java - PreferenceFragmentCompat 不显示

Question

我需要帮助来解决 PreferenceFragmentCompat 的问题，该问题根本不显示，控制台中没有错误，没有消息，什么也没有，只是一个空白页面。

该 fragment 显示为在抽屉导航中选择元素的结果。这是 Activity XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="false">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout
            android:id="@+id/list_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        </FrameLayout>

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|end"
            android:layout_marginBottom="24dp"
            android:layout_marginEnd="24dp"
            app:elevation="12dp"
            app:fabSize="normal"
            app:rippleColor="@color/nowControlsNormal"
            app:srcCompat="@android:drawable/ic_popup_sync" />

    </FrameLayout>

    <android.support.design.widget.NavigationView
        android:id="@+id/drawer"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:headerLayout="@layout/drawer_top"
        app:itemIconTint="@color/nowBlack"
        app:itemTextColor="@color/nowBlack"
        app:menu="@menu/drawer_menu" />

</android.support.v4.widget.DrawerLayout>

这是 Java Activity :

public class HomeActivity extends AppCompatActivity {

    SharedPreferences settings;
    private DrawerLayout drawerLayout;
    private ActionBarDrawerToggle drawerToggle;
    NavigationView nav;
    TextView drawerUsername;
    FloatingActionButton fab;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        settings = getSharedPreferences("NowCLOUD", 0);
        setContentView(R.layout.activity_home);
        drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        nav = (NavigationView) findViewById(R.id.drawer);
        fab = (FloatingActionButton) findViewById(R.id.fab);
        View headerView = nav.getHeaderView(0);
        drawerUsername = (TextView) headerView.findViewById(R.id.drawer_username);

        fab.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                //TODO: Gestire aggiornamento al click della FAB
            }
        });

        getSupportActionBar().setTitle("Home");

        drawerToggle = new ActionBarDrawerToggle(this, drawerLayout, R.string.drawer_open, R.string.drawer_close) {
            public void onDrawerClosed(View view) {
                super.onDrawerClosed(view);
            }
            public void onDrawerOpened(View drawerView) {
                super.onDrawerOpened(drawerView);
            }
        };

        drawerLayout.setDrawerListener(drawerToggle);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);

        getSupportFragmentManager().beginTransaction()
                .add(R.id.list_container, HomeFragment.newInstance())
                .commit();

        drawerUsername.setText(settings.getString("username", "Error"));

        nav.setNavigationItemSelectedListener(
                new NavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(MenuItem menuItem) {
                        menuItem.setChecked(true);
                        drawerLayout.closeDrawers();
                        displayView(menuItem.getItemId());
                        return true;
                    }
                });
    }

    public void displayView(int viewId) {

        Fragment fragment = null;
        String title = getString(R.string.app_name);

        switch (viewId) {
            case R.id.drawer_home:
                fragment = HomeFragment.newInstance();
                title  = "Home";
                break;

            case R.id.drawer_settings:
                fragment = SettingsFragment.newInstance();
                title = "Settings";
                break;
        }

        if (fragment != null) {
            getSupportFragmentManager().beginTransaction()
                    .replace(R.id.list_container, fragment)
                    .commit();
        }

        // set the toolbar title
        if (getSupportActionBar() != null) {
            getSupportActionBar().setTitle(title);
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);

    }
}

这是 fragment 的 XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.preference.PreferenceScreen
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="match_parent"
    android:layout_width="match_parent">

    <android.support.v7.preference.PreferenceCategory
        android:title="@string/settings_synchronization">

        <android.support.v7.preference.SwitchPreferenceCompat
            android:key="auto_updates"
            android:title="@string/settings_auto_sync" />

    </android.support.v7.preference.PreferenceCategory>

</android.support.v7.preference.PreferenceScreen>

这是 fragment 的 Java:

public class SettingsFragment extends PreferenceFragmentCompat {
    View rootView;

    @Override
    public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
        addPreferencesFromResource(R.xml.fragment_settings);
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        //rootView = inflater.inflate(R.xml.fragment_settings,container,false);
        return rootView;
    }

    @Override
    public PreferenceFragmentCompat getCallbackFragment() {
        return this;
    }

    public static SettingsFragment newInstance() {
        Bundle args = new Bundle();
        SettingsFragment fragment = new SettingsFragment();
        fragment.setArguments(args);
        return fragment;
    }
}

我已经删除了所有对此目的无用的代码。抱歉，代码量很大。

Answer 1

我自己想出来了:
当您使用preferencefragment时，您不能覆盖onCreateView方法，否则您将得到一个空白屏幕。