问为什么这个动画只起作用一次？

EN

-(void)handleLeftTap {

    self.player.direction = LEFT;

    if(!self.isAnimating && self.toTile.isWalkable) {
        for(UIView *currentView in self.subviews) {
            CABasicAnimation *moveAnimation = [CABasicAnimation animationWithKeyPath:@"position"];
            [moveAnimation setDuration:MOVE_ANIMATION_DURATION];
            [moveAnimation setDelegate:self];
            [moveAnimation setRemovedOnCompletion:NO];
            [moveAnimation setFillMode:kCAFillModeForwards];
            moveAnimation.toValue = [NSValue valueWithCGPoint:CGPointMake(currentView.center.x+TILE_WIDTH, currentView.center.y)];
            [currentView.layer addAnimation:moveAnimation forKey:nil];
        }
        NSLog(@"animated\n");
    }
}