Fetching data from a local device file system using Angular 2 and Ionic 2

Currently, I am working on developing an application that has a unique requirement - it must be able to function offline and have a synchronization mechanism with servers. This means that users should have the ability to sync the app with server data whenever needed.

To achieve this, I created a process that utilizes Cordova's 'FileTransfer' combined with Node.js to generate a json file containing the most up-to-date information, which is then downloaded to the local file system of the device. However, I encountered a challenge when attempting to fetch the data using a standard http request to this file.

After investigating the logcat of my device, I discovered that executing http requests to the 'file://' protocol was not feasible. As I reflect on this issue, it is beginning to make sense why the process did not work as expected.

My main question now is: How can I retrieve a file from the local file system? Is there a method to simulate a service running on the device for this purpose?

Thank you in advance for any guidance or solutions!

cordovaangulartypescript

Answer №1

The issue arises from the different paths of json files in a local browser (computer) and a device (android). To resolve this, create a new data folder within the src\assets directory and move your json file into it.

When you run ionic serve, the folder (with the file) will be moved to the www\assets folder. After that, follow these steps:

  1. Firstly, import the Platform service of ionic2

     import { Platform } from 'ionic-angular';


  1. Next, inject the Platform Service.

      constructor(private http: Http, private platform: Platform ) { }


  1. Lastly, utilize the Platform Service.

    public getItems() {

    var url = 'assets/data/Items.json'; 

    if (this.platform.is('cordova') && this.platform.is('android')) {
        url = "/android_asset/www/" + url;
    }

    return this.http.get(url)
        .map((res) => {
            return res.json()
        });
}


Answer №2

Instead of referencing the file as "/assets/data/Items.json", simply use "assets/data/Items.json" as the file path. This approach will ensure that it functions correctly on both web browsers and Android devices.

    this.http.get('assets/path/to/file').success((res) => {
       console.log(res);
    });

Answer №3

It's possible you've already discovered this, but:

Omit the protocol from your path, do not include 'file://'

Simply use the direct path to the file location, for instance on Android it might be '/assets/path/to/file'. like this:

this.http.get('/assets/path/to/file').then(function(response){ //perform action });

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