iphone - 如何显示指标

Question

我无法显示指标 View 。

ItemController.h

#import <UIKit/UIKit.h>


@interface ItemController : UITableViewController {
  UIView* loadingView;
  UIActivityIndicatorView* indicator;
}

@property (nonatomic, retain) UIView *loadingView;
@property (nonatomic, retain) UIActivityIndicatorView *indicator;

@end

ItemController.m

.....
- (void)netAccessStart {


  loadingView = [[UIView alloc] initWithFrame:[[self view] bounds]];
  [loadingView setBackgroundColor:[UIColor blackColor]];
  [loadingView setAlpha:0.5];
  indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
  [[self view] addSubview:loadingView];
  [loadingView addSubview:indicator];
  [indicator setFrame:CGRectMake ((320/2)-20, (480/2)-60, 40, 40)];
  [indicator startAnimating];

}

- (void)netAccessEnd {


  [indicator stopAnimating];
  [loadingView removeFromSuperview];

}

- (void)dealloc {
  [loadingView release];
  [indicator release];
    [super dealloc];
}
.....

继承类

- (void)viewWillAppear:(BOOL)animated {
  [super viewWillAppear:animated];
  [self netAccessStart];
  sleep(1);
  [self netAccessEnd];
}

Answer 1

sleep() 阻止执行，这意味着您的应用在 -viewWillAppear 调用上卡住，在调用结束时您的 loadingView 得到从其 super View 中删除。换句话说，[self netAccessStart]; 和 [self netAccessEnd]; 之间不会发生任何绘制。我假设您为了测试目的而立即调用一个，在这种情况下，我会将 -netAccessStart 命令移至 -viewDidAppear: 并替换 >sleep/-netAccessEnd 调用如下:

[self performSelector:@selector(netAccessEnd) withObject:nil afterDelay:1];

...这将具有相同的效果，但不会阻止执行。