Android only download images that are visible in horizontalScrollView

Question

I have a HorizontalScrollView which contains a LinearLayout to hold all my view. I add about 20 RelativeLayout which contains a ImageView and TextView to the LinearLayout. I would like to only load images if the ImageView is on the screen (as I scroll to the ImageView).

I tried following this post to use getHitRect(), on the thumbnail, however, the Rect (bounds) for the thumbnail is always 0, 0-0, 0, resulting in my method to return false. What am I doing wrong?

thumbnailLayout is my LinearLayout inside the HorizontalScrollView
thumbnailScroll is my HorizontalScrollView

runOnUiThread(new Runnable() {

    @Override
    public void run() {
           Log.e(TAG, "running");
           for (int i = 0; i < thumbnailLayout.getChildCount(); i++) {
                RelativeLayout view = (RelativeLayout) thumbnailLayout.getChildAt(i);
                ImageView thumbnail = (ImageView) view.findViewById(R.id.thumbnail);
                if (thumbnailIsOnScreen(thumbnail)) {
                    Log.e(TAG, items.get(i).getTitle() + " has downloaded");
                    app.setImage(items.get(i).getThumbnailSmall(), thumbnail);
                }
           }


       }
   });

private boolean thumbnailIsOnScreen(ImageView thumbnail) {
        Rect bounds = new Rect();
        thumbnail.getHitRect(bounds);

        Rect scrollBounds = new Rect(thumbnailScroll.getScrollX(), thumbnailScroll.getScrollY(),
                thumbnailScroll.getScrollX() + thumbnailScroll.getWidth(), thumbnailScroll.getScrollY()
                        + thumbnailScroll.getHeight());
        return Rect.intersects(scrollBounds, bounds);
    }

Edit I'm tred using TreeObserver and found that my method to check if the thumbails are on screen is wrong. It still grabs all the images, and constantly loops (because I'm using onPreDrawListener?)

thumbnailLayout.getViewTreeObserver().addOnPreDrawListener(new OnPreDrawListener() {

            @Override
            public boolean onPreDraw() {
                Log.e(TAG, "running");

                for (int i = 0; i < thumbnailLayout.getChildCount(); i++) {
                    RelativeLayout view = (RelativeLayout) thumbnailLayout.getChildAt(i);
                    ImageView thumbnail = (ImageView) view.findViewById(R.id.thumbnail);
                    if (thumbnailIsOnScreen(thumbnail)) {
                        Log.e(TAG, items.get(i).getTitle() + " has downloaded");
                        app.setImage(items.get(i).getThumbnailSmall(), thumbnail);
                    }
                }
                return true;
            }
        });

Where are you calling that Runnable from? Is it in the scroll listener? — dmon, Apr 18 '13 at 20:09
Im running it after I add the ImageViews to the LinearLayout. I was thinking after the imageViews are added to the LinearLayout, some images would have to load. Then i would use the scroll listener — heero, Apr 18 '13 at 20:16
I don't want my items centered, which is why I am not using the gallery — heero, Apr 23 '13 at 00:50
And also Gallery is now deprecated since API 16 so you shouldn't use it. — Mario Lenci, Apr 24 '13 at 16:02

score 0 · Answer 1 · edited Jul 20 '22 at 17:13

0

You need a ListView but there isn't native HorizontallListView in android. You can try HorizontallListView by DevSmart. It's works like a native list view, with adapters and custom views if you want.

edited Jul 20 '22 at 17:13

General Grievance

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answered Apr 28 '13 at 19:28

Daniel Argüelles

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score 0 · Answer 2 · answered Apr 29 '13 at 09:33

Have you thought about using ViewPager? http://developer.android.com/reference/android/support/v4/view/ViewPager.html

If that doesn't fit your design you need to override the ScrollView -> function onScrollChanged and there check if your image in screen check the image (left?) position compared to the scroll position.

Android only download images that are visible in horizontalScrollView

2 Answers2