源码阅读：AFNetworking（十五）——UIRefreshControl+AFNetworking-优快云博客

本文介绍如何使用AFNetworking为UIRefreshControl绑定任务，并根据任务状态自动控制刷新开始与结束。通过创建私有类AFRefreshControlNotificationObserver，利用NSNotification进行监听，实现了刷新控件与网络请求的联动。

该文章阅读的AFNetworking的版本为3.2.0。

这个分类可以为UIRefreshControl绑定一个task，然后根据task的加载状态自动开始和结束刷新。

1.接口文件

/**
 为UIRefreshControl绑定指定的task
 */
- (void)setRefreshingWithStateOfTask:(NSURLSessionTask *)task;
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2.AFRefreshControlNotificationObserver私有类

2.1.属性

/**
 保存要绑定task的刷新控件
 */
@property (readonly, nonatomic, weak) UIRefreshControl *refreshControl;
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2.2.方法

/**
 以指定刷新控件初始化的方法
 */
- (instancetype)initWithActivityRefreshControl:(UIRefreshControl *)refreshControl;

/**
 为UIRefreshControl绑定指定的task
 */
- (void)setRefreshingWithStateOfTask:(NSURLSessionTask *)task;
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2.3.实现

接口方法的实现

- (instancetype)initWithActivityRefreshControl:(UIRefreshControl *)refreshControl
{
    self = [super init];
    if (self) {
        // 用属性保存传入的参数
        _refreshControl = refreshControl;
    }
    return self;
}

- (void)setRefreshingWithStateOfTask:(NSURLSessionTask *)task {
    // 创建通知中心对象
    NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];

    // 先移除掉之前添加通知
    [notificationCenter removeObserver:self name:AFNetworkingTaskDidResumeNotification object:nil];
    [notificationCenter removeObserver:self name:AFNetworkingTaskDidSuspendNotification object:nil];
    [notificationCenter removeObserver:self name:AFNetworkingTaskDidCompleteNotification object:nil];

    // 如果传入的task不为nil
    if (task) {
        // 获取到传入的刷新控件
        UIRefreshControl *refreshControl = self.refreshControl;
        // 如果task的状态是正在运行中
        if (task.state == NSURLSessionTaskStateRunning) {
            // 刷新控件开始刷新
            [refreshControl beginRefreshing];

            // 注册通知监听task的开始、完成和暂停
            [notificationCenter addObserver:self selector:@selector(af_beginRefreshing) name:AFNetworkingTaskDidResumeNotification object:task];
            [notificationCenter addObserver:self selector:@selector(af_endRefreshing) name:AFNetworkingTaskDidCompleteNotification object:task];
            [notificationCenter addObserver:self selector:@selector(af_endRefreshing) name:AFNetworkingTaskDidSuspendNotification object:task];
        // 如果task的状态不是是正在运行中
        } else {
            // 刷新控件停止刷新
            [refreshControl endRefreshing];
        }
    }
}
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通知回调方法的实现

- (void)af_beginRefreshing {
    // 在主队列异步调用刷新控件的开始刷新
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.refreshControl beginRefreshing];
    });
}

- (void)af_endRefreshing {
    // 在主队列异步调用刷新控件的停止刷新
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.refreshControl endRefreshing];
    });
}
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生命周期方法实现

- (void)dealloc {
    // 移除掉添加通知
    NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
    
    [notificationCenter removeObserver:self name:AFNetworkingTaskDidCompleteNotification object:nil];
    [notificationCenter removeObserver:self name:AFNetworkingTaskDidResumeNotification object:nil];
    [notificationCenter removeObserver:self name:AFNetworkingTaskDidSuspendNotification object:nil];
}
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3.方法实现

- (AFRefreshControlNotificationObserver *)af_notificationObserver {
    // 先通过关联对象获取为分类创建的属性
    AFRefreshControlNotificationObserver *notificationObserver = objc_getAssociatedObject(self, @selector(af_notificationObserver));
    // 如果属性为空
    if (notificationObserver == nil) {
        // 创建刷新控件通知观察者对象
        notificationObserver = [[AFRefreshControlNotificationObserver alloc] initWithActivityRefreshControl:self];
        // 通过关联对象将创建的对象保存到属性中
        objc_setAssociatedObject(self, @selector(af_notificationObserver), notificationObserver, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    return notificationObserver;
}

- (void)setRefreshingWithStateOfTask:(NSURLSessionTask *)task {
    // 获取到刷新控件通知观察者对象并为之绑定task
    [[self af_notificationObserver] setRefreshingWithStateOfTask:task];
}
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