iPhone下载指示器不显示

Question

我下载某些数据，当它被下载时，这个方法被调用：

- (void)connectionDidFinishLoading:(NSURLConnection *)connection;

在这个方法中，我应该在视图控制器中呈现一个旋转图像，我用委托来做，当下载数据时，我删除这个旋转图像：

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

[delegate showIndicator];

//Complex data downloading

[delegate hideIndicator];
}

所以这些方法被调用时连接完成加载发生，但它们没有被调用。以下是它们的实现：

-(void)showIndicator;
{
    NSLog(@"Show indicator");
    UIImage *statusImage = [UIImage imageNamed:@"update.png"];
    activityImageView = [[UIImageView alloc] initWithImage:statusImage];
    // Make a little bit of the superView show through

    activityImageView.animationImages = [NSArray arrayWithObjects:
                                         [UIImage imageNamed:@"update.png"],
                                         [UIImage imageNamed:@"update2.png"],
                                         [UIImage imageNamed:@"update3.png"],
                                         [UIImage imageNamed:@"update4.png"],
                                         nil];
    activityImageView.frame=CGRectMake(13, 292, 43, 44);
    activityImageView.animationDuration = 1.0f;
    [rightView addSubview:activityImageView];
    [activityImageView startAnimating];
}
-(void)hideIndicator
{  NSLog(@"Hide indicator");
     [activityImageView removeFromSuperview];
}

这就是我创建 JManager 对象并为其调用 connectionFinished 事件的地方：

-(IBAction)update:(id)sender
{
///la la la updating
JManager *manager1=[[JManager alloc] initWithDate:dateString andCategory:@"projects"];
            manager1.delegate=self;
            [manager1 requestProjects];
}

为什么我的自定义指标添加不能代表 Jmanager 对象完成？谢谢！

Answer 1

假设您从主线程调用 NSURLConnection，该方法不是异步执行的，因此指示器没有机会在您启动和停止之间显示。

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    [delegate showIndicator];

    //Complex data downloading

    [delegate hideIndicator];
}

您应该在 - (void)connectionDidReceiveResponse 方法中调用 [delegate showIndicator]，如下所示：

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    //connection starts
    [delegate showIndicator];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    //connection ends
    [delegate hideIndicator];
}