的UITableView細胞奇怪的消失

Question

來你的團隊馬爾科

我們havign，使我們的表視圖細胞，通常出現像這樣一個令人難以置信的奇怪的問題：

出現像這樣的：

經審查，錯誤似乎發生，你當p讓iPhone進入睡眠狀態，然後重新打開應用程序並轉到放置桌面視圖的uiviewcontroller。不知何故，這使得cellForRowAtIndexPath不再被調用，即使委託和數據源仍然被設置爲self。我們的部分和行號仍然正常，我們可以在桌面上向下滾動。但由於cellForRowAtIndexPath沒有被調用，tableviewcells是隱藏的。

這是我們實現代碼如下設置（我從沒有任何與實現代碼如下這種巨大的文件拿出的東西：

// 
// SPHomeViewController.m 
// Spek 

@interface SPHomeViewController() <UITableViewDataSource, UITableViewDelegate, MKMapViewDelegate, SPCreationViewDelegate, UIAlertViewDelegate, CLLocationManagerDelegate> 
@property (nonatomic, strong) UITableView* tableView; 
@property (nonatomic, strong) NSMutableArray* tableDatasource; 
@property (nonatomic, strong) NSMutableArray* datasource; 
@property (nonatomic, strong) NSMutableArray* friendsDatasource; 
@property (nonatomic, strong) UISegmentedControl* userFilterSegment; 
@property (nonatomic) BOOL isLoadingData; 
@end 

@implementation SPHomeViewController 

@synthesize datasource = _datasource; 
@synthesize friendsDatasource = _friendsDatasource; 
@synthesize tableDatasource = _tableDatasource; 



- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
     // Custom initialization 
    } 
    return self; 
} 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    //[[SPLocationManager locationManager] startUpdatingLocationForSig]; 
    [self setNeedsStatusBarAppearanceUpdate]; 
    self.view.backgroundColor = [UIColor colorWithRed:230.0f/255.0f green:230.0f/255.0f blue:230.0f/255.0f alpha:1.0]; 
    self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height - kTopBarHeight)]; 
    self.tableView.separatorColor = [UIColor clearColor]; 
    self.tableView.backgroundColor = [UIColor clearColor]; 
    self.tableView.delegate = self; 
    self.tableView.dataSource = self; 
    [self.view addSubview:self.tableView]; 


} 

- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 

    if (self.creationView.center.y > self.view.frame.size.height) { 
     self.creationView = nil; 
    } 
    NSLog(@"Mem warning"); 
} 


//**************************************** 
//**************************************** 
#pragma mark - UITableViewDelegate/DataSource 
//**************************************** 
//**************************************** 

- (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { 
    NSLog(@"INDEX PATH ROW: %d AND SECTION: %d", indexPath.row, indexPath.section); 
    if (indexPath.section == 0) { 
     UITableViewCell* cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"SPMapCellSpace"]; 
     cell.backgroundColor = [UIColor clearColor]; 
     cell.backgroundView = [[UIView alloc] init]; 
     cell.selectedBackgroundView = [[UIView alloc] init]; 
     return cell; 
    } else if (indexPath.section == self.tableDatasource.count + 1) { 
     UITableViewCell* cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"SPBottomCellSpace"]; 
     cell.backgroundColor = [UIColor clearColor]; 
     cell.backgroundView = [[UIView alloc] init]; 
     cell.selectedBackgroundView = [[UIView alloc] init]; 

     return cell; 
    } 
    SPMark* mark = self.tableDatasource[indexPath.section - 1]; 
    NSString* reuseId = [SPHomeViewController cellIdentifierFromData:mark]; 
    SPTableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:reuseId]; 
    if (cell == nil) { 
     cell = [SPTableViewCell cellFromMark:mark reuseID:reuseId]; 
     [cell updateView:YES]; 
    } 
    [cell addDataToCell:mark]; 
    if (indexPath.section >= self.tableDatasource.count - 2 && !self.isLoadingData && self.pageNumber != -1) { 
     self.fetchNextPage = YES; // When the scrollview stops it will load more data if available. 
    } 

    return cell; 
} 

- (unsigned int)getPageNumber { 
    return (self.userFilterSegment.selectedSegmentIndex == 0) ? self.pageNumber : self.friendsPageNumber; 
} 

- (void)setCurrentPageNumber:(unsigned int)page { 
    if (self.userFilterSegment.selectedSegmentIndex == 0) { 
     self.pageNumber = page; 
    } else { 
     self.friendsPageNumber = page; 
    } 
} 

- (void)incrementCurrentPageNumber { 
    if (self.userFilterSegment.selectedSegmentIndex == 0) { 
     self.pageNumber++; 
    } else { 
     self.friendsPageNumber++; 
    } 
} 

// Every cell has a section header so this should be equal to the number of speks returned from the server 
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { 
    NSLog(@"section count is: %d",self.tableDatasource.count + 2); 
    return self.tableDatasource.count + 2; // Add two because the mapview needs to go on the top and extra spacing at the bottom. 
} 

// There is a section for every cell, so there is only one cell per section 
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { 
    return 1; 
} 

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath { 
    if (indexPath.section == 0) { 
     return kMapHeight+2; 
    } else if (indexPath.section == self.tableDatasource.count + 1) { 
     return kExtraSpaceBelowHomeView; 
    } 
    SPMark* mark = self.tableDatasource[indexPath.section - 1]; 
    return [SPTableViewCell cellHeightForMark:mark]; 
} 

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath { 
    if (indexPath.section == 0 || indexPath.section == self.tableDatasource.count + 1) { 
     cell.backgroundColor = [UIColor clearColor]; 
    } 
} 

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { 
    if (indexPath.section == 0 || indexPath.section == self.tableDatasource.count + 1) 
     return; 
    SPMark* mark = self.datasource[indexPath.section - 1 ]; 
    SPMarkViewController* markVC = [SPMarkViewController withMark:mark]; 
    [markVC displayData]; 
    [self.navigationController pushViewController:markVC animated:YES]; 
} 

-(void)reloadTableview { 
    [self.tableView setDelegate:self]; 
    dispatch_async(dispatch_get_main_queue(), ^{ 
     [self.tableView reloadData]; 
     [self.tableView setNeedsDisplay]; 
    }); 
} 

- (void)showNoItems { 
    if (self.tableDatasource.count == 0 && self.accuracyBad == NO) { 
     self.opaqueIcon.hidden = NO; 
     self.noItems.hidden = NO; 
     self.beTheFirst.hidden = NO; 
     self.downArrow.hidden = NO; 
     self.noItemsBackround.hidden = NO; 
     [self.view bringSubviewToFront:self.noItemsBackround]; 
     [self.view bringSubviewToFront:self.downArrow]; 
     [self.view bringSubviewToFront:self.beTheFirst]; 
     [self.view bringSubviewToFront:self.noItems]; 
     [self.view bringSubviewToFront:self.opaqueIcon]; 

    } 
} 

- (void)showTableView { 
    if (self.tableDatasource.count != 0) { 
     self.noItems.hidden = YES; 
     self.beTheFirst.hidden = YES; 
     self.downArrow.hidden = YES; 
     self.noItemsBackround.hidden = YES; 
     self.opaqueIcon.hidden = YES; 

     [self.view sendSubviewToBack:self.noItemsBackround]; 
     [self.view sendSubviewToBack:self.downArrow]; 
     [self.view sendSubviewToBack:self.beTheFirst]; 
     [self.view sendSubviewToBack:self.noItems]; 
     [self.view sendSubviewToBack:self.opaqueIcon]; 
    } 
} 

//**************************************** 
//**************************************** 
#pragma mark - Setters/Getters 
//**************************************** 
//**************************************** 

- (NSMutableArray*)datasource { 
    if (!_datasource) { 
     _datasource = [NSMutableArray array]; 
     if (!self.firstLoad) { 
      [self loadDataForPagination:NO]; 
     } 
    } 
    return _datasource; 
} 

- (NSMutableArray*)friendsDatasource { 
    if (!_friendsDatasource) { 
     _friendsDatasource = [NSMutableArray array]; 
     if (!self.firstLoad) { 
      [self loadDataForPagination:NO]; 
     } 
    } 
    return _friendsDatasource; 
} 

- (NSMutableArray*)tableDatasource { 
    if (!_tableDatasource) { 
     _tableDatasource = (self.userFilterSegment.selectedSegmentIndex == 0) ? self.datasource : self.friendsDatasource; 
    } 
    return _tableDatasource; 
} 

- (SPCreationView*)creationView { 
    if (!_creationView) { 
     UIView* window = [SPUtils getAppDelegate].window; 
     CGSize viewSize = window.frame.size; 
     CGRect startFrame = CGRectMake(0, viewSize.height, [SPUtils screenWidth], [SPUtils screenHeight]); 
     _creationView = [SPCreationView creationView:startFrame delegate:self]; 
     [window insertSubview:_creationView belowSubview:self.creationButton]; 
     _creationView.frame = startFrame; 
    } 
    return _creationView; 
} 

- (void)setTableDatasource:(NSMutableArray *)tableDatasource { 
    _tableDatasource = tableDatasource; 
    [self preFetchImages]; 
    dispatch_async(dispatch_get_main_queue(), ^{ 
     if(_tableDatasource == nil || _tableDatasource.count == 0) { 
      [self showNoItems]; 
     } else { 
      [self showTableView]; 
     } 
     [self reloadTableview]; 
    }); 
} 

- (void)setDatasource:(NSMutableArray *)datasource { 
    _datasource = datasource; 
} 

- (void)setFriendsDatasource:(NSMutableArray *)friendsDatasource { 
    _friendsDatasource = friendsDatasource; 
} 


@end 

最後，如果你認爲它是與我們的代表，我們不會觸摸視圖控制器那裏，所以我不明白這可能是一個問題。可能是內存問題或後臺線程問題？

Answer 1

問題是太多的後臺線程一次進行。當我們停止嘗試預取圖像時，問題就消失了。

Answer 2

這是很多的代碼，這是可能的問題可能在您的自定義中班，甚至沒有你提供的。

爲了加快速度，當您重現問題時，請進入調試器並轉儲視圖層次結構。您可以通過在視圖控制器上調用[self.view recursiveDescription]來完成此操作。這將導致整個子視圖層次結構被打印到控制檯，這會讓你看到你的單元格應該 - 但不是 - 正在顯示的內容。如果沒有給你任何喜悅，請在這裏發佈輸出。

但是，什麼是更加古怪的是，tableview中仍然存在，因爲你仍然可以滾動它不是一個子視圖的問題：

它可能仍然是一個子視圖的問題 - 實現代碼如下得到來自單獨調用的單元格的高度，因此與單元格本身無關。嘗試打印出層次結構，看看發生了什麼。