我有一个计时器:
[NSTimer scheduledTimerWithTimeInterval:(float)jpegInterval/1000 target:self selector:@selector(jpegDownloaderSelector:) userInfo:url repeats:YES];
jpegDownloaderSelector执行从url获取图像并将其设置为imageView,如下所示:
-(void) jpegDownloaderSelector:(NSTimer*)timer{
[self performSelectorInBackground:@selector(jpegDownloader:) withObject:(NSString*)[timer userInfo]];
}
-(void) jpegDownloader:(NSString*)imageUrl{
dispatch_async(dispatch_get_main_queue(), ^{
imgData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://10.8.9.100:509/jpeg"]];
imageView.image = [UIImage imageWithData:imgData];
});
}
我还用gestureRecognizer设置了imageView
[imageView addGestureRecognizer:singleTapRecognizer];
[imageView addGestureRecognizer:doubleTapRecognizer];
识别器定义为:
singleTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(functoCall:)];
singleTapRecognizer.numberOfTapsRequired = 1;
singleTapRecognizer.numberOfTouchesRequired = 1;
doubleTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(funcToCall2:)];
doubleTapRecognizer.numberOfTapsRequired = 2;
doubleTapRecognizer.numberOfTouchesRequired = 1;
我遇到的问题是,当计时器启动时,我双击图像视图,双击识别器没有响应,而是单击响应。
如果我为定时器重复参数设置了NO,则双击响应。因此,我怀疑由于运行由计时器调用的后台功能,双击没有响应。
任何人都建议我可以实现后台功能,并且没有识别双击的问题。
答案 0 :(得分:2)
执行此操作时:
dispatch_async(dispatch_get_main_queue(), ^{
你将任务推到主线程,只是在很短的延迟之后。因此,您的图像下载在主线程上完成,并阻止所有其他交互。
相反,您应该在后台线程(dispatch_get_global_queue
)上运行下载,然后再回到主线程来处理结果。
-(void) jpegDownloader:(NSString*)imageUrl {
dispatch_async(dispatch_get_global_queue(), ^{
imgData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://10.8.9.100:509/jpeg"]];
dispatch_async(dispatch_get_main_queue(), ^{
imageView.image = [UIImage imageWithData:imgData];
});
});
}