[objective-c] UITableView가 ReloadData를 완료 한 시점을 알리는 방법?

재로드는 다음 레이아웃 패스 중에 발생하며 일반적으로 제어를 실행 루프로 되돌릴 때 발생합니다 (예를 들어, 단추 동작 또는 모든 반환).

따라서 테이블 뷰를 다시로드 한 후 무언가를 실행하는 한 가지 방법은 테이블 뷰가 즉시 레이아웃을 수행하도록하는 것입니다.

[self.tableView reloadData];
[self.tableView layoutIfNeeded];
 NSIndexPath* indexPath = [NSIndexPath indexPathForRow: ([self.tableView numberOfRowsInSection:([self.tableView numberOfSections]-1)]-1) inSection: ([self.tableView numberOfSections]-1)];
[self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];

또 다른 방법은 후 레이아웃 코드가 다음을 사용하여 나중에 실행되도록 예약하는 것입니다 dispatch_async.

[self.tableView reloadData];

dispatch_async(dispatch_get_main_queue(), ^{
     NSIndexPath* indexPath = [NSIndexPath indexPathForRow: ([self.tableView numberOfRowsInSection:([self.tableView numberOfSections]-1)]-1) inSection:([self.tableView numberOfSections]-1)];

    [self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionBottom animated:YES];
});

최신 정보

추가 조사 후, 나는 테이블 뷰 보내는 것을 발견 tableView:numberOfSections:하고 tableView:numberOfRowsInSection:부터 반환하기 전에 데이터 소스에 reloadData. 대리자가을 구현 tableView:heightForRowAtIndexPath:하면 테이블 뷰는에서 반환하기 전에 (각 행에 대해)도 보냅니다 reloadData.

그러나 테이블보기는 tableView:cellForRowAtIndexPath:또는 tableView:headerViewForSection레이아웃 단계를 보내지 않습니다.이 단계는 제어를 실행 루프로 되돌릴 때 기본적으로 발생합니다.

또한 작은 테스트 프로그램에서 질문의 코드가 (보기 또는 보내기와 같은) 특별한 작업을 수행 하지 않고 테이블보기의 맨 아래로 올바르게 스크롤됩니다 .layoutIfNeededdispatch_async

답변

extension UITableView {
    func reloadData(completion:@escaping ()->()) {
        UIView.animateWithDuration(0, animations: { self.reloadData() })
            { _ in completion() }
    }
}

...somewhere later...

tableView.reloadData {
    println("done")
}

[UIView animateWithDuration:0 animations:^{
    [myTableView reloadData];
} completion:^(BOOL finished) {
    //Do something after that...
}];

CATransaction.begin()
CATransaction.setCompletionBlock({
    print("reload completed")
    //Your completion code here
})
print("reloading")
tableView.reloadData()
CATransaction.commit()

#import <UIKit/UIKit.h>

@interface CustomCollectionView: UICollectionView

- (void)reloadDataWithCompletion:(void (^)(void))completionBlock;

@end

#import "CustomCollectionView.h"

@interface CustomCollectionView ()

@property (nonatomic, copy) void (^reloadDataCompletionBlock)(void);

@end

@implementation CustomCollectionView

- (void)reloadDataWithCompletion:(void (^)(void))completionBlock
{
    self.reloadDataCompletionBlock = completionBlock;
    [self reloadData];
}

- (void)layoutSubviews
{
    [super layoutSubviews];

    if (self.reloadDataCompletionBlock) {
        self.reloadDataCompletionBlock();
        self.reloadDataCompletionBlock = nil;
    }
}

@end

[self.collectionView reloadDataWithCompletion:^{
    // reloadData is guaranteed to have completed
}];

final class UITableViewWithReloadCompletion: UITableView {
  private var reloadDataCompletionBlock: (() -> Void)?

  override func layoutSubviews() {
    super.layoutSubviews()

    reloadDataCompletionBlock?()
    reloadDataCompletionBlock = nil
  }


  func reloadDataWithCompletion(completion: @escaping () -> Void) {
    reloadDataCompletionBlock = completion
    self.reloadData()
  }
}

class UITableViewWithReloadCompletion: UITableView {

  var reloadDataCompletionBlock: (() -> Void)?

  override func layoutSubviews() {
    super.layoutSubviews()

    self.reloadDataCompletionBlock?()
    self.reloadDataCompletionBlock = nil
  }

  func reloadDataWithCompletion(completion:() -> Void) {
      reloadDataCompletionBlock = completion
      self.reloadData()
  }
}

tableView.reloadDataWithCompletion() {
 // reloadData is guaranteed to have completed
}

extension UICollectionView
{
    /// Calls reloadsData() on self, and ensures that the given closure is
    /// called after reloadData() has been completed.
    ///
    /// Discussion: reloadData() appears to be asynchronous. i.e. the
    /// reloading actually happens during the next layout pass. So, doing
    /// things like scrolling the collectionView immediately after a
    /// call to reloadData() can cause trouble.
    ///
    /// This method uses CATransaction to schedule the closure.

    func reloadDataThenPerform(_ closure: @escaping (() -> Void))
    {
        CATransaction.begin()
            CATransaction.setCompletionBlock(closure)
            self.reloadData()
        CATransaction.commit()
    }
}

myCollectionView.reloadDataThenPerform {
    myCollectionView.scrollToItem(at: indexPath,
            at: .centeredVertically,
            animated: true)
}

// change the data source

NSLog(@"Before reload / sections = %d, last row = %d",
      [self.tableView numberOfSections],
      [self.tableView numberOfRowsInSection:[self.tableView numberOfSections]-1]);

[self.tableView reloadData];

NSLog(@"After reload / sections = %d, last row = %d",
      [self.tableView numberOfSections],
      [self.tableView numberOfRowsInSection:[self.tableView numberOfSections]-1]);

[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:[self.tableView numberOfRowsInSection:[self.tableView numberOfSections]-1]-1
                                                          inSection:[self.tableView numberOfSections] - 1]
                      atScrollPosition:UITableViewScrollPositionBottom
                              animated:YES];