셀에 UIImageView 하위 뷰가있을 때 UITableView가 고르지 못한 스크롤을 경험합니다.

Question

이것은 하루의 더 좋은 날을 위해 나를 미치게했습니다.

나는 UIImageViews가있는 UITableView를 가지고있다. 이 imageviews는 tableview의 cellForRow-function에 로컬로 저장된 PNG 파일을로드합니다. 이미지 뷰가있는 셀이 말하자면 스크롤 할 때 tableview에서 스크롤을 멈추는 것을 제외하고는 정상적으로 작동합니다. 나는 StackOverflow와 구글을 대답 해 주었다. 그러나 나는 짧게 생각해 냈다 - 그래서 어떤 도움도 크게 감사 할 것이다. 여기

는 CellForRow 기능에 대한 내 코드입니다 : ...

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { 


    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"MyIdentifier"]; 



    if (cell == nil) { 
     cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"MyIdentifier"] autorelease]; 
     cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator; 
    } 

    if([currSection isEqualToString:@"composer"]){ 

     MySlide *s = [slidesArray objectAtIndex:indexPath.row]; 

     cell.textLabel.hidden = YES; 
     UIImageView *whiteView = [[UIImageView alloc] initWithFrame:CGRectMake((projectsTable.frame.size.width/2)-150, 4, 204.8, 153.6)]; 

     if([s.slideImage isEqualToString:@""] || s.slideImage == nil){ 
      //no custom image in this cell - go with default background image 

      whiteView.image = [UIImage imageNamed:@"cellback2.png"]; 
      whiteView.backgroundColor = [UIColor whiteColor]; 
     }else{ 
      cell.layer.shouldRasterize = YES; 
      cell.layer.rasterizationScale = [UIScreen mainScreen].scale; 

      NSData *data = [[NSData alloc] initWithContentsOfFile:s.slideImage]; 

      UIImage *im = [[UIImage alloc] initWithData:data]; 


      whiteView.image = im; 

      whiteView.image = [self imageWithImage:whiteView.image CovertToSize:CGSizeMake(204.8,153.6)]; 
      whiteView.backgroundColor = [UIColor whiteColor]; 

     } 


     [cell.contentView addSubview:whiteView]; 

     [whiteView release]; 



     cell.accessoryType = UITableViewCellAccessoryNone; 

    } 


    return cell; 
} 

Answer 1

먼저 떨어져, 만들어 질 변화의 몇 가지 있습니다 셀이 생성 될 때마다 tableView:cellForRowAtIndexPath:이 히트 (@Vishy가 제안하는 것) 할 때마다가 아니라 UIImageView을 추가해야합니다. 둘째로,로드중인 이미지를 문서 디렉토리에서 캐시해야합니다 ([UIImage imageNamed:] 번들 자원의 경우 자동으로 수행합니다). 일반적으로

@interface MyViewController() { 

    NSMutableDictionary *_imageCache; 
} 

@end 


@implementation MyViewController 

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    // other viewDidLoad stuff... 

    _imageCache = [[NSMutableDictionary alloc] init]; 
} 

- (void)viewDidUnload { 
    [super viewDidUnload]; 

    // other viewDidUnload stuff... 

    [_imageCache release]; 
    _imageCache = nil; 
} 

- (void)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { 

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"MyIdentifier"]; 

    if (cell == nil) { 
     cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"MyIdentifier"] autorelease]; 
     cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator; 

     UIImageView *whiteView = [[UIImageView alloc] initWithFrame:CGRectMake((projectsTable.frame.size.width/2)-150, 4, 204.8, 153.6)]; 
     whiteView.tag = 111; 
     whiteView.backgroundColor = [UIColor whiteColor]; 

     [cell.contentView addSubview:whiteView]; 

     [whiteView release]; 
     cell.accessoryType = UITableViewCellAccessoryNone; 
     cell.textLabel.hidden = YES; 
    } 

    UIImageView* iView = (UIImageView*) [cell.contentView viewWithTag:111]; 


    if([currSection isEqualToString:@"composer"]) { 

     MySlide *s = [slidesArray objectAtIndex:indexPath.row]; 

     if([s.slideImage isEqualToString:@""] || s.slideImage == nil) { 

      //no custom image in this cell - go with default background image 
      iView.image = [UIImage imageNamed:@"cellback2.png"]; 
     } 
     else { 

      cell.layer.shouldRasterize = YES; 
      cell.layer.rasterizationScale = [UIScreen mainScreen].scale; 

      // use the image path as the cache key 
      UIImage *theImage = [_imageCache objectForKey:s.slideImage]; 
      if (theImage == nil) { 

       // load the image and save into the cache 
       theImage = [UIImage imageWithContentsOfFile:s.slideImage]; 
       theImage = [self imageWithImage:theImage CovertToSize:CGSizeMake(204.8, 153.6)]; 

       [_imageCache setObject:theImage forKey:s.slideImage]; 
      } 

      iView.image = theImage; 
     } 
    } 
} 

@end 

, tableView:cellForRowAtIndexPath:는 빠른 나갈 필요가하는 방법이기 때문에 디스크에서 로딩 이미지는 가능한 한 피해야한다.

Answer 2

변경 아래에 따라 코드

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"MyIdentifier"]; 

if (cell == nil) 
{ 
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"MyIdentifier"] autorelease]; 
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator; 
    UIImageView *whiteView = [[UIImageView alloc] initWithFrame:CGRectMake((projectsTable.frame.size.width/2)-150, 4, 204.8, 153.6)]; 
    whiteView.tag = 111; 
    whiteView.backgroundColor = [UIColor whiteColor]; 

    [cell.contentView addSubview:whiteView]; 

    [whiteView release]; 
    cell.accessoryType = UITableViewCellAccessoryNone; 
    cell.textLabel.hidden = YES; 

} 

UIImageView* iView = (UIImageView*) [cell.contentView viewWithTag:111]; 


if([currSection isEqualToString:@"composer"]) 
{ 
    MySlide *s = [slidesArray objectAtIndex:indexPath.row]; 

    if([s.slideImage isEqualToString:@""] || s.slideImage == nil) 
    { 
     //no custom image in this cell - go with default background image 

     iView.image = [UIImage imageNamed:@"cellback2.png"]; 
    } 
    else 
    { 
     cell.layer.shouldRasterize = YES; 
     cell.layer.rasterizationScale = [UIScreen mainScreen].scale; 

     iView.image = [UIImage imageWithContentsOfFile:s.slideImage]; 
     iView.image = [self imageWithImage:iView.image CovertToSize:CGSizeMake(204.8,153.6)]; 

    } 
    } 
} 

Answer 3

각 UIImage가 처음으로 표시 될 때까지 지연이 있습니다. 오히려 표시 시간보다 캐시 시간에 작업을하라는 메시지에 대한 자세한 내용은이 게시물을 참조 :

Setting image property of UIImageView causes major lag