如何啓用長按事件

UILongPressGestureRecognizer *longPressGR = 
        [[UILongPressGestureRecognizer alloc] initWithTarget:self 
                                                      action:@selector(handleLongPress:)];
        longPressGR.minimumPressDuration = 0.2;
        [self addGestureRecognizer:longPressGR];
        [longPressGR release];


- (void)handleLongPress:(UIGestureRecognizer *)gestureRecognizer {
    NSLog(@"LONG PRESS");
}