[android] Add error message for unsupported handshake link version

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/AddContactViewModel.java

@@ -8,10 +8,13 @@ import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.UnsupportedVersionException;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.viewmodel.LiveResult;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 
@@ -39,7 +42,7 @@ public class AddContactViewModel extends AndroidViewModel {
 			new MutableLiveData<>();
 	private final MutableLiveEvent<Boolean> remoteLinkEntered =
 			new MutableLiveEvent<>();
-	private final MutableLiveData<Boolean> addContactResult =
+	private final MutableLiveData<LiveResult<Boolean>> addContactResult =
 			new MutableLiveData<>();
 	@Nullable
 	private String remoteHandshakeLink;
@@ -97,15 +100,20 @@ public class AddContactViewModel extends AndroidViewModel {
 		dbExecutor.execute(() -> {
 			try {
 				contactManager.addPendingContact(remoteHandshakeLink, nickname);
-				addContactResult.postValue(true);
+				addContactResult.postValue(new LiveResult<>(true));
+			} catch (UnsupportedVersionException e) {
+				logException(LOG, WARNING, e);
+				addContactResult
+						.postValue(new LiveResult<>(R.string.unsupported_link));
 			} catch (DbException | FormatException e) {
 				logException(LOG, WARNING, e);
-				addContactResult.postValue(false);
+				addContactResult.postValue(
+						new LiveResult<>(R.string.adding_contact_error));
 			}
 		});
 	}
 
-	LiveData<Boolean> getAddContactResult() {
+	public LiveData<LiveResult<Boolean>> getAddContactResult() {
 		return addContactResult;
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/NicknameFragment.java

@@ -103,15 +103,15 @@ public class NicknameFragment extends BaseFragment {
 		addButton.setVisibility(INVISIBLE);
 		progressBar.setVisibility(VISIBLE);
 
-		viewModel.getAddContactResult().observe(this, success -> {
-			if (success == null) return;
-			if (success) {
+		viewModel.getAddContactResult().observe(this, result -> {
+			if (result == null) return;
+			if (result.hasError()) {
+				Toast.makeText(getContext(), result.getErrorRes(), LENGTH_LONG)
+						.show();
+			} else {
 				Intent intent = new Intent(getActivity(),
 						PendingContactListActivity.class);
 				startActivity(intent);
-			} else {
-				Toast.makeText(getContext(), R.string.adding_contact_error,
-						LENGTH_LONG).show();
 			}
 			finish();
 		});

briar-android/src/main/java/org/briarproject/briar/android/viewmodel/LiveResult.java

@@ -0,0 +1,40 @@
+package org.briarproject.briar.android.viewmodel;
+
+import android.support.annotation.Nullable;
+import android.support.annotation.StringRes;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public class LiveResult<T> {
+
+	@Nullable
+	private T result;
+	@StringRes
+	private int errorRes;
+
+	public LiveResult(T result) {
+		this.result = result;
+		this.errorRes = 0;
+	}
+
+	public LiveResult(@StringRes int errorRes) {
+		this.result = null;
+		this.errorRes = errorRes;
+	}
+
+	@Nullable
+	public T getResultOrNull() {
+		return result;
+	}
+
+	@StringRes
+	public int getErrorRes() {
+		return errorRes;
+	}
+
+	public boolean hasError() {
+		return errorRes != 0;
+	}
+
+}

briar-android/src/main/res/values/strings.xml

@@ -200,6 +200,7 @@
 	<string name="own_link_error">Enter your contact\'s link, not your own</string>
 	<string name="nickname_missing">Please enter a nickname</string>
 	<string name="invalid_link">Invalid link</string>
+	<string name="unsupported_link">This link is not supported. Please upgrade Briar and try again.</string>
 	<string name="intent_own_link">You opened your own link. Use the one of the contact you want to add!</string>
 	<string name="missing_link">Please enter a link</string>
 	<!-- This is a numeral indicating the first step in a series of screens -->