To use menus Android provides two ways. First is the option menu which can be opened via the menu button. The option menu of your activity is filled in the method onCreateOptionsMenu() of your activity. You can register here a menu via your code or use a XML menu resources which you inflate via a "MenuInflator". You get a MenuInflator via your activity with the method getMenuInflator().

onCreateContextMenu() is only called once. If you want to influence the menu later you have to use the method onPrepareOptionsMenu().

The second option to display a menu is to use the context menu for a UI widget (view). A context menu is activated if the user "long presses" the view.

A context menu for a view is registered via the method registerForContextMenu(view). The method onCreateContextMenu() is called every time a context menu is activated as the context menu is discarded after its usage. The Android platform may also add options to your view, e.g. "EditText" provides context options to select text, etc.

This chapter will demonstrate how to create and evaluate a option menu, how to define preferences and how to navigate between activities via an intent . Create a project "de.vogella.android.preferences" with the activity "HelloPreferences". Change the UI in the file "/res/layout/main.xml" to the following:

				
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical" android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<Button android:id="@+id/Button01" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:text="Show Preferences"></Button>
	<Button android:id="@+id/Button02" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:text="Change Preferences"></Button>
</LinearLayout>

			

Menus can be defined via XML files. Select your project, right click on it and select New -> Other -> Android -> "Android XML File". Select the option "Menu", enter as File "menu.xml" and press the button "Finish".

Press Add and select "Item". Maintain the following value. This defines the entries in your menu. We will have only one entry.

Change your class "HelloPreferences" to the following. The OnCreateOptionsMenu method is used to create the menu. The behavior in "onOptionsItemSelected" is currently hard-coded to show a Toast and will soon call the preference settings. In case you want to disable or hide menu items you can use the method "onPrepareOptionsMenu" which is called every time the menu is called.

				
package de.vogella.android.preferences;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.Toast;

public class HelloPreferences extends Activity {
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		MenuInflater inflater = getMenuInflater();
		inflater.inflate(R.menu.menu, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		Toast.makeText(this, "Just a test", Toast.LENGTH_SHORT).show();
		return true;
	}
}

			

Run your application and press "Menu" on the emulator. Your menu should be displayed. If you select the menu entry you should see a small info message.

The two "Preference" buttons are not yet active. We will use them in the next chapter.