Add force legacy QR scanning switch.

app/src/main/java/org/thoughtcrime/securesms/DeviceAddFragment.java

@@ -18,6 +18,7 @@ import androidx.core.view.ViewCompat;
 
 import org.signal.qr.QrScannerView;
 import org.signal.qr.kitkat.ScanListener;
+import org.thoughtcrime.securesms.util.FeatureFlags;
 import org.thoughtcrime.securesms.util.LifecycleDisposable;
 import org.thoughtcrime.securesms.util.ViewUtil;
 
@@ -56,7 +57,7 @@ public class DeviceAddFragment extends LoggingFragment {
       });
     }
 
-    scannerView.start(getViewLifecycleOwner());
+    scannerView.start(getViewLifecycleOwner(), FeatureFlags.useQrLegacyScan());
 
     lifecycleDisposable.bindTo(getViewLifecycleOwner());
 

app/src/main/java/org/thoughtcrime/securesms/util/FeatureFlags.java

@@ -97,6 +97,7 @@ public final class FeatureFlags {
   private static final String USE_FCM_FOREGROUND_SERVICE        = "android.useFcmForegroundService.3";
   private static final String STORIES_AUTO_DOWNLOAD_MAXIMUM     = "android.stories.autoDownloadMaximum";
   private static final String GIFT_BADGES                       = "android.giftBadges.3";
+  private static final String USE_QR_LEGACY_SCAN                = "android.qr.legacy_scan";
 
   /**
    * We will only store remote values for flags in this set. If you want a flag to be controllable
@@ -146,7 +147,8 @@ public final class FeatureFlags {
       PAYMENTS_COUNTRY_BLOCKLIST,
       USE_FCM_FOREGROUND_SERVICE,
       STORIES_AUTO_DOWNLOAD_MAXIMUM,
-      GIFT_BADGES
+      GIFT_BADGES,
+      USE_QR_LEGACY_SCAN
   );
 
   @VisibleForTesting
@@ -206,7 +208,8 @@ public final class FeatureFlags {
       USE_HARDWARE_AEC_IF_OLD,
       USE_AEC3,
       PAYMENTS_COUNTRY_BLOCKLIST,
-      USE_FCM_FOREGROUND_SERVICE
+      USE_FCM_FOREGROUND_SERVICE,
+      USE_QR_LEGACY_SCAN
   );
 
   /**
@@ -510,6 +513,10 @@ public final class FeatureFlags {
     return getBoolean(GIFT_BADGES, Environment.IS_STAGING);
   }
 
+  public static boolean useQrLegacyScan() {
+    return getBoolean(USE_QR_LEGACY_SCAN, false);
+  }
+
   /** Only for rendering debug info. */
   public static synchronized @NonNull Map<String, Object> getMemoryValues() {
     return new TreeMap<>(REMOTE_VALUES);

qr/lib/src/main/java/org/signal/qr/QrScannerView.kt

@@ -8,6 +8,7 @@ import androidx.lifecycle.DefaultLifecycleObserver
 import androidx.lifecycle.LifecycleOwner
 import io.reactivex.rxjava3.core.Observable
 import io.reactivex.rxjava3.subjects.PublishSubject
+import org.signal.core.util.logging.Log
 
 /**
  * View for starting up a camera and scanning a QR-Code. Safe to use on an API version and
@@ -19,15 +20,15 @@ class QrScannerView @JvmOverloads constructor(
   context: Context,
   attrs: AttributeSet? = null,
   defStyleAttr: Int = 0
-) : FrameLayout(context, attrs, defStyleAttr), ScannerView {
+) : FrameLayout(context, attrs, defStyleAttr) {
 
-  private val scannerView: ScannerView
+  private var scannerView: ScannerView? = null
   private val qrDataPublish: PublishSubject<String> = PublishSubject.create()
 
   val qrData: Observable<String> = qrDataPublish
 
-  init {
+  private fun initScannerView(forceLegacy: Boolean) {
-    val scannerView: FrameLayout = if (Build.VERSION.SDK_INT >= 21) {
+    val scannerView: FrameLayout = if (Build.VERSION.SDK_INT >= 21 && !forceLegacy) {
       ScannerView21(context) { qrDataPublish.onNext(it) }
     } else {
       ScannerView19(context) { qrDataPublish.onNext(it) }
@@ -39,12 +40,23 @@ class QrScannerView @JvmOverloads constructor(
     this.scannerView = (scannerView as ScannerView)
   }
 
-  override fun start(lifecycleOwner: LifecycleOwner) {
+  fun start(lifecycleOwner: LifecycleOwner, forceLegacy: Boolean = false) {
-    scannerView.start(lifecycleOwner)
+    if (scannerView != null) {
+      Log.w(TAG, "Attempt to start scanning that has already started")
+      return
+    }
+
+    initScannerView(forceLegacy)
+
+    scannerView?.start(lifecycleOwner)
     lifecycleOwner.lifecycle.addObserver(object : DefaultLifecycleObserver {
       override fun onDestroy(owner: LifecycleOwner) {
         qrDataPublish.onComplete()
       }
     })
   }
+
+  companion object {
+    private val TAG = Log.tag(QrScannerView::class.java)
+  }
 }