如何从Android中的菜单项调用Activity？

// MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.menu_item) {
            // 执行菜单项的操作，例如启动另一个Activity
            Intent intent = new Intent(this, AnotherActivity.class);
            startActivity(intent);
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

<!-- menu_main.xml -->

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/menu_item"
        android:title="菜单项" />
</menu>