ProfileActivity: Refactor into clean layers of functionality

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

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

@@ -0,0 +1,75 @@
+package com.wireguard.android;
+
+import android.app.Activity;
+import android.content.ComponentName;
+import android.content.Context;
+import android.content.Intent;
+import android.content.ServiceConnection;
+import android.os.IBinder;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Base class for activities that maintain a connection to a background service.
+ */
+
+abstract class ServiceClientActivity<T> extends Activity implements ServiceConnectionProvider<T> {
+    private final ServiceConnectionCallbacks callbacks = new ServiceConnectionCallbacks();
+    private final List<ServiceConnectionListener<T>> listeners = new ArrayList<>();
+    private T service;
+    private final Class<?> serviceClass;
+
+    protected ServiceClientActivity(Class<?> serviceClass) {
+        this.serviceClass = serviceClass;
+    }
+
+    @Override
+    public void addServiceConnectionListener(ServiceConnectionListener<T> listener) {
+        listeners.add(listener);
+    }
+
+    public T getService() {
+        return service;
+    }
+
+    @Override
+    public void onStart() {
+        super.onStart();
+        bindService(new Intent(this, serviceClass), callbacks, Context.BIND_AUTO_CREATE);
+    }
+
+    @Override
+    public void onStop() {
+        super.onStop();
+        if (service != null) {
+            service = null;
+            unbindService(callbacks);
+            for (ServiceConnectionListener listener : listeners)
+                listener.onServiceDisconnected();
+        }
+    }
+
+    @Override
+    public void removeServiceConnectionListener(ServiceConnectionListener<T> listener) {
+        listeners.remove(listener);
+    }
+
+    private class ServiceConnectionCallbacks implements ServiceConnection {
+        @Override
+        public void onServiceConnected(ComponentName component, IBinder binder) {
+            @SuppressWarnings("unchecked")
+            final T localBinder = (T) binder;
+            service = localBinder;
+            for (ServiceConnectionListener<T> listener : listeners)
+                listener.onServiceConnected(service);
+        }
+
+        @Override
+        public void onServiceDisconnected(ComponentName component) {
+            service = null;
+            for (ServiceConnectionListener<T> listener : listeners)
+                listener.onServiceDisconnected();
+        }
+    }
+}