科尔多瓦/ iOS /混合应用-UITableView错误地加载了项目，并且无序

时间：2019-02-03 14:47:05

标签： ios objective-c uitableview cordova delegates

我的UITableView出现了奇怪的行为。它正在加载第0, 1, 2行-但是到达第3行时，它将加载第4行，然后对于第4行，它将加载第0行再一次，就像这样：

表中的行：

0
1
2
4
0

它显然应该按顺序0, 1, 2, 3, 4。这是我的代码：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(@"cellForRowAtIndexPath getting called - row: %li", indexPath.row);

    [self.items enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"items at every cell entry: %@", [obj valueForKey:@"item"]);
    }];

    //UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell1" forIndexPath:indexPath];
    //NSLog(@"indexPath.row: %li, %@", (long)indexPath.row, [self.items objectAtIndex:indexPath.row]);

    PoolsTableViewCell *cell = (PoolsTableViewCell*)[tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];

    if(cell.cellLeftImageView.image == nil) {

        NSInteger left = 2*indexPath.row;
        NSLog(@"left: %li", (long)left);

        NSObject* obj = (NSObject*)[self.items objectAtIndex:left];

        cell.cellLeftViewLabel.text = [obj valueForKey:@"item"];

        NSString *ImageURL = [obj valueForKey:@"downloadURL"];
        NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:ImageURL]];
        cell.cellLeftImageView.image = [UIImage imageWithData:imageData];

        NSInteger right = (2*indexPath.row)+1;
        NSLog(@"right: %li", (long)right);

        if(right < [self.items count]) {
            NSLog(@"inside right < self.items count conditional");
            NSObject* objPlus = (NSObject*)[self.items objectAtIndex:right];

            cell.cellRightViewLabel.text = [objPlus valueForKey:@"item"];

            NSString *secondImageURL = [objPlus valueForKey:@"downloadURL"];
            NSData *secondImageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:secondImageURL]];
            cell.cellRightImageView.image = [UIImage imageWithData:secondImageData];
        }
    }

    return cell;
}

我有这段代码，每次调用cellForRowAtIndex时都会记录所有项目：

[self.items enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, 
    BOOL * _Nonnull stop) {
    NSLog(@"items at every cell entry: %@", [obj valueForKey:@"item"]);
}];

我正在将self.items中的2个项目加载到每一行（每行本质上有2列）。控制台输出对于cellForRowAtIndexPath的每次调用都是正确的-因此，self.items永远都不应被无序引用，但这是-这是UITableView加载时我的控制台输出的一个示例： 

2019-02-02 22:01:30.121975-0500 HybridPool[1720:534623] cellForRowAtIndexPath getting called - row: 0
2019-02-02 22:01:30.122149-0500 HybridPool[1720:534623] items at ever cell entry: Table
2019-02-02 22:01:30.122263-0500 HybridPool[1720:534623] items at ever cell entry: Cord
2019-02-02 22:01:30.122373-0500 HybridPool[1720:534623] items at ever cell entry: Keys
2019-02-02 22:01:30.122645-0500 HybridPool[1720:534623] items at ever cell entry: Hshhdhdbd
2019-02-02 22:01:30.122769-0500 HybridPool[1720:534623] items at ever cell entry: Jhghhvhh
2019-02-02 22:01:30.122947-0500 HybridPool[1720:534623] items at ever cell entry: Book
2019-02-02 22:01:30.123054-0500 HybridPool[1720:534623] items at ever cell entry: Njhhnn
2019-02-02 22:01:30.123160-0500 HybridPool[1720:534623] items at ever cell entry: Tv
2019-02-02 22:01:30.123260-0500 HybridPool[1720:534623] items at ever cell entry: 9th item
2019-02-02 22:01:30.129478-0500 HybridPool[1720:534623] left: 0
2019-02-02 22:01:31.024184-0500 HybridPool[1720:534623] right: 1
2019-02-02 22:01:31.024302-0500 HybridPool[1720:534623] inside right < self.items count conditional
2019-02-02 22:01:31.719052-0500 HybridPool[1720:534623] cellForRowAtIndexPath getting called - row: 1
2019-02-02 22:01:31.719252-0500 HybridPool[1720:534623] items at ever cell entry: Table
2019-02-02 22:01:31.719374-0500 HybridPool[1720:534623] items at ever cell entry: Cord
2019-02-02 22:01:31.719481-0500 HybridPool[1720:534623] items at ever cell entry: Keys
2019-02-02 22:01:31.719584-0500 HybridPool[1720:534623] items at ever cell entry: Hshhdhdbd
2019-02-02 22:01:31.719687-0500 HybridPool[1720:534623] items at ever cell entry: Jhghhvhh
2019-02-02 22:01:31.719785-0500 HybridPool[1720:534623] items at ever cell entry: Book
2019-02-02 22:01:31.719884-0500 HybridPool[1720:534623] items at ever cell entry: Njhhnn
2019-02-02 22:01:31.720048-0500 HybridPool[1720:534623] items at ever cell entry: Tv
2019-02-02 22:01:31.720170-0500 HybridPool[1720:534623] items at ever cell entry: 9th item
2019-02-02 22:01:31.724875-0500 HybridPool[1720:534623] left: 2
2019-02-02 22:01:32.340747-0500 HybridPool[1720:534623] right: 3
2019-02-02 22:01:32.340969-0500 HybridPool[1720:534623] inside right < self.items count conditional
2019-02-02 22:01:32.776360-0500 HybridPool[1720:534623] cellForRowAtIndexPath getting called - row: 2
2019-02-02 22:01:32.776572-0500 HybridPool[1720:534623] items at ever cell entry: Table
2019-02-02 22:01:32.776685-0500 HybridPool[1720:534623] items at ever cell entry: Cord
2019-02-02 22:01:32.776877-0500 HybridPool[1720:534623] items at ever cell entry: Keys
2019-02-02 22:01:32.777113-0500 HybridPool[1720:534623] items at ever cell entry: Hshhdhdbd
2019-02-02 22:01:32.777244-0500 HybridPool[1720:534623] items at ever cell entry: Jhghhvhh
2019-02-02 22:01:32.777344-0500 HybridPool[1720:534623] items at ever cell entry: Book
2019-02-02 22:01:32.777443-0500 HybridPool[1720:534623] items at ever cell entry: Njhhnn
2019-02-02 22:01:32.777542-0500 HybridPool[1720:534623] items at ever cell entry: Tv
2019-02-02 22:01:32.777641-0500 HybridPool[1720:534623] items at ever cell entry: 9th item
2019-02-02 22:01:32.782148-0500 HybridPool[1720:534623] left: 4
2019-02-02 22:01:33.383439-0500 HybridPool[1720:534623] right: 5
2019-02-02 22:01:33.383649-0500 HybridPool[1720:534623] inside right < self.items count conditional
2019-02-02 22:01:34.534761-0500 HybridPool[1720:534623] cellForRowAtIndexPath getting called - row: 3
2019-02-02 22:01:34.534980-0500 HybridPool[1720:534623] items at ever cell entry: Table
2019-02-02 22:01:34.535099-0500 HybridPool[1720:534623] items at ever cell entry: Cord
2019-02-02 22:01:34.535206-0500 HybridPool[1720:534623] items at ever cell entry: Keys
2019-02-02 22:01:34.535310-0500 HybridPool[1720:534623] items at ever cell entry: Hshhdhdbd
2019-02-02 22:01:34.535412-0500 HybridPool[1720:534623] items at ever cell entry: Jhghhvhh
2019-02-02 22:01:34.535666-0500 HybridPool[1720:534623] items at ever cell entry: Book
2019-02-02 22:01:34.535787-0500 HybridPool[1720:534623] items at ever cell entry: Njhhnn
2019-02-02 22:01:34.535895-0500 HybridPool[1720:534623] items at ever cell entry: Tv
2019-02-02 22:01:34.536022-0500 HybridPool[1720:534623] items at ever cell entry: 9th item
2019-02-02 22:01:34.540261-0500 HybridPool[1720:534623] left: 6
2019-02-02 22:01:35.090979-0500 HybridPool[1720:534623] right: 7
2019-02-02 22:01:35.091111-0500 HybridPool[1720:534623] inside right < self.items count conditional
2019-02-02 22:01:35.886101-0500 HybridPool[1720:534623] cellForRowAtIndexPath getting called - row: 4
2019-02-02 22:01:35.886329-0500 HybridPool[1720:534623] items at ever cell entry: Table
2019-02-02 22:01:35.886446-0500 HybridPool[1720:534623] items at ever cell entry: Cord
2019-02-02 22:01:35.886554-0500 HybridPool[1720:534623] items at ever cell entry: Keys
2019-02-02 22:01:35.886658-0500 HybridPool[1720:534623] items at ever cell entry: Hshhdhdbd
2019-02-02 22:01:35.886978-0500 HybridPool[1720:534623] items at ever cell entry: Jhghhvhh
2019-02-02 22:01:35.887082-0500 HybridPool[1720:534623] items at ever cell entry: Book
2019-02-02 22:01:35.887184-0500 HybridPool[1720:534623] items at ever cell entry: Njhhnn
2019-02-02 22:01:35.887311-0500 HybridPool[1720:534623] items at ever cell entry: Tv
2019-02-02 22:01:35.887449-0500 HybridPool[1720:534623] items at ever cell entry: 9th item
2019-02-02 22:01:35.891688-0500 HybridPool[1720:534623] left: 8
2019-02-02 22:01:36.660758-0500 HybridPool[1720:534623] right: 9
2019-02-02 22:01:36.931630-0500 HybridPool[1720:534623] Item added! pool

要弄清我在表格中看到的self.items中项目的名称，是这样的：

**Row 0:**
Table, Cord
**Row 1:**
Keys, Hshhdhdbd
**Row 2:**
Jhghhvhh, Book
**Row 3:**
9th item, (blank - because there are only 9 items - not an even 10) --> this row should be last!
**Row 4:**
Table, Cord <- this is the first row again, this should be what is in **Row 3** - 9th item, blank.

如果在这里我做错了什么，我也应该展示一下：

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    if([self.items count] % 2 != 0) {
        return ([self.items count] + 1) / 2;
    }
    else {
        return [self.items count] / 2;
    }
}

对于上述情况，由于我要将两个项目加载到该行中，因此当项目数为偶数时（仅将[self.items count]除以2即可解决这种情况。 self.items，我将1除以2之前添加了一行，以便最后一个项目有一行可用（然后该行中的一个点留为空白），这对我来说似乎是正确的，但也许我在这里错过了一些棘手的错误？

从控制台输出来看，我不知道为什么行被无序加载，或者为什么Row 0重复Row 4，请帮忙，谢谢！

更新

与此相同的结果：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(@"cellForRowAtIndexPath getting called - row: %li", indexPath.row);

    [self.leftItems enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"leftItem: %@", [obj valueForKey:@"item"]);
    }];

    [self.rightItems enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSLog(@"rightItem: %@", [obj valueForKey:@"item"]);
    }];

    //UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell1" forIndexPath:indexPath];
    //NSLog(@"indexPath.row: %li, %@", (long)indexPath.row, [self.items objectAtIndex:indexPath.row]);

    PoolsTableViewCell *cell = (PoolsTableViewCell*)[tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];

    if(cell.cellLeftImageView.image == nil) { //Equivalent to cell == nil
        NSObject* leftObj = [self.leftItems objectAtIndex:indexPath.row];
        NSObject* rightObj = [self.rightItems objectAtIndex:indexPath.row];

        cell.cellLeftViewLabel.text = [leftObj valueForKey:@"item"];

        NSString *ImageURL = [leftObj valueForKey:@"downloadURL"];
        NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:ImageURL]];
        cell.cellLeftImageView.image = [UIImage imageWithData:imageData];

        if(![rightObj isEqual:[NSNull null]]) {
            cell.cellRightViewLabel.text = [rightObj valueForKey:@"item"];

            NSString *secondImageURL = [rightObj valueForKey:@"downloadURL"];
            NSData *secondImageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:secondImageURL]];
            cell.cellRightImageView.image = [UIImage imageWithData:secondImageData];
        }
        else {
            cell.cellRightViewLabel.text = @"";
            cell.cellRightImageView.image = nil;
        }
    }

    return cell;
}

控制台输出： 

2019-02-03 11:32:50.583214-0500 HybridPool[1827:594545] cellForRowAtIndexPath getting called - row: 0
2019-02-03 11:32:50.583377-0500 HybridPool[1827:594545] leftItem: Table
2019-02-03 11:32:50.583486-0500 HybridPool[1827:594545] leftItem: Keys
2019-02-03 11:32:50.583605-0500 HybridPool[1827:594545] leftItem: Jhghhvhh
2019-02-03 11:32:50.583997-0500 HybridPool[1827:594545] leftItem: Njhhnn
2019-02-03 11:32:50.584116-0500 HybridPool[1827:594545] leftItem: 9th item
2019-02-03 11:32:50.584224-0500 HybridPool[1827:594545] rightItem: Cord
2019-02-03 11:32:50.584328-0500 HybridPool[1827:594545] rightItem: Hshhdhdbd
2019-02-03 11:32:50.584429-0500 HybridPool[1827:594545] rightItem: Book
2019-02-03 11:32:50.584528-0500 HybridPool[1827:594545] rightItem: Tv
2019-02-03 11:32:50.584771-0500 HybridPool[1827:594545] rightItem: <null>
2019-02-03 11:32:54.647304-0500 HybridPool[1827:594545] cellForRowAtIndexPath getting called - row: 1
2019-02-03 11:32:54.647551-0500 HybridPool[1827:594545] leftItem: Table
2019-02-03 11:32:54.647666-0500 HybridPool[1827:594545] leftItem: Keys
2019-02-03 11:32:54.647773-0500 HybridPool[1827:594545] leftItem: Jhghhvhh
2019-02-03 11:32:54.647876-0500 HybridPool[1827:594545] leftItem: Njhhnn
2019-02-03 11:32:54.647992-0500 HybridPool[1827:594545] leftItem: 9th item
2019-02-03 11:32:54.648102-0500 HybridPool[1827:594545] rightItem: Cord
2019-02-03 11:32:54.648199-0500 HybridPool[1827:594545] rightItem: Hshhdhdbd
2019-02-03 11:32:54.648403-0500 HybridPool[1827:594545] rightItem: Book
2019-02-03 11:32:54.648519-0500 HybridPool[1827:594545] rightItem: Tv
2019-02-03 11:32:54.648769-0500 HybridPool[1827:594545] rightItem: <null>
2019-02-03 11:32:56.447403-0500 HybridPool[1827:594545] cellForRowAtIndexPath getting called - row: 2
2019-02-03 11:32:56.447610-0500 HybridPool[1827:594545] leftItem: Table
2019-02-03 11:32:56.447724-0500 HybridPool[1827:594545] leftItem: Keys
2019-02-03 11:32:56.447829-0500 HybridPool[1827:594545] leftItem: Jhghhvhh
2019-02-03 11:32:56.447931-0500 HybridPool[1827:594545] leftItem: Njhhnn
2019-02-03 11:32:56.448151-0500 HybridPool[1827:594545] leftItem: 9th item
2019-02-03 11:32:56.448281-0500 HybridPool[1827:594545] rightItem: Cord
2019-02-03 11:32:56.448389-0500 HybridPool[1827:594545] rightItem: Hshhdhdbd
2019-02-03 11:32:56.448490-0500 HybridPool[1827:594545] rightItem: Book
2019-02-03 11:32:56.448589-0500 HybridPool[1827:594545] rightItem: Tv
2019-02-03 11:32:56.448689-0500 HybridPool[1827:594545] rightItem: <null>
2019-02-03 11:32:57.981261-0500 HybridPool[1827:594545] cellForRowAtIndexPath getting called - row: 3
2019-02-03 11:32:57.981471-0500 HybridPool[1827:594545] leftItem: Table
2019-02-03 11:32:57.981625-0500 HybridPool[1827:594545] leftItem: Keys
2019-02-03 11:32:57.981745-0500 HybridPool[1827:594545] leftItem: Jhghhvhh
2019-02-03 11:32:57.981874-0500 HybridPool[1827:594545] leftItem: Njhhnn
2019-02-03 11:32:57.982081-0500 HybridPool[1827:594545] leftItem: 9th item
2019-02-03 11:32:57.982214-0500 HybridPool[1827:594545] rightItem: Cord
2019-02-03 11:32:57.982315-0500 HybridPool[1827:594545] rightItem: Hshhdhdbd
2019-02-03 11:32:57.982441-0500 HybridPool[1827:594545] rightItem: Book
2019-02-03 11:32:57.982539-0500 HybridPool[1827:594545] rightItem: Tv
2019-02-03 11:32:57.982638-0500 HybridPool[1827:594545] rightItem: <null>
2019-02-03 11:33:00.735076-0500 HybridPool[1827:594545] cellForRowAtIndexPath getting called - row: 4
2019-02-03 11:33:00.735252-0500 HybridPool[1827:594545] leftItem: Table
2019-02-03 11:33:00.735337-0500 HybridPool[1827:594545] leftItem: Keys
2019-02-03 11:33:00.735410-0500 HybridPool[1827:594545] leftItem: Jhghhvhh
2019-02-03 11:33:00.735480-0500 HybridPool[1827:594545] leftItem: Njhhnn
2019-02-03 11:33:00.735547-0500 HybridPool[1827:594545] leftItem: 9th item
2019-02-03 11:33:00.735692-0500 HybridPool[1827:594545] rightItem: Cord
2019-02-03 11:33:00.735762-0500 HybridPool[1827:594545] rightItem: Hshhdhdbd
2019-02-03 11:33:00.735830-0500 HybridPool[1827:594545] rightItem: Book
2019-02-03 11:33:00.735896-0500 HybridPool[1827:594545] rightItem: Tv
2019-02-03 11:33:00.735965-0500 HybridPool[1827:594545] rightItem: <null>
2019-02-03 11:33:01.876340-0500 HybridPool[1827:594545] Item added! pool
2019-02-03 11:33:03.352399-0500 HybridPool[1827:594545] cellForRowAtIndexPath getting called - row: 3
2019-02-03 11:33:03.352967-0500 HybridPool[1827:594545] leftItem: Table
2019-02-03 11:33:03.353179-0500 HybridPool[1827:594545] leftItem: Keys
2019-02-03 11:33:03.353377-0500 HybridPool[1827:594545] leftItem: Jhghhvhh
2019-02-03 11:33:03.353569-0500 HybridPool[1827:594545] leftItem: Njhhnn
2019-02-03 11:33:03.353755-0500 HybridPool[1827:594545] leftItem: 9th item
2019-02-03 11:33:03.353897-0500 HybridPool[1827:594545] rightItem: Cord
2019-02-03 11:33:03.354230-0500 HybridPool[1827:594545] rightItem: Hshhdhdbd
2019-02-03 11:33:03.354612-0500 HybridPool[1827:594545] rightItem: Book
2019-02-03 11:33:03.354739-0500 HybridPool[1827:594545] rightItem: Tv
2019-02-03 11:33:03.354848-0500 HybridPool[1827:594545] rightItem: <null>
2019-02-03 11:33:03.477654-0500 HybridPool[1827:594545] cellForRowAtIndexPath getting called - row: 4
2019-02-03 11:33:03.477863-0500 HybridPool[1827:594545] leftItem: Table
2019-02-03 11:33:03.477974-0500 HybridPool[1827:594545] leftItem: Keys
2019-02-03 11:33:03.478078-0500 HybridPool[1827:594545] leftItem: Jhghhvhh
2019-02-03 11:33:03.478178-0500 HybridPool[1827:594545] leftItem: Njhhnn
2019-02-03 11:33:03.478276-0500 HybridPool[1827:594545] leftItem: 9th item
2019-02-03 11:33:03.478374-0500 HybridPool[1827:594545] rightItem: Cord
2019-02-03 11:33:03.478472-0500 HybridPool[1827:594545] rightItem: Hshhdhdbd
2019-02-03 11:33:03.478569-0500 HybridPool[1827:594545] rightItem: Book
2019-02-03 11:33:03.478665-0500 HybridPool[1827:594545] rightItem: Tv
2019-02-03 11:33:03.478763-0500 HybridPool[1827:594545] rightItem: <null>

2 个答案:

答案 0 :(得分：1)

表视图中的视图被重用，因此对视图执行的所有操作也必须撤消。我的规则是，任何涉及到可重用视图的代码都不能在没有if的情况下拥有else。话虽这么说：

if(cell.cellLeftImageView.image == nil) {

是一个错误。第一次将正确设置视图，但是第二次重用视图时将完全不会设置视图。

如果是这样

if(right < [self.items count]) {

也是一个错误。如果没有正确的项目，则不会将图片设置为nil，而是保留之前的任何图片。

如果还有一个数据源，其中奇数和偶数意味着完全不同的东西很难跟踪和理解。你为什么要那样做？您可以包含具有leftImageURL，rightImageURL，leftText，rightText的对象。编码的一部分是与其他程序员沟通，而不是与编译器沟通。选择一个易于理解的数据构造函数可以使代码达到您的期望。

接下来，您正在使用dataWithContentsOfURL，它在请求图像时阻塞了主线程。我认为这只是文本代码，绝不会以任何严肃的方式使用。

此外，您为什么要使用valueForKey？ items是什么类型？如果它们是字典，则可以使用item [@“ downloadURL”]；如果它们是某些自定义对象，则应该可以仅使用item.downloadURL。

答案 1 :(得分：0)

此代码为我提供了正确的配置-leftItems的左列和右列分别是rightItems和UITableView。如果给定行的右侧不存在任何项目，则将[NSNull null]作为该项目的对象传递（来自rightItems）：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(@"cellForRowAtIndexPath getting called - row: %li", (long)indexPath.row);

    PoolsTableViewCell *cell = (PoolsTableViewCell*)[tableView dequeueReusableCellWithIdentifier:@"Cell"];

    if (cell == nil) {
        NSLog(@"cell == nil");
        cell = [[PoolsTableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"Cell"];
        cell.selectionStyle = UITableViewCellSelectionStyleNone;
    }

    NSURL* leftURL = [NSURL URLWithString:[[self.leftItems objectAtIndex:indexPath.row] valueForKey:@"downloadURL"]];
    [cell.cellLeftImageView sd_setImageWithURL:leftURL];
    cell.cellLeftViewLabel.text = [[self.leftItems objectAtIndex:indexPath.row] valueForKey:@"item"];

    if(![[self.rightItems objectAtIndex:indexPath.row] isEqual:[NSNull null]]) {
        NSURL* rightURL = [NSURL URLWithString:[[self.rightItems objectAtIndex:indexPath.row] valueForKey:@"downloadURL"]];
        [cell.cellRightImageView sd_setImageWithURL:rightURL];
        cell.cellRightViewLabel.text = [[self.rightItems objectAtIndex:indexPath.row] valueForKey:@"item"];
    }
    else {
        cell.cellRightImageView.image = nil;
        cell.cellRightViewLabel.text = @"";
    }

    return cell;
}

...

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    return [self.leftItems count];
}
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