README
Barcode Scanner
@dutchconcepts/capacitor-barcode-scanner
A fast and efficient (QR) barcode scanner for Capacitor.
Table of Contents
Maintainers
| Maintainer | GitHub | Social |
|---|---|---|
| tafelnl | tafelnl |
About
Supported barcodes
On iOS this library makes use of Apple's own AVFoundation. This means this list of barcodes should be supported.
On Android this library uses zxing-android-embedded which uses zxing under the hood. That means this list of barcodes is supported.
Installation
npm install @dutchconcepts/capacitor-barcode-scanner
npx cap sync
iOS
On iOS, no further steps are needed.
Android
On Android, register the plugin in your main activity:
import com.dutchconcepts.capacitor.barcodescanner.BarcodeScanner;
public class MainActivity extends BridgeActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Initializes the Bridge
this.init(
savedInstanceState,
new ArrayList<Class<? extends Plugin>>() {
{
// Additional plugins you've installed go here
// Ex: add(TotallyAwesomePlugin.class);
add(BarcodeScanner.class);
}
}
);
}
}
Configuration
iOS
For iOS you need to set a usage description in your info.plist file.
This can be done by either adding it to the Source Code directly or by using Xcode Property List inspector.
Adding it to the source code directly
- Open up the Info.plist (in Xcode right-click > Open As > Source Code)
- With
<dict></dict>change the following
<dict>
+ <key>NSCameraUsageDescription</key>
+ <string>To be able to scan barcodes</string>
</dict>
NOTE: "To be able to scan barcodes" can be substituted for anything you like.
Adding it by using Xcode Property List inspector
- Open up the Info.plist in Xcode (right-click > Open As > Property List)
- Next to "Information Property List" click on the tiny
+button. - Under
key, type "Privacy - Camera Usage Description" - Under
value, type "To be able to scan barcodes"
NOTE: "To be able to scan barcodes" can be substituted for anything you like.
More info here: https://developer.apple.com/documentation/bundleresources/information_property_list/nscamerausagedescription
Android
Within your AndroidManifest.xml file, change the following:
<?xml version="1.0" encoding="utf-8"?>
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
+ xmlns:tools="http://schemas.android.com/tools"
package="com.example">
<application
+ android:hardwareAccelerated="true"
>
</application>
+ <uses-permission android:name="android.permission.CAMERA" />
+ <uses-sdk tools:overrideLibrary="com.google.zxing.client.android" />
</manifest>
Usage
Scanning a (QR) barcode can be as simple as:
import { Plugins } from '@capacitor/core';
const startScan = async () => {
const { BarcodeScanner } = Plugins;
BarcodeScanner.hideBackground(); // make background of WebView transparent
const result = await BarcodeScanner.startScan(); // start scanning and wait for a result
// if the result has content
if (result.hasContent) {
console.log(result.content); // log the raw scanned content
}
};
Opacity of the WebView
Because of the fact that the Scanner View will be rendered behind the WebView, you will have to call hideBackground() to make the WebView and the <html> element transparent. Every other element that needs transparency, you will have to handle yourself.
The <html> element is made transparent by adding background: 'transparent'; to the style="" attribute. So in theory it is possible that this is overwritten by some CSS property in your setup. Because this plugins does not aim to fix every single scenario out there, you will have to think of a workaround for this yourself, if this applies to you (probably not).
Stopping a scan
After startScan() is resolved, the Scanner View will be automatically destroyed to save battery. But if you want to cancel the scan before startScan() is resolved (AKA no code has been recognized yet), you will have to call stopScan() manually. Example:
import { Plugins } from '@capacitor/core';
const stopScan = () => {
const { BarcodeScanner } = Plugins;
BarcodeScanner.showBackground();
BarcodeScanner.stopScan();
};
It is also important to think about cases where a users hits some sort of a back button (either hardware or software). It is advised to call stopScan() in these types of situations as well.
In Vue.js you could do something like this in a specific view where you use the scanner:
<script>
import { Plugins } from '@capacitor/core';
export default {
methods: {
stopScan() {
const { BarcodeScanner } = Plugins;
BarcodeScanner.showBackground();
BarcodeScanner.stopScan();
},
},
deactivated() {
this.stopScan();
},
beforeDestroy() {
this.stopScan();
},
};
</script>
Preparing a scan
To boost performance and responsiveness (by just a bit), a prepare() method is available. If you know your script will call startScan() sometime very soon, you can call prepare() to make startScan() work even faster.
For example:
import { Plugins } from '@capacitor/core';
const prepare = () => {
const { BarcodeScanner } = Plugins;
BarcodeScanner.prepare();
};
const startScan = async () => {
const { BarcodeScanner } = Plugins;
BarcodeScanner.hideBackground();
const result = await BarcodeScanner.startScan();
if (result.hasContent) {
console.log(result.content);
}
};
const stopScan = () => {
const { BarcodeScanner } = Plugins;
BarcodeScanner.showBackground();
BarcodeScanner.stopScan();
};
const askUser = () => {
prepare();
const c = confirm('Do you want to scan a barcode?');
if (c) {
startScan();
} else {
stopScan();
}
};
askUser();
This is fully optional and would work the same as:
const startScan = async () => {
const { BarcodeScanner } = Plugins;
BarcodeScanner.hideBackground();
const result = await BarcodeScanner.startScan();
if (result.hasContent) {
console.log(result.content);
}
};
const askUser = () => {
const c = confirm('Do you want to scan a barcode?');
if (c) {
startScan();
}
};
askUser();
The latter will just appear a little slower to the user.
Permissions
This plugin does not automatically handle permissions. But the plugin does have a utility method to check and request the permission. You will have to request the permission from JavaScript. A simple example follows:
const checkPermission = async () => {
const { BarcodeScanner } = Plugins;
// check or request permission
const status = await BarcodeScanner.checkPermission({ force: true });
if (status.granted) {
// the user granted permission
return true;
}
return false;
};
A more detailed and more UX-optimized example:
const didUserGrantPermission = async () => {
const { BarcodeScanner } = Plugins;
// check if user already granted permission
const status = await BarcodeScanner.checkPermission({ force: false });
if (status.granted) {
// user granted permission
return true;
}
if (status.denied) {
// user denied permission
return false;
}
if (status.asked) {
// system requested the user for permission during this call
// only possible when force set to true
}
if (status.neverAsked) {
// user has not been requested this permission before
// it is advised to show the user some sort of prompt
// this way you will not waste your only chance to ask for the permission
const c = confirm(
'We need your permission to use your camera to be able to scan barcodes',
);
if (!c) {
return false;
}
}
if (status.restricted || status.unknown) {
// ios only
// probably means the permission has been denied
return false;
}
// user has not denied permission
// but the user also has not yet granted the permission
// so request it
const statusRequest = await BarcodeScanner.checkPermission({ force: true });
if (statusRequest.asked) {
// system requested the user for permission during this call
// only possible when force set to true
}
if (statusRequest.granted) {
// the user did grant the permission now
return true;
}
// user did not grant the permission, so he must have declined the request
return false;
};
checkPermission();
If a user denied the permission for good, status.denied will be set to true. On Android this will happen only when the user checks the box never ask again. To get the permission anyway you will have to redirect the user to the settings of the app. This can be done simply be doing the following:
const checkPermission = async () => {
const { BarcodeScanner } = Plugins;
const status = await BarcodeScanner.checkPermission();
if (status.denied) {
// the user denied permission for good
// redirect user to app settings if they want to grant it anyway
const c = confirm(
'If you want to grant permission for using your camera, enable it in the app settings.',
);
if (c) {
BarcodeScanner.openAppSettings();
}
}
};
Troubleshooting
- I have a
Error: Plugin BarcodeScanner does not respond to method callerror message on iOS
In Xcode click on Product > Clean Build Folder and try to build again.
- I have a
Cannot resolve symbol BarcodeScannererror message in Android Studio
In Android Studio click File > Sync Project with Gradle Files and try to build again.
TODO
A non-exhaustive list of todos:
- Support for switching between cameras
- Support for toggling the flashlight
- Support for web