Use weak references for the static Activity in NativeLibrary.

Add in null checks as well.

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/NativeLibrary.java

@@ -12,13 +12,15 @@ import android.widget.Toast;
 import org.dolphinemu.dolphinemu.activities.EmulationActivity;
 import org.dolphinemu.dolphinemu.utils.Log;
 
+import java.lang.ref.WeakReference;
+
 /**
  * Class which contains methods that interact
  * with the native side of the Dolphin code.
  */
 public final class NativeLibrary
 {
-	public static EmulationActivity sEmulationActivity;
+	public static WeakReference<EmulationActivity> sEmulationActivity = new WeakReference<>(null);
 
 	/**
 	 * Button type for use in onTouchEvent
@@ -379,31 +381,48 @@ public final class NativeLibrary
 	public static void displayAlertMsg(final String alert)
 	{
 		Log.error("[NativeLibrary] Alert: " + alert);
-		sEmulationActivity.runOnUiThread(new Runnable()
+		final EmulationActivity emulationActivity = sEmulationActivity.get();
+		if (emulationActivity != null)
+		{
+			emulationActivity.runOnUiThread(new Runnable()
 			{
 				@Override
 				public void run()
 				{
-				Toast.makeText(sEmulationActivity, "Panic Alert: " + alert, Toast.LENGTH_LONG).show();
+					Toast.makeText(emulationActivity, "Panic Alert: " + alert, Toast.LENGTH_LONG).show();
 				}
 			});
 		}
+		else
+		{
+			Log.warning("[NativeLibrary] EmulationActivity is null, can't do panic toast.");
+		}
+	}
 
 	public static void endEmulationActivity()
 	{
 		Log.verbose("[NativeLibrary] Ending EmulationActivity.");
-		sEmulationActivity.exitWithAnimation();
+		EmulationActivity emulationActivity = sEmulationActivity.get();
+		if (emulationActivity != null)
+		{
+			emulationActivity.exitWithAnimation();
+		}
+		else
+		{
+			Log.warning("[NativeLibrary] EmulationActivity is null, can't end.");
+		}
 	}
 
 	public static void setEmulationActivity(EmulationActivity emulationActivity)
 	{
 		Log.verbose("[NativeLibrary] Registering EmulationActivity.");
-		sEmulationActivity = emulationActivity;
+		sEmulationActivity = new WeakReference<>(emulationActivity);
 	}
 
 	public static void clearEmulationActivity()
 	{
 		Log.verbose("[NativeLibrary] Unregistering EmulationActivity.");
-		sEmulationActivity = null;
+
+		sEmulationActivity.clear();
 	}
 }

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

@@ -1,6 +1,8 @@
 package org.dolphinemu.dolphinemu.utils;
 
+import android.app.Activity;
 import android.app.PendingIntent;
+import android.content.Context;
 import android.content.Intent;
 import android.hardware.usb.UsbConfiguration;
 import android.hardware.usb.UsbConstants;
@@ -15,7 +17,6 @@ import org.dolphinemu.dolphinemu.NativeLibrary;
 import org.dolphinemu.dolphinemu.services.USBPermService;
 
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.Map;
 
 public class Java_GCAdapter {
@@ -28,6 +29,9 @@ public class Java_GCAdapter {
 	static UsbEndpoint usb_out;
 
 	private static void RequestPermission()
+	{
+		Context context = NativeLibrary.sEmulationActivity.get();
+		if (context != null)
 		{
 			HashMap<String, UsbDevice> devices = manager.getDeviceList();
 			for (Map.Entry<String, UsbDevice> pair : devices.entrySet())
@@ -39,13 +43,19 @@ public class Java_GCAdapter {
 					{
 						Intent intent = new Intent();
 						PendingIntent pend_intent;
-					intent.setClass(NativeLibrary.sEmulationActivity, USBPermService.class);
+						intent.setClass(context, USBPermService.class);
-					pend_intent = PendingIntent.getService(NativeLibrary.sEmulationActivity, 0, intent, 0);
+						pend_intent = PendingIntent.getService(context, 0, intent, 0);
 						manager.requestPermission(dev, pend_intent);
 					}
 				}
 			}
 		}
+		else
+		{
+			Log.warning("Cannot request GameCube Adapter permission as EmulationActivity is null.");
+		}
+
+	}
 
 	public static void Shutdown()
 	{
@@ -124,14 +134,22 @@ public class Java_GCAdapter {
 						}
 					}
 
-					NativeLibrary.sEmulationActivity.runOnUiThread(new Runnable()
+					final Activity emulationActivity = NativeLibrary.sEmulationActivity.get();
+					if (emulationActivity != null)
+					{
+						emulationActivity.runOnUiThread(new Runnable()
 						{
 							@Override
 							public void run()
 							{
-							Toast.makeText(NativeLibrary.sEmulationActivity, "GameCube Adapter couldn't be opened. Please re-plug the device.", Toast.LENGTH_LONG).show();
+								Toast.makeText(emulationActivity, "GameCube Adapter couldn't be opened. Please re-plug the device.", Toast.LENGTH_LONG).show();
 							}
 						});
+					}
+					else
+					{
+						Log.warning("Cannot show toast for GameCube Adapter failure.");
+					}
 					usb_con.close();
 				}
 			}

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

@@ -1,6 +1,7 @@
 package org.dolphinemu.dolphinemu.utils;
 
 import android.app.PendingIntent;
+import android.content.Context;
 import android.content.Intent;
 import android.hardware.usb.UsbConfiguration;
 import android.hardware.usb.UsbDevice;
@@ -32,6 +33,9 @@ public class Java_WiimoteAdapter
 	public static byte[][] wiimote_payload = new byte[MAX_WIIMOTES][MAX_PAYLOAD];
 
 	private static void RequestPermission()
+	{
+		Context context = NativeLibrary.sEmulationActivity.get();
+		if (context != null)
 		{
 			HashMap<String, UsbDevice> devices = manager.getDeviceList();
 			for (Map.Entry<String, UsbDevice> pair : devices.entrySet())
@@ -44,13 +48,18 @@ public class Java_WiimoteAdapter
 						Log.warning("Requesting permission for Wii Remote adapter");
 						Intent intent = new Intent();
 						PendingIntent pend_intent;
-					intent.setClass(NativeLibrary.sEmulationActivity, USBPermService.class);
+						intent.setClass(context, USBPermService.class);
-					pend_intent = PendingIntent.getService(NativeLibrary.sEmulationActivity, 0, intent, 0);
+						pend_intent = PendingIntent.getService(context, 0, intent, 0);
 						manager.requestPermission(dev, pend_intent);
 					}
 				}
 			}
 		}
+		else
+		{
+			Log.warning("Cannot request Wiimote adapter permission as EmulationActivity is null.");
+		}
+	}
 
 	public static boolean QueryAdapter()
 	{