iOS 启动广告

思路
1.判断广告文件是否存在，以及初始化广告位
2.无论沙盒中是否存在广告图片，都需要重新调用获取广告接口，判断广告是否更新
3.异步下载图片，以及删除旧图片
4.广告页面的跳过按钮倒计时功能可以通过定时器或者GCD实现
5.为广告页面添加一个点击手势，跳转到广告页面

.h

#import 

NS_ASSUME_NONNULL_BEGIN

static NSString *const adImageName = @"adImageName";

typedef void(^TapBlock)(void);

@interface GLAdView : UIView

- (instancetype)initWithFrame:(CGRect)frame withTapBlock:(TapBlock)tapBlock;


/** 图片路径*/
@property (nonatomic, copy) NSString *filePath;

@end

NS_ASSUME_NONNULL_END

.m

#import "GLAdView.h"

@interface GLAdView()

@property (nonatomic, strong) UIImageView *adView;

@property (nonatomic, strong) UIButton *countBtn;

@property (nonatomic, strong) NSTimer *countTimer;

@property (nonatomic, assign) int count;

@property (nonatomic, copy) TapBlock tapBlock;

@end

// 广告显示的时间
static int const showtime = 5;

@implementation GLAdView

- (NSTimer *)countTimer
{
    if (!_countTimer) {
        _countTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(countDown) userInfo:nil repeats:YES];
    }
    return _countTimer;
}


- (instancetype)initWithFrame:(CGRect)frame withTapBlock:(TapBlock)tapBlock
{
    if (self = [super initWithFrame:frame]) {
        
        // 1.广告图片
        _adView = [[UIImageView alloc] initWithFrame:frame];
        _adView.userInteractionEnabled = YES;
        _adView.contentMode = UIViewContentModeScaleAspectFill;
        _adView.clipsToBounds = YES;
        UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(pushToAd)];
        [_adView addGestureRecognizer:tap];
        
        // 2.跳过按钮
        CGFloat btnW = 60;
        CGFloat btnH = 30;
        _countBtn = [[UIButton alloc] initWithFrame:CGRectMake(KScreenWidth - btnW - 24, kTopHeight, btnW, btnH)];
        [_countBtn addTarget:self action:@selector(dismiss) forControlEvents:UIControlEventTouchUpInside];
        [_countBtn setTitle:[NSString stringWithFormat:@"跳过%d", showtime] forState:UIControlStateNormal];
        _countBtn.titleLabel.font = [UIFont systemFontOfSize:15];
        [_countBtn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
        _countBtn.backgroundColor = [UIColor colorWithRed:38 /255.0 green:38 /255.0 blue:38 /255.0 alpha:0.6];
        _countBtn.layer.cornerRadius = 4;
        
        [self addSubview:_adView];
        [self addSubview:_countBtn];
        
        // 1.判断沙盒中是否存在广告图片，如果存在，直接显示
        NSString *filePath = [self getFilePathWithImageName:[[NSUserDefaults standardUserDefaults] valueForKey:adImageName]];
        
        BOOL isExist = [self isFileExistWithFilePath:filePath];
        if (isExist) {// 图片存在
            [self setFilePath:filePath];
            self.tapBlock = tapBlock;
            [self show];
        }
        // 2.无论沙盒中是否存在广告图片，都需要重新调用广告接口，判断广告是否更新
        [self getAdvertisingImage];
        
    }
    return self;
}

- (void)setFilePath:(NSString *)filePath
{
    _filePath = filePath;
    _adView.image = [UIImage imageWithContentsOfFile:filePath];
}

- (void)pushToAd{
    
    [self dismiss];
    
    if (self.tapBlock) {
        self.tapBlock();
    }
    
}

- (void)countDown
{
    _count --;
    [_countBtn setTitle:[NSString stringWithFormat:@"跳过%d",_count] forState:UIControlStateNormal];
    if (_count <= 0) {
        [self dismiss];
    }
}

- (void)show
{
    // 倒计时方法2：定时器
    if (showtime<=0) {
        return;
    }
    [self startTimer];
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    [window addSubview:self];
}

// 定时器倒计时
- (void)startTimer
{
    _count = showtime;
    [[NSRunLoop mainRunLoop] addTimer:self.countTimer forMode:NSRunLoopCommonModes];
}

// 移除广告页面
- (void)dismiss
{
    [self.countTimer invalidate];
    self.countTimer = nil;
    
    [UIView animateWithDuration:0.3f animations:^{
        self.alpha = 0.f;
    } completion:^(BOOL finished) {
        [self removeFromSuperview];
    }];
    
}


/**
 *  判断文件是否存在
 */
- (BOOL)isFileExistWithFilePath:(NSString *)filePath
{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    BOOL isDirectory = FALSE;
    return [fileManager fileExistsAtPath:filePath isDirectory:&isDirectory];
}

/**
 *  初始化广告页面
 */
- (void)getAdvertisingImage
{
    
    NSArray *imageArray = @[@"http://img5.imgtn.bdimg.com/it/u=3300305952,1328708913&fm=26&gp=0.jpg", @"http://pic.58pic.com/58pic/13/82/74/92q58PICeSI_1024.jpg", @"http://pic25.nipic.com/20121205/10197997_003647426000_2.jpg"];
    
    NSArray *stringArr = [imageUrl componentsSeparatedByString:@"/"];
    NSString *imageName = stringArr.lastObject;
    
    // 拼接沙盒路径
    NSString *filePath = [self getFilePathWithImageName:imageName];
    BOOL isExist = [self isFileExistWithFilePath:filePath];
    if (!isExist){// 如果该图片不存在，则删除老图片，下载新图片
        
        [self downloadAdImageWithUrl:imageUrl imageName:imageName];
        
    }
}
/**
 *  下载新图片
 */
- (void)downloadAdImageWithUrl:(NSString *)imageUrl imageName:(NSString *)imageName
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        
        NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]];
        UIImage *image = [UIImage imageWithData:data];
        NSString *filePath = [self getFilePathWithImageName:imageName]; // 保存文件的名称
        
        if ([UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES]) {// 保存成功
            DLog(@"广告页保存成功");
            [self deleteOldImage];
            [[NSUserDefaults standardUserDefaults] setValue:imageName forKey:adImageName];
            [[NSUserDefaults standardUserDefaults] synchronize];
            // 如果有广告链接，将广告链接也保存下来
        }else{
            DLog(@"广告页保存失败");
        }
        
    });
}

/**
 *  删除旧图片
 */
- (void)deleteOldImage
{
    NSString *imageName = [[NSUserDefaults standardUserDefaults] valueForKey:adImageName];
    if (imageName) {
        NSString *filePath = [self getFilePathWithImageName:imageName];
        NSFileManager *fileManager = [NSFileManager defaultManager];
        [fileManager removeItemAtPath:filePath error:nil];
    }
}

/**
 *  根据图片名拼接文件路径
 */
- (NSString *)getFilePathWithImageName:(NSString *)imageName
{
    if (imageName) {
        
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory,NSUserDomainMask, YES);
        NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:imageName];
        
        return filePath;
    }
    
    return nil;
}

@end