Swift中ScrollView无法实现无限重复滚动的问题求助

Hey there! Let's tackle why your ScrollView isn't repeating those images as expected. It’s super common to hit that blank spot at the end when setting up infinite scroll, so let’s break down the most likely issues and fixes step by step.

1. You’re not reusing/replenishing your image data source #

More often than not, infinite scroll fails because you only load one round of images and never add more when scrolling to the bottom. If you’re adding ImageViews directly to a LinearLayout inside your ScrollView, you need to listen for when you reach the end, then duplicate your original image views (or create new ones with the same resources) and add them to the container.

Example for Android: #

// Attach a scroll listener to your ScrollView
scrollView.getViewTreeObserver().addOnScrollChangedListener(() -> {
    View lastChild = scrollView.getChildAt(scrollView.getChildCount() - 1);
    // Calculate the difference between the bottom of the last child and ScrollView's visible area
    int scrollDiff = lastChild.getBottom() - (scrollView.getHeight() + scrollView.getScrollY());
    
    if (scrollDiff == 0) {
        // We've hit the bottom—add your images again!
        for (int imgRes : originalImageResources) {
            ImageView newImageView = new ImageView(getContext());
            newImageView.setImageResource(imgRes);
            // Don't forget layout params (match parent width, wrap content height, etc.)
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.WRAP_CONTENT
            );
            newImageView.setLayoutParams(params);
            yourLinearLayoutInsideScrollView.addView(newImageView);
        }
    }
});

2. Your "end of scroll" detection logic is wrong #

A lot of developers use flawed checks to detect the bottom (like comparing scrollY to the child view’s height minus the ScrollView’s height). This fails if your child views have margins, padding, or dynamic heights. The scrollDiff method above is more reliable because it directly measures the gap between the last child’s bottom and the ScrollView’s visible bottom.

3. You’re not using a view-recycling component (the better approach) #

ScrollView isn’t built for infinite scroll—it keeps every view you add in memory, which can cause performance issues. Instead, swap it out for a component with view recycling:

• Android: Use RecyclerView with a custom Adapter
• iOS: Use UICollectionView

For Android RecyclerView, here’s how to make it infinitely loop:

@Override
public int getItemCount() {
    // Return a huge number to simulate infinite scroll
    return Integer.MAX_VALUE;
}

@Override
public void onBindViewHolder(ImageViewHolder holder, int position) {
    // Use modulo to cycle through your original image list
    int realIndex = position % originalImageResources.size();
    holder.imageView.setImageResource(originalImageResources.get(realIndex));
}

This way, the RecyclerView reuses views that scroll off-screen instead of creating new ones—way more efficient!

4. Auto-scroll logic is interfering with content replenishment #

If you’re using smoothScrollBy() or similar to auto-scroll, make sure your auto-scroll logic keeps running after you add new images. For example, after adding the duplicate images, you can re-trigger the auto-scroll or ensure your scroll loop checks for new content continuously.

• Verify: Is your code actually triggering the "add duplicate images" logic when scrolling to the bottom? Add a log statement to confirm.
• Check: Are you using the correct layout parameters for your images? If images are zero-height, they won’t show up.
• Optimize: Ditch ScrollView for RecyclerView/UICollectionView if you can—it’s built for this use case.

内容的提问来源于stack exchange，提问作者Saeed Rahmatolahi