#Nativescript web image cache A minimalistic NativeScript plugin that wraps just the caching functionality of SDWebImageCache library for iOS and Facebook Fresco for android. Supports local Images.

License

Released under the MIT License, anybody can freely include this in any type of program -- However, if in need of support contract, changes, enhancements and/or a commercial license please contact me ([email protected]).

Installation

tns plugin add nativescript-web-image-cache

** Tested on NativeScript 2.3+ on both Angular 2 and VanillaJS, if any problems while running on previous versions, please update. This version of plugin has breaking changes, if you are using version 1.0.3 of this plugin, please migrate, it is easy to migrate and this version of plugin supports android as well , if you still prefer running on the previous version, use tns plugin add [email protected].**

Usage in Vue

In main.js:

const Vue = require("nativescript-vue") // you already have something like this
Vue.registerElement('WebImage', () => require('nativescript-web-image-cache').WebImage) // now add this

Then in any .vue file:

<OtherMarkup>
  <WebImage src="https://somedomain.com/images/img-file.png" stretch="aspectFill"></WebImage>
</OtherMarkup>

Usage in Angular

⚠️ This was changed in plugin version 5.0.0!

In app.module.ts, or any specific module you want to use this plugin:

import { registerElement } from "nativescript-angular";
registerElement("WebImage", () => require("nativescript-web-image-cache").WebImage);

After initialisation, the markup tag <WebImage></WebImage> can be used in templates of components.

    <GridLayout rows='*' columns='*'>
        <WebImage stretch="fill" row="0"
                     col="0" placeholder="localPlaceholderImgorResUrl"
                     src="#your image url here">
        </WebImage>
    </GridLayout>

Caching the images

• Add the element WebImage with the src attribute set to the url just like normal image tag wherever image caching is required.
• stretch attribute can take values specified here -https://docs.nativescript.org/api-reference/modules/\_ui_enums_.stretch.html
• placeholder accepts a local image url in file path (~/) or resource (res://) form
• placeholderStretch can be set for only android to specify the stretch for placeholder image, values same as that of stretch. For iOS, no separate stretch property for placeholder (native library does not seem to support).

Check if image is loading

• Get the reference to the WebImage view by using angular template variable references and @ViewChild decorator and check the isLoading property (same as that of NativeScript Image isLoading property).
• Access the reference only after view is initialised, i.e. after ngAfterViewInit is called, getting the reference in ngOnInit can return undefined ( for detailed info, read about angular component lifecycle hooks ).

The Markup

    <WebImage stretch="fill" row="0"
                 col="0"
                 src="#your image url" #container>
    </WebImage>

The Backing Component Class Snippet

     @ViewChild("container") container : any;
     ngAfterViewInit(){
          isLoading = this.container.nativeElement.isLoading;
     }

Clearing the cache

Import the module, call the method clearCache() , default time is for SDWebImageCache is 7 days, and for Fresco is 60 days, after which cache is automatically cleared.

 import {clearCache} from "nativescript-web-image-cache";
 clearCache();

Setting custom cache purge time

Default cache purge time can be specified in number of days.

import {setCacheLimit} from "nativescript-web-image-cache";
/* Add the code component at a a proper hook */
var cacheLimitInDays : number = 7;
setCacheLimit(cacheLimitInDays);

Usage in VanillaJS/TypeScript apps

IF on android, need to initialise the plugin before using or clearing the cache, initialisation not required for iOS

Initialising on android - in app.js

var imageCache = require("nativescript-web-image-cache");
if (application.android) {
    application.onLaunch = function (intent) {
            imageCache.initialize();
    };
}

After initialisation, add the namespace attribute xmlns:IC="nativescript-web-image-cache" to the opening page tag of xml. The markup tag <IC:WebImage></IC:WebImage> should be used to denote images.

    <Page xmlns:IC="nativescript-web-image-cache">
        <GridLayout rows='*' columns='*'>
            <IC:WebImage stretch="fill" row="0"
             col="0"  id="my-image-1" placeholder="urlToLocalPlaceholderImage"
             src="#image-url">
             </IC:WebImage>  
        </GridLayout>
    </Page>

Caching the images

• To the opening page tag of the xml, add xmlns:IC="nativescript-web-image-cache".
• Add the element IC:WebImage with the src attribute set to the url just like normal image tag wherever image caching is required.
• stretch attribute can take values specified here -https://docs.nativescript.org/api-reference/modules/\_ui_enums_.stretch.html
• placeholder accepts a local image url in file path (~/) or resource (res://) form
• placeholderStretch can be set for only android to specify the stretch for placeholder image, values same as that of stretch. For iOS, no separate stretch property for placeholder (native library does not seem to support).

Check if image is loading

• To check if an image is loading, get the reference to the WebImage view by using page.getViewById("myWebImage") , and check the isLoading property (same as that of NativeScript Image isLoading property).

var imageCacheModule=require("nativescript-web-image-cache");

var myImage1 = page.getViewById("my-image-1"),
    isLoading = myImage1.isLoading;

Clearing the cache

• Require the module, call the method clearCache() , default time for SDWebImageCache is 7 days, and for Fresco is 60 days, after which cache is automatically cleared.

var imageCacheModule=require("nativescript-web-image-cache");
imageCacheModule.clearCache();

Setting custom cache purge time

Default cache purge time can be specified in number of days.

var imageCache = require("nativescript-web-image-cache");
/* Add the code component at a a proper hook */
var cacheLimitInDays = 7;
imageCache.setCacheLimit(cacheLimitInDays);

for android, you need to initialize in the application onlaunch event before clearing the cache

Prefetching images

It is possible to prefetch images so that they are already loaded in the cache before use.

let urls = [
  url1,
  url2
]

preFetchImage(urls)
.then(() => { console.log('prefetch success!'); })
.catch((error) => { console.error('prefetch error: '+error); });

** note: on iOS calling preFetchImage multiple times before the promise resolves will cancel previous calls