Question

我试图在UICollectionView中预先选择第一个对象/ UICollectionViewCell？我试过了：

self.dateCollectionView.allowsMultipleSelection=NO;

[self.dateCollectionView selectItemAtIndexPath:0 animated:YES scrollPosition:UICollectionViewScrollPositionLeft];
[self collectionView:self.dateCollectionView didSelectItemAtIndexPath:0];
[self.dateCollectionView reloadData];

viewDidLoad中的

。

以下是我的UICollectionView方法;

 -(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{

  return self.titles.count;
 }

 -(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

    UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
    cell.backgroundColor= [UIColor clearColor];
    UILabel * dateLabel = (UILabel *)[cell viewWithTag:1];
    UILabel * subText = (UILabel *)[cell viewWithTag:2];
    subText.text=self.titles[indexPath.row];
    subText.adjustsFontSizeToFitWidth=YES;
    if (cell.selected) {
        cell.backgroundColor = [UIColor blueColor]; // highlight selection
    }
    else
    {
        cell.backgroundColor = [UIColor redColor]; // Default color
    }
    return cell;
}

-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath  {

    UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
    datasetCell.backgroundColor = [UIColor blueColor]; // highlight selection
}

-(void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath {

 UICollectionViewCell *datasetCell =[collectionView cellForItemAtIndexPath:indexPath];
datasetCell.backgroundColor = [UIColor redColor]; // Default color
}

- (BOOL)collectionView:(UICollectionView *)collectionView
 shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

- (BOOL)collectionView:(UICollectionView *)collectionView
 shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath;
{
    return YES;
}

Answer 1

在viewDidAppear：

NSIndexPath *indexPathForFirstRow = [NSIndexPath indexPathForRow:0 inSection:0];
[self.dateCollectionView selectItemAtIndexPath:indexPathForFirstRow animated:NO scrollPosition:UICollectionViewScrollPositionNone];
[self collectionView:self.dateCollectionView didSelectItemAtIndexPath:indexPathForFirstRow];

Answer 2

对于 Swift 3.0.1 您可以尝试：

self.collectionView.selectItem(at: indexPath, animated: true, scrollPosition: [])

或

self.collectionView.selectItem(at: indexPath, animated: true, scrollPosition: UICollectionViewScrollPosition(rawValue: 0))

对于Objective-C你可以试试这个：

self.collectionView selectItemAtIndexPath:indexPath animated:YES scrollPosition:UICollectionViewScrollPositionNone];

注意：您应该在 viewDidAppear

中使用它

Answer 3

对于swift 3

在此重载collectionView.selectItem

中使用collectionView(UICollectionView, IndexPath)

这是我的代码，在此代码中，我选择了indexPath.row = 0

行

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = ScenarioCollectionView.dequeueReusableCell(withReuseIdentifier: "ReuseScenarioCollectionViewCell", for: indexPath as IndexPath) as! ScenarioCollectionViewCell

    if (indexPath.row == 0){
        collectionView.selectItem(at: indexPath, animated: true, scrollPosition: UICollectionViewScrollPosition.centeredHorizontally)
        cell.layer.borderColor=UIColor.gray.cgColor        
    }else{
        cell.layer.borderColor=UIColor.white.cgColor
    }
    return cell
}


func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath)
    cell?.layer.borderColor = UIColor.gray.cgColor
        }

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    let cell = collectionView.cellForItem(at: indexPath as IndexPath)
    cell?.layer.borderColor = UIColor.white.cgColor
    collectionView.deselectItem(at: indexPath, animated: true)
}

Answer 4

我通过继承UICollectionView并在layoutSubviews中选择所需项目来解决这个问题：

class InitialSelectionCollectionView: UICollectionView {

   var initialSetupPerformed: Bool = false
   var initialSelectedIndexPath: IndexPath!

   override func layoutSubviews() {
       super.layoutSubviews()

       if !initialSetupPerformed && initialSelectedIndex != nil{
           selectItem(at: initialSelectedIndexPath, animated: false, scrollPosition: .centeredHorizontally)

           initialSetupPerformed = true
       }
   }
}

然后，当您初始化自定义集合视图时，只需将IndexPath设置为initialSelectedIndexPath

Answer 5

对我来说，将它放入viewDidAppear:会导致选择一秒，因此用户将看到两种状态（即未选择和选择）。为了避免这种情况，我把它放在viewWillAppear:而不是像魅力一样工作

override func viewWillAppear(_ animated: Bool) {
    let selectedIndexPath = IndexPath(item: 0, section: 0)
    collectionView.selectItem(at: selectedIndexPath, animated: false, scrollPosition: .left)
}

Answer 6

对于Swift 3：

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    //auto selected 1st item
    let indexPathForFirstRow = IndexPath(row: 0, section: 0)
    self.collectionView?.selectItem(at: indexPathForFirstRow, animated: true, scrollPosition: .top)
}

Answer 7

最初用于选择单元格的快捷代码

func selectinitialCell() {

    let cell = venueTypeCollectionView.cellForItemAtIndexPath(NSIndexPath(forItem: 0, inSection: 0)) as! SearchTypeCollectionViewCell
    self.indexPathOfSelectedItem = NSIndexPath(forItem: 0, inSection: 0)
    cell.venueType.textColor = UIColor.whiteColor()
    cell.selected = true
}

但是这不会调用委托函数，例如didSelectItemAtIndexPath，didDeselectItemAtIndexPath。

Answer 8

    [self.collectionView reloadData];
    [self.collectionView layoutIfNeeded]; //important
    NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
    [self.collectionView selectItemAtIndexPath:indexPath animated:NO scrollPosition:UICollectionViewScrollPositionNone];
    [self collectionView:self.collectionView didSelectItemAtIndexPath:indexPath];

Answer 9

this for passing function in props to component

就我而言。我通过用- - - - - - - - - - BEGIN REQUEST - - - - - - - - - - PUT https://nyc3.digitaloceanspaces.com/cmtz/UploadedFiles/Mixtapes/test-upload-mixtape-20/cover.jpg HTTP/1.1 Host: nyc3.digitaloceanspaces.com:443 image/jpeg: System.Byte[] x-amz-acl: public-read Content-Type: image/jpeg Content-MD5: **************** x-amz-content-sha256: UNSIGNED-PAYLOAD x-amz-date: 20191104T030850Z Authorization: AWS4-HMAC-SHA256 Credential=*****************/20191104/us-east-1/s3/aws4_request, SignedHeaders=content-md5;host;x-amz-acl;x-amz-content-sha256;x-amz-date, Signature=fa6945a220238a7f877fb62d898d5596d9199860455499cec6bedccfb9cae0ed - - - - - - - - - - END REQUEST - - - - - - - - - - - - - - - - - - - - BEGIN RESPONSE - - - - - - - - - - HTTP/1.1 403 Forbidden x-amz-request-id: tx00000000000000ae68c6c-005dbf9642-334525e-nyc3a Accept-Ranges: bytes Date: Mon, 04 Nov 2019 03:08:50 GMT Strict-Transport-Security: max-age=15552000; includeSubDomains; preload Content-Length: 192 Content-Type: application/xml <?xml version="1.0" encoding="UTF-8"?><Error><Code>SignatureDoesNotMatch</Code><RequestId>tx00000000000000ae68c6c-005dbf9642-334525e-nyc3a</RequestId><HostId>334525e-nyc3a-nyc</HostId></Error> - - - - - - - - - - END RESPONSE - - - - - - - - - -的{{1}}类子类解决了这个问题

        public async void uploadS3File(String filePath, String key, string type)
        {
            Console.WriteLine($"Uploading Object: {filePath}");
            try
            {
                Dictionary<string, string> map = new Dictionary<string, string>();
                map.Add("x-amz-acl", "public-read");
                var minio = new MinioClient(Configuration.S3_HOST_ENDPOINT,
                    Configuration.S3_ACCESS_KEY, Configuration.S3_SECRET_KEY).WithSSL();
                minio.SetTraceOn();

                await minio.PutObjectAsync(Configuration.Bucket,
                                         key, filePath, contentType: type, metaData: map);
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Minio Exception: {ex}");

            }
        }

然后在ViewController中使用它

UICollectionView

在第一次加载视图时预选择/突出显示UICollectionViewCell

9 个答案: