Android: Convert ControlReference to Kotlin

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

@@ -1,39 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-
-package org.dolphinemu.dolphinemu.features.input.model.controlleremu;
-
-import androidx.annotation.Keep;
-import androidx.annotation.Nullable;
-
-/**
- * Represents a C++ ControlReference.
- *
- * The lifetime of this class is managed by C++ code. Calling methods on it after it's destroyed
- * in C++ is undefined behavior!
- */
-public class ControlReference
-{
-  @Keep
-  private final long mPointer;
-
-  @Keep
-  private ControlReference(long pointer)
-  {
-    mPointer = pointer;
-  }
-
-  public native double getState();
-
-  public native String getExpression();
-
-  /**
-   * Sets the expression for this control reference.
-   *
-   * @param expr The new expression
-   * @return null on success, a human-readable error on failure
-   */
-  @Nullable
-  public native String setExpression(String expr);
-
-  public native boolean isInput();
-}

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/features/input/model/controlleremu/ControlReference.kt

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.dolphinemu.dolphinemu.features.input.model.controlleremu
+
+import androidx.annotation.Keep
+
+/**
+ * Represents a C++ ControlReference.
+ *
+ * The lifetime of this class is managed by C++ code. Calling methods on it after it's destroyed
+ * in C++ is undefined behavior!
+ */
+@Keep
+class ControlReference private constructor(private val pointer: Long) {
+    external fun getState(): Double
+
+    external fun getExpression(): String
+
+    /**
+     * Sets the expression for this control reference.
+     *
+     * @param expr The new expression
+     * @return null on success, a human-readable error on failure
+     */
+    external fun setExpression(expr: String): String?
+
+    external fun isInput(): Boolean
+}