ControllerInterface/Android: Implement hotplug

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/features/input/model/ControllerInterface.java

@@ -2,15 +2,50 @@
 
 package org.dolphinemu.dolphinemu.features.input.model;
 
+import android.content.Context;
+import android.hardware.input.InputManager;
+import android.os.Handler;
 import android.view.KeyEvent;
 import android.view.MotionEvent;
 
+import androidx.annotation.Keep;
+
+import org.dolphinemu.dolphinemu.DolphinApplication;
+import org.dolphinemu.dolphinemu.utils.LooperThread;
+
 /**
  * This class interfaces with the native ControllerInterface,
  * which is where the emulator core gets inputs from.
  */
 public final class ControllerInterface
 {
+  private static final class InputDeviceListener implements InputManager.InputDeviceListener
+  {
+    @Override
+    public void onInputDeviceAdded(int deviceId)
+    {
+      // Simple implementation for now. We could do something fancier if we wanted to.
+      refreshDevices();
+    }
+
+    @Override
+    public void onInputDeviceRemoved(int deviceId)
+    {
+      // Simple implementation for now. We could do something fancier if we wanted to.
+      refreshDevices();
+    }
+
+    @Override
+    public void onInputDeviceChanged(int deviceId)
+    {
+      // Simple implementation for now. We could do something fancier if we wanted to.
+      refreshDevices();
+    }
+  }
+
+  private static InputDeviceListener mInputDeviceListener;
+  private static LooperThread mLooperThread;
+
   /**
    * Activities which want to pass on inputs to native code
    * should call this in their own dispatchKeyEvent method.
@@ -28,4 +63,41 @@ public final class ControllerInterface
    * false if the event should be passed on to the default dispatchGenericMotionEvent.
    */
   public static native boolean dispatchGenericMotionEvent(MotionEvent event);
+
+  /**
+   * Rescans for input devices.
+   */
+  public static native void refreshDevices();
+
+  @Keep
+  private static void registerInputDeviceListener()
+  {
+    if (mLooperThread == null)
+    {
+      mLooperThread = new LooperThread("Hotplug thread");
+      mLooperThread.start();
+    }
+
+    if (mInputDeviceListener == null)
+    {
+      InputManager im = (InputManager)
+              DolphinApplication.getAppContext().getSystemService(Context.INPUT_SERVICE);
+
+      mInputDeviceListener = new InputDeviceListener();
+      im.registerInputDeviceListener(mInputDeviceListener, new Handler(mLooperThread.getLooper()));
+    }
+  }
+
+  @Keep
+  private static void unregisterInputDeviceListener()
+  {
+    if (mInputDeviceListener != null)
+    {
+      InputManager im = (InputManager)
+              DolphinApplication.getAppContext().getSystemService(Context.INPUT_SERVICE);
+
+      im.unregisterInputDeviceListener(mInputDeviceListener);
+      mInputDeviceListener = null;
+    }
+  }
 }

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/utils/LooperThread.java

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.dolphinemu.dolphinemu.utils;
+
+import android.os.Looper;
+
+public class LooperThread extends Thread
+{
+  private Looper mLooper;
+
+  public LooperThread()
+  {
+    super();
+  }
+
+  public LooperThread(String name)
+  {
+    super(name);
+  }
+
+  @Override
+  public void run()
+  {
+    Looper.prepare();
+
+    synchronized (this)
+    {
+      mLooper = Looper.myLooper();
+      notifyAll();
+    }
+
+    Looper.loop();
+  }
+
+  public Looper getLooper()
+  {
+    if (!isAlive())
+    {
+      throw new IllegalStateException();
+    }
+
+    synchronized (this)
+    {
+      while (mLooper == null)
+      {
+        try
+        {
+          wait();
+        }
+        catch (InterruptedException ignored)
+        {
+        }
+      }
+    }
+
+    return mLooper;
+  }
+}