iOS 如何在cell上面毫无卡顿的同时加载大量高清图片

//
//  ViewController.m
//  加载高清大图
//
//  Created by H on 17/1/12.
//  Copyright © 2017年 H. All rights reserved.
//

#import "ViewController.h"

//定义一个block
typedef BOOL(^RunloopBlock)(void);

static NSString *IDENTIFIER = @"IDENTIFIER";

static CGFloat CELL_HEIGHT = 135.f;

@interface ViewController ()
/** 存放任务的数组  */
@property(nonatomic,strong)NSMutableArray * tasks;
/** 任务标记  */
@property(nonatomic,strong)NSMutableArray * tasksKeys;
/** 最大任务数 */
@property(assign,nonatomic)NSUInteger max;

/** timer  */
@property(nonatomic,strong)NSTimer * timer;

@property (nonatomic, strong) UITableView *exampleTableView;

@end

@implementation ViewController
-(void)_timerFiredMethod{
    
}
- (void)viewDidLoad {
    [super viewDidLoad];
    _max = 18;
    _tasks = [NSMutableArray array];
    _tasksKeys = [NSMutableArray array];
    
    
    _timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(_timerFiredMethod) userInfo:nil repeats:YES];
    
    //注册Cell
    [self.exampleTableView registerClass:[UITableViewCell class] forCellReuseIdentifier:IDENTIFIER];
    
    //注册监听
    [self addRunloopObserver];
    
}

//MARK: 内部实现方法
//加载第一张
+(void)addImage1With:(UITableViewCell *)cell{
    //第一张
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(5, 20, 85, 85)];
    imageView.tag = 1;
    NSString *path1 = [[NSBundle mainBundle] pathForResource:@"spaceship" ofType:@"png"];
    UIImage *image = [UIImage imageWithContentsOfFile:path1];
    imageView.contentMode = UIViewContentModeScaleAspectFit;
    imageView.image = image;
    [UIView transitionWithView:cell.contentView duration:0.3 options:(UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionTransitionCrossDissolve) animations:^{
        [cell.contentView addSubview:imageView];
    } completion:nil];
}
//加载第二张
+(void)addImage2With:(UITableViewCell *)cell{
    //第二张
    UIImageView *imageView1 = [[UIImageView alloc] initWithFrame:CGRectMake(105, 20, 85, 85)];
    imageView1.tag = 2;
    NSString *path1 = [[NSBundle mainBundle] pathForResource:@"spaceship" ofType:@"png"];
    UIImage *image1 = [UIImage imageWithContentsOfFile:path1];
    imageView1.contentMode = UIViewContentModeScaleAspectFit;
    imageView1.image = image1;
    [UIView transitionWithView:cell.contentView duration:0.3 options:(UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionTransitionCrossDissolve) animations:^{
        [cell.contentView addSubview:imageView1];
    } completion:nil];
}
//加载第三张
+(void)addImage3With:(UITableViewCell *)cell{
    //第三张
    UIImageView *imageView2 = [[UIImageView alloc] initWithFrame:CGRectMake(200, 20, 85, 85)];
    imageView2.tag = 3;
    NSString *path1 = [[NSBundle mainBundle] pathForResource:@"spaceship" ofType:@"png"];
    UIImage *image2 = [UIImage imageWithContentsOfFile:path1];
    imageView2.contentMode = UIViewContentModeScaleAspectFit;
    imageView2.image = image2;
    [UIView transitionWithView:cell.contentView duration:0.3 options:(UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionTransitionCrossDissolve) animations:^{
        [cell.contentView addSubview:imageView2];
    } completion:nil];
}

//MARK:  UI初始化方法
//设置tableview大小
- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    self.exampleTableView.frame = self.view.bounds;
}

//Cell 高度
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return CELL_HEIGHT;
}

//加载tableview
- (void)loadView {
    self.view = [UIView new];
    self.exampleTableView = [UITableView new];
    self.exampleTableView.delegate = self;
    self.exampleTableView.dataSource = self;
    [self.view addSubview:self.exampleTableView];
}

#pragma mark - 
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return 399;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:IDENTIFIER];
    cell.selectionStyle = UITableViewCellSelectionStyleNone;
    
    //干掉contentView上面的子控件!! 节约内存!!
    for (NSInteger i = 1; i <= 3; i++) {
        //干掉contentView 上面的所有子控件!!
        [[cell.contentView viewWithTag:i] removeFromSuperview];
    }
    //不要直接加载图片!! 你将加载图片的代码!都给RunLoop!!
    [self addTask:^BOOL{
        [ViewController addImage1With:cell];
        return YES;
    } withKey:indexPath];
    [self addTask:^BOOL{
        [ViewController addImage2With:cell];
        return YES;
    } withKey:indexPath];
    [self addTask:^BOOL{
        [ViewController addImage3With:cell];
        return YES;
    } withKey:indexPath];
    
    

    return cell;
}




#pragma mark - 

//MARK: 添加任务
-(void)addTask:(RunloopBlock)unit withKey:(id)key{
    [self.tasks addObject:unit];
    [self.tasksKeys addObject:key];
    //保证之前没有显示出来的任务,不再浪费时间加载
    if (self.tasks.count > self.max) {
        [self.tasks removeObjectAtIndex:0];
        [self.tasksKeys removeObjectAtIndex:0];
    }
    
}



//MARK: 回调函数
//定义一个回调函数  一次RunLoop来一次
static void Callback(CFRunLoopObserverRef observer, CFRunLoopActivity activity, void *info){
    ViewController * vc = (__bridge ViewController *)(info);
    if (vc.tasks.count == 0) {
        return;
    }
    BOOL result = NO;
    while (result == NO && vc.tasks.count) {
        //取出任务
        RunloopBlock unit = vc.tasks.firstObject;
        //执行任务
        result = unit();
        //干掉第一个任务
        [vc.tasks removeObjectAtIndex:0];
        //干掉标示
        [vc.tasksKeys removeObjectAtIndex:0];
    }
    
}

//这里面都是C语言 -- 添加一个监听者
-(void)addRunloopObserver{
    //获取当前的RunLoop
    CFRunLoopRef runloop = CFRunLoopGetCurrent();
    //定义一个centext
    CFRunLoopObserverContext context = {
        0,
        ( __bridge void *)(self),
        &CFRetain,
        &CFRelease,
        NULL
    };
    //定义一个观察者defaultModeObsever
    static CFRunLoopObserverRef defaultModeObsever;
    //创建观察者
    defaultModeObsever = CFRunLoopObserverCreate(NULL,
                                                 kCFRunLoopBeforeWaiting,
                                                 YES,
                                                 NSIntegerMax - 999,
                                                 &Callback,
                                                 &context
                                                 );
    
    //添加当前RunLoop的观察者
    CFRunLoopAddObserver(runloop, defaultModeObsever, kCFRunLoopCommonModes);
    //c语言有creat 就需要release
    CFRelease(defaultModeObsever);
   
}


@end