I have a FlatList which renders a productInformation item, which you can scroll through (so you horizontally scroll through the products).
The Info items have a lot of pictures and since Android 9 there is a severe performance problem with lots of images in ScrollViews. So I want the FlatList to only render the visible item and unmount and not cache the previous shown items.
How can I achieve this?
Related
I try to render a dropdown-picker (react-native-dropdownpicker) in a sectionlist but it's impossable to scroll the content of the dropdown. It only shows the first results.
I tried many things with zIndex, view with flex: 1 as parent but im unable to find the solution.
Is it possible to render in a sectionlist or should i be looking for another solution?
sectionlist with dropdown-picker
I think this is what you want.
List Modes
You have 3 options when choosing the list mode.
DEFAULT
FLATLIST
SCROLLVIEW
MODAL
listMode="FLATLIST"
Notes
The FlatList component shouldn't be nested inside ScrollView or you'll come across the VirtualizedLists should never be nested inside plain ScrollViews warning.
If this happens to you and you only have a few items, consider using the SCROLLVIEW mode. Otherwise, you have to use the MODAL mode.
Take a look at this snack:
https://snack.expo.dev/#devsaeedhabibi/dropdown-picker
I am using flatlist for rendering a long list of items with different heights and when I scroll it fast, I see blank space and it doesn't work well. I tried react-native-big-list and react-native-largelist and recyclerlistview. These packages don't have that problems but they require a static height for items so I can not use them.
What is structure different between FlatList and ScrollView in react native?
It seems to they equal to each other for scrolling view in the application, but ScrollView is very simple rather than FlatList, so when we must use FlatList in code?
There's a big difference between FlatList and ScrollView
ScrollView will load the items (data for scrolling) immediately after the component has been loaded. As a result, all data will be stored in RAM, and you will be unable to use hundreds or thousands of items in it (due to low performance).
FlatList, on the other hand, has a better solution for this problem; it will mount 10 items (by default) to the screen, and as the user scrolls the view, other items will mount.
It's a significant advantage to use FlatList instead of ScrollView.
You can use ScrollView for a small number of items and FlatList for even 10000 items.
A really big difference that no one seems to be pointing out here is that component state is not maintained with the FlatList component but is maintained with ScrollView. This is due to the fact that ScrollView renders all the children in one go and maintains them. Meanwhile, FlatList unmounts components once they are way off the screen and recreates them from scratch once the item comes back from screen (thus state is lost).
They have different usages.
FlatList is built to render a large list of items. If you check the documentation, you need to pass an array of data and then render each item in the array with the renderItem callback. It is optimized to have very good performances with very large arrays because it actually only renders the items that need to be displayed at the moment.
ScrollView is built to render a generic content in a way that it scrolls when the content is bigger than the ScrollView itself. You don't pass an array of data, but you put elements inside the ScrollView in the same way you would use a normal View. Be careful however, it does not provide the same optimization of the flat list for very long content.
As a rule of thumb:
Do you need to render a list of similar items from an array? Use FlatList
Do you need to render generic content in a scrollable container? Use ScrollView
I am trying to develop a profile screen which has the persons profile pic, name, etc in the header as well as tabs that determines which data gets displayed in the FlatList below. I want the header component to be scrollable with the FlatList so that the header does not take up screen space while scrolling the FlatList. Also, the header's tabs will change the data that gets render in the list. I have tried two approaches but neither one has worked. Including the header and flatlist inside of a scrollview causes the flatlist to continually call onEndReach until all of the data is returned, but I also read that this is not recommended. The second approach was setting the ListHeaderComponent on the flatlist to the header component, but every time a tab is change the entire screen reloads. I am looking to have the header scrollable as if it were part of the flatlist, and only the flatlist re-render when a tab is pressed. Similar to what Instagram has with their profile screen. Any help with this issue would be much appreciated.
I need a ListView or Table or any other custom component that can have infinite scrolling in both horizontal and vertical directions. For example, 10,000 rows and 10,000 columns. We have the react-native's FlatList component but it can be used for either vertical or horizontal but not for both. If the data is finite, we can go with implementing a vertical scrollView inside a horizontal scrollView or vice-versa. But as we are looking for infinite scrolling, we are not able to use scrollView as it tries to load the entire content when the app is opened and the memory consumption is very huge so that the app automatically crashes. Does anyone have any idea if there are any third party libraries that can scroll both vertically and horizontally and also can look after the performance? Actually, is that possible to build such a component on our own in react-native? If so, please tell me if you have any ideas.