Replaced MLKit with ZXing for QR code scanning (#1630)

* Replaced MLKit with ZXing for QR code scanning

* Adjusted some comment spacing

* Adjusted some comment phrasing

* Renamed MaybeScanQrCode to QRScannerScreen & removed double-import of ZXing core + removed ZXing android-integration

---------

Co-authored-by: alansley <aclansley@gmail.com>

app/build.gradle

@@ -274,8 +274,6 @@ dependencies {
     implementation 'pl.tajchert:waitingdots:0.1.0'
     implementation 'com.vanniktech:android-image-cropper:4.5.0'
     implementation 'com.melnykov:floatingactionbutton:1.3.0'
-    implementation 'com.google.zxing:android-integration:3.1.0'
-    implementation 'com.google.zxing:core:3.2.1'
     implementation ('com.davemorrissey.labs:subsampling-scale-image-view:3.6.0') {
         exclude group: 'com.android.support', module: 'support-annotations'
     }
@@ -352,7 +350,6 @@ dependencies {
     testImplementation 'org.conscrypt:conscrypt-openjdk-uber:2.5.2' // For Robolectric
     testImplementation 'app.cash.turbine:turbine:1.1.0'
 
-
     implementation 'com.github.bumptech.glide:compose:1.0.0-alpha.5'
     implementation "androidx.compose.ui:ui:$composeVersion"
     implementation "androidx.compose.animation:animation:$composeVersion"
@@ -371,7 +368,8 @@ dependencies {
     implementation "androidx.camera:camera-lifecycle:1.3.2"
     implementation "androidx.camera:camera-view:1.3.2"
 
-    implementation "com.google.mlkit:barcode-scanning:17.2.0"
+    // Note: ZXing 3.5.3 is the latest stable release as of 2024/08/21
+    implementation "com.google.zxing:core:$zxingVersion"
 }
 
 static def getLastCommitTimestamp() {

app/src/main/java/org/thoughtcrime/securesms/conversation/start/newmessage/NewMessage.kt

@@ -48,7 +48,7 @@ import org.thoughtcrime.securesms.ui.LoadingArcOr
 import org.thoughtcrime.securesms.ui.components.AppBarCloseIcon
 import org.thoughtcrime.securesms.ui.components.BackAppBar
 import org.thoughtcrime.securesms.ui.components.BorderlessButtonWithIcon
-import org.thoughtcrime.securesms.ui.components.MaybeScanQrCode
+import org.thoughtcrime.securesms.ui.components.QRScannerScreen
 import org.thoughtcrime.securesms.ui.components.PrimaryOutlineButton
 import org.thoughtcrime.securesms.ui.components.SessionOutlinedTextField
 import org.thoughtcrime.securesms.ui.components.SessionTabRow
@@ -89,7 +89,7 @@ internal fun NewMessage(
         HorizontalPager(pagerState) {
             when (TITLES[it]) {
                 R.string.enter_account_id -> EnterAccountId(state, callbacks, onHelp)
-                R.string.qrScan -> MaybeScanQrCode(qrErrors, onScan = callbacks::onScanQrCode)
+                R.string.qrScan -> QRScannerScreen(qrErrors, onScan = callbacks::onScanQrCode)
             }
         }
     }

app/src/main/java/org/thoughtcrime/securesms/onboarding/loadaccount/LoadAccount.kt

@@ -26,7 +26,7 @@ import network.loki.messenger.R
 import org.thoughtcrime.securesms.onboarding.ui.ContinuePrimaryOutlineButton
 import org.thoughtcrime.securesms.ui.theme.LocalDimensions
 import org.thoughtcrime.securesms.ui.theme.PreviewTheme
-import org.thoughtcrime.securesms.ui.components.MaybeScanQrCode
+import org.thoughtcrime.securesms.ui.components.QRScannerScreen
 import org.thoughtcrime.securesms.ui.components.SessionOutlinedTextField
 import org.thoughtcrime.securesms.ui.components.SessionTabRow
 import org.thoughtcrime.securesms.ui.theme.LocalType
@@ -52,7 +52,7 @@ internal fun LoadAccountScreen(
         ) { page ->
             when (TITLES[page]) {
                 R.string.sessionRecoveryPassword -> RecoveryPassword(state, onChange, onContinue)
-                R.string.qrScan -> MaybeScanQrCode(qrErrors, onScan = onScan)
+                R.string.qrScan -> QRScannerScreen(qrErrors, onScan = onScan)
             }
         }
     }

app/src/main/java/org/thoughtcrime/securesms/onboarding/loadaccount/LoadAccountActivity.kt

@@ -6,6 +6,7 @@ import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.lifecycle.lifecycleScope
 import dagger.hilt.android.AndroidEntryPoint
+import javax.inject.Inject
 import kotlinx.coroutines.launch
 import network.loki.messenger.R
 import org.session.libsession.utilities.TextSecurePreferences
@@ -14,7 +15,6 @@ import org.thoughtcrime.securesms.onboarding.manager.LoadAccountManager
 import org.thoughtcrime.securesms.onboarding.messagenotifications.MessageNotificationsActivity
 import org.thoughtcrime.securesms.ui.setComposeContent
 import org.thoughtcrime.securesms.util.start
-import javax.inject.Inject
 
 @AndroidEntryPoint
 class LoadAccountActivity : BaseActionBarActivity() {

app/src/main/java/org/thoughtcrime/securesms/onboarding/loadaccount/LoadAccountViewModel.kt

@@ -4,6 +4,7 @@ import android.app.Application
 import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import javax.inject.Inject
 import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -17,7 +18,6 @@ import org.session.libsignal.crypto.MnemonicCodec
 import org.session.libsignal.crypto.MnemonicCodec.DecodingError.InputTooShort
 import org.session.libsignal.crypto.MnemonicCodec.DecodingError.InvalidWord
 import org.thoughtcrime.securesms.crypto.MnemonicUtilities
-import javax.inject.Inject
 
 class LoadAccountEvent(val mnemonic: ByteArray)
 
@@ -54,6 +54,7 @@ internal class LoadAccountViewModel @Inject constructor(
     }
 
     fun onScanQrCode(string: String) {
+
         viewModelScope.launch {
             try {
                 codec.decodeMnemonicOrHexAsByteArray(string).let(::onSuccess)

app/src/main/java/org/thoughtcrime/securesms/preferences/QRCodeActivity.kt

@@ -27,7 +27,7 @@ import org.thoughtcrime.securesms.conversation.v2.ConversationActivityV2
 import org.thoughtcrime.securesms.database.threadDatabase
 import org.thoughtcrime.securesms.ui.theme.LocalDimensions
 import org.thoughtcrime.securesms.ui.theme.LocalColors
-import org.thoughtcrime.securesms.ui.components.MaybeScanQrCode
+import org.thoughtcrime.securesms.ui.components.QRScannerScreen
 import org.thoughtcrime.securesms.ui.components.QrImage
 import org.thoughtcrime.securesms.ui.components.SessionTabRow
 import org.thoughtcrime.securesms.ui.contentDescription
@@ -54,7 +54,7 @@ class QRCodeActivity : PassphraseRequiredActionBarActivity() {
         }
     }
 
-    fun onScan(string: String) {
+    private fun onScan(string: String) {
         if (!PublicKeyValidation.isValid(string)) {
             errors.tryEmit(getString(R.string.this_qr_code_does_not_contain_an_account_id))
         } else if (!isFinishing) {
@@ -83,7 +83,7 @@ private fun Tabs(accountId: String, errors: Flow<String>, onScan: (String) -> Un
         ) { page ->
             when (TITLES[page]) {
                 R.string.view -> QrPage(accountId)
-                R.string.scan -> MaybeScanQrCode(errors, onScan = onScan)
+                R.string.scan -> QRScannerScreen(errors, onScan = onScan)
             }
         }
     }

app/src/main/java/org/thoughtcrime/securesms/ui/components/QR.kt

@@ -47,25 +47,27 @@ import com.google.accompanist.permissions.ExperimentalPermissionsApi
 import com.google.accompanist.permissions.isGranted
 import com.google.accompanist.permissions.rememberPermissionState
 import com.google.accompanist.permissions.shouldShowRationale
-import com.google.mlkit.vision.barcode.BarcodeScanner
-import com.google.mlkit.vision.barcode.BarcodeScannerOptions
-import com.google.mlkit.vision.barcode.BarcodeScanning
-import com.google.mlkit.vision.barcode.common.Barcode
-import com.google.mlkit.vision.common.InputImage
+import com.google.zxing.BinaryBitmap
+import com.google.zxing.ChecksumException
+import com.google.zxing.FormatException
+import com.google.zxing.NotFoundException
+import com.google.zxing.PlanarYUVLuminanceSource
+import com.google.zxing.Result
+import com.google.zxing.common.HybridBinarizer
+import com.google.zxing.qrcode.QRCodeReader
+import java.util.concurrent.Executors
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.launch
 import network.loki.messenger.R
 import org.session.libsignal.utilities.Log
-import org.thoughtcrime.securesms.ui.theme.LocalColors
 import org.thoughtcrime.securesms.ui.theme.LocalDimensions
 import org.thoughtcrime.securesms.ui.theme.LocalType
-import java.util.concurrent.Executors
 
 private const val TAG = "NewMessageFragment"
 
 @OptIn(ExperimentalPermissionsApi::class)
 @Composable
-fun MaybeScanQrCode(
+fun QRScannerScreen(
         errors: Flow<String>,
         onClickSettings: () -> Unit = LocalContext.current.run { {
             Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
@@ -137,17 +139,13 @@ fun ScanQrCode(errors: Flow<String>, onScan: (String) -> Unit) {
     runCatching {
         cameraProvider.get().unbindAll()
 
-        val options = BarcodeScannerOptions.Builder()
-            .setBarcodeFormats(Barcode.FORMAT_QR_CODE)
-            .build()
-        val scanner = BarcodeScanning.getClient(options)
-
         cameraProvider.get().bindToLifecycle(
             LocalLifecycleOwner.current,
             selector,
             preview,
-            buildAnalysisUseCase(scanner, onScan)
+            buildAnalysisUseCase(QRCodeReader(), onScan)
         )
+
     }.onFailure { Log.e(TAG, "error binding camera", it) }
 
     DisposableEffect(cameraProvider) {
@@ -211,32 +209,51 @@ fun ScanQrCode(errors: Flow<String>, onScan: (String) -> Unit) {
 
 @SuppressLint("UnsafeOptInUsageError")
 private fun buildAnalysisUseCase(
-    scanner: BarcodeScanner,
+    scanner: QRCodeReader,
     onBarcodeScanned: (String) -> Unit
 ): ImageAnalysis = ImageAnalysis.Builder()
     .setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
     .build().apply {
-        setAnalyzer(Executors.newSingleThreadExecutor(), Analyzer(scanner, onBarcodeScanned))
+        setAnalyzer(Executors.newSingleThreadExecutor(), QRCodeAnalyzer(scanner, onBarcodeScanned))
     }
 
-class Analyzer(
-    private val scanner: BarcodeScanner,
+class QRCodeAnalyzer(
+    private val qrCodeReader: QRCodeReader,
     private val onBarcodeScanned: (String) -> Unit
 ): ImageAnalysis.Analyzer {
+
+    // Note: This analyze method is called once per frame of the camera feed.
     @SuppressLint("UnsafeOptInUsageError")
     override fun analyze(image: ImageProxy) {
-        InputImage.fromMediaImage(
-            image.image!!,
-            image.imageInfo.rotationDegrees
-        ).let(scanner::process).apply {
-            addOnSuccessListener { barcodes ->
-                barcodes.forEach {
-                    it.rawValue?.let(onBarcodeScanned)
-                }
-            }
-            addOnCompleteListener {
-                image.close()
-            }
+        // Grab the image data as a byte array so we can generate a PlanarYUVLuminanceSource from it
+        val buffer = image.planes[0].buffer
+        buffer.rewind()
+        val imageBytes = ByteArray(buffer.capacity())
+        buffer.get(imageBytes) // IMPORTANT: This transfers data from the buffer INTO the imageBytes array, although it looks like it would go the other way around!
+
+        // ZXing requires data as a BinaryBitmap to scan for QR codes, and to generate that we need to feed it a PlanarYUVLuminanceSource
+        val luminanceSource = PlanarYUVLuminanceSource(imageBytes, image.width, image.height, 0, 0, image.width, image.height, false)
+        val binaryBitmap = BinaryBitmap(HybridBinarizer(luminanceSource))
+
+        // Attempt to extract a QR code from the binary bitmap, and pass it through to our `onBarcodeScanned` method if we find one
+        try {
+            val result: Result = qrCodeReader.decode(binaryBitmap)
+            val resultTxt = result.text
+            // No need to close the image here - it'll always make it to the end, and calling `onBarcodeScanned`
+            // with a valid contact / recovery phrase / community code will stop calling this `analyze` method.
+            onBarcodeScanned(resultTxt)
         }
+        catch (nfe: NotFoundException) { /* Hits if there is no QR code in the image           */ }
+        catch (fe: FormatException)    { /* Hits if we found a QR code but failed to decode it */ }
+        catch (ce: ChecksumException)  { /* Hits if we found a QR code which is corrupted      */ }
+        catch (e: Exception) {
+            // Hits if there's a genuine problem
+            Log.e("QR", "error", e)
+        }
+
+        // Remember to close the image when we're done with it!
+        // IMPORTANT: It is CLOSING the image that allows this method to run again! If we don't
+        // close the image this method runs precisely ONCE and that's it, which is essentially useless.
+        image.close()
     }
 }

app/src/main/java/org/thoughtcrime/securesms/util/QRCodeUtilities.kt

@@ -6,6 +6,7 @@ import com.google.zxing.BarcodeFormat
 import com.google.zxing.EncodeHintType
 import com.google.zxing.qrcode.QRCodeWriter
 import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel
+import org.session.libsignal.utilities.Log
 
 object QRCodeUtilities {
 
@@ -34,5 +35,8 @@ object QRCodeUtilities {
                 }
             }
         }
-    }.getOrNull()
+    }.getOrElse {
+        Log.e("QRCodeUtilities", "Failed to generate QR Code", it)
+        null
+    }
 }

gradle.properties

@@ -40,6 +40,7 @@ phraseVersion=1.2.0
 preferenceVersion=1.2.0
 protobufVersion=2.5.0
 testCoreVersion=1.5.0
+zxingVersion=3.5.3
 android.defaults.buildfeatures.buildconfig=true
 android.nonTransitiveRClass=false
 android.nonFinalResIds=false