1、监听UITextField文字的改变：
[textField addTarget:selfaction:@selector(textEditingChanged) forControlEvents:UIControlEventEditingChanged];
2、监听UITextView文字的改变：
（1）通知：
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onTextViewDidChange:) name:UITextViewTextDidChangeNotification object:nil];
- (void)onTextViewDidChange:(NSNotification *)aNotify
{
UITextView *textView = aNotify.object;
}
（2）代理：
- (void)textViewDidChange:(UITextView *)textView;
