Android - 应用程序栏操作按钮在设备定向横向时消失

Question

我设置了我的应用程序，以便在设备定位时更改为不同的布局，这样可以正常工作但现在我的操作按钮没有显示。我是否需要为横向创建新的应用栏xml文件？这是我的代码，感谢任何帮助。

MainActivity.java

<MasterDetailPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="TestApp.Views.Test2View">
  <MasterDetailPage.Master>
    <ContentPage Title="Currencies">
      <ContentPage.Icon>
        <OnPlatform x:TypeArguments="FileImageSource"
               Android="my-icon"
               WinPhone="Assets/my-icon.png" />
      </ContentPage.Icon>
    </ContentPage>
  </MasterDetailPage.Master>
  <MasterDetailPage.Detail>
    <NavigationPage>
      <x:Arguments>
        <ContentPage>

        </ContentPage>
      </x:Arguments>
    </NavigationPage>
  </MasterDetailPage.Detail>
</MasterDetailPage>

menu_main.xml - 我想在横向和纵向两个方向使用它，这意味着我想在两者上使用相同的动作按钮。

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    if (savedInstanceState != null) {
        int rotation = getWindowManager().getDefaultDisplay().getRotation();

        if (rotation == Surface.ROTATION_90 || rotation == Surface.ROTATION_270) {

            setContentView(R.layout.activity_main_landscape);
        }

    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.

    getMenuInflater().inflate(R.menu.menu_main, menu);

    return true;

}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
  }
}

activity_main_landscape.xml

<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="com.example.james.task02b.MainActivity">
    <item
        android:id="@+id/action_search"
        android:icon="@drawable/ic_search_white_24dp"
        android:title="@string/action_search"
        app:showAsAction="ifRoom"/>
    <item
        android:id="@+id/action_delete"
        android:icon="@drawable/ic_delete_white_24dp"
        android:title="@string/action_delete"
        app:showAsAction="ifRoom"/>
    <item
        android:id="@+id/action_settings"
        android:orderInCategory="100"
        android:title="@string/action_settings"
        app:showAsAction="never" />
</menu>