Question

In my application i create a custom Numberpad .How can i delete whole contents of the textfield on continuos tap on the clear button. Any idea?

Answer 1

This was a fun one.

Basically what I did was write a method to pull the last character out of the textField’s text String.

I added another method to be fired on the Button’s touchDown event, which first calls the method to erase the last character and then starts a timer to start repeating. Because the delay before repeating (at least on the native keyboard) is longer than repeat delay, I use two timers. The first one’s repeat option is set to NO. it calls a method that starts a second timer that repeats to call the erase last character method repeatedly.

In addition to the touchDown event. We also register for the touchUpInside event. When fired it calls a method that invalidates the current timer.

    #import <UIKit/UIKit.h> 

    #define kBackSpaceRepeatDelay 0.1f
    #define kBackSpacePauseLengthBeforeRepeting 0.2f

    @interface clearontapAppDelegate : NSObject <UIApplicationDelegate> {
        UIWindow *window;
        NSTimer *repeatBackspaceTimer; 
        UITextField *textField;
    }

    @property (nonatomic, retain) IBOutlet UIWindow *window;
    @property (nonatomic, retain) NSTimer *repeatBackspaceTimer;

    @end

    @implementation clearontapAppDelegate

    @synthesize window, 
    @synthesize repeatBackspaceTimer;

    - (void)applicationDidFinishLaunching:(UIApplication *)application {    
        textField = [[UITextField alloc] initWithFrame:CGRectMake(10, 40, 300, 30)];
        textField.backgroundColor = [UIColor whiteColor];
        textField.text = @"hello world........";

        UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
        button.frame = CGRectMake(10, 80, 300, 30);
        button.backgroundColor = [UIColor redColor];
        button.titleLabel.text = @"CLEAR";

        [button addTarget:self action:@selector(touchDown:) forControlEvents:UIControlEventTouchDown];
        [button addTarget:self action:@selector(touchUpInside:) forControlEvents:UIControlEventTouchUpInside];
        // Override point for customization after application launch


        [window addSubview:textField];
        [window addSubview:button];
        window.backgroundColor = [UIColor blueColor];
        [window makeKeyAndVisible];
    }


    -(void) eraseLastLetter:(id)sender {
        if (textField.text.length > 0) {
            textField.text = [textField.text substringToIndex:textField.text.length - 1];
        }
    }

    -(void) startRepeating:(id)sender {
        NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:kBackSpaceRepeatDelay
                                                          target:self selector:@selector(eraseLastLetter:)
                                                        userInfo:nil repeats:YES];
        self.repeatBackspaceTimer = timer;
    }

    -(void) touchDown:(id)sender {
        [self eraseLastLetter:self];
        NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:kBackSpacePauseLengthBeforeRepeting
                                                          target:self selector:@selector(startRepeating:)
                                                        userInfo:nil repeats:YES];
        self.repeatBackspaceTimer = timer;
    }

    -(void) touchUpInside:(id)sender {
        [self.repeatBackspaceTimer invalidate]; 
    }

    - (void)dealloc {
        [window release];
        [super dealloc];
    }

    @end