feat: added cancel for ux (#198)

* feat: added cancel for ux

* re(feat): apply cancel functionality to merged

* fix: return true

* fix(syntax): flashButton and cancelButton

* fix: syntax

android/src/main/kotlin/de/mintware/barcode_scan/BarcodeScannerActivity.kt

@@ -20,6 +20,7 @@ class BarcodeScannerActivity : Activity(), ZXingScannerView.ResultHandler {
 
     companion object {
         const val TOGGLE_FLASH = 200
+        const val CANCEL = 300
         const val EXTRA_CONFIG = "config"
         const val EXTRA_RESULT = "scan_result"
         const val EXTRA_ERROR_CODE = "error_code"
@@ -76,8 +77,12 @@ class BarcodeScannerActivity : Activity(), ZXingScannerView.ResultHandler {
         if (scannerView?.flash == true) {
             buttonText = config.stringsMap["flash_off"]
         }
-        val item = menu.add(0, TOGGLE_FLASH, 0, buttonText)
-        item.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS)
+        val flashButton = menu.add(0, TOGGLE_FLASH, 0, buttonText)
+        flashButton.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS)
+
+        val cancelButton = menu.add(0, CANCEL, 0, config.stringsMap["cancel"])
+        cancelButton.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS)
+
         return super.onCreateOptionsMenu(menu)
     }
 
@@ -87,6 +92,11 @@ class BarcodeScannerActivity : Activity(), ZXingScannerView.ResultHandler {
             this.invalidateOptionsMenu()
             return true
         }
+        if (item.itemId == CANCEL) {
+            setResult(RESULT_CANCELED)
+            finish()
+            return true
+        }
         return super.onOptionsItemSelected(item)
     }
 
@@ -151,4 +161,4 @@ class BarcodeScannerActivity : Activity(), ZXingScannerView.ResultHandler {
 
         return types
     }
-}
+}