeralloc]initWithTarget:selfaction:@selector(didSelectRow:)];

    [view addGestureRecognizer:tap];

    view.backgroundColor = [UIColorwhiteColor];

    view.frame =CGRectMake(0,0, tableView.frame.size.width,cellHeight - 1);

    UILabel *label = [[UILabelalloc]init];

    label.frame = view.bounds;

    label.textAlignment =NSTextAlignmentCenter;

    label.text = [self.delegateljbDropListView:selfcellForRow:section];

    label.textColor = [UIColorblackColor];

    label.font =self.resultLab.font;

    [view addSubview:label];

    

    UIView *lineView = [[UIViewalloc]init];

    lineView.frame =CGRectMake(0,CGRectGetMaxY(view.frame), view.frame.size.width,1);

    lineView.backgroundColor =kk_grayBg;

    [view addSubview:lineView];

    

    return view;

}

- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section {

    return0.001;

}

- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {

    returncellHeight;

}

- (void)didSelectRow:(UITapGestureRecognizer *)tap {

    UIView *view = tap.view;

    self.resultLab.text = [self.delegateljbDropListView:selfcellForRow:view.tag];

    [self.delegateljbDropListView:selfdidSelectRow:view.tag];

    [selftapHiddenTableView:nil];

}

- (void)setSuperMainView:(UIView *)superMainView {

    _superMainView = superMainView;

    

    if ([self.delegaterespondsToSelector:@selector(defaultShowRowLjbDropListView:)]) {

        NSInteger row = [self.delegatedefaultShowRowLjbDropListView:self];

        self.resultLab.text = [self.delegateljbDropListView:selfcellForRow:row];

        [self.delegateljbDropListView:selfdidSelectRow:row];

    }

    

}

//使用

- (NSInteger)ljbDropListView:(UIView *)dropListView {

    if (dropListView.tag ==1) {

        returnself.array1.count;

    }

    returnself.array2.count;

}

- (NSString *)ljbDropListView:(UIView *)dropListView cellForRow:(NSInteger)row {

    if (dropListView.tag ==1) {

        returnself.array1[row];

    }

    returnself.array2[row];

}

- (void)ljbDropListView:(UIView *)dropListView didSelectRow:(NSInteger)row {

    NSLog(@"tag:%zd,row:%zd",dropListView.tag,row);

}

- (NSInteger)defaultShowRowLjbDropListView:(UIView *)dropListView {

    if (dropListView.tag ==1) {

        return0;

    }

    return2;

}