UITextField subview of UITableViewCell to become first responder?

问题

I have a core data application which uses a navigation controller to drill down to a detail view and then if you edit one of the rows of data in the detail view you get taken to an Edit View for the that single line, like in Apples CoreDataBooks example (except CoreDataBooks only uses a UITextField on its own, not one which is a subview of UITableViewCell like mine)!

The edit view is a UITableviewController which creates its table with a single section single row and a UITextfield in the cell, programatically.

What I want to happen is when you select a row to edit and the edit view is pushed onto the nav stack and the edit view is animated moving across the screen, I want the textfield to be selected as firstResponder so that the keyboard is already showing as the view moves across the screen to take position. Like in the Contacts app or in the CoreDataBooks App.

I currently have the following code in my app which causes the view to load and then you see the keyboard appear (which isn't what I want, I want the keyboard to already be there)

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    [theTextField becomeFirstResponder];
}

You can't put this in -viewWillAppear as the textfield hasn't been created yet so theTextField is nil. In the CoreDataBooks App where they achieve what i want they load their view from a nib so they use the same code but in -viewWillAppear as the textfield has already been created!

Is there anyway of getting around this without creating a nib, I want to keep the implementation programatic to enable greater flexibility.

Many Thanks

回答1:

After speaking with the Apple Dev Support Team, I have an answer!

What you need to do is to create an offscreen UITextField in -(void)loadView; and then set it as first responder then on the viewDidLoad method you can set the UITextField in the UITableViewCell to be first responder. Heres some example code (remember I'm doing this in a UITableViewController so I am creating the tableview as well!

- (void)loadView
{
    [super loadView];

    //Set the view up.
    UIView *theView = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.view = theView;
    [theView release];

    //Create an negatively sized or offscreen textfield
    UITextField *hiddenField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, -10, -10)];
    hiddenTextField = hiddenField;
    [self.view addSubview:hiddenTextField];
    [hiddenField release];

    //Create the tableview
    UITableView *theTableView = [[UITableView alloc] initWithFrame:[[UIScreen mainScreen] bounds] style:UITableViewStyleGrouped];
    theTableView.delegate = self;
    theTableView.dataSource = self;
    [self.view addSubview:theTableView];
    [theTableView release];

    //Set the hiddenTextField to become first responder
    [hiddenTextField becomeFirstResponder];

    //Background for a grouped tableview
    self.view.backgroundColor = [UIColor groupTableViewBackgroundColor];
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    //Now the the UITableViewCells UITextField has loaded you can set that as first responder
    [theTextField becomeFirstResponder];
}

I hope this helps anyone stuck in the same position as me!

If anyone else can see a better way to do this please say.

回答2:

Try do it in viewDidAppear method, works for me.

回答3:

I think the obvious solution is to create the textfield in the init method of the view controller. That is usually where you configure the view because a view controller does require a populated view property.

Then you can set the textfield as first responder in viewWillAppear and the keyboard should be visible as the view slides in.