集团考勤最新的意见反馈需求，参照了京东的截屏反馈。
重点就是如何监听到 用户触发了系统级的截屏，并获取到当前截屏图片。
监听到用户截屏后，有两种处理方式：
- 方式一：模拟用户的截屏动作，用layer 去绘制当前app的window 展示的内容，然后进行图像处理（比较复杂），获得UIImage
- 方式二：在截屏后，去访问用户相册，拿到用户相册的最后一张图片，判断是不是截屏，然后采用。
一、注册监听通知 -- userDidTakeScreenshot
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(userDidTakeScreenshot:)
name:UIApplicationUserDidTakeScreenshotNotification object:nil];
二、监听用户截屏动作，并处理layer（方式一）
－(void)userDidTakeScreenshot:(NSNotification *)notification
{
NSLog(@"检测到截屏");
//人为截屏, 模拟用户截屏行为, 获取所截图片
UIImage *image_ = [self imageWithScreenshot];
//添加显示
UIImageView *imgvPhoto = [[UIImageView alloc]initWithImage:image_];
imgvPhoto.frame = CGRectMake(self.window.frame.size.width/2, self.window.frame.size.height/2, self.window.frame.size.width/2, self.window.frame.size.height/2);
//添加边框
CALayer * layer = [imgvPhoto layer];
layer.borderColor = [
[UIColor whiteColor] CGColor];
layer.borderWidth = 5.0f;
//添加四个边阴影
imgvPhoto.layer.shadowColor = [UIColor blackColor].CGColor;
imgvPhoto.layer.shadowOffset = CGSizeMake(0, 0);
imgvPhoto.layer.shadowOpacity = 0.5;
imgvPhoto.layer.shadowRadius = 10.0;
//添加两个边阴影
imgvPhoto.layer.shadowColor = [UIColor blackColor].CGColor;
imgvPhoto.layer.shadowOffset = CGSizeMake(4, 4);
imgvPhoto.layer.shadowOpacity = 0.5;
imgvPhoto.layer.shadowRadius = 2.0;
[self.window addSubview:imgvPhoto];
}
三、处理截屏图像（方式一）
- (UIImage *)imageWithScreenshot
{
NSData *imageData = [self dataWithScreenshotInPNGFormat];
return [UIImage imageWithData:imageData];
}
- (NSData *)dataWithScreenshotInPNGFormat
{
CGSize imageSize = CGSizeZero;
UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
if (UIInterfaceOrientationIsPortrait(orientation))
imageSize = [UIScreen mainScreen].bounds.size;
else
imageSize = CGSizeMake([UIScreen mainScreen].bounds.size.height, [UIScreen mainScreen].bounds.size.width);
UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
for (UIWindow *window in [[UIApplication sharedApplication] windows])
{
CGContextSaveGState(context);
CGContextTranslateCTM(context, window.center.x, window.center.y);
CGContextConcatCTM(context, window.transform);
CGContextTranslateCTM(context, -window.bounds.size.width * window.layer.anchorPoint.x, -window.bounds.size.height * window.layer.anchorPoint.y);
if (orientation == UIInterfaceOrientationLandscapeLeft)
{
CGContextRotateCTM(context, M_PI_2);
CGContextTranslateCTM(context, 0, -imageSize.width);
}
else if (orientation == UIInterfaceOrientationLandscapeRight)
{
CGContextRotateCTM(context, -M_PI_2);
CGContextTranslateCTM(context, -imageSize.height, 0);
} else if (orientation == UIInterfaceOrientationPortraitUpsideDown) {
CGContextRotateCTM(context, M_PI);
CGContextTranslateCTM(context, -imageSize.width, -imageSize.height);
}
if ([window respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)])
{
[window drawViewHierarchyInRect:window.bounds afterScreenUpdates:YES];
}
else
{
[window.layer renderInContext:context];
}
CGContextRestoreGState(context);
}
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return UIImagePNGRepresentation(image);
}
四、方式二：获取用户最后一张图片
static NSTimeInterval const latestAssetFetchInterval = 10;
@interface AJUserPhotoFetchManager ()
@property (nonatomic, strong, nullable) NSDate *lastAssetcreationDate;
@end
static NSString * const kLastAssetcreationDateKey = @"kLastAssetcreationDateKey";
@implementation AJUserPhotoFetchManager
#pragma mark - 单例方法
static AJUserPhotoFetchManager *sharedInstance;
+ (id)allocWithZone:(struct _NSZone *)zone
{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [super allocWithZone:zone];
sharedInstance.lastAssetcreationDate = [[NSUserDefaults standardUserDefaults] objectForKey:kLastAssetcreationDateKey];
});
return sharedInstance;
}
+ (AJUserPhotoFetchManager *)sharedUserPhotoFetchManager
{
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[AJUserPhotoFetchManager alloc]init];
sharedInstance.lastAssetcreationDate = [[NSUserDefaults standardUserDefaults] objectForKey:kLastAssetcreationDateKey];
});
return sharedInstance;
}
/** 点击“＋”号的时候获取相册列表，获取最新保存的一张图片。
* 根据图片保存时间，与当前时间戳进行计算，获得间隔时间。从而判断是否是需求的时间间隔。（时间间隔自定义）
*/
- (void)fetchLatestPhotoInTimeIntervalWithCompletion:(void (^)(UIImage *result, NSDictionary *info))completion{
// 此处不能主动获取权限，在用户同意的情况下可以去获取
PHAuthorizationStatus status = [PHPhotoLibrary authorizationStatus];
if (status == PHAuthorizationStatusAuthorized) {
// AJUserPhotoFetchManager *sharedUserPhotoFetchManager = [AJUserPhotoFetchManager sharedUserPhotoFetchManager];
PHAsset *latestAsset = [self fetchLatestPhotoAsset];
NSDate *nowDate = [NSDate date];
NSTimeInterval timeInterval = [nowDate timeIntervalSinceDate:latestAsset.creationDate];// 创建时间距离的时间间隔
if (timeInterval > latestAssetFetchInterval) { // 超出时间了
return;
}
// 对一张图片10s内两次获取，虽然是同一张图片，系统回调的图片结果地址不一致。
// 阅读了相关博客也不建议用回调的info里面字段作判断, 所以这里采用的图片的时间戳
if (self.lastAssetcreationDate && [self.lastAssetcreationDate compare:latestAsset.creationDate] != NSOrderedAscending) { // 上次已经获取过了
return;
}
PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
options.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;
[[PHImageManager defaultManager] requestImageForAsset:latestAsset targetSize:UIScreen.mainScreen.bounds.size contentMode:PHImageContentModeAspectFit options:options resultHandler:^(UIImage *result, NSDictionary *info) {
self.lastAssetcreationDate = latestAsset.creationDate;
[[NSUserDefaults standardUserDefaults] setObject:latestAsset.creationDate forKey:kLastAssetcreationDateKey];
completion(result, info);
}];
}
}
- (PHAsset *)fetchLatestPhotoAsset{
PHFetchOptions *options = [[PHFetchOptions alloc]init];
if (@available(iOS 9.0, *)) {
options.fetchLimit = 1;
}
options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
PHFetchResult *assetsFetchResults = [PHAsset fetchAssetsWithOptions:options];
return assetsFetchResults.firstObject;
}
+ (void)requestAuthorization:(void (^)(PHAuthorizationStatus))handler{
[PHPhotoLibrary requestAuthorization:handler];
}