The development community has made numerous requests to the Expo team to include support for fast-image, unfortunately this is not a priority at this time. This leaves us no options but to implement something ourselves.
Let's call our component CachedImage. We will be using the latest react version, which supports function hooks, as they are more efficient than Class based components. And the efficiency -- that's what we are after.
To make it work with Expo, we will be using expo's components that work in iOS and Android out of the box. For instance FileSystem from 'expo-file-system' npm. We will invoke our component like this:. Now, let's start working on our CachedImage component:. First we will declare filesystemURI, which derives from cacheKey prop and defines unique cache entry for our image.
Note, if the image is not cached yet on the first run , it will reference non existing file. Similarly, there are schemes for making phone calls and sending SMS. Read more about built-in URL schemes below. Just like using the mailto scheme, it's possible to link to other applications by using other url schemes. Like with Slack, you can tell the operating system that you want to handle a custom scheme.
Read more about configuring a scheme. When the Slack app opens, it receives the URL that was used to open it and can then act on the data that is made available through the url -- in this case, a secret string that will log the user in to a particular server.
This is often referred to as deep linking. Read more about handling deep links into your app. Deep linking with schemes isn't the only linking tool available to you. For example, if you're sending a notification email about a change to a record, you don't want to use a custom URL scheme in links in the email, because then the links would be broken on desktop. Expo supports these links on both platforms with some configuration. Expo also supports deferred deep links with Branch.
Linking from your app to other apps. Built-in URL Schemes. As mentioned in the introduction, there are some URL schemes for core functionality that exist on every platform.
The following is a non-exhaustive list, but covers the most commonly used schemes. Opening links from your app. Usually you don't open a URL without it being requested by the user -- here's an example of a simple Anchor component that will open a URL when it is pressed. Using WebBrowser instead of Linking for opening web links. The following example illustrates the difference between opening a web link with WebBrowser.
Often WebBrowser is a better option because it's a modal within your app and users can easily close out of it and return to your app. Update: "WebBrowser" is in a separate package so first install expo-web-browser like expo install expo-web-browser and use it like this:. Opening links to other apps. If you know the custom scheme for another app you can link to it. Some services provide documentation for deep linking, for example the Lyft deep linking documentation describes how to link directly to a specific pickup location and destination:.
We recommend using the library react-native-app-link for these cases. On iOS, Linking. You can use the ios. For example:. If you don't specify this list, Linking. Note that this configuration can only be tested in standalone apps, because it requires native changes that will not be applied when testing in Expo Go. Linking to your app. In the Expo Go app. Before continuing it's worth taking a moment to learn how to link to your app within the Expo Go app.
You can link to it from another app by using Linking. In a standalone app. To link to your standalone app, you need to specify a scheme for your app. You can register for a scheme in your app. If your app is ejected, note that like some other parts of app. It seems I have been able to successfully save the image base64 encoded with the following: await FileSystem.
What is the proper api usage to store and access jpg files in expo-file-system? Improve this question. Quddus George. Quddus George Quddus George 1 1 gold badge 5 5 silver badges 17 17 bronze badges.
I still have not had any luck getting this functioning. Even making an isolated dummy app with only this feature. Are you sure you're using writeAsStringAsync correctly? This also takes an options parameter that requires you to specify an encoding. Add a comment. Active Oldest Votes. It should also be used if the image is slightly bigger than the view.
Determines how to resize the image when the frame doesn't match the raw image dimensions. Defaults to cover. The image will keep its size and aspect ratio, unless it is larger than the view, in which case it will be scaled down uniformly so that it is contained in the view.
If the image is larger than the view, scale it down uniformly so that it is contained in the view. The image source either a remote URL or a local file resource. The native side will then choose the best uri to display based on the measured size of the image container. A cache property can be added to control how networked request interacts with the local cache.
For more information see Cache Control for Images. The currently supported formats are png , jpg , jpeg , bmp , gif , webp , psd iOS only. A unique identifier for this element to be used in UI Automation testing scripts.
Retrieve the width and height in pixels of an image prior to displaying it. This method can fail if the image cannot be found, or fails to download. In order to retrieve the image dimensions, the image may first need to be loaded or downloaded, after which it will be cached. A proper, supported way to preload images will be provided as a separate API.
Retrieve the width and height in pixels of an image prior to displaying it with the ability to provide the headers for the request. It also does not work for static image resources. Prefetches a remote image for later use by downloading it to the disk cache.
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