I need to make an image gallery that takes a JSON list of remote images and pre-loads them and disposes them on the fly as i scroll left or right. I cannt seem to find any examples of this other than a list of images being loaded on the fly. What I want to do is to load the next ones (left and right) while the previous one is on the screen, dumping the others as I go.
I see widget.gallery but is this suitable for this or should I use a Canvas and write my own?
Look at here. There is a ListView with lazy loading, this should show you the solution.
Lazy load of images in ListView
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I'm trying to replicate the functionality of Facebook's image upload. To briefly describe it you click the Photo button from the main screen of the app you are taken to an image picker that will let you select up to 30 images. Once selected the images load in some kind of list view that allows you to add a caption, remove the image from the list, or do some other Facebook-y things. If you scroll around the list can move very quickly, and if you only have 5-10 images you generally spend little to no time waiting for items to reload.
Right now I have a recycler view and am using Picasso to load the images from disk, resize them, and then display them. This works, but it's not smooth or fast. Even if I only have five or six images loaded they don't come up instantly if I scroll from the bottom back to the top. I have tried increasing the LRU Cache size in Picasso, but that didn't do anything at all. It seems like the scaled image isn't getting cached so it has to be scaled to fit the screen width every time. That's just my guess though.
Any suggestions on how to get this to run more smoothly?
I'm using Picasso Square library in my android application. The app is a very simple one and shows a grid of pictures. When you touch one it opens it in full screen and when swiping to the right the next in line should be displayed.
My problem is that for every swipe, the image is loaded by picasso method:
Picasso.with(getApplicationContext()).load(Properties.IMAGE_URL + i).transform(transformation).centerCrop().fit().into(imageView);
I would like to avoid the load wait time and simply cache the next 2 images to be displayed. how would I go about doing this?
I know that picasso caches the images if they were loaded before. Is there a way to load the next image with picasso without attaching it to a specific ui element to be displayed?
There is a way to do it – use fetch(). You can get more information from this question.
I am bulding up a grid of images for an app I'm building. It works like so:
Build up a list of Image IDs, which I must query using a different content provider each (these are images from MMS threads)
Create new activity, which hosts an ImageGridFragment. This fragment has a custom adapter that takes the grid of images, and loads each one as a bitmap asynchronously.
After images are loaded, they are cached in an LRU cache so I don't need to run unnecessary computation
So far, everything works quite well. However, I would like to pre-buffer images so that when the user scrolls down, s/he doesn't have to wait for images to load. They should already be loaded. The stock Android Gallery accomplishes. I've had a look at the source, but think there must be a more straightforward way.
To answer members' questions
Images are loaded one by one using the content://mms/part/xxx, where xxx is the ID of an image. These are MMS images, and to my knowledge, cannot be loaded as a batch process (though, maybe I'm wrong). I use a content provider in an AsyncTask to load each image
I've tried the following:
Pre buffer 30 images or so right when the fragment is created. This is not ideal because the massive I/O request, actually prevents the on-screen images from loading quickly (but the buffering does work well!)
Detect when the requested view to load is at the very bottom-right hand corner of the screen, which could work, but then would fail in the case that the GridView takes up only part of the screen. It also seems like there should be a cleaner way to do this
Thought about, but did not try, an OnScrollListener, but this will not pre-buffer images until I start scrolling, which is not ideal
So, my questions are:
Is there a good way to detect when the last GridView item is requested to load? I found that the GridView.getlastvisibleposition() method is not useful here, because it is actually returning the last element for which Adapter.getView() has been called for. If I can do this accurately, I can launch the buffer request at that time
Is there a better way to do this?
you can do right this
if(GridView.getlastvisibleposition() = mAdapter.count()-1)
how you load the images?
is it from URL or from sdcard?
are you using a image loader library?
I need to display a list of items each with text and various number of images.
I'm currently using a ListView with custom adapter to show these items. And for each item, I used a HorizontalScrollView with a LinearLayout in it to display the images. In the getView method of the ListView, I read the image URIs of each item and dynamically create ImageViews, then load the images asynchronously. I used a ViewHolder to hold the LinearLayout which contains all the ImageViews of each item.
The problem is, if I scroll down the ListView and scroll back, I'll lost the content of the item, which means I have to load the images again. And most of the images are too large and loads very slow. Actually on my app the screen can show only about 2 or 3 items once, so the scroll happens very frequently.
I have some ideas to improve this, but I'm not sure whether one of them will results better.
Since I'm just showing a thumbnail of each image, maybe I can save the thumbnails into a temp dir and load them dynamically, loading small images will be much faster. And I might have to clear that temp dir when it gets large.
I have at most 9 images for each item, so it might still be slow even if I cache the thumbnails and scroll frequently. And maybe I have to show the list manually instead of using ListView, so each item will not be reused, and the load will happen only once. But, the list will grow large in the future, if I preserve like 100 items in the LinearLayout my app may still crash.
Other better options...
Any advice will be helpful! Thanks!
You can use LazyLoading to display your image. You can use Universal Image Loader for this purpose. What lazyloading does is download an image once, cache it and display the image from cache during subsequent requests.
I currently have a gridview that displays some thumbnail images. The problem I am running into is that when I scroll through the images I can see the images switch from old to new as they are being replaced. So, I was wondering how I would fix this. Is there a way to load images that aren't on the screen so when I scroll the user doesn't have to see the change in images?
The best way to avoid that effect is to set the image first to null in the getView() method of your adapter. You can then check an LRU cache if the image is already loaded. If yes, then set it right away, if not then load it asynchronous as a bitmap. Set it to the view and add it to the LRU cache.