iOS开发弹窗池（顺序显示）

需求：app启动的时候总是会显示许许多多的弹窗，那么有一个需求就是让这种弹窗一个个的显示，点掉一个显示下一个。碰到这样的需求该如何搞定呢。
解决方案：有2种实现方案，第一种是创建一个弹窗池来管控弹窗顺序，第二种是利用线程、信号量来完成顺序执行。

第一种方案：

封装GYPopupManager弹窗池，里面维护了一个弹窗的数组。

//
//  GYPopupManager.h
//  testUI
//
//  Created by gaoyu on 2021/9/8.
//

/**
 ⚠️⚠️⚠️：GYPopupManager
 此管理类不关心弹窗的show和hide
 只约束弹窗是否被拦截一个一个展示、或者某几个同时展示
 */
#import 

///优先级枚举
typedef NS_ENUM(NSUInteger, GYPopupPriority) {
    GYPopupPriorityLow = 1,     /// 低
    GYPopupPriorityMedium,      /// 中
    GYPopupPriorityHigh         /// 高
};

/// 回调
typedef void (^GYPopupBlock)(void);

// MARK: - GYPopupConfig 弹出内容配置信息
@interface GYPopupConfig : NSObject

/// 是否被拦截：默认YES
@property (nonatomic, assign) BOOL isIntercept;
/// 当前弹窗是否在展示
@property (nonatomic, assign) BOOL isShowing;
/// 弹窗优先级：默认为High（相同优先级的弹窗后加入的先展示，因为字典添加元素后默认会在第一位，所以转化为数组后也是第一个）
@property (nonatomic, assign) GYPopupPriority priority;
/// 弹窗标识：以类名为标识，便于排查
@property (nonatomic, copy, nonnull) NSString *popupClassName;
/// 展示回调
@property (nonatomic, copy, nonnull) GYPopupBlock showBlock;
/// 隐藏回调
@property (nonatomic, copy, nullable) GYPopupBlock dismissBlock;

@end




// MARK: - GYPopupManager 弹出内容管理类
@interface GYPopupManager : NSObject

/// 单例对象
+ (instancetype _Nonnull)shared;

/// 展示弹窗
/// @param popupClass 弹出内容class
/// @param showBlock 展示回调
/// @param dismissBlock 隐藏回调
- (void)popupWithClass:(_Nonnull Class)popupClass show:(_Nonnull GYPopupBlock)showBlock dismiss:(_Nullable GYPopupBlock)dismissBlock;

/// 展示弹窗
/// @param popupClass 弹出内容class
/// @param priority 优先级
/// @param showBlock 展示回调
/// @param dismissBlock 隐藏回调
- (void)popupWithClass:(_Nonnull Class)popupClass priority:(GYPopupPriority)priority show:(_Nonnull GYPopupBlock)showBlock dismiss:(_Nullable GYPopupBlock)dismissBlock;

/// 展示弹窗
/// @param popupClass 弹出内容class
/// @param priority 优先级
/// @param isIntercept 是否需要被拦截
/// @param showBlock 展示回调
/// @param dismissBlock 隐藏回调
- (void)popupWithClass:(_Nonnull Class)popupClass priority:(GYPopupPriority)priority isIntercept:(BOOL)isIntercept show:(_Nonnull GYPopupBlock)showBlock dismiss:(_Nullable GYPopupBlock)dismissBlock;

/// 隐藏弹窗
- (void)dismissPopup;

@end

.m实现

//
//  GYPopupManager.m
//  testUI
//
//  Created by gaoyu on 2021/9/8.
//

#import "GYPopupManager.h"

// MARK: - PRAlertViewConfig
@implementation GYPopupConfig

- (instancetype)init {
    self = [super init];
    if (self) {
        self.isIntercept = YES;
        self.popupClassName = @"defaultName";
        self.priority = GYPopupPriorityHigh;
    }
    return self;
}

@end




// MARK: - GYPopupManager
@interface GYPopupManager()

/// 弹出池：key：弹窗className、value：config对象
@property (nonatomic, strong) NSMutableDictionary *popupPool;
/// 当前弹窗内容
@property (nonatomic, strong) GYPopupConfig *currnetPopup;

@end

@implementation GYPopupManager

static GYPopupManager *_instance = nil;

+ (instancetype)shared {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [[GYPopupManager alloc] init];
    });
    return _instance;
}

// MARK: - Public Methods
- (void)popupWithClass:(Class)popupClass show:(GYPopupBlock)showBlock dismiss:(GYPopupBlock)dismissBlock{
    [self popupWithClass:popupClass priority:GYPopupPriorityHigh isIntercept:YES show:showBlock dismiss:dismissBlock];
}

- (void)popupWithClass:(Class)popupClass priority:(GYPopupPriority)priority show:(GYPopupBlock)showBlock dismiss:(GYPopupBlock)dismissBlock {
    [self popupWithClass:popupClass priority:priority isIntercept:YES show:showBlock dismiss:dismissBlock];
}

- (void)popupWithClass:(Class)popupClass priority:(GYPopupPriority)priority isIntercept: (BOOL)isIntercept show:(GYPopupBlock)showBlock dismiss:(GYPopupBlock)dismissBlock {
    GYPopupConfig *config = [[GYPopupConfig alloc] init];
    config.popupClassName = NSStringFromClass(popupClass);
    config.priority = priority;
    config.isIntercept = isIntercept;
    [self popupWithConfig:config show:showBlock dismiss:dismissBlock];
    
}

// MARK: - Private Methods
- (void)popupWithConfig:(GYPopupConfig *)config show:(GYPopupBlock)showBlock dismiss:(GYPopupBlock)dismissBlock {
    config.showBlock = showBlock;
    config.dismissBlock = dismissBlock;
    config.isShowing = YES;
    
    // 加入弹出池，同一个弹窗避免重复添加
    [self.popupPool setObject:config forKey:config.popupClassName];
    
    // 当前有弹窗在显示：self.popupPool.allKeys.count > 1
    // 当前弹窗被拦截：isIntercept == YES
    if (config.isIntercept && self.popupPool.allKeys.count > 1) {
        config.isShowing = NO;
        return;
    }
    
    self.currnetPopup = config;
    
    //回主线程
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        showBlock ? showBlock() : nil;
    });
}


/// 清除弹出内容
- (void)dismissPopup {
    // 获取到当前弹出内容并删除
    [self deletePopupWithConfig:self.currnetPopup];
    
    // 是否有弹窗在显示 是：拦截其他未显示弹窗；否：查看是否有下一个可显示弹窗并显示
    if ([self isShowingSomeAlert]) {
        return;
    } else {
        // 优先级排序
        NSArray * values = [self.popupPool allValues];
        values = [self sortByPriority:values];
        
        // 当前没有正在展示的弹窗，则展示被拦截的弹窗
        if (values.count > 0) {
            // 查询是否有可以展示的弹窗：条件：1.已加入缓存、2.被拦截 3、实现了展示回调
            // 优先级 1 > 2 > 3
            // 找到一个立即展示，并退出循环（相同优先级的弹窗后加入的先展示，因为字典添加元素后默认会在第一位，所以转化为数组后也是第一个）
            for (GYPopupConfig *config in values) {
                GYPopupBlock showBlock = config.showBlock;
                if (config.isIntercept && showBlock) {
                    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                        config.isShowing = YES;
                        self.currnetPopup = config;
                        showBlock();
                    });
                    break;
                }
            }
        }
    }
}

/// 是否正在展示某个弹窗
- (BOOL)isShowingSomeAlert{
    __block BOOL isShowSomeAlert = NO;
    [self.popupPool enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
        GYPopupConfig *config = obj;
        if (config.isShowing) {
            isShowSomeAlert = YES;
            *stop = YES;
        }
    }];
    return isShowSomeAlert;
}

/// 根据优先级排序
/// @param configArray 弹窗配置数组
- (NSArray *)sortByPriority:(NSArray *)configArray {
    NSComparator comparator = ^(GYPopupConfig *obj1, GYPopupConfig *obj2) {
        if (obj1.priority > obj2.priority) {
            return NSOrderedAscending;
        }
        if (obj1.priority < obj2.priority) {
            return NSOrderedDescending;
        }
        return NSOrderedSame;
    };
    return [configArray sortedArrayUsingComparator:comparator];
}

/// 根据配置删除指定弹出内容
/// @param config 弹出配置
- (void)deletePopupWithConfig:(GYPopupConfig *)config {
    if (config == nil) return;
    GYPopupBlock dismissBlock = config.dismissBlock;
    dismissBlock ? dismissBlock() : nil;
    if ([self.popupPool.allKeys containsObject:config.popupClassName]) {
        [self.popupPool removeObjectForKey:config.popupClassName];
    }
    self.currnetPopup = nil;
}
 
// MARK: - Getters
- (NSMutableDictionary *)popupPool {
    if (!_popupPool) {
        _popupPool = [[NSMutableDictionary alloc] init];
    }
    return _popupPool;
}

@end

把弹窗全部加到封装好的GYPopupManager弹窗池中

[[GYPopupManager shared] popupWithClass:[Toast class] priority:GYPopupPriorityMedium show:^{
            // 弹窗的展示
            [[Toast shared] show];
} dismiss:^{

}];

// 弹窗消失
[[GYPopupManager shared] dismissPopup];

第二种方案：

通过子线程+信号量去阻塞后续弹窗的展示，来完成顺序弹窗

思路：
创建全局只容纳1个单位的信号量
Show的时候 Lock
Dismiss的时候 Release Lock

#import 

NS_ASSUME_NONNULL_BEGIN

@interface BaseAlertView : UIView

- (void)show;

- (void)dismiss;

@end

NS_ASSUME_NONNULL_END

.m实现

#import "BaseAlertView.h"

//全局信号量
dispatch_semaphore_t _globalInstancesLock;
//执行QUEUE的Name
char *QUEUE_NAME = "com.alert.queue";

//初始化 -- 借鉴YYWebImage的写法
static void _AlertViewInitGlobal() {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _globalInstancesLock = dispatch_semaphore_create(1);
    });
}

@implementation BaseAlertView
- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:[UIScreen mainScreen].bounds];
    if (self)
    {
        _AlertViewInitGlobal();
    }
    return self;
}

#pragma mark - public
- (void)show
{
    //位于非主线程 不阻塞
    dispatch_async(dispatch_queue_create(QUEUE_NAME, DISPATCH_QUEUE_SERIAL), ^{
        //Lock
        dispatch_semaphore_wait(_globalInstancesLock, DISPATCH_TIME_FOREVER);
        //保证主线程UI操作
        dispatch_async(dispatch_get_main_queue(), ^{
            [[UIApplication sharedApplication].windows.firstObject addSubview:(UIView *)self];
        });
    });
}

- (void)dismiss
{
    dispatch_async(dispatch_queue_create(QUEUE_NAME, DISPATCH_QUEUE_SERIAL), ^{
        //Release Lock
        dispatch_semaphore_signal(_globalInstancesLock);

        dispatch_async(dispatch_get_main_queue(), ^{
            [self removeFromSuperview];
        });
    });
}

@end

实现方法：弹窗的view继承于BaseAlertView，在展示的时候调用父类的show方法即可。

参考文档：
iOS弹窗顺序弹出管理
iOS 弹窗顺序显示 -- 信号量实践