1 files changed, 94 insertions, 0 deletions
diff --git a/app/src/main/java/com/wireguard/android/activity/BaseActivity.java b/app/src/main/java/com/wireguard/android/activity/BaseActivity.java
new file mode 100644
index 00000000..4bd3407e
--- /dev/null
+++ b/app/src/main/java/com/wireguard/android/activity/BaseActivity.java
@@ -0,0 +1,94 @@
+package com.wireguard.android.activity;
+
+import android.app.Activity;
+import android.databinding.CallbackRegistry;
+import android.databinding.CallbackRegistry.NotifierCallback;
+import android.os.Bundle;
+
+import com.wireguard.android.Application;
+import com.wireguard.android.model.Tunnel;
+import com.wireguard.android.model.TunnelManager;
+
+import java.util.Objects;
+
+/**
+ * Base class for activities that need to remember the currently-selected tunnel.
+ */
+
+public abstract class BaseActivity extends Activity {
+    private static final String TAG = BaseActivity.class.getSimpleName();
+
+    private final SelectionChangeRegistry selectionChangeRegistry = new SelectionChangeRegistry();
+    private Tunnel selectedTunnel;
+
+    public void addOnSelectedTunnelChangedListener(
+            final OnSelectedTunnelChangedListener listener) {
+        selectionChangeRegistry.add(listener);
+    }
+
+    public Tunnel getSelectedTunnel() {
+        return selectedTunnel;
+    }
+
+    @Override
+    protected void onCreate(final Bundle savedInstanceState) {
+        // Restore the saved tunnel if there is one; otherwise grab it from the arguments.
+        String savedTunnelName = null;
+        if (savedInstanceState != null)
+            savedTunnelName = savedInstanceState.getString(TunnelManager.KEY_SELECTED_TUNNEL);
+        else if (getIntent() != null)
+            savedTunnelName = getIntent().getStringExtra(TunnelManager.KEY_SELECTED_TUNNEL);
+        if (savedTunnelName != null) {
+            final TunnelManager manager = Application.getComponent().getTunnelManager();
+            selectedTunnel = manager.getTunnels().get(savedTunnelName);
+        }
+        // The selected tunnel must be set before the superclass method recreates fragments.
+        super.onCreate(savedInstanceState);
+    }
+
+    @Override
+    protected void onSaveInstanceState(final Bundle outState) {
+        if (selectedTunnel != null)
+            outState.putString(TunnelManager.KEY_SELECTED_TUNNEL, selectedTunnel.getName());
+        super.onSaveInstanceState(outState);
+    }
+
+    protected abstract Tunnel onSelectedTunnelChanged(Tunnel oldTunnel, Tunnel newTunnel);
+
+    public void removeOnSelectedTunnelChangedListener(
+            final OnSelectedTunnelChangedListener listener) {
+        selectionChangeRegistry.remove(listener);
+    }
+
+    public void setSelectedTunnel(final Tunnel tunnel) {
+        final Tunnel oldTunnel = selectedTunnel;
+        if (Objects.equals(oldTunnel, tunnel))
+            return;
+        // Give the activity a chance to override the tunnel change.
+        selectedTunnel = onSelectedTunnelChanged(oldTunnel, tunnel);
+        if (Objects.equals(oldTunnel, selectedTunnel))
+            return;
+        selectionChangeRegistry.notifyCallbacks(oldTunnel, 0, selectedTunnel);
+    }
+
+    public interface OnSelectedTunnelChangedListener {
+        void onSelectedTunnelChanged(Tunnel oldTunnel, Tunnel newTunnel);
+    }
+
+    private static final class SelectionChangeNotifier
+            extends NotifierCallback<OnSelectedTunnelChangedListener, Tunnel, Tunnel> {
+        @Override
+        public void onNotifyCallback(final OnSelectedTunnelChangedListener listener,
+                                     final Tunnel oldTunnel, final int ignored,
+                                     final Tunnel newTunnel) {
+            listener.onSelectedTunnelChanged(oldTunnel, newTunnel);
+        }
+    }
+
+    private static final class SelectionChangeRegistry
+            extends CallbackRegistry<OnSelectedTunnelChangedListener, Tunnel, Tunnel> {
+        private SelectionChangeRegistry() {
+            super(new SelectionChangeNotifier());
+        }
+    }
+}