For objective-C and iOS development, Is it possible to change textfield when user pushes a key.
For ex : User pushes the key 'k' but sees 'a' in the textfield. (the same usage in PeterAnswers.com )
Yes, I think this is possible. You should take a look at this UITextField delegate method:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;
You should be able to manipulate the input string before it is displayed in the actual textfield. A specific implementation of your question could be:
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
// if the user entered x...
if ([string isEqualToString:#"x"]){
textField.text = [NSString stringWithFormat:#"%#a", textField.text]; // ...append the previous string with the 'a' token instead!
return NO; // return NO to make sure the x isn't put in the textField
}
}
Don't forget to make sure to link the UITextField delegate to the class where you put this code.
Hope it helps!
Implement the textField:shouldChangeCharactersInRange:replacementString: method of the UITextFieldDelegate protocol.
Totally. Look at the apple documentation on UITextFieldDelegate. Everything you need is right there.
Related
I have tried the bellow code-
-(void)textFieldDidBeginEditing:(UITextField *)textField
{
if (self.textfield.text.length!=0)
{
self.image.image=[UIImage imageNamed:#"Free-Boiler-Circle.png"];
}
else
{
self.image.image=[UIImage imageNamed:#"GREY_CIRCLE.png"];
}
}
But when i tried this it change image when i go to the next field after entering value the previous field it change image.... but i want to do when i entering any single text in text field it will change image instantly.
please help me. thnx in advnce.
You have two options.
Either implement - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string and in there do your logic, or begin listening to UITextFieldTextDidChangeNotification notifications by registering in viewDidLoad, like so:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(textDidChange:) name:UITextFieldTextDidChangeNotification object:self.textfield];
This will be called every time your text field changes:
- (void)textDidChange:(NSNotification*)notification
{
if (self.textfield.text.length!=0)
{
self.image.image=[UIImage imageNamed:#"Free-Boiler-Circle.png"];
}
else
{
self.image.image=[UIImage imageNamed:#"GREY_CIRCLE.png"];
}
}
Don't forget to call removeObserver: in your view controller's dealloc.
I have multiple uitextfields but they all respond to the delegate the method. I tried using textfield description but that doesn't work. There must be a way to know which text field is active but I can't find it.
thanks.
According to the UITextFieldDelegate protocol reference, all the methods pass the UITextField that's calling the method. For example:
- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField
You can just check the text field against a known one:
- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField
{
if (textField == self.fooBarField)
{
//do magic
}
return YES;
}
Im trying to implement a delegate for a NSTextField object so I can detect the user input in real time and give some feedback about no allowed input in that particular field.
Especially, I want to simulate the onChange() method from JavaScript, detecting the user input in real time and show him a warning if it is writing a non supported value.
i.e. The app have a text field it only accept numeric values from 0 to 255 (like RGB values) and I want to know when the user is writing not numeric values or out of range values to instantly show him a warning message or change the text field background color, just a visual hint to let him know the input it's wrong.
Like you see on the pictures above, I want to show a warning sign every time the user inputs a forbidden value in the text field.
I have been reading a lot of the Apple's documentation but I don't understand which delegate to implement (NSTextFieldDelegate, NSTextDelegate, or NSTextViewDelegate), also, I have no idea how to implement it in my AppDelegate.m file and which method use and how to get the notification of user editing.
Right now, I already set the Delegate in my init method with something like this [self.textField setDelegate:self]; but I don't understand how to use it or which method implements.
I found a solution using the information posted in this question... Listen to a value change of my text field
First of all I have to declare the NSTextFieldDelegate in the AppDelegate.h file
#interface AppDelegate : NSObject <NSApplicationDelegate, NSTextFieldDelegate>
After that, I have to instantiate the delegate for the NSTextField object I want to modify while the user update it in the AppDelegate.m file.
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
[self.textField setDelegate:self];
}
Finally, I implement the methods to detect field editing with the changes I want to set.
- (void)controlTextDidChange:(NSNotification *)notification {
NSTextField *textField = [notification object];
if ([textField doubleValue] < 0 | [textField doubleValue] > 255) {
textField.textColor = [NSColor redColor];
}
}
- (void)controlTextDidEndEditing:(NSNotification *)notification {
NSTextField *textField = [notification object];
if ([textField resignFirstResponder]) {
textField.textColor = [NSColor blackColor];
}
}
Make your class conform to the NSTextFieldDelegate protocol. It need's to be that protocol because in the documentation it says the type of protocol the delegate conforms to.
#interface MyClass : NSObject
And implement the delegate's methods (just add them to your code). Example
- (BOOL)control:(NSControl *)control textShouldBeginEditing:(NSText *)fieldEditor
{
}
EDIT:
I think in your case it would be better to replace the TextField for a TextView and use a NSTextViewDelegate, in the delegate, the method of most interst of you should be
- (BOOL)textView:(NSTextView *)aTextView shouldChangeTextInRange:(NSRange)affectedCharRange replacementString:(NSString *)replacementString
{
BOOL isValid = ... // Check here if replacementString is valid (only digits, ...)
return isValid; // If you return false, the user edition is cancelled
}
I would like to be able to detect if some text is changed in a UITextField so that I can then enable a UIButton to save the changes.
Instead of observing notifications or implementing textField:shouldChangeCharacterInRange:replacementString:, it's easier to just add an event target:
[textField addTarget:self
action:#selector(myTextFieldDidChange:)
forControlEvents:UIControlEventEditingChanged];
- (void)myTextFieldDidChange:(id)sender {
// Handle change.
}
Note that the event is UIControlEventEditingChanged and not UIControlEventValueChanged!
The advantages over the other two suggested solutions are:
You don't need to remember to unregister your controller with the NSNotificationCenter.
The event handler is called after the change has been made which means textField.text contains the text the user actually entered. The textField:shouldChangeCharacterInRange:replacementString: delegate method is called before the changes have been applied, so textField.text does not yet give you the text the user just entered – you'd have to apply the change yourself first.
Take advantage of the UITextFieldTextDidChange notification or set a delegate on the text field and watch for textField:shouldChangeCharactersInRange:replacementString.
If you want to watch for changes with a notification, you'll need something like this in your code to register for the notification:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(textFieldDidChange:) name:UITextFieldTextDidChangeNotification object:theTextField];
Here theTextField is the instance of UITextField that you want to watch. The class of which self is an instance in the code above must then implement textFieldDidChange, like so:
- (void)textFieldDidChange:(NSNotification *)notification {
// Do whatever you like to respond to text changes here.
}
If the text field is going to outlive the observer, then you must deregister for notifications in the observer's dealloc method. Actually it's a good idea to do this even if the text field does not outlive the observer.
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self];
// Other dealloc work
}
For that, first you need to have your textfield have it delegate reference assigned. And the delgate, should preferably be, the vew controller which is the files owner of the view.
Which goes like
myTextField.delegate = myViewControllerReferenceVariable
And in your viewController interface, tell you will be implementing UITextFieldDelegate by
#interface MyViewController:UIViewController<UITextFieldDelegate>
And in your view controller implementation override
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
So the code will look like
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
text = [textfield.text stringByReplacingCharactersInRange:range withString:string];
if (textfield == refToTextFieldYouWantToCheck) {
if ( ! [textToCheck isEqualToString:text] ) {
[theButtonRef setEnabled:YES];
}
}
return YES; //If you don't your textfield won't get any text in it
}
You can also subscribe to notification which is sort of messy IMHO
You can find how to do it here.
Swift 3.0
Process 1
Create IBOutlet of UITextfiled and Add Target to text field.
m_lblTxt.addTarget(self, action: #selector(self.textFieldDidChange), for: UIControlEvents.editingChanged)
func textFieldDidChange(textField:UITextField)
{
NSLog(textField.text!)
}
Process 2
m_lblTxt.delegate = self
//MARK: - TextField Delegates
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool
{
print(textField.text!)
return true
}
This can be accomplished in Interface Builder on the Editing Changed event of UITextField. Drag from it to your code and create an IBAction.
For example:
#IBAction func textFieldChanged(_ sender: UITextField) {
print(sender.text)
}
This event is the same as described in other answers here in that the .text property contains the updated text input when it gets triggered. This can help clean up code clutter by not having to programmatically add the event to every UITextField in the view.
You could create a variable to store the original string, then register with the notification center to receive UITextFieldTextDidChangeNotification event:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(updateButton:) name:UITextFieldTextDidChangeNotification object:nil];
Then, create a method to receive the notification, and compare the current value of the text field with the original value
-(void) updateButton:(NSNotification *)notification {
self.myButton.enabled = ![self.myTextField.text isEqualToString:originalString];
}
Don't forget to de-register the notification when the view controller is deallocated.
[[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidChangeNotification object:nil];
You can add a class member like this NSString *changeTemp,then
changetemp = textfield;
if( change temp != textfild ){
changetemp=textfild;
NSLog(#" text is changed"
} else {
NSLog(#" text isn't changed"):
}
Hi i am new to the iOS,
i am using several text fields in my project, so i want use becomeFirstResponder for editing done for any one of text field. it is working fine in xcode 3.2.5 but it makes problem in xcode 4.2.1
In xcode 4.2.1 after calling the becomeFirstResponder i could not edit the text field, it is showing the virtual key board i could tap the keys but tapped keys are not entered in text field.
Please help me out.
Firstly add this delegates in interface:
#interface yourViewController : UIViewController<UITextFieldDelegate>
If using from xib then right click on UITextField and bind delegate with fileowner else
add this code in viewDidLoad's method.
yourTextField.delegate = self;
Add UITextField's delegate and it will be called
- (BOOL)textFieldShouldReturn:(UITextField *)textField //resign first responder for textfield
{
[textField resignFirstResponder];
return YES;
}
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
return YES;
}