从UIProgressView更新NSProgress

Question

我有一个观察者，我试图以这样的方式更新我的UIProgressView：

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSProgress *progress = object;
NSLog(@"PROG: %f", progress.fractionCompleted);
[progressBar setProgress:_progressReceive.fractionCompleted animated:YES];

// Check which KVO key change has fired
if ([keyPath isEqualToString:kProgressCancelledKeyPath]) {
    // Notify the delegate that the progress was cancelled
    [progressBar removeFromSuperview];
    NSLog(@"CANCEL");

}
else if ([keyPath isEqualToString:kProgressCompletedUnitCountKeyPath]) {
    // Notify the delegate of our progress change

    if (progress.completedUnitCount == progress.totalUnitCount) {
        // Progress completed, notify delegate
        NSLog(@"COMPLETE");
        [progressBar removeFromSuperview];
    }
}
}

NSLog正在显示数据：

...
2013-10-29 19:55:26.831 Cleverly[2816:6103] PROG: 0.243300
2013-10-29 19:55:26.835 Cleverly[2816:6103] PROG: 0.243340
2013-10-29 19:55:26.838 Cleverly[2816:6103] PROG: 0.243430
...

但是progressBar没有更新。我注意到，如果我使用的是NSTimer，那么它确实会更新：

-(void)progressSend:(NSTimer*)timer{
NSLog(@"Fraction Complete: %@", [NSNumber numberWithDouble:progressSend.fractionCompleted]);
[progressBar setProgress:progressSend.fractionCompleted animated:YES];
}

这是为什么？？

Answer 1

1. 确保这些值是正确的
2. 确保您的KVO在主线程上。
3. 如果不是，请将正在更改主队列上UI的代码块dispatch_async。

Answer 2

尝试在主线程上执行：

[self performSelectorOnMainThread:@selector(updateProgress:) withObject:[NSArray arrayWithObjects:progressBar, progress.fractionCompleted, nil] waitUntilDone:NO];

方法：

-(void) updateProgress:(NSArray*)array
{
    UIProgressView *progressBar = [array objectAtIndex:0];
    NSNumber *number = [array objectAtIndex:1];
    [progressBar setProgress:number.floatValue animated:YES];
}