如何以編程方式更改系統範圍的桌面圖片？

Question

我使用下面的代碼來設置桌面圖片：

NSURL* newImage = [[NSURL alloc] initFileURLWithPath:@"/Users/name/Pictures/test.png"]; 
[[NSWorkspace sharedWorkspace] setDesktopImageURL:newImage forScreen:screen options:nil error:&nserror]; 

它工作正常，當我需要的桌面圖片改變。但它不會更改系統範圍的桌面偏好設置（例如，每30分鐘更改一次圖片）。我如何更改系統範圍的桌面偏好？

Answer 1

看看Preferences and Settings Programming Guide。這應該有所幫助。

編輯：
下面是示例代碼：

NSString* newImgPath = @"/Users/cody/Desktop/stuff/imgs/Black_mac.png"; 

NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults]; 
NSMutableDictionary* desktopDict = [NSMutableDictionary dictionaryWithDictionary:[defaults persistentDomainForName:@"com.apple.desktop"]]; 
NSMutableDictionary* bgDict = [desktopDict objectForKey:@"Background"]; 
NSMutableDictionary* spaces = [bgDict objectForKey:@"spaces"]; 
[spaces enumerateKeysAndObjectsUsingBlock:^(NSString* key, NSMutableDictionary* obj, BOOL *stop) { 
    [obj enumerateKeysAndObjectsUsingBlock:^(id key, NSMutableDictionary* prefs, BOOL *stop) { 
     [prefs setObject:newImgPath forKey:@"ImageFilePath"]; 
     [prefs setObject:newImgPath forKey:@"NewImageFilePath"]; 
     [prefs setObject:@"Never" forKey:@"Change"]; 
    }]; 
}]; 

//NSLog(@"%@", desktopDict); 

[defaults setPersistentDomain:desktopDict forName:@"com.apple.desktop"]; 
if ([defaults synchronize] == NO) 
    NSLog(@"synchronize failed"); 

// Restart dock 
system ("/usr/bin/killall Dock");