我有一个UITableView的Instagram Feed。我已经实现了UIRefreshControl来提升刷新功能。
拖动并释放刷新控件后，当微调器移动时，我可以向下拖动tableview而不会导致应用程序崩溃。但是，如果我向上滚动tableview，应用程序崩溃（可能是因为单元格2,3等？）
以下是显示问题的视频：http://www.screenmailer.com/v/DukT4lt2aUGm8c5MLRlGMg/2586/3a23tXo7uXs.mp4
为什么会这样？
.m文件的代码：
#import "InstagramViewController.h"
#import "InstagramCell.h"
#import <InstagramKit/InstagramKit.h>
#import "UIImageView+AFNetworking.h"
@interface InstagramViewController ()
{
NSMutableArray *mediaArray;
}
@property (nonatomic, strong) InstagramPaginationInfo *currentPaginationInfo;
@end
@implementation InstagramViewController
- (id)initWithStyle:(UITableViewStyle)style
{
self = [super initWithStyle:style];
if (self) {
//mediaArray = [[NSMutableArray alloc] init];
}
return self;
}
- (void)viewDidLoad
{
mediaArray = [[NSMutableArray alloc] init];
[super viewDidLoad];
[self loadMedia];
self.refreshControl = [[UIRefreshControl alloc] init];
[self.refreshControl addTarget:self action:@selector(reloadMedia) forControlEvents:UIControlEventValueChanged];
// Uncomment the following line to preserve selection between presentations.
// self.clearsSelectionOnViewWillAppear = NO;
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem;
}
-(void)reloadMedia
{
self.currentPaginationInfo = nil;
[mediaArray removeAllObjects];
[self loadMedia];
}
-(IBAction)loadMedia
{
// start network indicator
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
[[InstagramEngine sharedEngine] getMediaWithTagName:@"AUFsommer" count:10 maxId:self.currentPaginationInfo.nextMaxId withSuccess:^(NSArray *media, InstagramPaginationInfo *paginationInfo) {
if (paginationInfo)
{
self.currentPaginationInfo = paginationInfo;
}
[mediaArray addObjectsFromArray:media];
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
[self reloadData];
} failure:^(NSError *error) {
NSLog(@"Search Media Failed");
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
}];
}
-(void)reloadData
{
[self.refreshControl endRefreshing];
[self.tableView reloadData];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark - Table view data source
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section
{
UIView *headerView = [[UIView alloc] init];
headerView.backgroundColor = [UIColor colorWithWhite:1.0f alpha:0.9f];
InstagramMedia *media = mediaArray[section];
// create imageview for profile photo
AsyncImageView *profilePhoto = [[AsyncImageView alloc] initWithFrame:CGRectMake(8, 8, 32, 32)];
profilePhoto.layer.borderColor = [[UIColor colorWithRed:204.0/255.0f green:204.0/255.0f blue:204.0/255.0f alpha:1.0f] CGColor];
profilePhoto.layer.borderWidth = 1;
profilePhoto.layer.masksToBounds = YES;
profilePhoto.layer.cornerRadius = 16.0;
[profilePhoto loadImageFromURL:[media.user.profilePictureURL absoluteString]];
// uifont settings
UIFont *labelFont = [UIFont boldSystemFontOfSize:13.0];
// create label for username
UILabel *usernameLabel = [[UILabel alloc] initWithFrame:CGRectMake(48, 0, 210, 48)];
usernameLabel.text = media.user.username;
usernameLabel.font = labelFont;
usernameLabel.textColor = [UIColor colorWithRed:235.0/255.0 green:24.0/255.0 blue:22.0/255.0 alpha:1.0f];
// create label for timestamp
UILabel *timestampLabel = [[UILabel alloc] initWithFrame:CGRectMake(250, 0, 54, 48)];
timestampLabel.textAlignment = NSTextAlignmentRight;
timestampLabel.font = labelFont;
// timestampLabel.text = [self stringForDisplayFromDate:media.createdDate];
// add to view
[headerView addSubview:profilePhoto];
[headerView addSubview:usernameLabel];
[headerView addSubview:timestampLabel];
return headerView;
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return mediaArray.count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return 1;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
InstagramCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[InstagramCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
// clear photo
[cell.igPhoto setImage:nil];
if (mediaArray.count >= indexPath.section+1)
{
InstagramMedia *media = mediaArray[indexPath.section];
cell.title.text = media.caption.text;
[cell.igPhoto loadImageFromURL:[media.standardResolutionImageURL absoluteString]];
}
return cell;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
InstagramMedia *media = mediaArray[indexPath.section];
CGSize maximumLabelSize = CGSizeMake(304.0f, 20000.0f);
CGSize expectedLabelSize = [media.caption.text sizeWithFont:[UIFont systemFontOfSize:13.0f] constrainedToSize:maximumLabelSize lineBreakMode:NSLineBreakByWordWrapping];
return (320.0f + expectedLabelSize.height + 20.0f);
}
-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
CGFloat currentOffset = scrollView.contentOffset.y;
CGFloat maximumOffset = scrollView.contentSize.height - scrollView.frame.size.height;
if (maximumOffset - currentOffset < 10.0)
{
[self loadMedia];
}
}
@end
答案 0 :(得分：6)
您应该做的第一件事是在项目中add an exception breakpoint，这样您就会知道崩溃的原因和地点。
您的应用崩溃的原因是您尝试读取空数组。在方法reloadMedia中，您可以执行以下操作：
self.currentPaginationInfo = nil;
[mediaArray removeAllObjects];
所以在这一点上，你的数组是空的，但你的UITableView并不知道。通过在重新加载数据之前滚动，将调用方法cellForRowAtIndexPath并尝试访问空数组中的索引。
要解决此问题，您可以在[self.tableView reloadData];之后致电[mediaArray removeAllObjects];。这样，UITableView将调用它来知道它应该有多少行和部分，并且会知道没有更多的行和部分。
或者，如果您希望旧信息在加载过程中仍然在UITableView，请不要currentPaginationInfo或mediaArray中reloadMedia }，