1
我想通过单击重新加载按钮来更新UILabel。另外,我想在后台更新标签,因为它是从我的网站通过XML获取新数据。当然,应用程序打开时自动更新标签会很好。并有我的问题:从applicationDidBecomeActive更新UILabel?
当用户手动点击按钮时,我能够使它工作良好。但我不明白如何通过“applicationDidBecomeActive”调用我的方法来做同样的事情。我试图以同样的方式来做,但它显然不起作用,因为我的标签返回零。
我想我的理解存在问题,解决方案应该很容易。感谢您的输入!注意:我是Objective-C的初学者,有时会遇到“简单”问题。 ;-)
下面是重要的部分代码摘要:
的AppDelegate
- (void)applicationDidBecomeActive:(UIApplication *)application {
[[MyViewController alloc] reloadButtonAction];
}
MyViewController
@synthesize label
- (void)reloadButtonAction {
[self performSelectorInBackground:@selector(updateData) withObject:nil];
}
- (void)updateData {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
// Parse the XML File and save the data via NSUserDefaults
[[XMLParser alloc] parseXMLFileAtURL];
// Update the labels
[self performSelectorOnMainThread:@selector(updateLabels) withObject:nil waitUntilDone:NO];
[pool release];
}
- (void)updateLabels {
NSUserDefaults *variable = [NSUserDefaults standardUserDefaults];
myLabel.text = [variable stringForKey:@"myLabelText"];
// myLabel is nil when calling all of this via AppDelegate
// so no changes to the myLabel are done in that case
// but: it works perfectly when called via button selector (see below)
NSLog(@"%@",myLabel.text);
}
-(void)viewDidLoad {
// Reload button in the center
UIButton *reloadButton = [UIButton buttonWithType:UIBarButtonSystemItemRefresh];
reloadButton.frame = CGRectMake(145,75,30,30);
[reloadButton setTitle:@"" forState:UIControlStateNormal];
[reloadButton addTarget:self action:@selector(reloadButtonAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:reloadButton];
}
你真的很好!这已经解决了我的问题! – andreas 2011-02-16 17:39:11