UICollectionView：以编程方式查看标题视图 [英] UICollectionView: header view programmatically

问题描述

这是我处理标题的方式。

This is the way i am working on header.

  //    viewDidLoad

  [self.collectionView registerClass:[UICollectionViewCell class]forCellWithReuseIdentifier:@"Cell"];

[self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];

UICollectionViewFlowLayout *layout= [[UICollectionViewFlowLayout alloc]init];

self.collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, 390, 300) collectionViewLayout:layout];
layout.collectionView.backgroundColor = [UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0];
[self.collectionView registerClass:[UICollectionViewCell class]
        forCellWithReuseIdentifier:@"Cell"];
self.collectionView.delegate=self;
self.collectionView.dataSource=self;
layout.minimumInteritemSpacing = 15;

[layout setScrollDirection:UICollectionViewScrollDirectionVertical];

self.collectionView.collectionViewLayout = layout;
self.collectionView.showsHorizontalScrollIndicator = NO;
self.collectionView.showsVerticalScrollIndicator = NO;
[self.collectionView setBounces:YES];
self.collectionView.allowsMultipleSelection = YES;
[self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"HorizontalPickerCell"];
[self.view addSubview:self.collectionView];

   - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
  {
  if (section == 0) {
    return CGSizeMake(0, kHeaderHeight);
  }
  return CGSizeMake(0, kHeaderHeight + kInterSectionMargin);
  }

  - (NSInteger)numberOfSectionsInCollectionView: (UICollectionView *)collectionView
  {
NSLog(@"levels count:%d", [arrLevels count]);
return [arrLevels count];
  }

  - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
 {
 NSLog(@"vals count:%d", [arrSeats count]);
 for(int i=0; i<[arrLevels count]; i++)
 {
    if(section == i)
    {
        int c;
        NSString *cnt = [NSString stringWithFormat:@"%@",[arrTot objectAtIndex:i]];
        c = [cnt intValue];
        return c;
    }
 }
 return 1;
 }

 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [self.collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];

//cell.selectedBackgroundView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"blue_s.png"]];

if (cell.selected) {
    [UIColor colorWithPatternImage:[UIImage imageNamed:@"blue_s.png"]]; // highlight selection
 }
else
 {
    cell.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"yellow_seat.png"]]; // Default color
 }

return cell;
 }

 - (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
return UIEdgeInsetsMake(10, 12, 10, 10);
 }

 - (CGSize)collectionView:(UICollectionView *)collectionView layout:  (UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
CGSize retval =  CGSizeMake(22, 20);
return retval;
}

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
UICollectionReusableView *reusableview = nil;

if (kind == UICollectionElementKindSectionHeader) {
    UICollectionReusableView *headerView = [self.collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:nil forIndexPath:indexPath];

        self.lblHeader = [[UILabel alloc]initWithFrame:CGRectMake(120, 10, 100, 30)];
        self.lblHeader.backgroundColor = [UIColor whiteColor];
        self.lblHeader.textColor = [UIColor redColor];
        self.lblHeader.text = @"Level 1";
        [self.collectionView addSubview:self.lblHeader];
}
return reusableview;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
printf("Selected View index=%d",indexPath.row);

itemPaths  = [self.collectionView indexPathsForSelectedItems];

UICollectionViewCell* cell=[self.collectionView cellForItemAtIndexPath:indexPath];
cell.contentView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"blue_s.png"]];
 }

 - (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath
 {
UICollectionViewCell* cell=[self.collectionView cellForItemAtIndexPath:indexPath];
cell.contentView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"yellow_seat.png"]];
 }

推荐答案

您看到的错误非常清楚。您正在尝试将可重用视图出列，但集合视图对您传递的重用标识符一无所知。

The error you're seeing is pretty clear. You're trying to dequeue a reusable view but the collection view doesn't know anything about the reuse identifier you're passing.

你需要在 dequeueReusableSupplementaryViewOfKind：withReuseIdentifier：forIndexPath之前调用 registerClass：forSupplementaryViewOfKind：withReuseIdentifier： ：被调用。我通常调用 viewDidLoad 中的一个注册方法，所以所有的设置都完成了，我可以调用dequeue方法。如果您从nib加载自定义页眉和页脚视图，则可以使用 registerNib：forSupplementaryViewOfKind：withReuseIdentifier：方法。

You need to call registerClass:forSupplementaryViewOfKind:withReuseIdentifier: before dequeueReusableSupplementaryViewOfKind:withReuseIdentifier:forIndexPath: is called. I typically call one of the register methods in viewDidLoad so all the setup is done and I can just call the dequeue method. If you're loading your custom header and footer views from nib you can use the registerNib:forSupplementaryViewOfKind:withReuseIdentifier: method.

我看到你更新了代码。你需要移动这些行

I see you updated the code. You need to move these lines

UICollectionViewFlowLayout *layout= [[UICollectionViewFlowLayout alloc]init];

self.collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, 390, 300) collectionViewLayout:layout];

在您调用寄存器类方法的行之上。在分配和初始化对象之前，无法向对象发送消息。

above the lines where you're calling the register class methods. You cannot send messages to an object before you allocate and initialize it.

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