Brett Schumann, welcome to brettworld

iPhone Multiline Textbox for SMS style chat

15 January 2010

So you want to build an iPhone application and you would like it to have a chat facility with the style and functionality of the iPhone’s SMS application but you don’t know where to start. This is not the perfect tutorial on how to build the full application this is just a little bit of sample code and tech knowhow that I came up with after the problems I have had with the multiple lines growing text input field.

I used two UIViews in my main view. The top view contains a UITableView and the bottom view contains a UITextview and two UIButtons. Here is the complete code for my for header (.h) file

#import 
@interface MultilineTextboxViewController : UIViewController {
    IBOutlet UIView *viewTable;
    IBOutlet UIView *viewForm;
    IBOutlet UITextView *chatBox;
    IBOutlet UIButton	*chatButton;
}

@property (nonatomic, retain) UIView *viewTable;
@property (nonatomic, retain) UIView *viewForm;
@property (nonatomic, retain) UITextView *chatBox;
@property (nonatomic, retain) UIButton *chatButton;

- (IBAction)chatButtonClick:(id)sender;
@end

With that done and while we are setting everything up lets go and add our items to our main (.m) file at the same time not forgetting to de-allocate them as well.

@synthesize viewTable;
@synthesize viewForm;
@synthesize chatBox;
@synthesize chatButton;

- (void)dealloc{
    [viewTable release];
    [viewForm release];
    [chatBox release];
    [chatButton release];
    [super dealloc];
}

In the (void)viewDidLoad method we need to add some notification observers so that we can see when the keyboard is shown or hidden and when the user presses a key on the keyboard.

- (void)viewDidLoad {
	//set notification for when keyboard shows/hides
	[[NSNotificationCenter defaultCenter] addObserver:self 
	                    selector:@selector(keyboardWillShow:) 
	                    name:UIKeyboardWillShowNotification 
	                    object:nil];
	[[NSNotificationCenter defaultCenter] addObserver:self 
	                    selector:@selector(keyboardWillHide:) 
	                    name:UIKeyboardWillHideNotification 
	                    object:nil];

	//set notification for when a key is pressed.
	[[NSNotificationCenter defaultCenter] addObserver:self 
	                    selector: @selector(keyPressed:) 
	                    name: UITextViewTextDidChangeNotification 
	                    object: nil];

	//turn off scrolling and set the font details.
	chatBox.scrollEnabled = NO;
	chatBox.font = [UIFont fontWithName:@"Helvetica" size:14]; 
	
	[super viewDidLoad];
}

When focus is set on the textview the keyboard will be shown. Because the textview and buttons are both in the lower viewForm on the screen, the keyboard is going to ride up and go over these. So what we want to do is adjust the height of viewTable and the position of viewForm. We do this in the following method.

-(void) keyboardWillShow:(NSNotification *)note{
    // get keyboard size and loction
	CGRect keyboardBounds;
    [[note.userInfo valueForKey:UIKeyboardBoundsUserInfoKey] getValue: &keyboardBounds];

	// get the height since this is the main value that we need.
	NSInteger kbSizeH = keyboardBounds.size.height;

	// get a rect for the table/main frame
	CGRect tableFrame = viewTable.frame;
	tableFrame.size.height -= kbSizeH;

	// get a rect for the form frame
	CGRect formFrame = viewForm.frame;
	formFrame.origin.y -= kbSizeH;

	// animations settings
	[UIView beginAnimations:nil context:NULL];
	[UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDuration:0.3f];

	// set views with new info
	viewTable.frame = tableFrame;
	viewForm.frame = formFrame;

	// commit animations
	[UIView commitAnimations];
}

Now that the keyboard is shown and our views have been adjusted we want to capture the text the user is entering and see if we need to make any adjustments to the chatBox. Lucky for us we can use the CGSize object, pass it some text, and tell the object what size we would want to constrain the text to and from that we can calculate get height.

Now this is where a little trial and error comes in. The line varies with the size of the font and your width of your CGSize object will vary with the width of your UITextview so you will have to experiment a little. The value of 12 use in the code below is the difference in height between the starting height of my chatBox and the line height based on the font that I have set.

-(void) keyPressed: (NSNotification*) notification{
	// get the size of the text block so we can work our magic
	CGSize newSize = [chatBox.text 
	            sizeWithFont:[UIFont fontWithName:@"Helvetica" size:14] 
	            constrainedToSize:CGSizeMake(222,9999) 
	            lineBreakMode:UILineBreakModeWordWrap];
	NSInteger newSizeH = newSize.height;
	NSInteger newSizeW = newSize.width;

    // I output the new dimensions to the console 
    // so we can see what is happening
	NSLog(@"NEW SIZE : %d X %d", newSizeW, newSizeH);
	if (chatBox.hasText)
	{
        // if the height of our new chatbox is
        // below 90 we can set the height
		if (newSizeH <= 90)
		{
			[chatBox scrollRectToVisible:CGRectMake(0,0,1,1) animated:NO];

			// chatbox
			CGRect chatBoxFrame = chatBox.frame;
			NSInteger chatBoxH = chatBoxFrame.size.height;
			NSInteger chatBoxW = chatBoxFrame.size.width;
			NSLog(@"CHAT BOX SIZE : %d X %d", chatBoxW, chatBoxH);
			chatBoxFrame.size.height = newSizeH + 12;
			chatBox.frame = chatBoxFrame;

			// form view
			CGRect formFrame = viewForm.frame;
			NSInteger viewFormH = formFrame.size.height;
			NSLog(@"FORM VIEW HEIGHT : %d", viewFormH);
			formFrame.size.height = 30 + newSizeH;
			formFrame.origin.y = 199 - (newSizeH - 18);
			viewForm.frame = formFrame;

			// table view
			CGRect tableFrame = viewTable.frame;
			NSInteger viewTableH = tableFrame.size.height;
			NSLog(@"TABLE VIEW HEIGHT : %d", viewTableH);
			tableFrame.size.height = 199 - (newSizeH - 18);
			viewTable.frame = tableFrame;
		}

        // if our new height is greater than 90
        // sets not set the height or move things
        // around and enable scrolling
		if (newSizeH > 90)
		{
			chatBox.scrollEnabled = YES;
		}
	}
}

Once we are and the user presses the send button we want to do something with our text, the keyword will disappear and we want to reset our view back as they were. So how do we do that?

- (IBAction)chatButtonClick:(id)sender{
	// hide the keyboard, we are done with it.
	[chatBox resignFirstResponder];
	chatBox.text = nil;

	// chatbox
	CGRect chatBoxFrame = chatBox.frame;
	chatBoxFrame.size.height = 30;
	chatBox.frame = chatBoxFrame;
	// form view
	CGRect formFrame = viewForm.frame;
	formFrame.size.height = 45;
	formFrame.origin.y = 415;
	viewForm.frame = formFrame;

	// table view
	CGRect tableFrame = viewTable.frame;
	tableFrame.size.height = 415;
	viewTable.frame = tableFrame;
}

The resignFirstResponder is going to hide the keyboard and then all we have to do is set the views and chatBox back to their original states.

-(void) keyboardWillHide:(NSNotification *)note{
    // get keyboard size and loction

	CGRect keyboardBounds;
    [[note.userInfo valueForKey:UIKeyboardBoundsUserInfoKey] getValue: &keyboardBounds];

	// get the height since this is the main value that we need.
	NSInteger kbSizeH = keyboardBounds.size.height;

	// get a rect for the table/main frame
	CGRect tableFrame = viewTable.frame;
	tableFrame.size.height += kbSizeH;

	// get a rect for the form frame
	CGRect formFrame = viewForm.frame;
	formFrame.origin.y += kbSizeH;

	// animations settings
	[UIView beginAnimations:nil context:NULL];
	[UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDuration:0.3f];

	// set views with new info
	viewTable.frame = tableFrame;
	viewForm.frame = formFrame;

	// commit animations
	[UIView commitAnimations];
}

And there you go, a textview that starts off as a single line and grows in size as the user enters text to a max size before becoming a scrolling textview. If you have any comments or questions why not send me a message.

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