自定义菜单图标不显示

Question

我正在尝试使用here显示的自定义菜单，而我只是单独获得list of items而没有任何图标。所需的所有图标都放在正确的文件夹中，但它不起作用。请一些人告诉我，我做错了。我的代码如下所示，并提前感谢。

MeunTest.java

public class MenuTest extends Activity {

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

// Initiating Menu XML file (menu.xml)
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
    MenuInflater menuInflater = getMenuInflater();
    menuInflater.inflate(R.menu.main, menu);
    return true;
}

/**
 * Event Handling for Individual menu item selected
 * Identify single menu item by it's id
 * */
@Override
public boolean onOptionsItemSelected(MenuItem item)
{

    switch (item.getItemId())
    {
        case R.id.menu_bookmark:
            // Single menu item is selected do something
            // Ex: launching new activity/screen or show alert message
            Toast.makeText(MenuTest.this, "Bookmark is Selected", Toast.LENGTH_SHORT).show();
            return true;

        case R.id.menu_save:
            Toast.makeText(MenuTest.this, "Save is Selected", Toast.LENGTH_SHORT).show();
            return true;

        case R.id.menu_search:
            Toast.makeText(MenuTest.this, "Search is Selected", Toast.LENGTH_SHORT).show();
            return true;

        case R.id.menu_share:
            Toast.makeText(MenuTest.this, "Share is Selected", Toast.LENGTH_SHORT).show();
            return true;

        case R.id.menu_delete:
            Toast.makeText(MenuTest.this, "Delete is Selected", Toast.LENGTH_SHORT).show();
            return true;

        case R.id.menu_preferences:
            Toast.makeText(MenuTest.this, "Preferences is Selected", Toast.LENGTH_SHORT).show();
            return true;

        default:
            return super.onOptionsItemSelected(item);
    }
}
 }

menu.xml文件

<?xml version="1.0" encoding="utf-8"?>
  <menu xmlns:android="http://schemas.android.com/apk/res/android">
<!-- Single menu item
     Set id, icon and Title for each menu item
-->
<item android:id="@+id/menu_bookmark"
    android:icon="@drawable/icon_bookmark"
    android:title="Bookmark" />
<item android:id="@+id/menu_save"
    android:icon="@drawable/icon_save"
    android:title="Save" />
<item android:id="@+id/menu_search"
    android:icon="@drawable/icon_search"
    android:title="Search" />
<item android:id="@+id/menu_share"
    android:icon="@drawable/icon_share"
    android:title="Share" />
<item android:id="@+id/menu_delete"
    android:icon="@drawable/icon_delete"
    android:title="Delete" />
<item android:id="@+id/menu_preferences"
    android:icon="@drawable/icon_preferences"
    android:title="Preferences" />
 </menu>