判断textField为空时让按钮不可用的代码

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range

replacementString:(NSString *)string

{

NSMutableString *newValue = [[self.TextField.text mutableCopy] autorelease];

[newValue replaceCharactersInRange:range withString:string];

if ([newValue length]== 0) {

self.navigationItem.rightBarButtonItem.enabled = NO;

}

else {

self.navigationItem.rightBarButtonItem.enabled = YES;

}

return YES;

}

- (BOOL)textFieldShouldClear:(UITextField *)textField{

self.navigationItem.rightBarButtonItem.enabled = NO;

return YES;

}