布局中的Android菜单选项不显示图标

我刚刚在我的活动中添加了一个菜单。此外，我想为每个菜单项设置一些图标。因此，我尝试了这两种方法，但在设备上看不到这些图标。我做错了什么

我尝试了XML方式：

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/help"
    android:icon="@drawable/help"
    android:title="@string/menu_help" />
    <item android:id="@+id/settings"
    android:icon="@drawable/settings"
    android:title="@string/menu_settings" />
    <item android:id="@+id/num"
    android:icon="@drawable/num_icon"
    android:title="@string/menu_num" />
</menu>

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还有，谁能告诉我这些图标的大小应该有多大？我的是256x256像素。谢谢，android sdk菜单中的图标大小如下：

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256x256太大。

使用以下代码可能会对您有所帮助。。 menu.xml

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你只需要在你的清单文件中根据你的需要做一些小的改变，你可以改变主题，我通过小的改变就可以解决上面的问题，也就是说，即使使用任何版本的android，它也可以工作（2.3到最新版本4.4 kitkat）

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android 4.x之后的菜单中没有图标（好吧，如果菜单按钮在ActionBar上，那么，是的，它可以有图标，但不在菜单覆盖中（“三点”按钮或硬菜单按钮）？选中此项，您将获得问题的解决方案

public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu, menu);
        //Set icon for the menu button
        Drawable num_icon = getResources().getDrawable(R.drawable.num_icon);
        menu.getItem(2).setIcon(num_icon);
        Drawable settings_icon = getResources().getDrawable(R.drawable.settings);
        menu.getItem(1).setIcon(settings_icon);
        Drawable help_icon = getResources().getDrawable(R.drawable.help);
        menu.getItem(0).setIcon(help_icon);
        return true;

ldpi 32 x 32 px
mdpi: 36 x 36 px
hdpi: 48 x 48 px
xhdpi: 64 x 64 px

<?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>

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 AndroidMenusActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    // Initiating Menu XML file (menu.xml)
    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate(R.layout.menu, 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(AndroidMenusActivity.this, "Bookmark is Selected", Toast.LENGTH_SHORT).show();
            return true;

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

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

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

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

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

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

}

  <application
        android:allowBackup="true"
        android:debuggable="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
         android:theme="@android:style/Theme.WithActionBar">