我正在寻找一种方法,让我的应用程序在用户使用 Command-Shift-3
或 Command-Shift-4
截屏时接收通知。
像 Droplr 和 Cloud App 这样的应用程序就是一个例子,它们可以自动上传截屏。
我已经搜索了一些资料,发现这可能与 Darwin 通知有关,但我不确定从何处开始。
我正在寻找一种方法,让我的应用程序在用户使用 Command-Shift-3
或 Command-Shift-4
截屏时接收通知。
像 Droplr 和 Cloud App 这样的应用程序就是一个例子,它们可以自动上传截屏。
我已经搜索了一些资料,发现这可能与 Darwin 通知有关,但我不确定从何处开始。
这在早期的一些评论中提到过,但是您可以使用一个 NSMetadataQuery
来搜索kMDItemIsScreenCapture = 1
的文件。这是一个特殊属性,会添加到屏幕截图文件中。
我刚刚创建了一个小演示程序,在github上发布:
https://github.com/davedelong/Demos/blob/master/ScreenShot%20Detector
这是我完成它的方法,有点复杂,但我会尝试一步一步地带你完成:
在开始之前,在您的头文件中声明以下变量和方法:
BOOL shouldObserveDesktop;
NSDictionary *knownScreenshotsOnDesktop;
NSString *screenshotLocation;
NSString *screenshotFilenameSuffix;
- (void)startObservingDesktop;
- (void)stopObservingDesktop;
- (NSDictionary *)screenshotsOnDesktop;
- (NSDictionary *)screenshotsAtPath:(NSString *)dirpath modifiedAfterDate:(NSDate *)lmod;
- (void)checkForScreenshotsAtPath:(NSString *)dirpath;
- (NSDictionary *)findUnprocessedScreenshotsOnDesktop;
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
screenshotLocation = [[NSString stringWithString:@"~/Desktop"] retain];
screenshotFilenameSuffix = [[NSString stringWithString:@".png"] retain];
knownScreenshotsOnDesktop = [[self screenshotsOnDesktop] retain];
[self startObservingDesktop];
}
这将为调用所有方法时设置变量。接下来添加:
- (void)onDirectoryNotification:(NSNotification *)n {
id obj = [n object];
if (obj && [obj isKindOfClass:[NSString class]]) {
[self checkForScreenshotsAtPath:screenshotLocation];
}
}
- (void)startObservingDesktop {
if (shouldObserveDesktop)
return;
NSDistributedNotificationCenter *dnc = [NSDistributedNotificationCenter defaultCenter];
[dnc addObserver:self selector:@selector(onDirectoryNotification:) name:@"com.apple.carbon.core.DirectoryNotification" object:nil suspensionBehavior:NSNotificationSuspensionBehaviorDeliverImmediately];
shouldObserveDesktop = YES;
}
- (void)stopObservingDesktop {
if (!shouldObserveDesktop)
return;
NSDistributedNotificationCenter *dnc = [NSDistributedNotificationCenter defaultCenter];
[dnc removeObserver:self name:@"com.apple.carbon.core.DirectoryNotification" object:nil];
shouldObserveDesktop = NO;
}
在这里,我们观察将在截屏时调用的通知,并传递要调用的方法(在本例中为onDirectoryNotification:
)。还有一种方法可以停止观察桌面/通知。通知调用checkForScreenshotsAtPath:
,它将检查桌面上的截图。以下是该方法及其调用的其他方法的代码:
-(void)checkForScreenshotsAtPath:(NSString *)dirpath {
NSDictionary *files;
NSArray *paths;
// find new screenshots
if (!(files = [self findUnprocessedScreenshotsOnDesktop]))
return;
// sort on key (path)
paths = [files keysSortedByValueUsingComparator:^(id a, id b) { return [b compare:a]; }];
// process each file
for (NSString *path in paths) {
// Process the file at the path
}
}
-(NSDictionary *)findUnprocessedScreenshotsOnDesktop {
NSDictionary *currentFiles;
NSMutableDictionary *files;
NSMutableSet *newFilenames;
currentFiles = [self screenshotsOnDesktop];
files = nil;
if ([currentFiles count]) {
newFilenames = [NSMutableSet setWithArray:[currentFiles allKeys]];
// filter: remove allready processed screenshots
[newFilenames minusSet:[NSSet setWithArray:[knownScreenshotsOnDesktop allKeys]]];
if ([newFilenames count]) {
files = [NSMutableDictionary dictionaryWithCapacity:1];
for (NSString *path in newFilenames) {
[files setObject:[currentFiles objectForKey:path] forKey:path];
}
}
}
knownScreenshotsOnDesktop = currentFiles;
return files;
}
-(NSDictionary *)screenshotsOnDesktop {
NSDate *lmod = [NSDate dateWithTimeIntervalSinceNow:-5]; // max 5 sec old
return [self screenshotsAtPath:screenshotLocation modifiedAfterDate:lmod];
}
以下是通知调用的前3种方法,最终的方法是screenshotsAtPath:modifiedAfterDate:
,需要注意的是这个方法非常长,因为它必须确认文件确实是屏幕截图:
-(NSDictionary *)screenshotsAtPath:(NSString *)dirpath modifiedAfterDate:(NSDate *)lmod {
NSFileManager *fm = [NSFileManager defaultManager];
NSArray *direntries;
NSMutableDictionary *files = [NSMutableDictionary dictionary];
NSString *path;
NSDate *mod;
NSError *error;
NSDictionary *attrs;
dirpath = [dirpath stringByExpandingTildeInPath];
direntries = [fm contentsOfDirectoryAtPath:dirpath error:&error];
if (!direntries) {
return nil;
}
for (NSString *fn in direntries) {
// always skip dotfiles
if ([fn hasPrefix:@"."]) {
//[log debug:@"%s skipping: filename begins with a dot", _cmd];
continue;
}
// skip any file not ending in screenshotFilenameSuffix (".png" by default)
if (([fn length] < 10) ||
// ".png" suffix is expected
(![fn compare:screenshotFilenameSuffix options:NSCaseInsensitiveSearch range:NSMakeRange([fn length]-5, 4)] != NSOrderedSame)
)
{
continue;
}
// build path
path = [dirpath stringByAppendingPathComponent:fn];
// Skip any file which name does not contain a space.
// You want to avoid matching the filename against
// all possible screenshot file name schemas (must be hundreds), we make the
// assumption that all language formats have this in common: it contains at least one space.
if ([fn rangeOfString:@" "].location == NSNotFound) {
continue;
}
// query file attributes (rich stat)
attrs = [fm attributesOfItemAtPath:path error:&error];
if (!attrs) {
continue;
}
// must be a regular file
if ([attrs objectForKey:NSFileType] != NSFileTypeRegular) {
continue;
}
// check last modified date
mod = [attrs objectForKey:NSFileModificationDate];
if (lmod && (!mod || [mod compare:lmod] == NSOrderedAscending)) {
// file is too old
continue;
}
// find key for NSFileExtendedAttributes
NSString *xattrsKey = nil;
for (NSString *k in [attrs keyEnumerator]) {
if ([k isEqualToString:@"NSFileExtendedAttributes"]) {
xattrsKey = k;
break;
}
}
if (!xattrsKey) {
// no xattrs
continue;
}
NSDictionary *xattrs = [attrs objectForKey:xattrsKey];
if (!xattrs || ![xattrs objectForKey:@"com.apple.metadata:kMDItemIsScreenCapture"]) {
continue;
}
// ok, let's use this file
[files setObject:mod forKey:path];
}
return files;
}
好的,这就是我如何检测用户截屏的方法,可能有一些bug,但目前看起来运行良好。如果您想要全部代码,可以在pastebin.com上找到以下链接:
Header - http://pastebin.com/gBAbCBJB
Implementation - http://pastebin.com/VjQ6P3zQ
com.apple.screencapture
默认值不存在。 - JoshuaNSDictionary *xattrs = [attrs objectForKey:@"NSFileExtendedAttributes"];
- user102008NSMetadataQuery
搜索kMDItemIsScreenCapture = 1
文件:https://github.com/davedelong/Demos/tree/master/ScreenShot%20Detector - Dave DeLong当用户截屏时,您需要注册一个对象来接收系统通知。
因此:
[[NSNotificationCenter defaultCenter] addObserver: theObjectToRecieveTheNotification selector:@selector(theMethodToPerformWhenNotificationIsRecieved) name:@"theNameOftheScreenCapturedNotification" object: optionallyAnObjectOrArgumentThatIsPassedToTheMethodToBecalled];
不确定通知名称是什么,但可能已经存在。
在dealloc中不要忘记注销自己:
[[NSNotificationCenter defaultCenter] removeObserver:self];