Smoothed drawing in a scrollview.

SmoothedSmoothedBIView.mm

#import "ScrolledSmoothedBIView.h"
#import "SmoothedBIView.h"

@implementation ScrolledSmoothedBIView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        SmoothedBIView *smoothedBIView = [[SmoothedBIView alloc] initWithFrame:CGRectMake(0, 0, frame.size.width*2, frame.size.height*2)];
        [self addSubview:smoothedBIView];
        self.contentSize = smoothedBIView.frame.size;
        self.multipleTouchEnabled = NO;
        self.delaysContentTouches = NO;
        self.scrollEnabled = NO;
        self.showsHorizontalScrollIndicator = YES;
        self.showsVerticalScrollIndicator = YES;
        
        UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc]
                                                        initWithTarget:self
                                                        action:@selector(handlePan:)];
        panGestureRecognizer.delegate = self;
        panGestureRecognizer.minimumNumberOfTouches = 2;
        panGestureRecognizer.maximumNumberOfTouches = 2;
        [self addGestureRecognizer:panGestureRecognizer];
        
        UIButton *left = [[UIButton alloc] initWithFrame:CGRectMake(20, 50, 100, 40)];
        [left setBackgroundColor:[UIColor greenColor]];
        [left setTitle:@"left" forState:UIControlStateNormal];
        [left addTarget:self action:@selector(leftPressed:) forControlEvents:UIControlEventTouchUpInside];
        [self addSubview:left];
        
        UIButton *right = [[UIButton alloc] initWithFrame:CGRectMake(frame.size.width-150, 50, 100, 40)];
        [right setBackgroundColor:[UIColor greenColor]];
        [right setTitle:@"right" forState:UIControlStateNormal];
        [right addTarget:self action:@selector(rightPressed:) forControlEvents:UIControlEventTouchUpInside];
        [self addSubview:right];
    }
    return self;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

- (void)handlePan:(UIPanGestureRecognizer *)gestureRecognizer
{
    CGPoint velocity = [gestureRecognizer velocityInView:self];
    NSLog(@"pan velocity (%.0lf,%.0lf)", velocity.x, velocity.y);
//    if (velocity.x < 20 && velocity.y < 20) {
//        return;
//    }
    double newx = self.contentOffset.x - velocity.x;
    double newy = self.contentOffset.y - velocity.y;
    if (newx < 0) newx = 0;
    if (newy < 0) newy = 0;
    [self scrollRectToVisible:CGRectMake(newx, newy, self.frame.size.width, self.frame.size.height) animated:YES];
}

- (void)rightPressed:(id)sender
{
    [self scrollRectToVisible:CGRectMake(self.contentOffset.x+self.frame.size.width/2.0, self.frame.origin.y, self.frame.size.width, self.frame.size.height) animated:YES];
}

- (void)leftPressed:(id)sender
{
    [self scrollRectToVisible:CGRectMake(self.contentOffset.x-self.frame.size.width/2.0, self.frame.origin.y, self.frame.size.width, self.frame.size.height) animated:YES];
}

/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
}
*/

@end