docs.sheetjs.com/docz/docs/04-getting-started/03-demos/19-mobile.md

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19	iOS and Android Apps

Many mobile app frameworks mix JavaScript / CSS / HTML5 concepts with native extensions and libraries to create a hybrid development experience. Developers well-versed in web technologies can now build actual mobile applications that run on iOS and Android!

:::warning

The ecosystem has broken backwards-compatibility many times!

iOS and Android, as well as the underlying JavaScript frameworks, make breaking changes regularly. The demos were tested against emulators / real devices at some point in time. A framework or OS change can render the demos inoperable.

Each demo section will mention test dates and platform versions.

:::

The "JavaScript Engines" section includes samples for JavaScript engines used in the mobile app frameworks. SheetJS libraries have been tested in the relevant engines and should "just work" with some caveats.

:::caution readFile and writeFile

XLSX.readFile and XLSX.writeFile do not work in mobile apps! The demos include platform-specific details for fetching file data for XLSX.read and writing file data generated by XLSX.write.

Some platforms provide this functionality as part of the standard library. Other platforms, including React Native, do not. When the platform does not provide, usually there are third-party modules to provide needed functionality.

:::

NativeScript

:::note

This demo was tested on an Intel Mac on August 10 2022. NativeScript version (as verified with ns --version) is 8.3.2. The iOS simulator runs iOS 15.5 on an iPhone SE 3rd generation.

:::

:::warning Binary Data issues

NativeScript will not safely transmit binary or UTF8 strings. XLSB, NUMBERS, XLSX, XLS, ODS, SYLK, and DBF exports are known to be mangled.

This is a known NativeScript bug

This demo will focus on ASCII CSV files. Once the bug is resolved, XLSX and other formats will be supported.

:::

The @nativescript/core/file-system package provides classes for file access.

Integration Details

Reading and writing data require a file handle. The following snippet searches typical document folders for a specified filename:

import { File, Folder, knownFolders, path } from '@nativescript/core/file-system';

function get_handle_for_filename(filename: string): File {
  const target: Folder = knownFolders.documents() || knownFolders.ios.sharedPublic();
  const url: string = path.normalize(target.path + "///" + filename);
  return File.fromPath(url);
}

The encoding ISO_8859_1 spiritually resembles the "binary" SheetJS type

Reading data

File#readText(encoding.ISO_8859_1) returns strings compatible with "binary"

/* get binary string */
const bstr: string = await file.readText(encoding.ISO_8859_1);

/* read workbook */
const wb = read(bstr, { type: "binary" });

Writing data

File#writeText with the ISO_8859_1 encoding accepts "binary" strings with the caveat listed in the warning at the top of this section:

/* generate binary string */
const bstr: string = write(wb, { bookType: 'csv', type: 'binary' });

/* attempt to save binary string to file */
await file.writeText(bstr, encoding.ISO_8859_1);

Demo

The demo builds off of the NativeScript + Angular example. Familiarity with with Angular and TypeScript is assumed.

Complete Example (click to show)

0. Follow the official Environment Setup instructions (tested with "macOS + iOS")

1. Create a skeleton NativeScript + Angular app:

ns create SheetJSNS --ng

2. Launch the app in the iOS simulator to verify that the demo built properly:

cd SheetJSNS
ns run ios

(this may take a while)

Once the simulator launches and the test app is displayed, end the script by selecting the terminal and entering the key sequence CTRL + C

3. From the project folder, install the library:

npm install --save https://cdn.sheetjs.com/xlsx-latest/xlsx-latest.tgz

4. To confirm the library was loaded, change the title to show the version. The differences are highlighted.

src/app/item/items.component.ts imports the version string to the component:

// highlight-next-line
import { version } from 'xlsx';
import { Component, OnInit } from '@angular/core'

import { Item } from './item'
import { ItemService } from './item.service'

@Component({
  selector: 'ns-items',
  templateUrl: './items.component.html',
})
export class ItemsComponent implements OnInit {
  items: Array<Item>
  // highlight-next-line
  version = `SheetJS - ${version}`;

  constructor(private itemService: ItemService) {}

  ngOnInit(): void {
    this.items = this.itemService.getItems()
  }
}

src/app/item/items.component.html references the version in the title:

<!-- highlight-next-line -->
<ActionBar [title]="version"></ActionBar>

<GridLayout>
  <ListView [items]="items">
    <ng-template let-item="item">
      <StackLayout [nsRouterLink]="['/item', item.id]">
        <Label [text]="item.name"></Label>
      </StackLayout>
    </ng-template>
  </ListView>
</GridLayout>

Relaunch the app with ns run ios and the title bar should show the version.

5. Add the Import and Export buttons to the template:

<ActionBar [title]="version"></ActionBar>

<!-- highlight-start -->
<StackLayout>
  <StackLayout orientation="horizontal">
    <Button text="Import File" (tap)="import()" style="padding: 10px"></Button>
    <Button text="Export File" (tap)="export()" style="padding: 10px"></Button>
  </StackLayout>
<!-- highlight-end -->
  <ListView [items]="items">
    <ng-template let-item="item">
      <StackLayout [nsRouterLink]="['/item', item.id]">
        <Label [text]="item.name"></Label>
      </StackLayout>
    </ng-template>
  </ListView>
<!-- highlight-next-line -->
</StackLayout>

// highlight-start
import { version, utils, read, write } from 'xlsx';
import { Dialogs } from '@nativescript/core';
import { encoding } from '@nativescript/core/text';
import { File, Folder, knownFolders, path } from '@nativescript/core/file-system';
// highlight-end
import { Component, OnInit } from '@angular/core'

import { Item } from './item'
import { ItemService } from './item.service'

// highlight-start
function get_handle_for_filename(filename: string): [File, string] {
  const target: Folder = knownFolders.documents() || knownFolders.ios.sharedPublic();
  const url: string = path.normalize(target.path + "///" + filename);
  return [File.fromPath(url), url];
}
// highlight-end

@Component({
  selector: 'ns-items',
  templateUrl: './items.component.html',
})
export class ItemsComponent implements OnInit {
  items: Array<Item>
  version: string = `SheetJS - ${version}`;

  constructor(private itemService: ItemService) {}

  ngOnInit(): void {
    this.items = this.itemService.getItems()
  }

  // highlight-start
  /* Import button */
  async import() {
  }

  /* Export button */
  async export() {
  }
  // highlight-end
}

Restart the app process and two buttons should show up at the top:

6. Implement import and export:

import { version, utils, read, write } from 'xlsx';
import { Dialogs } from '@nativescript/core';
import { encoding } from '@nativescript/core/text';
import { File, Folder, knownFolders, path } from '@nativescript/core/file-system';
import { Component, OnInit } from '@angular/core'

import { Item } from './item'
import { ItemService } from './item.service'

function get_handle_for_filename(filename: string): [File, string] {
  const target: Folder = knownFolders.documents() || knownFolders.ios.sharedPublic();
  const url: string = path.normalize(target.path + "///" + filename);
  return [File.fromPath(url), url];
}

@Component({
  selector: 'ns-items',
  templateUrl: './items.component.html',
})
export class ItemsComponent implements OnInit {
  items: Array<Item>
  version: string = `SheetJS - ${version}`;

  constructor(private itemService: ItemService) {}

  ngOnInit(): void {
    this.items = this.itemService.getItems()
  }

  /* Import button */
  async import() {
    // highlight-start
    /* find appropriate path */
    const [file, url] = get_handle_for_filename("SheetJSNS.csv");

    try {
      /* get binary string */
      const bstr: string = await file.readText(encoding.ISO_8859_1);

      /* read workbook */
      const wb = read(bstr, { type: "binary" });

      /* grab first sheet */
      const wsname: string = wb.SheetNames[0];
      const ws = wb.Sheets[wsname];

      /* update table */
      this.items = utils.sheet_to_json<Item>(ws);
      Dialogs.alert(`Attempting to read to ${filename} in ${url}`);
    } catch(e) { Dialogs.alert(e.message); }
    // highlight-end
  }

  /* Export button */
  async export() {
    // highlight-start
    /* find appropriate path */
    const [file, url] = get_handle_for_filename("SheetJSNS.csv");

    try {
      /* create worksheet from data */
      const ws = utils.json_to_sheet(this.items);

      /* create workbook from worksheet */
      const wb = utils.book_new();
      utils.book_append_sheet(wb, ws, "Sheet1");

      /* generate binary string */
      const wbout: string = write(wb, { bookType: 'csv', type: 'binary' });

      /* attempt to save binary string to file */
      await file.writeText(wbout, encoding.ISO_8859_1);
      Dialogs.alert(`Wrote to ${filename} in ${url}`);
    } catch(e) { Dialogs.alert(e.message); }
    // highlight-end
  }
}

Restart the app process.

Testing

The app can be tested with the following sequence in the simulator:

• Hit "Export File". A dialog will print where the file was written

• Open that file with a text editor. It will be a 3-column CSV:

id,name,role
1,Ter Stegen,Goalkeeper
3,Piqué,Defender
4,I. Rakitic,Midfielder
...

After the header row, add the line 0,SheetJS,Library:

id,name,role
0,SheetJS,Library
1,Ter Stegen,Goalkeeper
3,Piqué,Defender
...

• Hit "Import File". A dialog will print the path of the file that was read. The first item in the list will change: