Detecting finger touch on text

Question

Hi All,

I want to read the string displayed on the screen with finger touch, means as my finger moves over the text displayed on screen, the text below the finger should get highlighted. Is there any way to do this using UITextView or any other class. Also i want to play the sound associated with that word from a sound file which has the sentence already recorded. If anyone knows it kindly reply. Thanks in advance.

Answer 1

So that's two questions.

To know where your finger is pointing in the text you need to know where the UITextView has laid out the characters. This is not something the UITextView is documented to support, so next up is drawing text yourself. This stackoverflow question on embedding a custom font has a few links and even some code that will do the trick. What you need to add is keeping track of character advances so you know exactly where each character is rendered (or you could even use other core graphics functions to get exact bounding boxes of each character).

Clearly once you know what character has been tapped you also know the word it is part of. You'll would probably have the best quality if the sentence is recorded both in full and as single words, so that you can play back either when needed. This other stackoverflow question on playing sounds loaded from the internet has a few links and snippets which relate to loading and playing back audio.

Answer 2

Hi,

I am doing this in an iPhone text editor I am writing. For multiple reasons, I have subclassed a UIView to draw the text (instead of a UITextView) and I had to implement something like this to provide a movable cursor like a text view has. What I did was use a fixed-width font (Courier to be exact), then I took the x-coordinate of the touch and divided it by the width of the character and rounded the answer down. This gives you a character index.

However, if it is possible, find a way to do this without drawing the text yourself (if the text is user entered or really anything other than hardcoded) because Apple provides a lot of functionality in its UITextView class that is a pain to replicate: editing, cursor, word wrap, scrolling, etc.

It might be possible, if you can't get touch events from a subclassed UITextView, to put a transparent view/layer over the top of the text and get touch events from that, then you would only have to figure out a way to turn this on and off for editing.

Kyle

Answer 3

Jyotsna, Did you ever get this to work? If so, how?

Thanks, Todd

Edit:

I came up with a handy trick to do this. In drawRect, mimic the text that the UITextView will draw, but don't actually draw the text. Set the font to Helvetica 17-point, and the only semi-tricky part is handling word wrapping. You already have the text to be displayed, and you can get the size of each word in that default font by calling sizeWithFont. Then save the rectangles for each word, and when the user touches the view, find which of the stored rectangles contains the touched point. To test and calibrate the geometry (line spacing, etc), draw the text yourself in a different color. When you get it so that you can only see one of the font colors, you've got it perfect.

I can post my code for this if someone wants it.

Answer 4

please post code here thanks in advance...