UITableView 崩溃

Question

我在 UITableView 中显示一个数组对象，其中包含插入、更新和删除，即使我正在仔细处理更改，偶尔也会出现以下异常。我在 GitHub 上有完整的代码示例。

https://github.com/brennanMKE/TableMaddness

此示例项目使用实现 NSCoding 和 NSCopying 以及 isEqual 的对象，以便使用插入、更新和删除来更新表可以模拟我在具有相同问题的真实应用程序中所做的事情。我正在避免使用会使用 NSFetchedResultsController 的 Core Data，所以我想知道如果我不使用 Core Data 是否应该使用某些东西。

断言失败 -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-2903.23/UITableView.m:1330 2013-11-25 14:43:20.217 TableMaddness [13411:70b] 由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因：“无效更新：第 0 节中的行数无效。之后现有节中包含的行数更新 (4) 必须等于更新 (4) 之前该节中包含的行数，加上或减去从该节中插入或删除的行数（插入 1，删除 0）加上或减去数字移入或移出该部分的行数（0 移入，0 移出）。'

下面是相关代码。

    // determine items which need to be inserted, updated or removed
    NSMutableArray *inserts = [@[] mutableCopy];
    NSMutableArray *deletes = [@[] mutableCopy];
    NSMutableArray *reloads = [@[] mutableCopy];

    // look for inserts
    for (NSUInteger row=0; row<fetchedItems.count; row++) {
        SSTItem *item = fetchedItems[row];
        if (![self.currentItems containsObject:item]) {
            // inserts are items which are not already in self.items
            [inserts addObject:[NSIndexPath indexPathForRow:row inSection:0]];
        }
        else {
            NSUInteger otherIndex = [self.currentItems indexOfObject:item];
            SSTItem *otherItem = [self.currentItems objectAtIndex:otherIndex];
            if (![item.modified isEqualToDate:otherItem.modified]) {
                [reloads addObject:[NSIndexPath indexPathForRow:row inSection:0]];
            }
        }
    }

    // look for deletes
    for (NSUInteger row=0; row<self.currentItems.count; row++) {
        SSTItem *item = self.currentItems[row];
        if (![fetchedItems containsObject:item]) {
            [deletes addObject:[NSIndexPath indexPathForRow:row inSection:0]];
        }
    }

    static NSString *lock = @"LOCK";

    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (kDelay / 4) * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
        // lock is required to prevent inconsistencies when changing view orientation during rotation
        @synchronized(lock) {
            self.currentItems = fetchedItems;

            NSUInteger numberOfRowsInSection = [self tableView:self.tableView numberOfRowsInSection:0];
            DebugLog(@"numberOfRowsInSection: %li", numberOfRowsInSection);
            DebugLog(@"self.items: %li", self.currentItems.count);

            MAAssert(self.currentItems.count == numberOfRowsInSection, @"Match is required");

            if (inserts.count || deletes.count || reloads.count) {
                [self.tableView beginUpdates];
#ifndef NDEBUG
                for (NSIndexPath *indexPath in inserts) {
                    DebugLog(@"Inserting at %li", (long)indexPath.row);
                }
                for (NSIndexPath *indexPath in deletes) {
                    DebugLog(@"Deleting at %li", (long)indexPath.row);
                }
                for (NSIndexPath *indexPath in reloads) {
                    DebugLog(@"Reloading at %li", (long)indexPath.row);
                }
#endif
                [self.tableView insertRowsAtIndexPaths:inserts withRowAnimation:UITableViewRowAnimationAutomatic];
                [self.tableView deleteRowsAtIndexPaths:deletes withRowAnimation:UITableViewRowAnimationAutomatic];
                [self.tableView reloadRowsAtIndexPaths:reloads withRowAnimation:UITableViewRowAnimationAutomatic];
                [self.tableView endUpdates];
            }
        }

        index++;
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kDelay * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
            [self runNextUpdate];
        });
    });

Answer 1

- (void)runNextUpdate {
if (index >= self.dataSets.count) {
    index = 0;

    [self runNextUpdate]; // remove this line
    return;               // or add this line.
}

因为如果这个条件为真，你的代码会几乎同时运行两次，但是数据源并没有更新。