Wierd issues when performing selector “selectAll”

问题:

I am facing the the wierdest bug (ether in my app or in IOS 7.1) ever. After many hours I managed to create a simple app that demonstrate the problem.

Two UITextField - Dragged and dropped from interface builder and wired to t1, t2. the ViewController:

@implementation ViewController
@synthesize t1;
@synthesize t2;
#pragma mark - UITextFieldDelegate


-(void)textFieldDidBeginEditing:(UITextField *)iTextField {
    NSLog(@"textFieldDidBeginEditing");
    [iTextField performSelector:@selector(selectAll:) withObject:iTextField afterDelay:0.0];
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    return YES;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    t1.delegate = self;
    t2.delegate = self;
}

@end

When tapping on t1 and t2 at the same time, both textFields become first responder in an endless loop! When omitting ether the PerformSelector statement or the textField:shouldChangeCharactersInRange: implementation, problem is gone.

Can someone explain why does it happen?

回答1:

Edit: Also set the exclusiveTouch property of each UITextField to: YES to prevent them from editing at the same time.

- (void)viewDidLoad
{
    [super viewDidLoad];
    t1.exclusiveTouch = YES;
    t2.exclusiveTouch = YES;
    t1.delegate = self;
    t2.delegate = self;
}

- (void)textFieldDidBeginEditing:(UITextField *)iTextField
{
    [iTextField performSelector:@selector(selectAll:) withObject:nil afterDelay:0.0];
}

Or more simply without using the exclusiveTouch properties:

- (BOOL)textFieldShouldBeginEditing:(UITextField *)iTextField
{
    if (iTextField == t1 && t2.isFirstResponder == NO)
    {
        return YES;
    }
    else if (iTextField == t2 && t1.isFirstResponder == NO)
    {
        return YES;
    }

    return NO;
}