iCarousel 滚动不顺畅

Posted 2023-03-10

【中文标题】iCarousel 滚动不顺畅

【英文标题】：iCarousel not scrolling smoothly

【发布时间】：2013-07-09 16:51:12

【问题描述】：

我正在使用 iCarousel 滚动标签。在模拟器上一切正常，但在 iPad/iPhone 上滚动并不顺畅和快速

这是代码。

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

并在我的视图控制器 alloc/initWithFrame CitiesListView 并添加到 self.view。

我做错了什么。我需要像示例中那样平滑滚动的标签。

谢谢。

【问题讨论】：

您可能希望在 Instruments 中分析您的代码，以查看是否存在影响应用性能的特定区域。使用 Time Profiler 仪器。有关如何使用 Instruments 的更多信息，请参阅 Apple 文档：developer.apple.com/library/ios/#documentation/DeveloperTools/…

当我配置文件和使用分配工具轮播时滚动流畅。找不到问题并修复

Allocations 会告诉您内存使用情况，但 Time Profiler 会告诉您每个方法执行所需的时间。这可能有助于找出导致绘图速度变慢的原因。确保您也在设备上进行分析。

【参考方案1】：

在你的 setUp 方法中，调用这个：

carousel.centerItemWhenSelected = YES;

也可以使用carousel.scrollSpeed（值：0.0 到 1.0，默认 1.0 表示最快）来改变滚动速度。

【讨论】：

我试过 scrollSpeed 和 centerItemWhenSelected 没有帮助

你在这里做的事情是可疑的。您是否正在向图像视图添加标签？为什么不添加一个图像视图，然后将标签添加到 UIView 本身？ Imageview 的布局与 UIView 不同，这可能是绘制延迟的原因。

【参考方案2】：

使用任何一种方法

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

（或）

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

【参考方案3】：

问题在于您试图一次将太多图像加载到内存中（视图数 x 每个视图的动画帧数）。

您需要找到一种动态加载框架的方法。试试我的 GLView 库 (https://github.com/nicklockwood/GLView)，其中包含使用可以实时加载的 PVR 图像播放动画的说明。 GLView 库包含一个 GLImageView 类，它的工作方式与 UIImageView 类似，但您可以指定要播放的图像文件名数组，而不必提前加载所有图像。

【参考方案4】：

这可能对某人有所帮助。我遇到了类似的问题，即 iCarousel 滚动不顺畅。原来我在名为 - (void)carouselCurrentItemIndexDidChange:(iCarousel *)carousel的方法中进行了一些繁重的验证（图像比较）

一旦我只保留了轻量级的相关验证，问题就解决了。