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我将块存储在NSDictionary. 这是这些块之一：

void(^RunningApplications)(void) = ^{
        NSArray *runningApps = [[NSWorkspace sharedWorkspace] runningApplications];
        NSMutableArray *appNames = [[NSMutableArray alloc] initWithCapacity:[runningApps count]];
        for (NSRunningApplication *app in runningApps)
            [appNames addObject:[app localizedName]];
        NSLog(@"%@", [[NSWorkspace sharedWorkspace] runningApplications]);
    };

第一次访问此块时，我会看到当前正在运行的应用程序NSLog。但是，如果我打开另一个应用程序，然后再次调用该块，我只会看到显示的原始列表，而不是新打开的应用程序的新列表。如何通过此块接收更新的列表？

4

1 回答 1

3

您的问题与块（或字典）无关，与您 (ab) 使用的方式有关-runningApplications。从文档：

类似于 NSRunningApplication 类的属性，这个属性只有在主运行循环以普通模式运行时才会改变。使用键值观察来通知此数组属性的更改，而不是轮询。

为此，以下演示了正确的行为：

#import "AppDelegate.h"

const static NSString *runningApplicationsContext = @"running applications observation";

@implementation AppDelegate

@synthesize window = _window;

- (void)dealloc
{
    [[NSWorkspace sharedWorkspace] removeObserver:self
                                       forKeyPath:@"runningApplications"
                                          context:&runningApplicationsContext];
    [super dealloc];
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    [[NSWorkspace sharedWorkspace] addObserver:self
                                    forKeyPath:@"runningApplications"
                                       options:NSKeyValueObservingOptionNew
                                       context:&runningApplicationsContext];
}

- (void)observeValueForKeyPath:(NSString *)keyPath 
                      ofObject:(id)object 
                        change:(NSDictionary *)change 
                       context:(void *)context
{
    if (context == &runningApplicationsContext) {
        NSArray *runningApps = [(NSWorkspace *)object runningApplications];
        NSMutableArray *appNames = [[NSMutableArray alloc] initWithCapacity:[runningApps count]];
        for (NSRunningApplication *app in runningApps) {
            [appNames addObject:[app localizedName]];
        }
        NSLog(@"%@", [[NSWorkspace sharedWorkspace] runningApplications]);
        [appNames release];
    }
}

这还有另一个好处：您可以检查change字典以确定哪些应用程序触发了通知，以防您感兴趣。这使您免于缓存/跟踪以前的runningApplications结果。

编辑：跟进您的评论，这里有一些代码可以很好地与您的块（剥离了我认为在您的较大应用程序中执行某些操作的死代码）存储在字典中并从观察者方法调用：

#import "AppDelegate.h"

const static NSString *runningApplicationsContext = @"running applications observation";

@interface AppDelegate () {
    NSDictionary *_blocks;
}

@end

@implementation AppDelegate

@synthesize window = _window;

- (void)dealloc
{
    [[NSWorkspace sharedWorkspace] removeObserver:self
                                       forKeyPath:@"runningApplications"
                                          context:&runningApplicationsContext];
    [_blocks release];
    [super dealloc];
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    _blocks = [[NSDictionary alloc] initWithObjectsAndKeys:(id)
               ^{
                   NSLog(@"%@", [[NSWorkspace sharedWorkspace] runningApplications]);
               }, @"RunningApplications",
               nil];

    [[NSWorkspace sharedWorkspace] addObserver:self
                                    forKeyPath:@"runningApplications"
                                       options:NSKeyValueObservingOptionNew
                                       context:&runningApplicationsContext];
}

- (void)observeValueForKeyPath:(NSString *)keyPath 
                      ofObject:(id)object 
                        change:(NSDictionary *)change 
                       context:(void *)context
{
    if (context == &runningApplicationsContext) {
        dispatch_block_t getRunningApplications = [_blocks objectForKey:@"RunningApplications"];
        getRunningApplications();
    }
}

@end
于 2012-04-17T02:12:51.953 回答