Trying to understand when viewWillAppear is called in simple app...

Question

This test application contains one button and one label. It was created with XCode 3.2.4 for the iPhone. I created it using the View-based application template in XCode.
When the application launches, the label displays "Clear when Home Button is pressed". This string is located inside of - (void) viewWillAppear:(BOOL)animated. Then when the button is pressed, the text inside of the label changes to "Label text should change when the application quits.".
The problem is when I press the Home Button to close the application, and then relaunch it, "Clear when Home Button is pressed" should be automatically displayed. Below is the code:
//removeLabelWhenClosedViewController.h
#import <UIKit/UIKit.h>
@interface removeLabelWhenClosedViewController : UIViewController {
IBOutlet UILabel *removeTextWhenClosed;
@property (nonatomic, retain) IBOutlet UILabel *removeTextWhenClosed;
- (IBAction)pressButton: (id)sender;
@end
//removeLabelWhenClosedViewController.m
#import "removeLabelWhenClosedViewController.h"
@implementation removeLabelWhenClosedViewController
@synthesize removeTextWhenClosed;
- (IBAction)pressButton: (id)sender
NSString *displayLabel = [[NSString alloc] initWithFormat:@"Should go away with application quits."];
removeTextWhenClosed.text = displayLabel;
[displayLabel release];
- (void) viewWillAppear:(BOOL)animated
NSString *clearLabel = [[NSString alloc] initWithFormat:@"Clear when Home Button is pressed"];
removeTextWhenClosed.text= clearLabel;
//playNumber.text = @"";
//NSLog(@"viewWillDisappear");
[clearLabel release];
- (void)dealloc {
[super dealloc];
@end

Answer 1

T2TU wrote:
The problem is when I press the Home Button to close the application, and then relaunch it, "Clear when Home Button is pressed" should be automatically displayed.
Are you sure you're actually relaunching the app? By default, when your app is in the foreground on iOS 4, pressing the home button will place the app in the background. I.e. the app will either be suspended or continue running in the background, but it won't exit. When you subsequently tap its icon, the app will move to the foreground, but the currently "visible" view won't get a viewWillAppear: message.
I think the easiest fix would be to send viewWillAppear to the active (and in your case, only) view controller from [applicationWillEnterForeground:|http://developer.apple.com/library/ios/documen tation/UIKit/Reference/UIApplicationDelegateProtocol/Reference/Reference.html#//appleref/doc/uid/TP40006786-CH3-SW21]:
// MyAppDelegate.m
- (void)applicationWillEnterForeground:(UIApplication *)application {
[viewController viewWillAppear:NO];
- Ray
p.s.: As usual, xnav replied while I was in the editor Just to clarify the difference between our advice, I think x is suggesting you ensure the app actually terminates when the home button is pressed--another approach which will solve your problem. - R
Message was edited by: RayNewbie