Android 无法显示菜单项的图标

我无法在工具栏上显示菜单图标。有什么想法吗？ 以下是menu_main.xml中的编码：

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context=".MainActivity">

<item
    android:id="@+id/menu_date"
    android:icon="@drawable/clock_logo"
    android:orderInCategory="100"
    android:title="Date and Time"
    app:showAsAction="always"/>
<item
    android:id="@+id/menu_location"
    android:icon="@drawable/location"
    android:orderInCategory="100"
    android:title="Location"
    app:showAsAction="ifRoom"/>

   </menu>

---

在您的主要活动中添加

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

---

您的java文件中有哪些内容？你看过这篇文章了吗？共享您的java codecheck如果这一行缺少“”如下：请参考上面我的编码。ThxStill不工作。请参考我的java代码，Thx

public class MainActivity extends Activity implements View.OnClickListener {

private Button analogButton, digitalButton;
private Toolbar toolbar;


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

    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setActionBar(toolbar);
    getActionBar().setTitle("Clock");
    toolbar.setSubtitle("tells the time");
    toolbar.setLogo(R.drawable.clock_logo);
    toolbar.inflateMenu(R.menu.menu_main);


    analogButton = (Button) findViewById(R.id.button_analog);
    analogButton.setOnClickListener(this);
    digitalButton = (Button) findViewById(R.id.button_digital);
    digitalButton.setOnClickListener(this);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_main, menu);

    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    Fragment fragment;

    int id = item.getItemId();
    switch (id) {
        case R.id.menu_date:
            startActivity(new Intent(android.provider.Settings
                    .ACTION_DATE_SETTINGS));
            break;
        case R.id.menu_location:
            startActivity(new Intent(android.provider.Settings
                    .ACTION_LOCALE_SETTINGS));
            break;
        case R.id.menu_sleep:
            startActivity(new Intent(android.provider.Settings
                    .ACTION_SOUND_SETTINGS));
            break;
    }
    return super.onOptionsItemSelected(item);
}

@Override
public void onClick(View v) {
    Fragment fragment;
    if (v == analogButton) {
        fragment = new AnalogFragment();
    } else {
        fragment = new DigitalFragment();
    }
    replaceFragment(fragment);
}

public void replaceFragment(Fragment fragment) {
    FragmentManager manager = getFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
    transaction.replace(R.id.fragment_container, fragment);
    transaction.addToBackStack(null);
    transaction.commit();
}
}