UICollectionView reloadData仅刷新第一项

Question

当我执行[self.collectionView reloadData]; ，只有我的第一项被重新加载。

即使- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section; 会被调用并存储例如两个项目，然后(UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath对于第一个项目仅被调用一次。

我已验证，在numberOfItemsInSection ，边框的大小足以存储至少三个项目。

numberOfItemsInSection:2 frame: {{0, 0}, {400, 150}} and bounds {{0, 0}, {400, 150}}

每个UICollectionViewCell为{0，0}，{400,45}，并按init方法中的指定垂直存储。

我已经阅读了UICollectionView和ios7的一些错误，但是前面介绍的解决方案均不适用于我的情况。 我已经尝试过reloadItemsAtIndexPaths和reloadSections但是那没有用，有时会给我例外。

我也厌倦了以编程方式添加项目，但没有成功：

[self.collectionView insertItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:   (self.currentPeripherals.count -1) inSection:0]]];

这是我的UICollectionViewController样子：

- (instancetype)init
{
    UICollectionViewFlowLayout *aFlowLayout = [[UICollectionViewFlowLayout alloc] init];
    [aFlowLayout setItemSize:CGSizeMake(400, 150)];
    [aFlowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
    self = [self initWithCollectionViewLayout:aFlowLayout];
    if (self) {
        self.view.frame=CGRectMake(0,0,400,150);
        self.view.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
        self.collectionView.backgroundView=[[UIView alloc] initWithFrame:CGRectZero];;
        self.view.layer.backgroundColor=[UIColor clearColor].CGColor;
        self.collectionView.backgroundColor=[UIColor clearColor];
        self.collectionView.delegate = self;
        self.collectionView.dataSource = self;
    }
    return self;
}

- (void)sharedInit {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleBTPOSHostDidUpdatePeripheralsNotification:) name:BTPOSHostDidUpdatePeripheralsNotification object:nil];
}

-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section
{
    return self.currentPeripherals.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    DeviceCell *deviceCell = [cv dequeueReusableCellWithReuseIdentifier:CellID forIndexPath:indexPath];

    if(!deviceCell.label)
    {
        [deviceCell prepareForReuse];
        PeripheralTracking *peripheral=self.currentPeripherals[indexPath.item];
        [deviceCell configureLabelWithPeripheralTracking:peripheral forItem:indexPath.item];
        [deviceCell.contentView addSubview:deviceCell.label];
    }

    return deviceCell;
}

- (void)handleBTPOSHostDidUpdatePeripheralsNotification:(NSNotification *)notification
{
    NSUInteger oldCount = self.currentPeripherals.count;

    NSDictionary *trackedPeripherals = notification.userInfo[BTPOSHostDidUpdatePeripheralsNotificationPeripheralsKey];
    [self sortPeripheralsDictionary:trackedPeripherals];
    [self.collectionView reloadData];
}

这是我的外围设备的排序方式：

-(void)sortPeripheralsDictionary:(NSDictionary*)peripheralsDictionary
{
    NSMutableArray *dictValues = [[peripheralsDictionary allValues] mutableCopy];

    if(dictValues.count>1)
    {
        [dictValues sortUsingComparator: (NSComparator)^(PeripheralTracking *a, PeripheralTracking *b)
         {
             NSNumber *RSSI1 = 0;
             NSNumber *RSSI2 = 0;
             NSComparisonResult result = 0;

             if(a.averageRSSI)
             {
                 PeripheralTrackingRSSI doubleRSSIa = a.averageRSSI;
                 RSSI1 = [NSNumber numberWithDouble:doubleRSSIa];
             }
             if(b.averageRSSI)
             {
                 PeripheralTrackingRSSI doubleRSSIb = b.averageRSSI;
                 RSSI2 = [NSNumber numberWithDouble:doubleRSSIb];
             }

             if(RSSI1 && RSSI2)
             {
                 result = [RSSI2 compare:RSSI1];
             }

             return result;
         }
         ];
    }

    self.currentPeripherals = dictValues;
}

Answer 1

您将每个单元格的高度设置为150：

[aFlowLayout setItemSize:CGSizeMake(400, 150)]

尝试将其更改为45：

[aFlowLayout setItemSize:CGSizeMake(400, 45)]

或者，如果您的单元格大小因单元而异，则可以实现collectionView:layout:sizeForItemAtIndexPath: 之所以只看到一次对collectionView:cellForItemAtIndexPath:调用，是因为您的集合视图只能显示一个单元格。 如果滚动它，则应该看到另一个。

Answer 2

尝试使用这个：

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath
 {
   KKMDeviceCell *deviceCell = [cv dequeueReusableCellWithReuseIdentifier:kCellID forIndexPath:indexPath];

    if(!deviceCell.label)
     {
       [deviceCell prepareForReuse];

        [deviceCell.contentView addSubview:deviceCell.label];
     }

        PeripheralTracking *peripheral=self.currentPeripherals[indexPath.item];
        [deviceCell configureLabelWithPeripheralTracking:peripheral forItem:indexPath.item];
   return deviceCell;
}