UIImage＆UITableViewCell尺寸

Question

我通過URL動態加載到我的UITableViewCells不同大小的圖像。我希望能夠根據下載圖像的大小調整Cell的大小。我可以提取維度，然後更改每個單元格的heightForRowAtIndexPath？

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
NSData *receivedData = [NSData dataWithContentsOfURL:[NSURL URLWithString:[arrayOfImages objectAtIndex:indexPath.row]] 
              options:NSUncachedRead  
               error: &error]; 

UIImage *image = [[UIImage alloc] initWithData:receivedData]; 

imgView.image = image; 

[cell.contentView addSubview:imgView]; 

.... 

Answer 1

簡短的回答：一旦你有圖像，然後image.size.height應該給你你想要的。然而，heightForRowAtIndexPath：在cellForRowAtIndexPath：之前被調用。所以你可能會想要實現一些類型的異步圖像加載器。查看蘋果示例LazyTableImages以獲得完整的實現。

長答案：我做了幾個捷徑來回答你的問題，而不寫1000行代碼，但是這應該證明這個想法。重要的位是cellForRowAtIndexPath：和heightForRowAtIndexPath :.

RootViewController.m

#import "RootViewController.h" 

@interface RootViewController() 
- (void)loadImagesForOnscreenRows; 
- (void)loadImageForIndexPath:(NSIndexPath *)indexPath; 
@end 

@implementation RootViewController 

static NSMutableDictionary *images; 
static NSDictionary *pathAndName; 

#pragma mark - 
#pragma mark NSObject 
- (void)dealloc { 
    [images release]; 
    [pathAndName release]; 
    [super dealloc]; 
} 


#pragma mark UIViewController 
- (void)viewDidLoad { 

    // image paths from WikiMedia 
    pathAndName = [[NSDictionary alloc] initWithObjectsAndKeys: 
        @"http://upload.wikimedia.org/wikipedia/commons/8/89/Crystal_Clear_app_virus_detected_2.png", @"Big Virus", 
        @"http://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Crystal_Clear_app_virus_detected.png/64px-Crystal_Clear_app_virus_detected.png", @"Little Virus", 
        nil]; 

    images = [[NSMutableDictionary alloc] initWithCapacity:[pathAndName allKeys].count]; 
} 

- (void)viewDidUnload { 
    [images release]; 
    images = nil; 

    [pathAndName release]; 
    pathAndName = nil; 
} 


#pragma mark UIScrollViewDelegate 
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate { 
    if (!decelerate) { 
     [self loadImagesForOnscreenRows]; 
    } 
} 

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { 
    [self loadImagesForOnscreenRows]; 
} 


#pragma mark UITableViewDataSource 
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { 
    return [pathAndName allKeys].count; 
} 

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

    // typical cell creation 
    static NSString *CellIdentifier = @"Cell"; 
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; 
    if (cell == nil) { 
     cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; 
    } 

    // if the image is downloaded, then set the cell image. 
    NSString *key = [[pathAndName allKeys] objectAtIndex:indexPath.row]; 
    UIImage *image = [images objectForKey:key]; 
    if (image) { 
     [cell.imageView setImage:image]; 
    } 

    [cell.textLabel setText:key]; 
    return cell; 
} 

#pragma mark UITableViewDelegate 
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath { 

    NSString *key = [[pathAndName allKeys] objectAtIndex:indexPath.row]; 
    UIImage *image = [images objectForKey:key]; 
    if (image) { 
     return image.size.height; 
    } 

    // if the image is not yet downloaded, kick off downloading it and return a default row height. 
    [self performSelector:@selector(loadImageForIndexPath:) withObject:indexPath afterDelay:0.1f]; 
    return tableView.rowHeight; 
} 


#pragma mark - 
#pragma mark RootViewController 
#pragma mark Private Extension 
- (void)loadImagesForOnscreenRows { 
    NSArray *visiblePaths = [self.tableView indexPathsForVisibleRows]; 
    for (NSIndexPath *indexPath in visiblePaths) { 
     [self loadImageForIndexPath:indexPath]; 
    } 
} 

// This is a big shortcut from the Apple sample, LazyTableImages. 
- (void)loadImageForIndexPath:(NSIndexPath *)indexPath { 

    NSString *key = [[pathAndName allKeys] objectAtIndex:indexPath.row]; 
    if ([images objectForKey:key]) return; 

    NSString *path = [pathAndName objectForKey:key]; 

    NSError *error = nil; 
    NSData *receivedData = [NSData dataWithContentsOfURL:[NSURL URLWithString:path] 
               options:NSUncachedRead  
                error: &error]; 
    if (error) return; 

    UIImage *image = [[UIImage alloc] initWithData:receivedData]; 
    [images setObject:image forKey:key]; 
    [image release]; 
    NSArray *indexPaths = [NSArray arrayWithObject:indexPath]; 
    [self.tableView reloadRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade]; 
} 


@end