QR Mobile Vision

Reading QR codes and other barcodes using Firebase's MLKit.

This plugin uses Android & iOS native APIs for reading images from the device's camera. It then pipes these images both to the MLKit Vision Barcode API which detects barcodes/qrcodes etc, and outputs a preview image to be shown on a flutter texture.

The plugin includes a widget which performs all needed transformations on the camera output to show within the defined area.

Android Models

With this new version of MLKit, there are two separate models you can use to do the barcode scanning. Currently, this apk chooses to use the build-in model. This will increase your code size by ~2.2MB but will result in better scanning and won't require a separate package to be downloaded in the background for barcode scanning to work properly.

You could also use the Google Play Services and tell your app to download it on install from the play store. See the instruction on the ml-kit barcode-scanning documentation page for android. You would also have to remove the com.google.mlkit:barcode-scanning dependency; this hasn't been tested but would probably go something like this:

configurations.all {
    exclude group: "com.google.mlkit", module:"barcode-scanning"
}
//  ...
dependencies {
  // ...
  // Use this dependency to use the dynamically downloaded model in Google Play Services
  implementation 'com.google.android.gms:play-services-mlkit-barcode-scanning:16.1.4'
}

Note that if you do this, you should tell your app to automatically download the model as in the above linked docs.MLKit

<application ...>
    ...
    <meta-data
        android:name="com.google.mlkit.vision.DEPENDENCIES"
        android:value="barcode" />
    <!-- To use multiple models: android:value="barcode,model2,model3" -->
</application>

If this doesn't work for you please open an issue.

iOS

For recent versions of Google's Barcode Scanning library ('GoogleMLKit/BarcodeScanning'), an iOS version of 15.5+ is required.

The podspec has not been updated to reflect this requirement as usage of older versions of the dependency library is still possible (and necessary if you use an older Firebase version). However, if you are having dependency errors when updating this plugin in conjunction with the Firebase libraries, ensuring that your project has a version of 15.5+ might be required.

The example project has been updated to reflect this.

Usage

See the example for how to use this plugin; it is the best resource available as it shows the plugin in use. However, these are the steps you need to take to use this plugin.

First, figure out the area that you want the camera preview to be shown in. This is important as the preview needs to have a constrained size or it won't be able to build. This is required due to the complex nature of the transforms needed to get the camera preview to show correctly on both iOS and Android, while still working with the screen rotated etc.

It may be possible to get the camera preview to work without putting it in a SizedBox or Container, but the recommended way is to put it in a SizedBox or Container.

You then need to include the package and instantiate the camera.

import 'package:qr_mobile_vision/qr_camera.dart';

...

new SizedBox(
  width: 300.0,
  height: 600.0,
  child: new QrCamera(
    qrCodeCallback: (code) {
      ...
    },
  ),
)

The QrCodeCallback can do anything you'd like, and wil keep receiving QR codes until the camera is stopped.

There are also optional parameters to QrCamera.

`fit`

Takes as parameter the flutter BoxFit. Setting this to different values should get the preview image to fit in different ways, but only BoxFit = cover has been tested extensively.

`notStartedBuilder`

A callback that must return a widget if defined. This should build whatever you want to show up while the camera is loading (which can take from milliseconds to seconds depending on the device).

`child`

Widget that is shown on top of the QrCamera. If you give it a specific size it may cause weird issues so try not to.

`key`

Standard flutter key argument. Can be used to get QrCameraState with a GlobalKey.

`cameraDirection`

Uses a camera of the specified direction. Default is to use BACK

These are the support types:

  FRONT,
  BACK

`offscreenBuilder`

A callback that must return a widget if defined. This should build whatever you want to show up when the camera view is 'offscreen'. i.e. when the app is paused. May or may not show up in preview of app.

`onError`

Callback for if there's an error.

`formats`

A list of supported formats, all by default. If you use all, you shouldn't define any others.

These are the supported types:

  ALL_FORMATS,
  AZTEC,
  CODE_128,
  CODE_39,
  CODE_93,
  CODABAR,
  DATA_MATRIX,
  EAN_13,
  EAN_8,
  ITF,
  PDF417,
  QR_CODE,
  UPC_A,
  UPC_E

`direction`

Whether you want the front or the back camera to be used.

Toggle flash

When the camera is running, you can use the QrCamera.toggleFlash() or QrMobileVision.toggleFlash() methods to turn the flash on or off. A better solution is in the works for this, but I can't make a commitment for when I'll have time to finish it.

Push and Pop

If you push a new widget on top of a the current page using the navigator, the camera doesn't necessarily know about it.

Contributions

Anyone wanting to contribute to this project is very welcome to! I'll take a look at PR's as soon as I can, and any bug reports are appreciated. I've only a few devices on which to test this so feedback about other devices is appreciated as well.

This has been tested on:

Nexus 5x
Nexus 4
Pixel 3a
iPhone 7