I am using tab bar based iPhone application.I have set NSTimer in first two tabs.i want to invalidate this timer. so i am invalidating in viewDidDisappear. But when i am clicking on different tab, it will never call viewDidDisappear. I don't know how to call this method?please help me...thanking you in advance...
are you put [super viewWillDisappear:animated]; in viewWillDisappear some time it happaned becouse we forget to put this line in to viewWillDisappear
- (void) viewWillDisappear:(BOOL) animated {
[super viewWillDisappear:animated];
}
set time invalid in viewWillDisappear: method , like bellow..
-(void)viewWillDisappear:(BOOL)animated
{
[yourTimer invalidate];
yourTimer = nil;
}
Related
I am using the [performSelector:#selector(reloadData) withObject:nil afterDelay:0.01] inside IBAction of a UIButton, the reloadData method draw some subviews on the main view in a particular way, the issue is when I tap the button quickly and repeatedly the selector "ReloadData" executed multiple times, event though I am canceling the all previous requests to that selector, and this results in duplication for the subviews in the main view
-(IBAction) myButtonIsTapped
{
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:#selector(reloadData) object:nil];
[self performSelector:#selector(reloadData) withObject:nil afterDelay:0.01];
}
and reload data method like the following:
-(void) reloadData
{
#synchronized(self){
// clear all subviews from the main view
// draw new subviews
}
}
What about this:
-(IBAction) myButtonIsTapped
{
[self.myButton setUserInteractionEnabled:NO];
[self performSelector:#selector(reloadData) withObject:nil afterDelay:0.01];
}
-(void) reloadData
{
// Long task...
// Enable the button again:
[self.myButton setUserInteractionEnabled:YES];
}
Sometimes is just easier to control what the user is doing (UI), than logically dealing with what he has done.
Do one Thing create one BOOL variable and set in viewdidload yes and check in function if it is yes then method call and also make it no in buttonmake method.
I am making an application with TabBar. But TabBarController is not RootViewController. In the Tab Bar there are 4 tabs. One of those tabs is history which is linked with a table view which shows history. I want to refresh that view every time when i click that so that i can get updated tableview. How can i do that? Thanks in advance.
use - (void) viewWillAppear:(BOOL)animated to update any content in your view.
- (void) viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// You code here to update the view.
}
This method will be called every time the view is about to be displayed.
below code added plz ^^
If you change a tabBarIndex, At the same time -(void)viewWillAppear called.
-(void)viewWillAppear:(BOOL)animated
{
// force the tableview to load
[tableView reloadData];
}
refer a Apple Sample Code: that is amazing great tutorial for you about UITabBarController
http://developer.apple.com/library/ios/#samplecode/TheElements/Introduction/Intro.html
Apple Sample Code is no added [super viewWillAppear:animated];
-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:YES];
if ([Globals sharedInstance].isFromFindSimiler)
{
[self.view addSubview:_findSimilerView];
[_historyTableView setFrame:CGRectMake(0, 85, 320, 490)];
}
else
{
[self history_webservice];
}
}
I have achieved this. In this case, whenever user tabs on History screen I call web service for history and update tableview.
instead of using (void)ViewDidLoad use viewWillAppear:(BOOL)animated
- (void) viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
//your code
}
I have a view with a navigation bar in my iphone app. The navigation bar has a back button on it to go the the previous view. Within the view is a webview. If the webview is loading while the user presses the back button on the navigation bar, the app crashes with the error message:
[WebViewController respondsToSelector:]: message sent to deallocated instance
I am assuming that I release some things when the view unloads. I believe my viewWillDisapear method takes care of stopping the webview from loading... But still, when I press back while the view is not fully loaded, it crashes.
It seems to happen when I let the view finish loading about 20% of the time - and only if I press the back button really quickly after the page finishes loading.
Here is the code that I believe runs during this shinanigans....:
- (void)viewDidLoad {
[super viewDidLoad];
webView.scalesPageToFit = YES;
[webview loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString: url]]];
[addressBar setText:url];
}
and then when the webview is loading:
- (void)webViewDidStartLoad:(UIWebView *)webView {
if (first) {
//mtns is a uiimageview
mtns.alpha = .8;
first = NO;
}
[activityIndicator startAnimating];
}
and after a suggestion, I added this method:
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[self.webView stopLoading];
self.webView.delegate = nil;
}
I don't know why it is crashing so I am sort of at a loss
Thanks,
R
You could override -viewWillDisappear: to stop the UIWebView from loading and set the delegate to nil.
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[self.webView stopLoading];
self.webView.delegate = nil;
}
This may be because of before the execution code that you have written in viewwillDisapper application crashes.try to put breakpoint and check whether viewwillDisapper method is called or not.If its not called then write the code that mark has suggested before the application navigates to second view controller.
You have to be sure to set the delegate property of the web view to nil before it goes away. Do this both in your dealloc and viewDidUnload methods, since viewDidUnload is not always called before dealloc. What’s happening is that after your view controller is deallocated, the web view still has a reference to its address, and is trying to send it a message (-respondsToSelector:).
- (void)dealloc {
webView.delegate = nil;
[super dealloc];
}
- (void)viewDidUnload {
webView.delegate = nil;
[super viewDidUnload];
}
I need to hide something on the screen when the user has activates the application by switching it to the foreground.
I have tried inserting my code within applicationDidBecomeActive or applicationWillEnterForeground and although it runs OK the old screen with the text I want to hide is displayed momentarily.
How can I hide the field before the screen is redrawn?
Thanks
iphaaw
I think the problem is, iOS will capture a screenshot from your app in the moment it goes to the background, so the animation will work in an instant.
The only way in my opinion to do this is to hide / cover your view in moment the app goes to the background.
Write some code in applicationWillResignActive: to 'hide' whatever you need to hide.
I faced a similar situation but, instead of hiding, I wanted to show a block code screen to grant access. Anyway I think that the solution also applies to your needs.
I often implement a custom base view controller in my iOS applications. So instead of dealing with applicationDidBecomeActive: or applicationWillResignActive: I setup this view controller to listen for the equivalent notifications:
#interface BaseViewController : UIViewController
- (void)prepareForGrantingAccessWithNotification:(NSNotification *)notification;
- (void)grantAccessWithNotification:(NSNotification *)notification;
#end
#implementation BaseViewController
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
[self addNotificationHandler:#selector(grantAccessWithNotification:)
forNotification:UIApplicationDidBecomeActiveNotification];
[self addNotificationHandler:#selector(prepareForGrantingAccessWithNotification:)
forNotification:UIApplicationWillResignActiveNotification];
}
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
- (void)prepareForGrantingAccessWithNotification:(NSNotification *)notification {
// Hide your views here
myCustomView.alpha = 0;
// Or in my case, hide everything on the screen
self.view.alpha = 0;
self.navigationController.navigationBar.alpha = 0;
}
- (void)grantAccessWithNotification:(NSNotification *)notification {
// This is only necessary in my case
[self presentBlockCodeScreen];
self.view.alpha = 1;
self.navigationController.navigationBar.alpha = 1;
...
}
#end
I have a strange problem with a UIView :
I want to show an Activity Indicator View that I created with Interface Builder to indicate long running activity.
In the viewDidLoad function of my principal viewController I init the ActivityIndicator View like this :
- (void)viewDidLoad {
[super viewDidLoad];
appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
load = [[ActivityIndicatorViewController alloc] init];
...
When I push a button it call this IBAction :
- (IBAction)LaunchButtonPressed{
// Show the Activity indicator view.
[self.view addSubview:load.view];
// eavy work
[self StartWorking];
// Hide the loading view.
[load.view removeFromSuperview];
}
In the StartWorking function, I ask a request to an internet serveur and parse the XML file that it return me.
The problem is that if I Call my StartWorking function, the application do not start by showing the Activity Indicator view but with the StartWorking function.
Whereas if I remove the call to StartWorking function, the view is shown.
Is someone able to explain me why? :s
Have you tried to call the StartWorking method on a different thread?
Maybe its heavy process prevents other instructions to take place.
Look at the NSThread class, especially the detachNewThreadSelector:toTarget:withObject: method.
EDIT: About the pool problem, you need to create a pool in your StartWorking method, if it's called on a different thread:
- ( void )StartWorking
{
NSAutoreleasePool * pool = [ [ NSAutoreleasePool alloc ] init ];
/* Code here... */
[ pool release ];
}
Replace :
[self.view addSubview:load.view];
With :
[self performSelector:#selector(addLoadingSubview) afterDelay:0.1f];
And create the method :
-(void)addLoadingSubview{[self.view addSubview:load.view];}
Ok, I found a solution based on santoni answer :
- (IBAction)LaunchButtonPressed{
// Show the Activity indicator view.
[self performSelector:#selector(ShowActivityIndicatorView) withObject:nil afterDelay:0];
// eavy work
[self performSelector:#selector(StartWorking) withObject:nil afterDelay:2];
// Hide the loading view.
[load.view removeFromSuperview];
}
The Activity Indicator view is dislayed before the call to the eavy function.
Thank's for answering.