I was researching this since last year from time to time. I always wonder how Instagram handles the feeds screen?
What kind a component they using for it?
I'm sure it's not a ScrollView becouse it's much more performant than a ScrollView.
It is not also a FlatList becouse I know the basics of the FlatList how it renders the rows etc... and I am sure that they don't use it. For example a FlatList renders the items on top of each other like a card stack. In this behavior you cannot achieve the current Pinch Zoom feature that they have.
I thought maybe they use flipkart's RecyclerListView which is based on Java and much more performant than ScrollView and FlatList, but I am not quite sure about that too.
Any ideas about what they using to achieve current functionality on the feeds screen?
I mean, is there a method or specific listing component to achieve same behavior with all the functions like Double Tap to Like, like Pinch Zoom with overlaying everything.
#Quick note about pinch zooming, it's nearly impossible to build a component with current states of ScrollView and FlatList which will be performant and has same functionality.
You can check out my other topic about that here
Long story short, I have tried a lot of methods and 3rd party components to achieve same thing, but still could not do it.
Thanks for your thoughts!
Related
In my application I want to create a couple animations on my FlatList.
For example, after fetching the data and feeding it to the list I want the items that should be visible to slide from the left. When I'm scrolling each item (at the top) that supposed to disappear will slide out to the right and each item that should appear (at the bottom) should slide from the left. Is it possible in React Native?
I only managed to create one type of animation - items sliding right when they are about to disappear, but I don't have any idea how to make the items to appear from the left.
My Animated.View can receive only one type of transform. So how can create different types of input/output ranges for the top and the bottom of the list?
I tried to find some examples on the internet but couldn't find any for multiple animations, only for one type.
I think you will find React Native Reanimated's Entering and Exiting Animations API
useful for this task. It greatly simplifies animations like this in my experience.
In case you want to get more control. Using a FlatList, you can also use its onScroll prop to get the current value for YOffset (contentOffset.y) via the Reanimated useAnimatedScrollHandler. Thus you can figure out how much has been scrolled.
Which you could then use to manually apply any translateX's required to the Animated.View of whatever items the flatlist is rendering. The logic you'll of course have to figure out though. But it's a start.
Be sure to do any animation interpolates using UI thread worklets on Reanimated only. Good luck!
I am trying to use pull to refresh from FlatList. Is it possible to move the spinner to where the data actually starts rendering instead of the top of the screen? I found the progressViewOffset that works on Android but I am trying to find how I can implement this behaviour on iOS too. I feel like my solution is to watch scroll interactions and go on from there.
Any idea is appreciated. Thanks in advance.
I want to display several components (maybe up to 6) in my React Native app that continuously change their position, i.e. slowly but fluently float on the screen and change their moving direction randomly or based on an angle at which they approach the edge of their parent, if they do. What I don't know is how to change their position dynamically in a performance friendly way. Because I also want to let the user interact with them by tapping on them, it cannot be a video in a background or something similar.
If I were dealing with a standard React app running in a browser, I think I would simply manipulate the element's style attributes top and left. Since I want to implement this in React Native, I think there must be a solution that is way more performant and elegant, involving manipulation of the native elements that back the React Native views or using some animation mechanism, because re-rendering a view with like 6 components at least 30 times per second doesn't seem like an appropriate solution and an overhead in general.
Googling things like "react native dynamically move element" or "react native dynamically change element position" did not bring any obviously appropriate results. I came across a native element method setNativeProps, though, but couldn't find any information on what props I could set to change the element's position on the screen and how performant that would be. I also looked into React Native's Animated API, but could not quite relate my problem to the solutions that this API offers from a first glance.
Does anyone know a mechanism or maybe a library that would be appropriate to use in the situation that I described?
I would like to create a carousel that scrolls automatically until the user scrolls / touches the ScrollView itself.
The auto-scrolling itself works fine with using scrollView.scrollTo but how could I detect if the user is interacting with the ScrollView? I took a look at the onScroll event but this does not seem to distinct between a user generated event and an event that was generated by calling scrollTo.
Also I'd like to know if it is possible to get the current scroll position from the ScrollView directly instead of reading it everytime from the onScroll event.
I'm very thankful for any tips and suggestions.
By digging into ScrollView's source code you can notice a few undocumented callbacks that will help you achieve what you're after, namely onTouchStart and onTouchEnd. These two callbacks are triggered only when user interacts with the ScrollView and not when you scroll programmatically.
You will probably want to clear your auto-scroll interval on onTouchStart and restart it after a delay on onTouchEnd.
Regarding your next question, the answer is no. As far as I know, no getter is currently exposed to retrieve the current scroll position. Therefore, you need to rely on the event passed to onScroll, retrieve event.nativeEvent.contentOffset['x' or 'y'], and store it in your component's state.
Note that if you're doing some heavy animations that need to follow scroll position closely (e.g. animated header or parallax image), it would be a good idea to use the native driver for Animated.event. You can learn more about it on React Native's blog.
I'm working on a chat like application and I have seen examples using ListView and ScrollView. What are the advantages of either? I need to render different looking items through out the chat (inputs vs. responses OR text vs. images). Does one handle this case better?
I think your question is "ScrollView vs FlatList - which one to use"?
According to React-Native docs:
ScrollView vs FlatList - which one to use?
ScrollView simply renders all its react child components at once. That makes it very easy to understand and use.
On the other hand, this has a performance downside. Imagine you have a very long list of items you want to display, maybe several screens worth of content. Creating JS components and native views for everythign all at once, much of which may not even be shown, will contribute to slow rendering and increased memory usage.
This is where FlatList comes into play. FlatList renders items lazily, just when they are about to appear, and removes items that scroll way off screen to save memory and processing time.
FlatList is also handy if you want to render separators between your items, multiple columns, infinite scroll loading, or any number of other features it supports out of the box.
I would use FlatList. This is what u need. It's more effective & lazy loads your data only when needed.