add export to c# button

proguard/examples/android-agp3-agp4/src/com/example/HelloWorldActivity.java

@@ -0,0 +1,29 @@
+/*
+ * Sample application to illustrate processing with ProGuard.
+ *
+ * Copyright (c) 2012-2020 Guardsquare NV
+ */
+package com.example;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.view.Gravity;
+import android.widget.TextView;
+
+/**
+ * Sample activity that displays "Hello world!".
+ */
+public class HelloWorldActivity extends Activity
+{
+    @Override
+    public void onCreate(Bundle savedInstanceState)
+    {
+        super.onCreate(savedInstanceState);
+
+        // Display the message.
+        TextView view = new TextView(this);
+        view.setText("Hello World");
+        view.setGravity(Gravity.CENTER);
+        setContentView(view);
+    }
+}