A base Activity class that allows the compatibility menu button (AKA "the menu button of shame") to be displayed for applications whose targetSdkVersion >= 11. On devices with a hard menu key there is no effect. Useful if you want to launch some sort of in-app debug UI from an on-screen affordance without altering your application's user interfa…

ShameActivity.java

package com.example.shame;

import android.annotation.TargetApi;
import android.app.Activity;
import android.os.Build;
import android.view.KeyEvent;
import android.view.ViewConfiguration;

public abstract class ShameActivity extends Activity {

	/**
	 * Flag for a window belonging to an activity that responds to {@link KeyEvent#KEYCODE_MENU}
	 * and therefore needs a Menu key. For devices where Menu is a physical button this flag is
	 * ignored, but on devices where the Menu key is drawn in software it may be hidden unless
	 * this flag is set.
	 *
	 * (Note that Action Bars, when available, are the preferred way to offer additional
	 * functions otherwise accessed via an options menu.)
	 *
	 * {@hide}
	 */
	private static final int FLAG_NEEDS_MENU_KEY = 0x08000000;

	private boolean mCompatMenuKeyEnabled = false;

	/**
	 * Enable the compatibility menu button on devices that don't have
	 * a permanent menu key.
	 * 
	 * @param enabled true to enable the compatibility menu button, false to disable it.
	 */
	@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
	protected void setCompatMenuKeyEnabled(boolean enabled) {
		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
			ViewConfiguration vc = ViewConfiguration.get(this);
			if (!vc.hasPermanentMenuKey()) {
				if (enabled) {
					getWindow().addFlags(FLAG_NEEDS_MENU_KEY);
				} else {
					getWindow().clearFlags(FLAG_NEEDS_MENU_KEY);
				}
				mCompatMenuKeyEnabled = enabled;
			}
		}
	}

	@Override
	public boolean dispatchKeyEvent(KeyEvent event) {
		if (mCompatMenuKeyEnabled) {
			if (event.getKeyCode() == KeyEvent.KEYCODE_MENU && event.getAction() == KeyEvent.ACTION_UP) {
				onCompatMenuKeyPressed();
				// returning true creates an unfortunate side effect with the 
				// overflow menu, so it will still open here (if present)
				return false;
			}
		}
		return super.dispatchKeyEvent(event);
	}

	/**
	 * Override to implement a compatibility menu key press action. 
	 */
	protected abstract void onCompatMenuKeyPressed();

}

Unfortunately that does not work on Android 5+.

So I added this:

    private void showMenuKeyIfNecessaryOnAndroid5OrHigher() {
        String TAG = "MENU_BUTTON";
        Window w = getWindow();


        for (Class clazz = w.getClass(); clazz != null; clazz = clazz.getSuperclass()) {
            try {
                Method method = clazz.getDeclaredMethod("setNeedsMenuKey", int.class);
                method.setAccessible(true);
                try {
                    method.invoke(w, 1);  // 1 == WindowManager.LayoutParams.NEEDS_MENU_SET_TRUE
                    return;
                } catch (IllegalAccessException e) {
                    Log.d(TAG, "IllegalAccessException on window.setNeedsMenuKey");
                } catch (java.lang.reflect.InvocationTargetException e) {
                    Log.d(TAG, "InvocationTargetException on window.setNeedsMenuKey");
                }
            } catch (NoSuchMethodException e) {
                // Log.d(TAG, "NoSuchMethodException");
            }
        }
    }