android: Convert YuzuApplication to Kotlin

src/android/app/src/main/java/org/yuzu/yuzu_emu/YuzuApplication.java

@@ -1,59 +0,0 @@
-// Copyright 2019 Citra Emulator Project
-// Licensed under GPLv2 or any later version
-// Refer to the license.txt file included.
-
-package org.yuzu.yuzu_emu;
-
-import android.app.Application;
-import android.app.NotificationChannel;
-import android.app.NotificationManager;
-import android.content.Context;
-import android.os.Build;
-
-import org.yuzu.yuzu_emu.model.GameDatabase;
-import org.yuzu.yuzu_emu.utils.DocumentsTree;
-import org.yuzu.yuzu_emu.utils.DirectoryInitialization;
-import org.yuzu.yuzu_emu.utils.GpuDriverHelper;
-
-public class YuzuApplication extends Application {
-    public static GameDatabase databaseHelper;
-    public static DocumentsTree documentsTree;
-    private static YuzuApplication application;
-
-    private void createNotificationChannel() {
-        // Create the NotificationChannel, but only on API 26+ because
-        // the NotificationChannel class is new and not in the support library
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-            CharSequence name = getString(R.string.app_notification_channel_name);
-            String description = getString(R.string.app_notification_channel_description);
-            NotificationChannel channel = new NotificationChannel(getString(R.string.app_notification_channel_id), name, NotificationManager.IMPORTANCE_LOW);
-            channel.setDescription(description);
-            channel.setSound(null, null);
-            channel.setVibrationPattern(null);
-            // Register the channel with the system; you can't change the importance
-            // or other notification behaviors after this
-            NotificationManager notificationManager = getSystemService(NotificationManager.class);
-            notificationManager.createNotificationChannel(channel);
-        }
-    }
-
-    @Override
-    public void onCreate() {
-        super.onCreate();
-        application = this;
-        documentsTree = new DocumentsTree();
-
-        DirectoryInitialization.start(getApplicationContext());
-        GpuDriverHelper.initializeDriverParameters(getApplicationContext());
-        NativeLibrary.LogDeviceInfo();
-
-        // TODO(bunnei): Disable notifications until we support app suspension.
-        //createNotificationChannel();
-
-        databaseHelper = new GameDatabase(this);
-    }
-
-    public static Context getAppContext() {
-        return application.getApplicationContext();
-    }
-}

src/android/app/src/main/java/org/yuzu/yuzu_emu/YuzuApplication.kt

@@ -0,0 +1,56 @@
+package org.yuzu.yuzu_emu
+
+import android.app.Application
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.content.Context
+import org.yuzu.yuzu_emu.model.GameDatabase
+import org.yuzu.yuzu_emu.utils.DirectoryInitialization.start
+import org.yuzu.yuzu_emu.utils.DocumentsTree
+import org.yuzu.yuzu_emu.utils.GpuDriverHelper
+
+class YuzuApplication : Application() {
+    private fun createNotificationChannel() {
+        // Create the NotificationChannel, but only on API 26+ because
+        // the NotificationChannel class is new and not in the support library
+        val name: CharSequence = getString(R.string.app_notification_channel_name)
+        val description = getString(R.string.app_notification_channel_description)
+        val channel = NotificationChannel(
+            getString(R.string.app_notification_channel_id),
+            name,
+            NotificationManager.IMPORTANCE_LOW
+        )
+        channel.description = description
+        channel.setSound(null, null)
+        channel.vibrationPattern = null
+        // Register the channel with the system; you can't change the importance
+        // or other notification behaviors after this
+        val notificationManager = getSystemService(NotificationManager::class.java)
+        notificationManager.createNotificationChannel(channel)
+    }
+
+    override fun onCreate() {
+        super.onCreate()
+        application = this
+        documentsTree = DocumentsTree()
+        start(applicationContext)
+        GpuDriverHelper.initializeDriverParameters(applicationContext)
+        NativeLibrary.LogDeviceInfo()
+
+        // TODO(bunnei): Disable notifications until we support app suspension.
+        //createNotificationChannel();
+        databaseHelper = GameDatabase(this)
+    }
+
+    companion object {
+        var databaseHelper: GameDatabase? = null
+
+        @JvmField
+        var documentsTree: DocumentsTree? = null
+        private var application: YuzuApplication? = null
+
+        @JvmStatic
+        val appContext: Context
+            get() = application!!.applicationContext
+    }
+}