android get barcode scanner input without edittext

Question

I have a physical barcode scanner and I want to get it's input, i.e the barcode, in the app without having a focused EditText.

I tried adding a KeyListener in my Activity. However, none of its implemented methods (onKeyUp, onKeyDown etc) was called.

Then I added the dispatchKeyEvent, which worked, but is never called as many times as the barcode length. Instead, before the barcode is read, some random button in my view gets focus from the barcode scanner.

String barcode = "";

@Override
public boolean dispatchKeyEvent(KeyEvent e) {
    char pressedKey = (char) e.getUnicodeChar();
    barcode += pressedKey;
    if (e.getKeyCode() == KeyEvent.KEYCODE_ENTER) {
        Toast.makeText(getApplicationContext(), "barcode--->>>" + barcode, Toast.LENGTH_LONG)
                .show();
    }

    return super.dispatchKeyEvent(e);
}

I've seen a few questions out there in SO but none really gave a concrete answer.

Answer 1

For me, for a barcode scanner (USB, reference STA pcs) works the next code:

@Override
public boolean dispatchKeyEvent(KeyEvent e) {

    if(e.getAction()==KeyEvent.ACTION_DOWN){
        Log.i(TAG,"dispatchKeyEvent: "+e.toString());
        char pressedKey = (char) e.getUnicodeChar();
        barcode += pressedKey;
    }
    if (e.getAction()==KeyEvent.ACTION_DOWN && e.getKeyCode() == KeyEvent.KEYCODE_ENTER) {
        Toast.makeText(getApplicationContext(), 
            "barcode--->>>" + barcode, Toast.LENGTH_LONG)
        .show();

        barcode="";
    }

    return super.dispatchKeyEvent(e);
}

Answer 2

First, thank you all. Since my App has to look up the barcode in the DB I had to not add the ENTER_KEY input to the Barcode String, also to prevent any focused button of going off I made the Method return false.

String barcode = "";
@Override
public boolean dispatchKeyEvent(KeyEvent e) {
    if(e.getAction()==KeyEvent.ACTION_DOWN
            && e.getKeyCode() != KeyEvent.KEYCODE_ENTER){ //Not Adding ENTER_KEY to barcode String
        char pressedKey = (char) e.getUnicodeChar();
        barcode += pressedKey;
    }
    if (e.getAction()==KeyEvent.ACTION_DOWN 
            && e.getKeyCode() == KeyEvent.KEYCODE_ENTER) {
        Log.i(TAG,"Barcode Read: "+barcode);
        barcodeLookup(barcode);// or Any method handling the data
        barcode="";
    }
        return false;
}

Answer 3

Using kotlin

private val barcode = StringBuffer()

override fun dispatchKeyEvent(event: KeyEvent?): Boolean {

    if (event?.action == KeyEvent.ACTION_DOWN) {
        val pressedKey = event.unicodeChar.toChar()
        barcode.append(pressedKey)
    }
    if (event?.action == KeyEvent.ACTION_DOWN && event?.keyCode == KeyEvent.KEYCODE_ENTER) {
        Toast.makeText(baseContext, barcode.toString(), Toast.LENGTH_SHORT).show()
        barcode.delete(0, barcode.length)
    }

    return super.dispatchKeyEvent(event)
}

Answer 4

e.getCharacters() should give you the complete barcode. This works for me on a PL-40L device with embedded 2d barcode reader, running Android 5.1 dispatchKeyEvent(KeyEvent e) is triggered once for each read barcode, not for each character in the barcode Hope this helps

Answer 5

DispatchKeyEvent Hardware key events are always delivered to the View currently in focus. They are dispatched starting from the top of the View hierarchy, and then down, until they reach the appropriate destination. If your View (or a child of your View) currently has focus, then you can see the event travel through the dispatchKeyEvent() method. In short, dispatchKeyEvent() will be only called if TextView/EditText is in focus.

Answer 6

You can do it even without any focused View. You need to subscribe for broadcast intent like this:

const val QR_ACTION: String = "android.intent.ACTION_DECODE_DATA"
const val QR_EXTRA: String = "barcode_string"

private val receiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            try {
                Timber.d("Get intent ${intent.action}")
                if (QR_ACTION == intent.action) {
                    if (intent.hasExtra(QR_EXTRA)) {
                       val code = intent.getStringExtra(QR_EXTRA)
                       Timber.d("New QR code $code")
                       // now you have qr code here 
                    }
                }                    }
            } catch (t: Throwable) {
                // handle errors
            }
        }
    }

Please check QR_ACTION and QR_EXTRA in your scanner settings first, it can be different for different brands.