I am making an app with post feeds and implemented RecyclerViews
But my posts have highquality images consuming much memory when set on imageViews
So its kind of annoying to set the views everytime one scrolls to the post...
How can I not reuse the viewholders already designated?
First of all am I right that you want to avoid the RecyclerView from recycling inflated views? So if I am right I can tell you that this is the main purpose of the RecyclerView not to inflate new layouts. Instead the RecyclerView reuses already inflated layouts that are currently not used.
As you want to hold all your already inflated Views I recommend you to use a ListView instead of a RecyclerView. AFAIK all your inflated Views will stay.
BUT: There is one little problem. If you want to set many highquality images into your listview then you may be confronted with a memory out of bounds exception if your RAM usage overruns a specific limit (have a look here: memory out of bound exception using high quality images in Gallery).
Maybe the official developer homepage can help you with this topic: https://developer.android.com/training/displaying-bitmaps/cache-bitmap.html
Related
I use a flatList to make my activity feed.
However, I have a problem with the fluidity of my list
Each item can render up to 80 static images of 25kb, each in an absolute view, I still have to play with the performance when I mount my components but when I scroll, if I have my 80 images per item, my list is absolutely not fluid!
However, when I check my rendering number, I have very few because I use PureComponent for my items.
I check the RAM, and everything looks good!
My UI and JS Threads are constantly at 60!
Could this be due to the number of views I see in "Perf Monitor" that goes up to more than 3000? If it's that, how do I fix it?
Hoping to have a solution,
Thank you
Viktor
I've been facing the same issue , but after reading docs ive implemented the below :
You can use the community packages (such as react-native-fast-image
from #DylanVann) for more performant images. Every image in your list
is a new Image() instance. The faster it reaches the loaded hook, the
faster your Javascript thread will be free again.
You should always use react-native-fast-image for more images.
Hope it helps. Feel free for doubts
I had issue in my android version. I set resizeMethod="resize". This gave me massive performance boost.
I was loading lot of large images in section list and FlatList. Using resizeMethod as resize resolved my issue, and scroll is buttery smooth after this.
In relation to How to determine if a user has scrolled to the end of an NSTableView
Thanks Josh.
Is there a way to use this mechanism to implement a NSTableView that provides some sort of infinite scroll or pagination.
The idea is to tell NSTableView to load up to a certain number of records, say 1k records at once and than as user scrolls closer to the end pull another 1k records and maybe forget the first 1k records.
This pattern is well defined/used in web applications and java. Only the visible number of rows is loaded initially and the rest is pulled async as user scrolls up and down the table.
I am interested in some obj-c code or tips on how to code this.
I know about filtering/limiting the number of records that go into the tableview but lets ignore that for a moment.
Thanks.
Given the details you've provided, I'll generalize a bit but here's how I might solve it:
First, I'd set a MUCH SMALLER batch size than 1000 records. If the result count or "the most anybody is ever going to want to see" is indeterminate (and it sounds like it is in your case), the user probably doesn't even care past the first 100 or so. If your user often requests a large, expensive list and immediately wants to see stuff so far away from the beginning they hurl the scroller downward for two minutes straight before they stop and look around, perhaps a more intuitive sort order is needed instead of asking Google Image for 1000 more animated kitten gifs. ;-)
The controller behind the (definitely view-based for view reuse) table view will need some sort of request queue since I assume you're batching things in because they're expensive to retrieve individually. This will manage the asynchronous requesting/okay-now-it's-loaded machinery (I know that's vague but more detail is needed to get more specific). You'll make sure any "currently alive" views will somehow get this "it's ready" notification and will go from some "busy" UI state to displaying the ready item (since we NEVER want to keep the table waiting for a ready-to-display view for the object at a given row, so the view should at least show some "still waiting for details" indication so quick scrolls over lots of rows won't stall anything).
Using a view-based NSTableView and associated data source methods will let the table view handle only keeping enough copies of your custom NSTableCellView around to reuse during scrolling. Since you have to provide a configured view when asked, the view's default state can either be "draw nothing if not ready" or some visually generic placeholder until the object is realized and ready (then you can just reload that row instead of the whole table). This way the table keeps scrolling and drawing rapidly because it doesn't care about what your controller is doing to fulfill the promise of updating the visible rows (that custom cell view of yours will observe its represented object's updates).
You probably want the scrollers to reflect the total number of rows batched in so far if the upper bound is astronomical - reflecting that size would make the scroll grip both tiny and very sensitive. Instead, just grow the scroller (via the table view's row count) by what the user has "requested" so far, all the way back to the beginning of the list. Any time more are batched in, you'll want to add the batch size to your controller's total batched row count. This still lets the scroller zoom by rows the user couldn't distinguish at that speed anyway. You communicate the row count change to the table view by sending it -noteNumberOfRowsChanged and replying to its resulting data source request ( -numberOfRowsInTableView: ) with the updated total row count you stashed in a property of your controller. It'll ask for views for the newly visible rows as needed (which will be in some neutral, unfulfilled visual state until it's realized as before), update the scroll view, lather, rinse, repeat.
You could use NSCache to keep memory usage low. Set its countLimit to several times your batch size and let it drop previous batches if it decides it needs to dump the first n model objects, then batch them back in if the table view suddenly asks for a view for a row no longer in the batch window's range.
Without knowing more about your requirements and architecture, it's hard to get more specific. If I haven't hit the mark, consider editing your question to include more detail. If I'm totally off base from what you're asking for, please clarify. :-)
I know more about iOS, but I think the answer is similar. Table views are intrinsically finite, but you can roll your own custom scroll view to do this. The trick is to set a large content size and implement layout in your subclass (which will get called on every scroll change). In that method, check to see if the content offset is near zero or near the content size. If it is, then translate the content offset back to the center of the content size and translate all the subviews (keep them on one parent content view) by the same distance so the user doesn't see any motion. Make a datasource protocol and keep asking your datasource for "cells" that tile the visible part of the view.
It should be up to the datasource to recognize what we would have called a page-fault in the olden days, to decide that some of the model in memory should be discarded in favor of the model where the user is scrolling.
I poked around for an NS equivalent, but didn't see one on cursory search. Here's a decent-looking reference on the idea done in iOS.
I have already sort of asked this question already here (Previous Question) but it only got a handful of views and zero answers/comments so I thought I'd give it a go again with some more info that I've found.
I basically have a Windows Store DirectX + XAML app that I'm developing. I currently have the problem that the Rendering event of the SwapChainBackgroundPanel that I use for DirectX rendering (as per the Windows 8 example on MSDN) sometimes isn't called when the user is interacting with the app.
It will continue to update if I am doing something with the camera such as changing what it's looking at based on touch/mouse position but it won't be called if I am picking and I don't know why.
I use the standard GPU picking method (where I render the scene with a unique color for each object and then take a 1x1 texture of the press area to find the selected object) but when I am using this picking technique to select multiple objects (the user drags their finger/mouse over many objects) Rendering isn't being called. So in effect what happens is, lots of objects get selected but the user only sees this when they remove their finger/stop pressing the mouse button.
Is there any reason why this is happening? Is it because of the GPU picking method? And if so is there a way around it rather than using the ray-trace picking method (which considerably slows down picking for a large number of objects)?
Has anyone else had this problem? Is there an explanation from Microsoft anywhere that it is deliberate that rendering doesn't get called while this is happening?
Thanks for your time.
Are there known and proven ways to manage memory with scrolling components like tables or grids other than recycling cells as is used in Cocoa? The sequence of calculations and datasource/delegation calls needed to make this way of laying out views works but also makes coordinating complex animations with the cells and a scroll view error prone as you have to pay careful attention to the sequence of calls as it reloads data, scrolls to an offset and other mechanisms of the layout that affect the target frame of your animations. I am looking for a more declarative approach to providing content to the scroll view and having it figure out a smart way to manage it's memory as is done by a browser when you load the DOM with a long vertical layout of pictures.
I found it easier to create my own custom layout classes that only do layout on my views and not to impose an elaborate protocol such as NSTableViewDataSource and the like that makes animation difficult to program. I like to know exactly where my views are at all times, the complete hierarchy of each view and I don't like to keep a model in sync with my views so I store data on the views themselves. In my mind the objects on screen are the one and only objects I like to orchestrate as a programmer. I want direct declarative control over them kind of like a game programer. By subclassing a scroll view directly and following very simple layout rules outside of the normal layoutSubviews methods of Cocoa to avoid surprise layouts, I was able to control my animations better and do more complex and fluid animations. Hope this inspires someone to do the same.
I have a large data set (some 3500 objects) that returns from a remote server via HTTP. Currently the data is being presented in an NSCollectionView. One aspect of the data is a path pack to the server for a small image that represents the data (think thumbnail for simplicity).
Bindings works fantastically for the data that is already returned, and binding the image via a valueurl binding is easy to do. However, the user interface is very sluggish when scrolling through the data set - which makes me think that the NSCollectionView is retrieving all the image data instead of just the image data used to display the currently viewable images.
I was under the impression that Cocoa controls were smart enough to only retrieve data for the information that is actually being output to the user interface through lazy loading. This certainly seems to be the case with NSTableView - but I could be misguided on this thought.
Should valueurl binding act lazily and, moreover, should it act lazily in an NSCollectionView?
I could create a caching mechanism (in fact I already have such a thing in place for another application - see my post here if you are interested Populating NSImage with data from an asynchronous NSURLConnection) but I really don't want to go this route if I don't have to for this specific implementation as the user could potentially change data sets often and may only want small sub-sets of the data.
Any suggested approaches?
Thanks!
Update
After some more testing it seems that the problem arises because a scroll action through the data set causes each image to be requested from the server. Once all the images have been passed over in the data set the response is very fast.
So question... is there any way of turning off the valueurl fetch while scrolling and turning it back on when scrolling has finished?
My solution is to use a custom caching mechanism like the one I already use for another application. The problem manifests itself because as you scroll past images that have not yet been downloaded, the control triggers itself to go and fetch the as yet non-downloaded files.
Once downloaded the images are available locally and therefore scrolling speed normalizes. The solution is to check to see if the image is available locally and present an alternate app-bundle graphic while the image is being downloaded in the background. Once the image has been downloaded, update the model with the image replacing the stub image that came from the bundle.
This leaves the UI in a very responsive state throughout, leaves the user with the ability to interact and allows for a custom background management of the images.
Of course it would have been nice if Cocoa id all this for me, but then what would I be left to do? :-)