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!
Related
Before I begin trying to build something I want to check my strategy.
I think the best way to define what I would like to achieve is to build a component using a FlatList that adjusts fontSize dynamically based on the size of the View (or other more appropriately defined size limiting area) in which it is being displayed.
For example, let's say I want a FlatList of items (of data returned from an API call) that displays full-screen on Screen 1 of my app, but in a small corner of Screen 2 of my app. Here's a quick mock of the behavior I would want:
It seems like the alignment of items, flex, other styles could be written so that the proportions/positions stay the same regardless of parent view in which the FlatList is displayed, so I might only have to adjust fontSize.
Can this behavior be achieved using a FlatList and a reference to a dynamic fontSize? If so, where should the "awareness" of the parent View be stored/passed?
I'm looking for general input as to how to achieve this simply, with or without FlatList. I like using FlatList because of how well it works off the shelf for my simple tasks. Hopefully I'm not trying to make it do something it cant.
Thanks!
I watched this presentation and there's a section on how to build an IOS Maps like UI. When dragging from the bottom to top, it drags to the top, and after it reaches the top, it continues scrolling up. Also, when scrolling down, when it reached the top content of the ScrollView, it continues to drag down.
It is suggested that it can be done using ScrollView by adding an empty transparent cell as the first element on the ScrollView. I have tried implementing the same which can be found in this snack. In my case, instead of Maps, I am using another ScrollView.
But the problem is that the first element (transparent element) does not allow to interact with the First ScrollView elements. I have tried with pointerEvents inside the first transparent view and even in its parent ScrollView. But this does not help. Has anyone tried implementing this kind of use case with react-native? All I found was this library, but I think it's not maintained properly.
you need to set the z-index of the transparent view to send it under/behind the interactive content, here is a good resource:
https://philipwalton.com/articles/what-no-one-told-you-about-z-index/
Edit: Actually I could not accomplish it, it seems like everything inside a scrollview will always be behind or in front of other elements, it seems like you can't have part of the scrollview behind something else and another part in front of something else.
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.
Right now, React Native ListView supports loading more data only in one direction, towards the end. If I add data towards the beginning, then it'll jump the scroll position.
Also, the ListView calls onEndReached in only in one direction.
Is there any way to implement a bi-directional ListView so that I can load more items in either direction without jumping the scroll position?
This is useful in case like, say the user came from a notification to an old item. So it'll be ideal to take the user to that part. Then as the user can scroll in either direction, I'll need to load data in either direction, without affecting scroll position.