Cancel biometric prompt on pause

app/src/main/java/eu/faircode/email/ActivityMain.java

@@ -206,7 +206,7 @@ public class ActivityMain extends ActivityBase implements FragmentManager.OnBack
             };
 
             if (Helper.shouldAuthenticate(this))
-                Helper.authenticate(ActivityMain.this, null,
+                Helper.authenticate(ActivityMain.this, ActivityMain.this, null,
                         new Runnable() {
                             @Override
                             public void run() {

app/src/main/java/eu/faircode/email/FragmentOptionsPrivacy.java

@@ -159,7 +159,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
             public void onClick(View v) {
                 final boolean biometrics = prefs.getBoolean("biometrics", false);
 
-                Helper.authenticate(getActivity(), biometrics, new Runnable() {
+                Helper.authenticate(getActivity(), getViewLifecycleOwner(), biometrics, new Runnable() {
                     @Override
                     public void run() {
                         try {

app/src/main/java/eu/faircode/email/Helper.java

@@ -44,7 +44,6 @@ import android.os.LocaleList;
 import android.os.Parcel;
 import android.os.PowerManager;
 import android.os.StatFs;
-import android.provider.DocumentsContract;
 import android.security.KeyChain;
 import android.security.KeyChainAliasCallback;
 import android.security.KeyChainException;
@@ -1079,7 +1078,7 @@ public class Helper {
         return false;
     }
 
-    static void authenticate(final FragmentActivity activity,
+    static void authenticate(final FragmentActivity activity, final LifecycleOwner owner,
                              Boolean enabled, final
                              Runnable authenticated, final Runnable cancelled) {
         final Handler handler = new Handler();
@@ -1104,7 +1103,7 @@ public class Helper {
                     ? R.string.title_setup_biometrics_disable
                     : R.string.title_setup_biometrics_enable));
 
-            BiometricPrompt prompt = new BiometricPrompt(activity, executor,
+            final BiometricPrompt prompt = new BiometricPrompt(activity, executor,
                     new BiometricPrompt.AuthenticationCallback() {
                         @Override
                         public void onAuthenticationError(final int errorCode, @NonNull final CharSequence errString) {
@@ -1140,6 +1139,16 @@ public class Helper {
                     });
 
             prompt.authenticate(info.build());
+
+            owner.getLifecycle().addObserver(new LifecycleObserver() {
+                @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
+                public void onPause() {
+                    prompt.cancelAuthentication();
+                    handler.post(cancelled);
+                    owner.getLifecycle().removeObserver(this);
+                }
+            });
+
         } else {
             final View dview = LayoutInflater.from(activity).inflate(R.layout.dialog_pin_ask, null);
             final EditText etPin = dview.findViewById(R.id.etPin);