i want to let the user type in the name of a new file, so there are certain characters i want to prevent entry on. is there a special keyboard i can use or can i disable certain keys on the iphones keyboard.
is the answer to just run a regular expression on the input text and tell the user the filename is invalid (if so what would that regular expression be?)
ANSWER: (or what i ended up doing)
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
BOOL valid;
//if the user has put in a space at the beginning
if ([string isEqualToString:#" "]){
if (range.location == 0){
valid = NO;
}
else{
valid = YES;
}
}
//otherwise test for alpha numeric
else{
NSCharacterSet *alphaSet = [NSCharacterSet alphanumericCharacterSet];
valid = [[string stringByTrimmingCharactersInSet:alphaSet] isEqualToString:#""];
}
//print the warning label
if (valid == NO){
[errorLabel setText:#"Invalid input"];
}
else{
[errorLabel setText:nil];
}
return valid;
}
You can implement the delegate method
For UITextField,
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string; // return NO to not change text
For UITextview
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text;
and decide weather to append the entered characters or not.
You can implement the UITextFieldDelegate protocol and use textField:shouldChangeCharactersInRange:replacementString: to watch the text entry and prevent unwanted characters by returning NO.
Related
I want to know the current input character the user just inputted.Comparing the old and the new input string seems to work, but it must be the last thing I'd like to try.Any suggestion? I guess there are some methods in iOS SDK that can do this in a better way.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
from the UITextFieldDelegate should help you.
It is not only called for replacing text, also whenever the user presses a key on keyboard.
(length of range will be 0 then and the location will be the current insertation position).
See the documentation for more information:
http://developer.apple.com/library/ios/#documentation/uikit/reference/UITextFieldDelegate_Protocol/UITextFieldDelegate/UITextFieldDelegate.html#//apple_ref/doc/uid/TP40006991-CH3-SW9
If you want to compare the strings as the characters come in, your better off using
[textField addTarget:self action:#selector(compareInput) forControlEvents:UIControlEventEditingChanged];
-(void)compareInput
{
if ([textField.text isEqualToString:compareString])
NSLog(#"They're the same!");
}
than the delegate:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
If you literally just want to compare characters, then the delegate method is fine. The variable string contains the typed character.
For example, this is what happens with the above methods when a user types foo into the UITextField:
User types: f, this happens:
[textField addTarget:self action:#selector(compareInput) forControlEvents:UIControlEventEditingChanged];
calls compareInput immediately, and the letter f is available via textField.text:
-(void)compareInput
{
NSLog(textField.text); //prints `f`
}
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSLog(textField.text); //prints nothing
return YES;
//after returning YES, textField.text will contain `f`
}
User types: o, this happens:
[textField addTarget:self action:#selector(compareInput) forControlEvents:UIControlEventEditingChanged];
calls compareInput immediately, and the string fo is available via textField.text:
-(void)compareInput
{
NSLog(textField.text); //prints `fo`
}
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSLog(textField.text); //prints `f`
return YES;
//after returning YES, textField.text will contain `fo`
}
I'm probably not very clear, but I hope it gives you some insight!
This method will show current input in UITextField
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSString *letters;
if ([textField.text isEqualToString:#""]){
letters = string;
}else if ([string isEqualToString:#""]){
if ([textField.text length] > 0) {
letters = [textField.text substringToIndex:[textField.text length] - 1];
}
}else{
letters = [textField.text stringByAppendingString:string];
}
NSLog(#"letters %#\n", letters);
return YES;
}
I need to make sure that the user is only entering numbers into my textfield. I have the keyboard set to numbers, but if the user is using an external keyboard they might enter a letter. How can I detect if any characters in my textfield.text are characters instead of numbers?
Thanks!
You can choose what characters can input into the textField
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
/* this ensures that ONLY numbers can be entered, no matter what kind of keyboard is used */
NSCharacterSet *myCharSet = [NSCharacterSet characterSetWithCharactersInString:#"0123456789"];
for (int i = 0; i < [string length]; i++) {
unichar c = [string characterAtIndex:i];
if (![myCharSet characterIsMember:c]) {
return NO;
}
}
/* this allows you to choose how many characters can be used in the textField */
NSUInteger newLength = [textField.text length] + [string length] - range.length;
return (newLength > 7) ? NO : YES;
}
Whenever the user enters a key this textfield delegate will be called.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
Inside this check whether the text contains characters. if it is do your action. like promptimg a alert or something.
Implement textField:shouldChangeCharactersInRange:replacementString: in the text field's delegate and return NO if the passed string contains invalid characters.
I want to have the user type in something. And I want to verify each character inputed. How could I do this? I want it to be in real time. So as its typed its being verified and color coded.
You could compare what I want to do to an programmers IDE how it checks the syntax as you type it.
Any help is appreciated!
Connect the UITextField delegate to the app delegate and do something like:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if([string isEqual:#"b"]) {
// User typed 'b'
// Insert string with specific color
// [...]
} else {
// User typed something else
// Insert string without specific color
textField.text = [textField.text stringByReplacingCharactersInRange:range withString:string];
}
return YES;
}
I have an UITextField and I would like that for every tap on a character, the first character is deleted. So that I just have one character in my textField every time. Moreover I would like it to display every tap in the console log.
How can I do this?
You need to implement shouldChangeCharactersInRange method in your text field delegate:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:
(NSRange)range replacementString:(NSString *)string{
textField.text = #"";
return YES;
}
You may need to check for range and string values to cover all possible cases (like copy/paste actions). This code just sets the text field's value to the last typed character.
UITextField inherits from UIControl, so you can use the target-action mechanism that is part of the UIControl class:
[textField addTarget:self action:#selector(updateTextField) forControlEvents:UIControlEventValueChanged];
In the action method, you can replace the UITextField's text with only the last character and log that character in the console. Note that since changing the UITextField's text will again result in the "updateTextField" message being sent a second time to the target, you will need some kind of mechanism for determining whether to update or not:
- (void)updateTextField {
if(updateTextField == YES) {
updateTextField = NO;
NSString *lastChar = [textField.text substringFromIndex:[textField.text length]];
[textField setText:lastChar];
NSLog(#"%#", lastChar);
} else {
updateTextField = YES;
}
}
Or something like that anyway...
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if (textField.text.length > 8) {
return NO;
}
return YES;
}
I have a UITextField in my application. I'd like to restrict the set of characters that can be can be entered into the field to a set that I have defined. I could filter the characters entered into the field when the text is committed using the UITextFieldDelegate method:
- (BOOL)textFieldShouldReturn:(UITextField*)textField
However, this gives the user a false impression as although restricted characters are removed from the final value, they were still visibly entered into the text field before pressing Return/Done/etc. What is the best approach that would prevent restricted characters appearing in the text field as they are selected on the keyboard?
Note: I am operating under the assumption that I have little control over which keys are provided by the iPhone keyboard(s). I am aware that I can switch between various keyboard implementations but am under the impression that I can't disable specific keys. This assumption may be incorrect.
I did as marcc suggested and it worked well. Sample implementation follows.
Note: Variable names were selected for brevity and do not reflect my coding standards:
...
myCharSet = [NSCharacterSet characterSetWithCharactersInString:#"xyzXYZ"];
...
}
- (BOOL) textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)textEntered {
for (int i = 0; i < [textEntered length]; i++) {
unichar c = [textEntered characterAtIndex:i];
if (![myCharSet characterIsMember:c]) {
return NO;
}
}
return YES;
}
Look at textField:shouldChangeCharactersInRange
This method is called by the UITextFieldDelegate whenever new characters are typed or existing characters are deleted from the text field. You could return NO to not allow the change.
Here is one of the cleanest approaches to restricting characters entered in a UITextField. This approach allows the use of multiple predefined NSCharacterSets.
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
NSMutableCharacterSet *allowedCharacters = [NSMutableCharacterSet alphanumericCharacterSet];
[allowedCharacters formUnionWithCharacterSet:[NSCharacterSet whitespaceCharacterSet]];
[allowedCharacters formUnionWithCharacterSet:[NSCharacterSet symbolCharacterSet]];
if([string rangeOfCharacterFromSet:allowedCharacters.invertedSet].location == NSNotFound){
return YES;
}
return NO;
}
Look at the UITextViewDelegate method - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string.
It's exactly what you need.
This is what I use to restrict the user to uppercase A-Z. Adjust the regex variable according to taste:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSString* regex = #"[^A-Z]";
return ([string rangeOfString: regex
options:NSRegularExpressionSearch].location == NSNotFound);
};
How about this?
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSString* regex = #"[^a-z]";
return ([[string lowercaseString] rangeOfString: regex
options:NSRegularExpressionSearch].location == NSNotFound);
};
Note:
I am making all characters to lower case [string lowercaseString] so that you don't need to write in regex for captial/small letters.
You could loop and keep checking if the UITextField.text property has changed once the DidBeginEditing method gets called. If it has, check the text and remove an bad characters.