Scan Barcode And QRcode Using Zxing Android Kotlin Programmatically

<uses-permission android:name="android.permission.CAMERA" />

Note: If you are targeting SDK version above 22 (Above Lollipop)  then you need to ask a user for granting runtime permissions. Check marshmallow runtime permission for more information.

Step 4: Updating activity_main.xml file:

Copy following code into android_main.xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.parsaniahardik.kotlin_scanxing.MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btn"
        android:text="Scan Barcode or QR code" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/tvresult"
        android:textColor="#000"
        android:layout_marginTop="10dp"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Result will be here"/>
</LinearLayout>

Step 5: Updating MainActivity.kt file:

Update MainActivity.kt as per below code:

import android.content.Intent
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.TextView

class MainActivity : AppCompatActivity() {
    private var btn: Button? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        tvresult = findViewById(R.id.tvresult) as TextView

        btn = findViewById(R.id.btn) as Button

        btn!!.setOnClickListener {
            val intent = Intent(this@MainActivity, ScanActivity::class.java)
            startActivity(intent)
        }

    }

    companion object {

        var tvresult: TextView? = null
    }
}

Here we will open ScanActivity on the button’s click.

Step 6: Opening new activity in android studio

To open new activity in the android studio, click on File tab which is present at the left top bar.

Now go to File->New->Activity->Empty Activity and place name of activity as ScanActivity.

Step 7: Updating ScanActivity.kt file:

Add below code to ScanActivity.kt

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import com.google.zxing.Result
import me.dm7.barcodescanner.zxing.ZXingScannerView

/**
 * Created by Parsania Hardik on 19-Mar-18.
 */
class ScanActivity : AppCompatActivity(), ZXingScannerView.ResultHandler {

    private var mScannerView: ZXingScannerView? = null

    public override fun onCreate(state: Bundle?) {
        super.onCreate(state)
        mScannerView = ZXingScannerView(this)   // Programmatically initialize the scanner view
        setContentView(mScannerView)                // Set the scanner view as the content view
    }

    public override fun onResume() {
        super.onResume()
        mScannerView!!.setResultHandler(this) // Register ourselves as a handler for scan results.
        mScannerView!!.startCamera()          // Start camera on resume
    }

    public override fun onPause() {
        super.onPause()
        mScannerView!!.stopCamera()           // Stop camera on pause
    }

    override fun handleResult(rawResult: Result) {
        // Do something with the result here
        // Log.v("tag", rawResult.getText()); // Prints scan results
        // Log.v("tag", rawResult.getBarcodeFormat().toString()); // Prints the scan format (qrcode, pdf417 etc.)

        MainActivity.tvresult!!.setText(rawResult.text)
        onBackPressed()

        // If you would like to resume scanning, call this method below:
        //mScannerView.resumeCameraPreview(this);
    }
}

Note: We do not need to update activity_scan.xml file because we will open camera preview here so no need to do anything in layout file.

Step 8: Brief Description of ScanActivity.java

• In onCreate() method, we have set the view as scannerview instead of xml file layout.
• In onResume() method, we have set the resulthandler and started camera preview.
• In onPause() method, we are stopping camera preview.

Step 9: Explaining handleResult() method

 override fun handleResult(rawResult: Result) {
        // Do something with the result here
        // Log.v("tag", rawResult.getText()); // Prints scan results
        // Log.v("tag", rawResult.getBarcodeFormat().toString()); // Prints the scan format (qrcode, pdf417 etc.)

        MainActivity.tvresult!!.setText(rawResult.text)
        onBackPressed()

        // If you would like to resume scanning, call this method below:
        //mScannerView.resumeCameraPreview(this);
    }

• As you can see in above code, we get result object which contains resulting Barcode or QRcode after scanning is completed.
• We will get final result by running result.getText() method and we have set it into TextView of MainActivity.