Question

It takes a long to start up the application I write on an iPhone. I hope to display a waiting progress bar to indicate the percentage of the startup progress. Can anyone help me? I am new to the Development of IOS.

Answer 1

You can’t.
The application needs to be started before you can show any dynamic content.
After your first ViewController is loaded you can of course show a progress bar and do loading.
Before that, you can only show a static image Default.png & [e-mail].
If you delay the heavy loading to after your -[ViewController viewDidLoad]-method is finished you can show any kind of GUI while doing the heavy work.

Edit:
This example will detach a new thread in your viewDidLoad and do some heavy work (in this case sleep for 1 second) and update a UIProgressView and log the progress as it sleeps 10 times, incrementing the progressview with 0.1 each time.

- (void)viewDidLoad
{
 // .....
   [NSThread detachNewThreadSelector:@selector(workerBee) toTarget:self withObject:nil];
}

- (void)workerBee
{
    NSAutoreleasePool* workerPool = [[NSAutoreleasePool alloc] init];

    // Put your image loading between this line and [workerpool release]

    for (float i = 0; i<1; i+= 0.1)
    {
        [self performSelectorInBackground:@selector(updateProgress:) withObject:[NSNumber numberWithFloat:i]];
        sleep(1000);
    }
    [workerPool release];
}

- (void)updateProgress:(NSNumber*)number
{
    NSLog("Progress is now: %@", number);
    [progressView setProgress:[number floatValue]];
}