Android自定义Toolbar（含PopupMenu）不显示问题求助

问题根源 #

1. 你的toolbar_fragment未被添加到Activity布局中，导致其菜单逻辑完全未执行
2. 即便添加Fragment，也未启用菜单功能（缺少setHasOptionsMenu(true)）
3. 菜单Item未配置showAsAction属性，系统无法识别要将其放入溢出菜单

方案一：直接在Activity中实现（最简单高效） #

1. 修改主Activity代码

public class activity_test extends AppCompatActivity {

    private Toolbar toolbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);
        ActivityHolder.get_instance().set_last_activity(this);

        toolbar = findViewById(R.id.test_toolbar);
        setSupportActionBar(toolbar);
        // 可选：设置Toolbar标题
        getSupportActionBar().setTitle("自定义标题");
    }

    // 加载菜单布局
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);
        return true;
    }

    // 处理菜单点击事件
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.settings:
                Toast.makeText(this, "设置", Toast.LENGTH_SHORT).show();
                return true;
            case R.id.downloads:
                Toast.makeText(this, "下载", Toast.LENGTH_SHORT).show();
                return true;
            case R.id.bookmarks:
                Toast.makeText(this, "书签", Toast.LENGTH_SHORT).show();
                return true;
            case R.id.about_us:
                Toast.makeText(this, "关于我们", Toast.LENGTH_SHORT).show();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

2. 修改菜单布局（main_menu.xml）

添加app命名空间，并配置showAsAction="never"确保Item进入溢出菜单：

<?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/settings"
        android:title="settings"
        app:showAsAction="never"/>
    <item
        android:id="@+id/downloads"
        android:title="downloads"
        app:showAsAction="never"/>
    <item
        android:id="@+id/bookmarks"
        android:title="bookmarks"
        app:showAsAction="never"/>
    <item
        android:id="@+id/about_us"
        android:title="about_us"
        app:showAsAction="never"/>

</menu>

方案二：使用Fragment处理菜单（若坚持架构需求） #

1. 修改Activity布局，添加Fragment容器

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <include layout="@layout/toolbar"
        android:id="@+id/test_toolbar"/>

    <!-- 添加Fragment容器 -->
    <FrameLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintTop_toBottomOf="@id/test_toolbar"
        app:layout_constraintBottom_toBottomOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

2. 修改Activity代码，添加Fragment

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test);
    ActivityHolder.get_instance().set_last_activity(this);

    toolbar = findViewById(R.id.test_toolbar);
    setSupportActionBar(toolbar);

    // 将Toolbar Fragment添加到Activity
    getSupportFragmentManager().beginTransaction()
            .replace(R.id.fragment_container, new toolbar_fragment())
            .commit();
}

3. 修改Toolbar Fragment代码，启用菜单功能

public class toolbar_fragment extends Fragment {

    public toolbar_fragment(){
        super(R.layout.toolbar);
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 启用Fragment菜单功能
        setHasOptionsMenu(true);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        return inflater.inflate(R.layout.toolbar, container, false);
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.main_menu, menu);
        super.onCreateOptionsMenu(menu, inflater);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.settings:
                Toast.makeText(getContext(), "设置", Toast.LENGTH_SHORT).show();
                return true;
            case R.id.downloads:
                Toast.makeText(getContext(), "下载", Toast.LENGTH_SHORT).show();
                return true;
            case R.id.bookmarks:
                Toast.makeText(getContext(), "书签", Toast.LENGTH_SHORT).show();
                return true;
            case R.id.about_us:
                Toast.makeText(getContext(), "关于我们", Toast.LENGTH_SHORT).show();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}

额外验证：确保Toolbar布局正确 #

你的toolbar.xml需为标准AndroidX Toolbar：

<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:theme="?attr/actionBarTheme">

</androidx.appcompat.widget.Toolbar>

内容的提问来源于stack exchange，提问作者mohammad