PlaceholderFragment: Simple fragment that shows a message

This is used for the detail pane when no profile is selected.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/android/PlaceholderFragment.java

@@ -0,0 +1,18 @@
+package com.wireguard.android;
+
+import android.app.Fragment;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+/**
+ * Fragment containing a simple placeholder message.
+ */
+
+public class PlaceholderFragment extends Fragment {
+    @Override
+    public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {
+        return inflater.inflate(R.layout.placeholder_fragment, parent, false);
+    }
+}

app/src/main/res/layout/placeholder_fragment.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:gravity="center"
+    android:text="@string/placeholder_text" />

app/src/main/res/values/strings.xml

@@ -3,5 +3,6 @@
     <string name="app_name">WireGuard</string>
     <string name="connected">Connected</string>
     <string name="disconnected">Disconnected</string>
+    <string name="placeholder_text">No profile selected.</string>
     <string name="settings">Settings</string>
 </resources>