自定义ActionBar不显示图标

Question

我已经完成了https://developer.android.com/training/appbar文档中提到的所有内容。

这是onCreate方法

@RequiresApi(api = Build.VERSION_CODES.M)
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    getLocationBtn = findViewById(R.id.get_location_btn);
    saveLocationBtn = findViewById(R.id.save_btn);
    longText = findViewById(R.id.long_text);
    latText = findViewById(R.id.lat_text);
    attractionNameText = findViewById(R.id.location_name_text);
    ratingBar = findViewById(R.id.ratingBar);
    detailsText = findViewById(R.id.detailsText);
    getViewSavedLocationBtn = findViewById(R.id.view_saved_location_btn);
    attractionTypeText = findViewById(R.id.attractionTypeText);
    updateToFirebaseBtn = findViewById(R.id.update_to_firebase);
    db = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, "app_database")
            .allowMainThreadQueries()
            .build();
    getViewSavedLocationBtn.setOnClickListener(this);
    updateToFirebaseBtn.setOnClickListener(this);


   toolbar = findViewById(R.id.app_bar);
    setSupportActionBar(toolbar);
}

这是app_bar xml文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/app_bar"
    android:background="@color/colorAccent"
    >
</android.support.v7.widget.Toolbar>

这是main_manu.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/enter_attraction"
        android:icon="@drawable/upload_icon"
        android:title="@string/upload_icon_title"
        app:showAsAction="always"
        />

</menu>

模拟器上的输出

Answer 1

在活动中添加getSupportActionBar().setDisplayHomeAsUpEnabled(true)

在片段中将setHasOptionsMenu(true);添加到onCreate

此问题已解决