iOS 根据重用机制简单实现tableview索引

• ViewReusePool 类 (通过队列实现重用机制)

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
/*
 实现重用机制的类
*/
@interface ViewReusePool : NSObject

// 从重用池中取出一个可重用的view
-(UIView *)dequeueReusableView;

// 向重用池当中添加一个视图
-(void)addUsingView:(UIView *)view;

// 重置 将当前使用的视图放到可重用队列中
-(void)reset;

@end

#import "ViewReusePool.h"

@interface ViewReusePool ()

@property(nonatomic,strong)NSMutableSet *waitUsedQueue;// 等待使用的队列
@property(nonatomic,strong)NSMutableSet *usingQueue; // 使用中的队列

@end

@implementation ViewReusePool

-(instancetype)init
{
    self = [super init];
    if (self) {
        _waitUsedQueue = [[NSMutableSet alloc] init];
        _usingQueue = [[NSMutableSet alloc] init];
    }
    return self;
}

-(UIView *)dequeueReusableView
{
    UIView *view = [_waitUsedQueue anyObject]; // 等待队列中返回任意一个view
    if (view == nil) {
        return nil;
    }
    // 队列移动
    [_waitUsedQueue removeObject:view];
    [_usingQueue addObject:view];
    return view;
}

- (void)addUsingView:(UIView *)view
{
    if (view == nil) {
        return;
    }
    // 将视图添加到使用的队列中
    [_usingQueue addObject:view];
}

-(void)reset
{
    UIView *view = nil;
    while ((view = [_usingQueue anyObject])) {
        
        NSLog(@"view - %@",view);
        
        // 从使用队列中移除
        [_usingQueue removeObject:view];
        // 加入等待队列中
        [_waitUsedQueue addObject:view];
    }
}

@end

• IndexTableView 类(继承于uitableview,实现索引按钮的重用功能)

#import <UIKit/UIKit.h>

@protocol IndexTableViewDataSource <NSObject>

// 获取tableview的字母索引数据的方法
-(NSArray *)indexTitlesForIndexTableView:(UITableView *)tableView;

@end

@interface IndexTableView : UITableView

@property(nonatomic,weak)id<IndexTableViewDataSource> indexDataSource;

@end

#import "IndexTableView.h"
#import "ViewReusePool.h"

@interface IndexTableView ()

@property(nonatomic,strong)UIView *containerView;
@property(nonatomic,strong)ViewReusePool *reusePool;

@end

@implementation IndexTableView

-(void)reloadData
{
    [super reloadData];
    
    if (_containerView == nil) {
        _containerView = [[UIView alloc] initWithFrame:CGRectZero];
        _containerView.backgroundColor = [UIColor whiteColor];
        // 避免索引条随着table滚动
        [self.superview insertSubview:_containerView aboveSubview:self];
    }
    
    if (_reusePool == nil) {
        _reusePool = [[ViewReusePool alloc] init];
    }
    // 标记所有视图为可重用状态
    [_reusePool reset];
    
    [self reloadIndexedBar];
}

-(void)reloadIndexedBar
{
    NSArray *arrayTitles = nil;
    if ([self.indexDataSource respondsToSelector:@selector(indexTitlesForIndexTableView:)]) {
        arrayTitles = [self.indexDataSource indexTitlesForIndexTableView:self];
    }
    
    // 判断字母索引是否为空
    if (!arrayTitles || arrayTitles.count <= 0) {
        [_containerView setHidden:YES];
        return;
    }
    
    NSUInteger count = arrayTitles.count;
    CGFloat buttonWidth = 60.0f;
    CGFloat buttonHeight = self.frame.size.height / count;
    for (NSInteger i = 0; i < arrayTitles.count; i++) {
        NSString *title = [arrayTitles objectAtIndex:i];
        // 从重用池取出一个button来
        UIButton *button = (UIButton *)[_reusePool dequeueReusableView];
        if (button == nil) {
            button = [[UIButton alloc] initWithFrame:CGRectZero];
            button.backgroundColor = [UIColor whiteColor];
            [_reusePool addUsingView:button];
            NSLog(@"创建一个button");
        } else {
            NSLog(@"button重用了");
        }
        [_containerView addSubview:button];
        [button setTitle:title forState:UIControlStateNormal];
        [button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
        button.frame = CGRectMake(0, i * buttonHeight, buttonWidth, buttonHeight);
    }
    [_containerView setHidden:NO];
    _containerView.frame = CGRectMake(self.frame.origin.x + self.frame.size.width - buttonWidth, self.frame.origin.y, buttonWidth, self.frame.size.height);
}

• ViewController 实现

@interface ViewController ()<UITableViewDataSource,UITableViewDelegate,IndexTableViewDataSource>

@property(nonatomic,strong)IndexTableView *tableView;
@property(nonatomic,strong)UIButton *button;
@property(nonatomic,copy)NSMutableArray *dataSource;

@end

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 创建一个tableview
    _tableView = [[IndexTableView alloc] initWithFrame:CGRectMake(0.0f, 60.0f, self.view.frame.size.width, self.view.frame.size.height - 60.0f) style:UITableViewStylePlain];
    _tableView.delegate = self;
    _tableView.dataSource = self;
    _tableView.indexDataSource = self;
    [self.view addSubview:_tableView];
    
    // 创建一个按钮
    _button = [UIButton buttonWithType:UIButtonTypeCustom];
    _button.frame = CGRectMake(0.0f, 20.0f, self.view.frame.size.width, 40.0f);
    _button.backgroundColor = [UIColor redColor];
    [_button setTitle:@"reload" forState:UIControlStateNormal];
    [_button addTarget:self action:@selector(reloadAction) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:_button];
    
    // 数据
    _dataSource = [[NSMutableArray alloc] init];
    for (NSInteger i = 0; i < 100; i++) {
        [_dataSource addObject:@(i+1)];
    }
    
}

#pragma mark - UITableViewDataSource
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return _dataSource.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *identifier = @"reused";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier];
    }
    cell.textLabel.text = [[_dataSource objectAtIndex:indexPath.row] stringValue];
    return cell;
}

#pragma mark - UITableViewDelegate
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 40.0f;
}

#pragma mark - IndexTableViewDataSource
-(NSArray *)indexTitlesForIndexTableView:(UITableView *)tableView
{
    // 奇数次调用返回6个字母 偶数次返回11个
    static BOOL change = NO;
    if (change) {
        change = NO;
        return @[@"A",@"B",@"C",@"E",@"F",@"G",@"H",@"I",@"J",@"K"];
    } else {
        change = YES;
        return @[@"A",@"B",@"C",@"D",@"E",@"F"];
    }
}

#pragma mark - action method
-(void)reloadAction
{
    NSLog(@"reloadAction");
    [_tableView reloadData];
}