Moving Content That Is Located Under the Keyboard Beginners Guide - ios

Question

I'm building a project based on the App on the lessons I learned in Apple's "Start Developing iOS Apps Today" documentation. I created a basic View Controller Class with a Text box and two buttons. However, when I started to type the keyboard covered my content.
I have search all over the internet for a clear concise explanation to implementing Apple's sample code provided in there "Moving Content That Is Located Under the Keyboard" section in there development guide:
Listing 5-1 Handling the keyboard notifications
// Call this method somewhere in your view controller setup code.
- (void)registerForKeyboardNotifications
{
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWasShown:)
name:UIKeyboardDidShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillBeHidden:)
name:UIKeyboardWillHideNotification object:nil];
}
// Called when the UIKeyboardDidShowNotification is sent.
- (void)keyboardWasShown:(NSNotification*)aNotification
{
NSDictionary* info = [aNotification userInfo];
CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
scrollView.contentInset = contentInsets;
scrollView.scrollIndicatorInsets = contentInsets;
// If active text field is hidden by keyboard, scroll it so it's visible
// Your app might not need or want this behavior.
CGRect aRect = self.view.frame;
aRect.size.height -= kbSize.height;
if (!CGRectContainsPoint(aRect, activeField.frame.origin) ) {
[self.scrollView scrollRectToVisible:activeField.frame animated:YES];
}
}
// Called when the UIKeyboardWillHideNotification is sent
- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{
UIEdgeInsets contentInsets = UIEdgeInsetsZero;
scrollView.contentInset = contentInsets;
scrollView.scrollIndicatorInsets = contentInsets;
}
I received several errors immediately after I import this code into my implementation block of the class:
Use of undeclared identifier 'activeField'
Unknown type name 'scrollView'; did you mean 'UIScrollView'?
Property 'scrollView' not found on object of type 'SignInViewController *'
Following some research and back to basics programming I declared the identifiers in the header file:
UIScrollView *scrollView;
// The UIScrollView class provides support for displaying content that is larger than the size of the application’s window. It enables users to scroll within that content by making swiping gestures, and to zoom in and back from portions of the content by making pinching gestures.
UITextField *activeField;
// A UITextField object is a control that displays editable text and sends an action message to a target object when the user presses the return button. You typically use this class to gather small amounts of text from the user and perform some immediate action, such as a search operation, based on that text.
Also, I declared the property "scollView" for the object of type "SignInViewController" in the interface block of the class:
#property(nonatomic, readonly, retain) UIScrollView *scrollView;
All of the compiling errors cleared.
Unfortunately, following compiling and building this code the content located underneath my keyboard did not move. What did I do incorrectly in writing this code? Could you please explain it simply with examples if possible as I'm trying to get up to speed with Object Oriented C.
I'm including the finished code below. Thank you for your help!:
Header File: SignInViewController.h
#import <UIKit/UIKit.h>
#interface SignInViewController : UIViewController
#end
UIScrollView *scrollView;
// The UIScrollView class provides support for displaying content that is larger than the size of the application’s window. It enables users to scroll within that content by making swiping gestures, and to zoom in and back from portions of the content by making pinching gestures.
UITextField *activeField;
// A UITextField object is a control that displays editable text and sends an action message to a target object when the user presses the return button. You typically use this class to gather small amounts of text from the user and perform some immediate action, such as a search operation, based on that text.
Main file: SignInViewController.m
#import "SignInViewController.h"
#interface SignInViewController ()
//Declared property scrollView
#property(nonatomic, readonly, retain) UIScrollView *scrollView;
#end
#implementation SignInViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
// Code to dismiss the keyboard
- (IBAction)dismissKeyboard:(id)sender
{
[activeField resignFirstResponder];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
/*
#pragma mark - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
// Get the new view controller using [segue destinationViewController].
// Pass the selected object to the new view controller.
}
*/
//Moving Content That Is Located Under the Keyboard
// Call this method somewhere in your view controller setup code.
- (void)registerForKeyboardNotifications
{
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWasShown:)
name:UIKeyboardDidShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyboardWillBeHidden:)
name:UIKeyboardWillHideNotification object:nil];
}
// Called when the UIKeyboardDidShowNotification is sent.
- (void)keyboardWasShown:(NSNotification*)aNotification
{
NSDictionary* info = [aNotification userInfo];
// Get the size of the keyboard
CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
// Adjust the bottom content inset of your scroll view by the keyboard height.
UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
scrollView.contentInset = contentInsets;
scrollView.scrollIndicatorInsets = contentInsets;
// If active text field is hidden by keyboard, scroll it so it's visible
// Your app might not need or want this behavior.
// Scroll the target text field into view.
// Check if the active text field is under the keyboard. If it isn’t under the keyboard, the scrollview won’t update the content offset. If the active text field is under the keyboard we update the scroll view’s content offset.
CGRect aRect = self.view.frame;
aRect.size.height -= kbSize.height;
if (!CGRectContainsPoint(aRect, activeField.frame.origin) ) {
[self.scrollView scrollRectToVisible:activeField.frame animated:YES];
}
}
// Called when the UIKeyboardWillHideNotification is sent
- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{
UIEdgeInsets contentInsets = UIEdgeInsetsZero;
scrollView.contentInset = contentInsets;
scrollView.scrollIndicatorInsets = contentInsets;
}
- (void)textFieldDidBeginEditing:(UITextField *)textField
{
activeField = textField;
}
- (void)textFieldDidEndEditing:(UITextField *)textField
{
activeField = nil;
}
#end