Double Tap on UITabBarItem to Scroll up and Reload like Twitter App

Question

How do you implement a double tap on UITabBarItem so that it will scroll up the UITableView, like what the Twitter App does? Or any reference for this, will do

Thanks

Answer 1

You can keep track of last touch date and compare to the current touch date. If the difference is small enough (0.7sec) you can consider it a double tap.

Implement this in a subclass of UITabVarController using a delegate method shouldSelectViewController.

Here is a working code that I am using.

#import "TabBarController.h"
#import "TargetVC.h"

@interface TabBarController ()

@property(nonatomic,retain)NSDate *lastTouchDate;

@end

@implementation TabBarController

//Remeber to setup UINavigationController of each of the tabs so that its restorationIdentifier is not nil
//You can setup the restoration identifier in the IB in the identity inspector for you UIViewController or your UINavigationController
- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController{
    NSString *tab = viewController.restorationIdentifier;

    if([tab isEqualToString:@"TargetVC"]){

        if(self.lastTouchDate){

            UINavigationController *navigationVC = (UINavigationController*)viewController;
            TargetVC *targetVC = (TargetVC*)navigationVC.viewControllers[0];

            NSTimeInterval ti = [[NSDate date] timeIntervalSinceDate:self.lastTouchDate];
            if(ti < 0.7f)
               [targetVC scrollToTop];

        }

        self.lastTouchDate = [NSDate date];
    }

    return YES;
}