以编程方式滚动集合视图

Question

我有一个水平收藏视图。 我想要的是添加一个按钮，并在按下时自动滚动到下一个单元格。如何做到这一点？

我尝试了这种方法，但它不起作用：

- (IBAction)scrollCollection:(id)sender {

    NSIndexPath *newIndexPath = [NSIndexPath indexPathForRow:0 inSection:0];

    NSArray *indexPaths = [self.notesCollection indexPathsForSelectedItems];
    if ( indexPaths.count > 0 )
    {
        NSIndexPath *oldIndexPath = indexPaths[0];
        NSInteger oldRow = oldIndexPath.row;
        newIndexPath = [NSIndexPath indexPathForRow:oldRow + 1 inSection:oldIndexPath.section];
    }
}

还有这个：

- (IBAction)scrollCollection:(id)sender {

    UICollectionViewFlowLayout *layout = (UICollectionViewFlowLayout *)[self.notesCollection collectionViewLayout];
    [self.notesCollection setPagingEnabled:YES];
    layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
     self.notesCollection.contentOffset = self.scrollingPoint;
    // Here you have to respond to user interactions or else the scrolling will not stop until it reaches the endPoint.
    if (CGPointEqualToPoint(self.scrollingPoint, self.endPoint)) {
        [self.scrollingTimer invalidate];
    }
    // Going one pixel to the right.
    self.scrollingPoint = CGPointMake(self.scrollingPoint.x, self.scrollingPoint.y+1);
}

Answer 1

你可以试试这个

@property (nonatomic, assign) CGPoint scrollingPoint, endPoint;
@property (nonatomic, strong) NSTimer *scrollingTimer;
@synthesize scrollingPoint, endPoint;
@synthesize scrollingTimer;

- (void)scrollSlowly {
    // Set the point where the scrolling stops.
    self.endPoint = CGPointMake(0, 300);
    // Assuming that you are starting at {0, 0} and scrolling along the x-axis.
    self.scrollingPoint = CGPointMake(0, 0);
    // Change the timer interval for speed regulation. 
    self.scrollingTimer = [NSTimer scheduledTimerWithTimeInterval:0.015 target:self selector:@selector(scrollSlowlyToPoint) userInfo:nil repeats:YES];
}

- (void)scrollSlowlyToPoint {
    self.collectionView.contentOffset = self.scrollingPoint;
    // Here you have to respond to user interactions or else the scrolling will not stop until it reaches the endPoint.
    if (CGPointEqualToPoint(self.scrollingPoint, self.endPoint)) {
        [self.scrollingTimer invalidate];
    }
    // Going one pixel to the right.
    self.scrollingPoint = CGPointMake(self.scrollingPoint.x, self.scrollingPoint.y+1);
}

或者你也可以使用这个代码。

NSInteger section = [self numberOfSectionsInCollectionView:collectionView] - 1;
NSInteger item = [self collectionView:collectionView numberOfItemsInSection:section] - 1;
NSIndexPath *lastIndexPath = [NSIndexPath indexPathForItem:item inSection:section];
[collectionView scrollToItemAtIndexPath:lastIndexPath atScrollPosition:UICollectionViewScrollPositionBottom animated:YES];