Ytukyg

I am using the quickstart-android code provided by google but after many attempts I cam unable to find a context that is not returning null. The BarcodeScannerProcessor is not itself an Activity, so I have attempted to create an instance of the LivePreviewActivity and use that as the context in the intent, but it's null.

The goal is to once a valid barcode is recognized I want to open a new activity that allows a user to verify value and on the push of a button call a webservice to post the barcode to a database via API. I am having a hard time finding a valid context and the app is crashing when it trys to execute the Intent.

Starting at line 97-107:

https://github.com/jamiekeefer/quickstart-android/blob/master/mlkit/app/src/main/java/com/google/firebase/samples/apps/mlkit/java/barcodescanning/BarcodeScanningProcessor.java

        for (int i = 0; i < barcodes.size(); ++i) {

        FirebaseVisionBarcode barcode = barcodes.get(i);

        BarcodeGraphic barcodeGraphic = new BarcodeGraphic(graphicOverlay, barcode);

        graphicOverlay.add(barcodeGraphic);



        System.out.println(barcode.getRawValue());



        if (!barcode.getRawValue().equals("") ) {



            System.out.println("Got the number:" + barcode.getRawValue() + " Context: " + mContext); //OLD SCHOOL DEBUG OUTPUT



            //enter code to start activity



                Intent intent = new Intent(mContext, SendScannedBarcode.class);

                String message = scannedBarcode;

                intent.putExtra(EXTRA_MESSAGE, message);

                mContext.startActivity(intent);

        }





    }

You can back up in the repo to see the instance of the LivePreviewActivity where I trying to get context.

I have tried a number of things and read about Context, Views and Activities and basically have completely confused myself. The only tuts I can find are using Kotlin, which is not helping clarify things.

I appreacite any help in indentifying or contruting a valid Intent from this Context. Thank you.

So I am assuming that in your LivePreviewActivity you are creating an object of the class BarcodeScanningProcessor. What you can do is change the constructor in the BarcodeScanningProcessor class to accept a context and then you pass in your LivePreviewActivity's context.

This is what the code should look like:

In BarcodeScanningProcessor:

  public BarcodeScanningProcessor(Context context) {

    // Note that if you know which format of barcode your app is dealing with, detection will be

    // faster to specify the supported barcode formats one by one, e.g.

    // new FirebaseVisionBarcodeDetectorOptions.Builder()

    // .setBarcodeFormats(FirebaseVisionBarcode.FORMAT_QR_CODE)

    // .build();

    detector = FirebaseVision.getInstance().getVisionBarcodeDetector();

    this.mContext = context;

}

Then in LivePreviewActivity:

In the particular case of your activity you would do:

  case BARCODE_DETECTION:

          Log.i(TAG, "Using Barcode Detector Processor");

          cameraSource.setMachineLearningFrameProcessor(new BarcodeScanningProcessor(getApplicationContext()));

          break;

Or if you just wanted to create an object of the class you could do:
BarcodeScanningProcessor bsp = new BarcodeScanningProcessor(getApplicationContext());

This should now give your BarcodeScanningProcessor class the context of your activity. Now, in BarcodeScanningProcessor, mContext should not be null and will have the context of your activity. I hope this answers your question.

try this create Application class

import android.app.Application;



public class MyApplication  extends Application {

    static MyApplication instance;



    @Override

    public void onCreate() {

        super.onCreate();

        instance=this;

    }



    public static MyApplication getInstance() {

        return instance;

    }

}

Register in manifest file

<application

        ..

        android:name="com.yourpackage.MyApplication"

        ..>

.

.

.

</application>

start activity using this MyApplication.

Intent intent = new Intent(MyApplication.getInstance(), SendScannedBarcode.class);

                String message = scannedBarcode;

                intent.putExtra(EXTRA_MESSAGE, message);

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

               MyApplication. getInstance().startActivity(intent);

Another way of handling the issue is create new constructor of BarcodeScanningProcessor which takes interface call back and once processing is done pass back result to caller.

   public interface BarcodeUpdateListener {

      @UiThread

      void onBarcodeDetected(Barcode barcode);

   } 





   private BarcodeUpdateListener callback;



   public BarcodeScanningProcessor(BarcodeUpdateListener callback){

      this.callback = callback;

      detector = FirebaseVision.getInstance().getVisionBarcodeDetector();

   } 

Once you get the result pass result to caller

callback.onBarcodeDetected(<Barcode>)