image-cache.md

title	contributors
ImageCache	Ombuweb NathanWalker

ImageCache allows you to cache an image from an HTTP request. You can alternatively use a plugin that auto handles image caching like @triniwiz/nativescript-image-cache-it.

Using ImageCache

For consistency, you should use a single ImageCache instance throughout your app.

import { ImageCache } from '@nativescript/core'

const imageCache = new ImageCache()

Save an image to cache

To retrieve an image from a remote server and cache it, use either the push or enqueue method. These methods cache the android.graphics.Bitmap (Android) or UIImage (iOS) instance.

imageCache.enqueue({
  url: this.url,
  key: 'cat',
  completed(image: android.graphics.Bitmap | UIImage, key) {
    console.log('Successfully retrived and cached the cat image')
  },
  error(key) {
    console.log('cache error')
  },
})

:::tip Note To call the push method instead, just replace enqueue with push :::

Getting an image from cache

To get an image from the cache, use the get method.

const cachedImage = imageCache.get('cat')

API

constructor

const imageCache = new ImageCache()

Creates an ImageCache instance.

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placeholder

imageCache.placeholder = imageSource

The image to be used to notify for a pending download request - e.g. loading indicator.

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maxRequests

imageCache.number = 2

The maximum number of simultaneous download requests. Defaults to 5

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push

imageCache.push(request)

Adds a new image to the start of the cache. request is an object with the following members:

• url(string): The url of the image.
• key(string): The name to uniquely identify the image in the cache.
• Optional: completed is a function to be called upon caching an image successfully.
• Optional: error is a function to be called when error has occured during caching.

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enqueue

imageCache.enqueue(request)

Adds a new image to the end of the cache. For more details about the request parameter, see the push() method.

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get

imageCache.get(key)

Gets the image with a given key from the cache, or undefined if it's not in the cache.

remove

imageCache.remove(imageKey)

Remove the specified image from the cache.

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clear

imageCache.clear()

Clears all the images from the cache.

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