I only want to confirm back navigation for one of the the view I have. The specific view is a UICollectionViewController. I know my exact coding in the if statement isn't right. I'm not quite sure how to do it. Fill in the blanks for me?
CollectionViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
BOOL isThisViewACollectionView = YES;
}
-(void) viewWillDisappear:(BOOL)animated {
if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
// back button was pressed. We know this is true because self is no longer
// in the navigation stack.
if (isThisViewACollectionView) {
UIAlertView *cameraAlertView = [[UIAlertView alloc] initWithTitle:#"Camera Not Available" message:#"The camera feature isn't available on your device." delegate:nil cancelButtonTitle:#"Okay" otherButtonTitles:nil];
[cameraAlertView show];
}
}else{
[super viewWillDisappear:animated];
}
}
There is an issue with the logic,
The following statement is called when you already dropped the viewcontroller
if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
}
So a better solution would be to hold a value somewhere "above (before)" viewWillDisappear which knows if the viewcontroller is uicollectionView (let's say a BOOL)
and assuming this value is true alert the user (filling your missing code).
Related
For a specific server notification I am supposed to show an UIActionSheet. But problem here is when that event comes, at the same time if any UIAlertView already showing on any view controller, it make the UIActionSheet disabled( After pressed ok for alert view I am not able to select anything on view controller , view got disabled because of UIActionSheet). Anyone faced this kind of problem, Any idea how to solve it?
I have tried by dismissing alert view before showing action sheet, however which alert view do I need to dismiss as I have many alert view in many controller. All are local to that controllers. How to solve this problem.
Note:
Same problem won't come for iPod, as it wont allow to click ok before responding to UIActionSheet.
Take a Global Alert view named it as activeAlertView. Now when you show a alert view please check that alert view and then show and assign. Like
declare a property in .h and synthesize it
#property (nonatomic, retain) UIAlertView *activeAlertView;
then use the below code when try to show an alert.
if(self.activeAlertView){
[self.activeAlertView dismissWithClickedButtonIndex:0 animated:YES];
}
UIAlertView *localAlert = [[UIAlertView alloc] initWithTitle:#"Title" message:#"Your message" delegate:nil cancelButtonTitle:#"cancel" otherButtonTitles:nil, nil ];
[localAlert show];
self.activeAlertView = localAlert;
[localAlert release];
this way your activeAlertview will keep the current aler view's reference and before show the actionSheet dismiss the alert view.
For Identified which alert-view you must set Tag or alert-view.
Ex:-
alertviewName.tag=1;
Then you can check is there alert-view Open in Particular view-controller sub-views use bellow code like:-
- (BOOL) doesAlertViewExist {
for (UIView* view in yuorviewcontroller.view.subviews) {
BOOL alert = [view isKindOfClass:[UIAlertView class]];
if (alert)
{
return YES;
}
}
return NO;
}
After this method called you get BOOL value YES or NO If Yes then dismiss it using UIAlertview's Delegate:-
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex;
and put your Actionsheet appear code into didDismissWithButtonIndex method.
When the message comes, first check if there is an alert view.
Show the action sheet after the alert view is dismissed. In didDismiss... you can check a BOOL flag if you now have to show the action sheet or not.
In this case, you should use
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
method rather than,
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
so your code wil be:
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
if (buttonIndex == 0)
{
UIActionSheet *actionSheet = ...
[actionSheet showFromTabBar:self.tabBarController.tabBar];
}
}
Thanks
try this:
for (UIWindow* w in [UIApplication sharedApplication].windows)
{
for (NSObject* obj in w.subviews)
{
if ([obj isKindOfClass:[UIAlertView class]])
{
[(UIAlertView*)obj dismissWithClickedButtonIndex:[(UIAlertView*)obj
cancelButtonIndex] animated:YES];
}
}
}
When popping a view I want to save some data, by asking confirmation. I'm asking confirmation using UIActionSheet. But irrespective of my response in action sheet, the view is changing in background, it creates some problem for me to use the response. I'm using navigation controller to switch views. How can I solve this
TIA
Better option is to use uialertview for asking confirmation.To do this follow this step:
Insure your header file contains the following:
#interface YourViewController : UIViewController <UIAlertViewDelegate>
Now when asked confirmation add this code:
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Message" message:#"Are You Sure" delegate:self cancelButtonTitle:#"YES" otherButtonTitles:#"NO", nil];
[alert show];
[alert release];
Now after pressing one button below delegate will be called so add in .m file of app
- (void)alertView:(UIAlertView *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
// the user clicked one of the YES/NO buttons
if (buttonIndex == 0)
{
NSLog(#"NO button pressed");
}
else
{
//Save data here
NSLog(#"YES button pressed");
}
}
#PooLas If I understood you correctly, You use uiactionsheet for user confirmation, while in background (actually under actionsheet) you change view controllers. Well, you can't do that, because delegate must be attached to controller which shows it up (if i am wrong, correct me). So when you click button, you can only first dismiss actionsheet and then change view controller, but not opposite – PooLaS
I read a lot about that. People say it will not autorotate whene its parent is not set to auto rotate. I tried everything but no luck.
I created view-based app (v4.2) with a button that executes this:
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:#"Title" delegate:self cancelButtonTitle:#"Cancel Button" destructiveButtonTitle:#"Destructive Button" otherButtonTitles:#"Other Button 1", nil];
actionSheet.actionSheetStyle = UIActionSheetStyleBlackOpaque;
[actionSheet showInView:self.view];
The root controller is set to auto-rotate. The actionSheet does not. Note that when I rotate the simulator none of the root controller's orientation methods are called. Is there a problem with the delegate? What is wrong?
Well, here's my solution to this problem:
Basically what we do is:
Listen to the rotation event.
Listen to click event.
Dismiss the actionSheet and present it again after the rotation is done. (we need to wait a small delay in order for it to take.
for example:
#interface ViewController ()
{
UIActionSheet *_sheet;
BOOL _isClicked;
}
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(didRotate:) name:UIDeviceOrientationDidChangeNotification object:nil];
}
- (IBAction)click:(id)sender
{
_isClicked = YES;
[self showActionSheet];
}
- (void)didRotate:(NSNotification *)note
{
[_sheet dismissWithClickedButtonIndex:1 animated:YES];
[self performSelector:#selector(showActionSheet) withObject:nil afterDelay:1.0];
}
- (void)showActionSheet
{
if (!_isClicked) return;
_sheet = [[UIActionSheet alloc] initWithTitle:#"title" delegate:self cancelButtonTitle:#"cancel" destructiveButtonTitle:#"new" otherButtonTitles:#"bla", nil];
[_sheet showInView:self.view];
}
I found that I was running into this problem when I was presenting the action sheet in a delegate method from a subordinate view (which I had pushed using the navigation controller). The problem was that my view was not the current one, the subordinate view was still up at the point where I was trying to show the action sheet.
By changing my code a little bit so that the delegate method made a note of the interaction needed with the user, and deferring the action sheet presentation to this view’s viewDidAppear method, the sheet appeared at the proper time in the logical interface animation, and the auto-rotation problem went away. You might want to see if that helps you.
In other words, the flow became:
Subordinate view called delegate method to report choices the user made when leaving.
Parent view recorded this information for later.
Navigation controller was told to pop off subordinate view.
Parent view’s viewDidLoad: method detected the note made in the delegate method.
Action sheet was presented; rotation was now correct.
A UIAlertView is displayed if an error occurs. But in the meantime the view on which the UIAlertView were called has been dismissed (and therefore released). If the user clicks on OK the app crashes because a message to a released instance is sent. This will cause your app crashing:
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"test" message:#"test" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alertView show];
[alertView release];
alertView = nil;
[self.navigationController popViewControllerAnimated:YES];
I thought the UIAlertView is an independent unit. But it seems it isn't. Is there a way how I could avoid the app crashing (except not dismissing the view)?
The delegate is called when the UIAlertView is dismissed, so in your case:
delegate:self
Delegates are not retained, like an object added to an array, or a subview would be. So in your case, when you call:
[self.navigationController popViewControllerAnimated:YES];
self is most likely being released, and when the the user dismisses the alert, self is called, but has been dealloc'd so it no longer exists.
An easy way to check this is to put a logger statement, like NSLog(#"I'm gone"); in self's dealloc method, if it's ran, then you know your self isn't around anymore, and any messages sent to it will cause a crash.
Make the UIAlertView a retained property of your view controller so that you can refer to it in your dealloc, then set the alert view's delegate to nil when the view controller is deallocated.
Be sure to properly release the retained alert view once it's been dismissed and on dealloc.
For instance:
#interface MyViewController : UIViewController <UIAlertViewDelegate> {
UIAlertView *alertView;
}
#property (nonatomic, retain) UIAlertView *alertView;
#implementation MyViewController
#synthesize alertView;
- (void)showAlert {
if (alertView) {
// if for some reason the code can trigger more alertviews before
// the user has dismissed prior alerts, make sure we only let one of
// them actually keep us as a delegate just to keep things simple
// and manageable. if you really need to be able to issue multiple
// alert views and be able to handle their delegate callbacks,
// you'll have to keep them in an array!
[alertView setDelegate:nil];
self.alertView = nil;
}
self.alertView = [[[UIAlertView alloc]
initWithTitle:#"Error"
message:#"Something went wrong"
delegate:self
cancelButtonTitle:#"Cancel"
otherButtonTitles:#"Retry",nil] autorelease];
[alertView show];
}
- (void)alertView:(UIAlertView *)alertViewParam didDismissWithButtonIndex:(NSInteger)buttonIndex {
self.alertView = nil; // release it
// do something...
}
- (void)dealloc {
[alertView setDelegate:nil]; // this prevents the crash in the event that the alertview is still showing.
self.alertView = nil; // release it
[super dealloc];
}
The downside here is that you will not be able to handle the alert view's callback when the user dismisses it. However, since your controller is already gone/released, presumably you don't need to. If you do, you have to set the alert view's delegate to something that will persist.
If the UIAlertView object is to be usable from anywhere in the app, not just on the current view, then retain it inside something that is available from anywhere in the app, either some persistant root view controller under the entire possible view stack, or the app delegate.
Added:
This top level object can also retain the alert view's delegate until after it's done being needed (after alert view dismissal).
(People might wonder I am late by years in answering this question,but it might help someone else)
I guess your problem lies some where in popping the view controller,you are displaying the alert view and at the same time trying to navigate the user back to a view.I would recommend you to follow a hierarchal approach here i.e.:
First of all declare your alert view as a global object,i.e.
#property(nonatomic,retain) UIAlertView *sampleAlert;
Now write your alert view display code where ever desired,say for instance:
-(IBAction)buttonClicked:(id)sender
{
self.sampleAlert = [[UIAlertView alloc] initWithTitle:#"test" message:#"test" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[sampleAlert show];
[sampleAlert release];
}
Finally try to navigate the user to the desired view when the "Ok" button is pressed,i.e. you need to make use of alertView didDismissWithButtonIndex method,i.e.
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
if(alertView == sampleAlert)
{
[self.navigationController popViewControllerAnimated:YES];
}
}
Please note that if you have alert view with multiple buttons,you also need to check for button index for distinguishing actions,i.e. check using
if(alertView == sampleAlert && buttonIndex == 0)
{
//Do your stuff
}
else
{
//Do something else
}
This will definitely avoid application crash,thanks :)
Easier way that worked for me is to hold all the alert views in a Array and when the parent view is deallocated enumerate alertViews array and assign the delegate to nil. This will ensure that the touch event is ignored and app will function.
// ARC world
#property (strong, nonatomic) NSMutableArray *alertViews;
- (void)dealloc
{
[self.alertViews makeObjectsPerformSelector:#selector(setDelegate:) withObject:nil];
}
Make sure you are implementing the UIAlertViewDelegate protocol.
If you don't care about when the alert is dismissed just init with delegate as nil.
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"test" message:#"test" delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
I'm new to the iPhone and I would like to be able to use UIAlertView in a manner similar to the Windows MessageBox() or the MessageDlg() in Delphi.
For example, I have a method that needs to ask the user for confirmation on something, and proceed based on their response.
E.g. (pseudocode):
-(void)doSomething
{
[doStep1];
[doStep2];
var myValue = [getDefaultValue];
if (myValue = nil)
{
if [promptUser(#"No value in setting. Use the default value?")] //UIAlertView here?
{
myValue = #"defaultValue";
}
else
return; // bug out of the routine 'cause we have no value.
}
[doStep3 withValue:myValue];
}
Or, put put it another way- is there a way of using UIAlertView to ask the user a question within a routine as a way of controlling the logic flow of that routine?
There's no reason to subclass UIAlertView at all. That's what delegates are for. All you need is a class (such as your view controller) supporting the UIAlertViewDelegate protocol, and set the UIAlertView's delegate property to that class. You then implement the alertView:clickedButtonAtIndex: method in this class, and the alertViewCancel: method if you want to specifically handle cancellations differently.
You can read more about it in the UIAlertView documentation and in the UIAlertViewDelegate documentation.
I have no idea what MessageDlg() is, but you can certainly subclass UIAlertView and handle the dialog response, based on which button is pressed, e.g.:
Set up the UIAlertView subclass header:
//
// ARReachabilityAlertView.h
//
#import <UIKit/UIKit.h>
#interface ARReachabilityAlertView : UIAlertView <UIAlertViewDelegate> {
}
#end
Set up the UIAlertView subclass implementation:
//
// ARReachabilityAlertView.m
//
#import "ARReachabilityAlertView.h"
#implementation ARReachabilityAlertView
- (id)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
[self setTitle:#"Error"];
[self setMessage:#"This application won't run without a network connection. Do you want to quit?"];
[self addButtonWithTitle:#"Quit"];
[self addButtonWithTitle:#"Continue"];
[self setDelegate:self];
}
return self;
}
- (void) alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if (buttonIndex == 0)
exit(0); // quit application if "Quit" is pressed; otherwise, do nothing
}
- (void) drawRect:(CGRect)rect {
[super drawRect:rect];
}
- (void) dealloc {
[super dealloc];
}
#end
Note the alertView:clickedButtonAtIndex: delegate method. This handles the conditionals you use to decide how the application proceeds. You can send an NSNotification from here, or call a method in the application delegate, whatever you want.
In my example, this UIAlertView is instantiated if there is no network connection, and the application is closed if the user clicks "Quit" in the alert view. Otherwise, if the user clicks "Continue" the application keeps running as usual.
Note that the implementation of the subclass requires the drawRect: method be called. I'm not sure if this is a bug or not, since I'd expect the drawRect: method to be called in the super-class; I filed a bug report with Apple on this one, but I haven't heard anything. Comment it out if you want to see what the effect will be — it's kind of interesting.
I believe you're looking to use UIAlertView as a modal alert box (in the sense that you'd like your code to stop running until the user makes a selection). There's no easy way to do this, and it's really recommended that you NOT code for the iPhone in this manner. I think Alex's explanation is a good solution.
To do this, what you can do is to run the mainloop manually. I have not managed to stop the mainloop directly, so I instead run the mainloop for 0.5 seconds and wait until the user responds.
I ran into this question while researching the problem for a C#/MonoTouch user on the iPhone. The sample below is written for MonoTouch/C# but should be trivial to translate to Objective-C
The following function shows how you could implement a modal query with the above approach:
int WaitForClick ()
{
int clicked = -1;
var x = new UIAlertView ("Title", "Message", null, "Cancel", "OK", "Perhaps");
x.Show ();
bool done = false;
x.Clicked += (sender, buttonArgs) => {
Console.WriteLine ("User clicked on {0}", buttonArgs.ButtonIndex);
clicked = buttonArgs.ButtonIndex;
};
while (clicked == -1){
NSRunLoop.Current.RunUntil (NSDate.FromTimeIntervalSinceNow (0.5));
Console.WriteLine ("Waiting for another 0.5 seconds");
}
Console.WriteLine ("The user clicked {0}", clicked);
return clicked;
}
Just a quick tip: if you want a class to be a delegate for more than one UIAlertView, just use tag property to tell who is who:
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Clear all" message:#"Are you sure you want to erase everything?" delegate:self cancelButtonTitle:#"Cancel" otherButtonTitles:#"OK", nil];
alert.tag = ALERT_DELETE_TAG;
[alert autorelease];
[alert show];
Delegate methods are called with UIAlertView as first argument, and you can check who's the originator there.
Thanks to #miguel.de.icaza I found my solution like below (part of the code):
#interface MyClass: NSObject <UIAlertViewDelegate>
{
int confirmed;
}
- (BOOL) removeObjectAtIndex:(NSUInteger)index;
#end
#implementation
- (BOOL) removeObjectAtIndex:(NSUInteger)index
{
// delete confirmation alert
confirmed = -1;
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Delete confirmation" message:#"Are you sure to delete object" delegate:self cancelButtonTitle:#"Yes" otherButtonTitles: #"No", nil];
alert.tag = 2;
[alert show];
[alert release];
// wait for confirm (0 or 1)
while (confirmed == -1) {
// this is what you need!!!
[[NSRunLoop mainRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.5]];
}
if (confirmed) {
[myObjects removeObjectAtIndex:index];
return YES;
}
else
return NO;
}
- (void) alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
switch (alertView.tag) {
case 1:
// ...
break;
case 2:
if (buttonIndex == 0) // delete confirmed
confirmed = 1;
else // dismiss
confirmed = 0;
break;
default:
break;
}
}
#end