iCarousel not scrolling smoothly

问题

I'm using iCarousel to scroll labels. Everything works fine on Simulator, but on iPad/iPhone scrolling is not smoothly and quick

Here is code.

CitiesListView.h

#import <UIKit/UIKit.h>
#import "iCarousel.h"

@interface CitiesListView : UIView <iCarouselDataSource, iCarouselDelegate>

@property (nonatomic, retain)  iCarousel *carousel;


@end

CitiesListView.m

#import "CitiesListView.h"

@interface CitiesListView ()


@property (nonatomic, retain) NSMutableArray *items;

@end

@implementation CitiesListView

@synthesize carousel;
@synthesize items;

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self setUp];
    }
    return self;
}

- (void)setUp
{
    carousel = [[iCarousel alloc]initWithFrame:CGRectMake(0, 0, 300, 200)];
       items = [NSMutableArray arrayWithObjects:@"city1", @"city2", @"city3", @"city4", @"city5", @"city6", nil];
    [self addSubview:carousel];
    carousel.delegate = self;
    carousel.dataSource = self;
    carousel.type = iCarouselTypeRotary;

}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    if ((self = [super initWithCoder:aDecoder]))
    {
        [self setUp];
    }
    return self;
}

#pragma mark iCarousel methods

- (NSUInteger)numberOfItemsInCarousel:(iCarousel *)carousel
{
    return [items count];
}

- (UIView *)carousel:(iCarousel *)carousel viewForItemAtIndex:(NSUInteger)index reusingView:(UIView *)view
{
    UILabel *label = nil;

    //create new view if no view is available for recycling
    if (view == nil)
    {
        view = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 200.0f, 200.0f)];
        ((UIImageView *)view).image = [UIImage imageNamed:@"labelBackground.png"];
        view.contentMode = UIViewContentModeCenter;
        label = [[UILabel alloc] initWithFrame:view.bounds];
        label.backgroundColor = [UIColor clearColor];
        label.textAlignment = UITextAlignmentCenter;
        label.font = [label.font fontWithSize:26];
        label.tag = 1;
        [view addSubview:label];
    } else {
        //get a reference to the label in the recycled view
        label = (UILabel *)[view viewWithTag:1];
    }

    //set item label
    //remember to always set any properties of your carousel item
    //views outside of the `if (view == nil) {...}` check otherwise
    //you'll get weird issues with carousel item content appearing
    //in the wrong place in the carousel
    label.text = [items objectAtIndex:index];
    return view;
}

- (NSUInteger)numberOfPlaceholdersInCarousel:(iCarousel *)carousel
{
    //note: placeholder views are only displayed on some carousels if wrapping is disabled
    return 2;
}

- (UIView *)carousel:(iCarousel *)carousel placeholderViewAtIndex:(NSUInteger)index reusingView:(UIView *)view
{
    UILabel *label = nil;

    //create new view if no view is available for recycling
    if (view == nil)
    {
        //don't do anything specific to the index within
        //this `if (view == nil) {...}` statement because the view will be
        //recycled and used with other index values later
        view = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 200.0f, 200.0f)];
        ((UIImageView *)view).image = [UIImage imageNamed:@"labelBackground.png"];
        view.contentMode = UIViewContentModeCenter;

        label = [[UILabel alloc] initWithFrame:view.bounds];
        label.backgroundColor = [UIColor clearColor];
        label.textAlignment = UITextAlignmentCenter;
        label.font = [label.font fontWithSize:50.0f];
        label.tag = 1;
        [view addSubview:label];
    } else {
        //get a reference to the label in the recycled view
        label = (UILabel *)[view viewWithTag:1];
    }

    //set item label
    //remember to always set any properties of your carousel item
    //views outside of the `if (view == nil) {...}` check otherwise
    //you'll get weird issues with carousel item content appearing
    //in the wrong place in the carousel
    label.text = (index == 0)? @"[": @"]";

    return view;
}

- (CATransform3D)carousel:(iCarousel *)_carousel itemTransformForOffset:(CGFloat)offset baseTransform:(CATransform3D)transform
{
    //implement 'flip3D' style carousel
    transform = CATransform3DRotate(transform, M_PI / 8.0f, 0.0f, 1.0f, 0.0f);
    return CATransform3DTranslate(transform, 0.0f, 0.0f, offset * carousel.itemWidth);
}

- (CGFloat)carousel:(iCarousel *)_carousel valueForOption:(iCarouselOption)option withDefault:(CGFloat)value
{
    //customize carousel display
    switch (option)
    {
        case iCarouselOptionSpacing:
        {
            //add a bit of spacing between the item views
            return value * 1.05f;
        }
        case iCarouselOptionFadeMax:
        {
            if (carousel.type == iCarouselTypeCustom)
            {
                //set opacity based on distance from camera
                return 0.0f;
            }
            return value;
        }
        default:
        {
            return value;
        }
    }
}

#pragma mark iCarousel taps

- (void)carousel:(iCarousel *)carousel didSelectItemAtIndex:(NSInteger)index
{
    NSNumber *item = [self.items objectAtIndex:index];
    NSLog(@"Tapped view number: %@", item);
}

@end

And in my view controller alloc/initWithFrame CitiesListView and added to self.view.

What I'm doing wrong. I need labels to scroll smooth like in examples.

Thanks.

回答1:

Inside your setUp method, call this:

carousel.centerItemWhenSelected = YES;

Also play with carousel.scrollSpeed (values: 0.0 to 1.0, default 1.0 which means fastest) to change the scrolling speed.

回答2:

Use any one method

(UIView *)carousel:(iCarousel *)carousel placeholderViewAtIndex:(NSUInteger)index reusingView:(UIView *)view

(Or)

(UIView *)carousel:(iCarousel *)carousel viewForItemAtIndex:(NSUInteger)index reusingView:(UIView *)view

回答3:

The problem is fundamentally that you are trying to load too many images into memory at once (number of views x number of animation frames per view).

You'll need to find a way to load the frames dynamically. Try my GLView library (https://github.com/nicklockwood/GLView) which includes instructions for playing animations using PVR images which can be loaded in real time. The GLView library includes a GLImageView class that works just like a UIImageView but let's you specify an array of image filenames to play instead of having to load all the images in advance.

回答4:

This might help someone.I had similar issue where iCarousel was not scrolling smooth. Turns out i was doing some heavy validation(image comparison) in the method named - (void)carouselCurrentItemIndexDidChange:(iCarousel *)carousel

Once i kept only relevant validation which was light weight, issue was resolved.

来源：https://stackoverflow.com/questions/17553854/icarousel-not-scrolling-smoothly

标签

ios

icarousel