GPUImage锁定视图

Question

在我的应用程序中，我有一个对象CameraHandler，它使用GPUImage来检测摄像机中的某些运动。它是在我的GameViewController中初始化的。

它(CameraHandler)能够成功地检测运动，并启动相关方法，但在屏幕上显示任何更改之前，它会锁定GameViewController的视图相当长的时间(~5至10秒)。一旦CameraHandler检测到更改，它将触发一个方法，该方法将更改视图控制器上顶部视图的背景，并显示一个UIAlertView (用于测试目的)。就像我说的，这只发生在5-10秒后，从它被调用的那一刻起。我知道程序本身并没有冻结，因为我从方法中获得了相关的日志输出。我尝试过不同的方法来解决这个问题，但是我已经空手而归好几个星期了。

In GameViewController (在这里调用和启动CameraHandler):

-(void)startRound{
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);
    dispatch_async(queue, ^{
        [_shotDetector captureStillImage];
        dispatch_sync(dispatch_get_main_queue(), ^{
            NSLog(@"finish capture still image thread");

        });
    });
}

/* this method gets called from CameraHandler once it detects movement */
-(void)shotLifted:(NSNumber*)afterTime{
    NSLog(@"shot lifted fired");
    UIAlertView *lost = [[UIAlertView alloc]initWithTitle:@"Good Job!" message:@"Shot lifted in time" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [lost show];
    [_questionView setBackgroundColor:[UIColor whiteColor]];
    NSLog(@"shot lifted done");

}

CameraHandler.h

@interface CameraHandler : NSObject <GPUImageVideoCameraDelegate>

@property (strong) GPUImageOutput<GPUImageInput> *filter,*emptyFilter;
@property (strong) GPUImageVideoCamera *videoCamera;
@property (strong) GPUImagePicture *sourcePicture;
@property (strong) GPUImageOutput *pictureOutput;
@property (strong) GPUImageStillCamera *stillCamera;
@property (strong) __block UILabel *shotRemovedLabel;
@property (strong) __block NSDate *startTime;
@property (strong) NSMutableArray *averageLum;
@property (strong) id delegate;
@property (strong) GPUImageLuminosity *lumin;

CameraHandler.m相关方法

-(void)startBlackoutShotMotionAnalysis{
    NSLog(@"starting shot motion analysis");


    [_videoCamera addTarget:self.filter];
    [_sourcePicture processImage];
    [_sourcePicture addTarget:self.filter];
    [_videoCamera startCameraCapture];

    _lumin = [[GPUImageLuminosity alloc] init];
    [self.filter addTarget:_lumin];

    __block int i =0;
     __unsafe_unretained GameViewController* weakDelegate = self.delegate;
    //begin luminosity detecting of live-video from uiimage
    [(GPUImageLuminosity *)_lumin setLuminosityProcessingFinishedBlock:^(CGFloat luminosity, CMTime frameTime) {
        if(i<60){
            if(i>10){
                _startTime = [NSDate date];
                [_averageLum addObject:[NSNumber numberWithFloat:luminosity]];
            }
            i++;
        }
        else{
            CGFloat average = [[_averageLum valueForKeyPath:@"@avg.floatValue"]floatValue];
            CGFloat difference = fabsf(luminosity-average);

            if(difference > 0.05){
                NSTimeInterval liftedAfter = [_startTime timeIntervalSinceDate:[NSDate date]];
                [weakDelegate performSelector:@selector(shotLifted:) withObject:[NSNumber numberWithFloat:liftedAfter]];
                [_videoCamera stopCameraCapture];
                NSLog(@"should turn white now");                    
                return ;
            }
        }
    }];
    NSLog(@"finished returning executing starBlackoutMotionAnalysis Method");
}

NSLOG产出：

2014-04-08 20:22:45.450 Groupy[2887:5c0f] starting shot motion analysis
2014-04-08 20:22:46.152 Groupy[2887:5c0f] finished returning executing starBlackoutMotionAnalysis Method
2014-04-08 20:22:48.160 Groupy[2887:1303] shot lifted fired
2014-04-08 20:22:48.221 Groupy[2887:1303] shot lifted done
2014-04-08 20:22:48.290 Groupy[2887:1303] should turn white now

任何正确方向的帮助都将是巨大的。我一直在努力弄明白这个out.Thanks！

Answer 1

当我看到UI中异常延迟的更新时，我通常首先看到的是我的UI更新代码是否正在主队列上执行。除了少数例外情况外，您应该始终将任何与UI相关的代码分派到主队列，否则会出现这样的奇怪行为。

根据我所看到的，您可以直接在shotLifted:内执行luminosityProcessingFinishedBlock选择器。我们可以放心地假设GPUImage将调用主线程之外的那个块。这意味着初始化和显示警报视图的代码也发生在主线程上。

要改变这一点，您应该尝试将对shotLifted:的调用包装在一个块中，并将其分派到主队列：

dispatch_async(dispatch_get_main_queue(), ^{
    [weakDelegate performSelector:@selector(shotLifted:) withObject:obj];
}

或者你也可以这样做：

[weakDelegate performSelectorOnMainThread:@selector(shotLifted:) withObject:obj waitUntilDone:NO];