Storing UITextField contents before view pops

问题:

I am sure this is in the Apple documentation or must have been answered somewhere on this forum, since it seems so basic, but I could not find it nor a particularly elegant solution myself.

What I have is a UIViewController that pushes an editing view on its navigation stack. The editing view has a bunch of UITextFields in it. If one of them is being editing when the back button is touched, the original view's ViewWillAppear method is called before either the UITextField delegate methods of textFieldShouldEndEditing or textFieldDidEndEditing, or the IB linked action textFieldEditingEnded method are called.

Here is some code that I hope will make it clearer:

In the UIViewController:

- (void) viewWillAppear: (BOOL) animated {
    [super viewWillAppear: animated];
    NSLog( @"Entering view will appear for master view" );
    nameLabelField.text = objectToEdit.name;
}
- (IBAction) editMyObject: (id) sender {
    NSLog( @"Editing the object" );
    EditViewController *evc = [[EditViewController alloc] initWithNibName: @"EditTableView" bundle: nil];
    evc.editedObject = objectToEdit;
    [self.navigationController pushViewController: evc animated: YES];
    [evc release];
}

In the EditViewController <UITextFieldDelegate>:

- (void) viewWillAppear: (BOOL) animated {
    [super viewWillAppear: animated];
    nameField.text = editedObject.name;
}
- (void) viewWillDisappear: (BOOL) animated {
    [super viewWillDisappear: animated];
    NSLog( @"In viewWillDisappear" );
    if( [self.navigationController.viewControllers indexOfObject: self] == NSNotFound ) {
        NSLog( @"-- We are not in controller stack... the back button has been pushed" );
    }
}
- (BOOL) textFieldShouldEndEditing: (UITextField *) textField {
    NSLog( @"In textFieldShouldEndEditing" );
    // Store text field value here???
    // editedObject.name = nameField.text;
    return YES;
}
- (void) textFieldDidEndEditing: (UITextField *) textField {
    NSLog( @"In textFieldDidEndEditing" );
    // Store text field value here???
    // editedObject.name = nameField.text;
}
- (IBAction) textFieldEditingEnded: (id) sender {
    NSLog( @"In textFieldEditingEnded" );
    // Store text field value here???
    // editedObject.name = nameField.text;
}

The log ends up with:

[...] Entering view will appear for master view
[...] Editing the object
[...] In viewWillDisappear
[...] -- We are not in controller stack... the back button has been pushed
[...] Entering view will appear for master view
[...] In textFieldShouldEndEditing
[...] In textFieldEditingEnded
[...] In textFieldDidEndEditing

I want to set self.editedObject.name = nameField.text before the label gets set in viewWillAppear for the UIViewController.

I thought about in the viewWillDisappear method for the EditViewController checking to see if any of my text fields are currently the first responder and if so getting their text and storing it, but this seems like such a kludge that will be a pain to maintain if I add or change text fields.

I can also implement the textFieldEditingChanged IB linked action to set the text in the edited object after every keystroke but this is also quite a bit of overhead since I have to figure out which text field I am in every keystroke (remember I only showed name but there are a whole bunch of them).

All I need is for the editing to be ended or to know the editing will be ended before viewWillAppear is called in the UIViewController so the nameFieldLabel is properly set.

回答1:

OK, I figured out a simple solution after a lot of web-surfing, forum reading, and manual reading. It was, as I suspected, very simple, only one line of code added. In the viewWillDisappear method of the EditViewContorller I simply added:

    [self.view.window endEditing: YES];

Now textFieldShouldEndEditing, textFieldEditingEnded, and textFieldDidEndEditing all get fired off before the viewWillAppear of the master view does.

So now the viewWillDisappear method looks like:

- (void) viewWillDisappear: (BOOL) animated {
    [super viewWillDisappear: animated];
    NSLog( @"In viewWillDisappear" );
    // Force any text fields that might be being edited to end so the text is stored
    [self.view.window endEditing: YES];
}

And the methods already in place to handle the 'Return' on the keyboard also handle the 'Back' button on the Navigation controller.

Thank you Aaron and Jeff for your assistance and helping me think this through.

回答2:

Why not just create your own Back button with that logic in its action method?

回答3:

I would think that from a UX perspective, you should display an alert to determine if the user wants to cancel the edit action they were in the middle of before exiting the current view.

By alerting the user, you can see if they hit the button by accident or if they did decide to leave the view, take the appropriate action.

// add this to the field(s) to be edited, selector will be called as the changes
// are being made... still difficult to handle a cancel, but should work
[objectToEdit addTarget:self action:@selector(updateNameField:) 
                         forControlEvents:UIControlEventEditingChanged];

additional code here...

// the method called to update object from parent view
- (void)updateNameField:(id)sender {
    <OBJECT TO UPDATE>.text = ((UITextField *)sender).text;
}