ios - NSRunLoop cancelPerformSelectorsWithTarget 不工作

Question

我有以下代码，但没有得到预期的结果。

#import "CancelPerformSelectorTestAppDelegate.h"
@implementation CancelPerformSelectorTestAppDelegate
@synthesize window;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
    [window makeKeyAndVisible];
    for(unsigned int i = 0; i < 10; i++){
        NSTimeInterval waitThisLong = i;
        [self performSelector:@selector(foo) withObject:nil afterDelay: waitThisLong];
    }

    [[NSRunLoop currentRunLoop] cancelPerformSelectorsWithTarget: self];

    return YES;
}

- (void) foo {
    static unsigned int timesCalled = 0;
    ++timesCalled;
    NSLog(@"%s: I am called for the %d-st/nd/th time", __func__, timesCalled);
}

- (void)applicationWillResignActive:(UIApplication *)application {}
- (void)applicationDidBecomeActive:(UIApplication *)application {}
- (void)applicationWillTerminate:(UIApplication *)application {}
- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application {}
- (void)dealloc {
    [window release];
    [super dealloc];
}

@end

我预计该函数将被调用大约 0 次，如果 CPU 运行缓慢，则可能调用 1 次。

该函数将执行 10 次! :( 总是。我做错了什么，我怎样才能达到预期的结果？

非常感谢， 尼克

Answer 1

您想使用 NSObject 取消请求类方法 +cancelPreviousPerformRequestsWithTarget:

例如，

[NSObject cancelPreviousPerformRequestsWithTarget:self];

Event Handling Guide for multitouch events 的“处理点击手势”部分有一个示例