Add dialog to appear when user wants to learn more

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationSettingsFragment.java

@@ -8,6 +8,7 @@ import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.Button;
 import android.widget.Switch;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
@@ -96,6 +97,11 @@ public class ConversationSettingsFragment extends BaseFragment {
 					viewModel.setAutoDeleteTimerEnabled(value);
 				});
 
+		Button buttonLearnMore = contentView.findViewById(R.id.buttonLearnMore);
+		buttonLearnMore.setOnClickListener(e -> {
+			showLearnMoreDialog();
+		});
+
 		viewModel = ViewModelProviders.of(requireActivity(), viewModelFactory)
 				.get(ConversationViewModel.class);
 
@@ -145,10 +151,17 @@ public class ConversationSettingsFragment extends BaseFragment {
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
 		if (item.getItemId() == R.id.action_help) {
-			// TODO: display dialog
+			showLearnMoreDialog();
 			return true;
 		}
 		return super.onOptionsItemSelected(item);
 	}
 
+	private void showLearnMoreDialog() {
+		ConversationSettingsLearnMoreDialog
+				dialog = new ConversationSettingsLearnMoreDialog();
+		dialog.show(requireActivity().getSupportFragmentManager(),
+				ConversationSettingsLearnMoreDialog.TAG);
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationSettingsLearnMoreDialog.java

@@ -0,0 +1,44 @@
+package org.briarproject.briar.android.conversation;
+
+import android.app.Dialog;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.briar.R;
+
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.FragmentActivity;
+
+@MethodsNotNullByDefault
+public class ConversationSettingsLearnMoreDialog extends DialogFragment {
+
+	final static String TAG =
+			ConversationSettingsLearnMoreDialog.class.getName();
+
+	static ConversationSettingsLearnMoreDialog newInstance() {
+		return new ConversationSettingsLearnMoreDialog();
+	}
+
+	@Override
+	public Dialog onCreateDialog(Bundle savedInstanceState) {
+		FragmentActivity activity = requireActivity();
+
+		AlertDialog.Builder builder =
+				new AlertDialog.Builder(activity, R.style.BriarDialogTheme);
+
+		LayoutInflater inflater = LayoutInflater.from(getContext());
+		View view = inflater.inflate(
+				R.layout.fragment_conversation_settings_learn_more, null);
+		builder.setView(view);
+
+		builder.setTitle(R.string.disappearing_messages_title);
+		builder.setNeutralButton(R.string.ok, null);
+
+		return builder.create();
+	}
+
+
+}

briar-android/src/main/res/layout/fragment_conversation_settings_learn_more.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:paddingHorizontal="?dialogPreferredPadding">
+
+	<TextView
+		android:id="@+id/textView"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:text="@string/disappearing_messages_explanation_long"
+		app:layout_constraintBottom_toBottomOf="parent"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>