java - 为什么我的工具栏没有显示任何内容，即使它显示并放置正确？

Question

我试图在我的 SettingsActivity 上添加一个 Toolbar，它显示正确，但由于某种原因，我根本无法让它填充其内容。它只是以空白状态出现。这是我的代码:

SettingsActivity.java:

public class SettingsActivity extends AppCompatActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getFragmentManager().beginTransaction()
                .replace(android.R.id.content, new SettingsFragment())
                .commit();
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }

    @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_settings, 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) {
            Intent i = new Intent(this, SettingsActivity.class);
            startActivity(i);
        }

        return super.onOptionsItemSelected(item);
    }

    public static class SettingsFragment extends PreferenceFragment {
        @Override
        public void onCreate(final Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            // Load the preferences from an XML resource
            addPreferencesFromResource(R.xml.preferences);
        }

        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            super.onCreateView(inflater, container, savedInstanceState);
            final View rootview = inflater.inflate(R.layout.activity_settings, container, false);
            return rootview;
        }
    }
}

activity_settings.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="pt.ismai.a26800.readr.activities.SettingsActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.design.widget.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/AppTheme.PopupOverlay" />

        </android.support.design.widget.AppBarLayout>

        <include layout="@layout/content_settings" />

    </LinearLayout>

</android.support.design.widget.CoordinatorLayout>

content_settings.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/settings"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></ListView>

</LinearLayout>

menu_settings.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="pt.ismai.a26800.readr.activities.SettingsActivity">
    <item
        android:id="@+id/action_settings"
        android:orderInCategory="100"
        android:title="@string/action_settings"
        app:showAsAction="never" />
</menu>

AndroidManifest.xml:

<activity
            android:name=".activities.SettingsActivity"
            android:label="@string/action_settings"
            android:theme="@style/AppTheme.NoActionBar" />

Answer 1

这是由于操作顺序造成的。您当前正在设置工具栏，然后加载包含工具栏的 fragment 。这意味着当您调用 setSupportActionBar(toolbar); 时，工具栏当前将为空。

您可以通过调用以下命令从 SettingsFragment 中设置工具栏来解决此问题:

final View rootview = inflater.inflate(R.layout.activity_settings, container, false);
Toolbar toolbar = (Toolbar) rootview.findViewById(R.id.toolbar);
((AppCompatActivity) getActivity()).setSupportActionBar(toolbar);

这会获取 fragment 父 Activity 并相应地设置工具栏。