android - 带抽屉导航的 PreferenceActivity 抛出空指针异常

Question

我有一个运行良好的 PreferenceActivity。然后，我决定向它添加一个抽屉导航，并根据我的其他 Activity 布局编辑布局，这些布局也有工作抽屉导航。但是，这样做之后，我的 PreferenceActivity 停止打开并开始在开始时抛出 NPE。我什至不能再打开那个 Activity 了。显然，问题出在 onCreate 中，也出在 logcat 中所述的 onClick 方法中。然而，在这个 onCreate Activity 中有两个 onClick，我没有看到它们如何导致 NPE，因为它们在我的其他工作 Activity 中完全相同。根据默认的 DrawerLayout 实现，我的布局 xml 被分成 3 个 xml。事不宜迟，这里是代码和 xml:

偏好 Activity :

public class FirstYearCoursesActivity extends PreferenceActivity
    implements NavigationView.OnNavigationItemSelectedListener {

private AppCompatDelegate mDelegate;
Toolbar toolbar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    getDelegate().installViewFactory();
    getDelegate().onCreate(savedInstanceState);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_first_year_courses);
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar((toolbar));
    Window window = this.getWindow();
    window.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
    window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
    window.setStatusBarColor(this.getResources().getColor(R.color.colorPrimaryDark));
    addPreferencesFromResource(R.xml.prefs);
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view2);
    navigationView.setNavigationItemSelectedListener(this);
    View headerView = navigationView.getHeaderView(0);
    ImageButton logoutButton = (ImageButton) headerView.findViewById(R.id.logoutButton);
    logoutButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(FirstYearCoursesActivity.this, LoginActivity.class);
            startActivity(intent);
        }
    });
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
protected void onPause() {
    final DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    final Handler handler = new Handler();
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                drawer.closeDrawer(GravityCompat.START);
            }
        }, 200);
        super.onPause();
    } else {
        super.onPause();
    }
}
private void setSupportActionBar(@Nullable Toolbar toolbar) {
    getDelegate().setSupportActionBar(toolbar);
}

private AppCompatDelegate getDelegate() {
    if (mDelegate == null) {
        mDelegate = AppCompatDelegate.create(this, null);
    }
    return mDelegate;
}

@Override
public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {

    String key = preference.getKey();
        switch (key) {
            case "math119":
                Intent intent = new Intent(FirstYearCoursesActivity.this, Math119Activity.class);
                startActivity(intent);
                break;
            default:
                Toast.makeText(this, "Other Click", Toast.LENGTH_SHORT).show();
                break;
        }

    return super.onPreferenceTreeClick(preferenceScreen, preference);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
   // to be filled
    int id = item.getItemId();

    if (id == R.id.nav_camera) {

    } else if (id == R.id.nav_gallery) {

    } else if (id == R.id.nav_slideshow) {

    } else if (id == R.id.nav_manage) {

    } else if (id == R.id.nav_share) {

    } else if (id == R.id.nav_send) {

    }
    return true;
}
}

activity.xml:

<android.support.v4.widget.DrawerLayout
android:id="@+id/drawer_layout"
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"
android:fitsSystemWindows="true">

<include
    layout="@layout/app_bar_first_year_courses"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

<android.support.design.widget.NavigationView
    android:id="@+id/nav_view2"
    android:layout_width="250dp"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true"
    app:headerLayout="@layout/nav_header_main"
    app:menu="@menu/activity_main_drawer"
    android:background="#ffffffff"
    app:itemTextColor="#000000"
    app:itemTextAppearance="@style/TextAppearance.AppCompat.Body1"/>
</android.support.v4.widget.DrawerLayout>

app_bar.xml:

<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=".activities.FirstYearCoursesActivity">

<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_first_year_courses"/>

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

content.xml:

<LinearLayout
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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".activities.FirstYearCoursesActivity"
tools:showIn="@layout/app_bar_first_year_courses"
android:orientation="vertical">

</LinearLayout>

nav_header.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:layout_width="match_parent"
          android:layout_height="140dp"
          android:background="@drawable/profilebanner"
          android:gravity="bottom"
          android:orientation="vertical"
          android:theme="@style/ThemeOverlay.AppCompat.Dark"
          android:id="@+id/header">

<ImageButton
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/logoutButton"
    android:src="@drawable/ic_power_settings_new_white_18dp"
    android:background="#00ffffff"
    android:layout_alignParentTop="true"
    android:layout_alignParentEnd="true"
    android:layout_marginTop="30dp"
    android:layout_marginRight="10dp"/>

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/headerClick"
    android:layout_alignParentBottom="true"
    android:layout_alignParentStart="true"
    android:paddingLeft="10dp"
    android:paddingRight="10dp"
    android:paddingBottom="10dp"
    android:paddingTop="20dp">

    <ImageView
        android:layout_width="65dp"
        android:layout_height="65dp"
        android:id="@+id/imageView"
        android:background="@drawable/onur"
        android:layout_centerVertical="true"
        android:layout_alignParentStart="false"
        android:layout_alignBottom="@+id/textView3"
        android:layout_marginBottom="-20dp"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Onur Çevik"
        android:textAppearance="@style/TextAppearance.AppCompat.Body1"
        android:id="@+id/textView2"
        android:textSize="13sp"
        android:layout_toRightOf="@+id/imageView"
        android:layout_marginLeft="25dp"
        android:layout_marginTop="45dp"/>

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Environmental Engineering"
        android:textSize="11sp"
        android:layout_toRightOf="@+id/imageView"
        android:layout_marginLeft="25dp"
        android:layout_below="@+id/textView2"
        android:layout_alignParentStart="false"/>

</RelativeLayout>

</RelativeLayout>

prefs.xml:

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
android:key="firstyearprefs">
<Preference
    android:title="Math-119"
    android:key="math119"/>
<Preference
    android:title="Math-120"
    android:key="math120"/>
<Preference
    android:title="Phys-105"
    android:key="phys105"/>
<Preference
    android:title="Phys-106"
    android:key="phys106"/>
<Preference
    android:title="Chem-107"
    android:key="chem107"/>
<Preference
    android:title="Eng-101"
    android:key="eng101"/>
<Preference
    android:title="Eng-102"
    android:key="eng102"/>
<Preference
    android:title="Ce-101"
    android:key="ce101"/>

</PreferenceScreen>

日志:

02-08 02:10:35.415 30815-30815/com.theoc.proto E/AndroidRuntime: FATAL EXCEPTION: main
                                                             Process: com.theoc.proto, PID: 30815
                                                             java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setOnItemClickListener(android.widget.AdapterView$OnItemClickListener)' on a null object reference
                                                                 at android.preference.PreferenceScreen.bind(PreferenceScreen.java:143)
                                                                 at android.preference.PreferenceActivity.bindPreferences(PreferenceActivity.java:1419)
                                                                 at android.preference.PreferenceActivity.access$000(PreferenceActivity.java:123)
                                                                 at android.preference.PreferenceActivity$1.handleMessage(PreferenceActivity.java:230)
                                                                 at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                 at android.os.Looper.loop(Looper.java:135)
                                                                 at android.app.ActivityThread.main(ActivityThread.java:5272)
                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                 at java.lang.reflect.Method.invoke(Method.java:372)
                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:909)
                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:704)

编辑:

值得一提的是，我对 Activity 进行了三重检查，它是在列表项单击时导致此 PreferenceActivity 的适配器。我反转了我所有的抽屉布局实现，并且我能够通过父 Activity 打开此 PreferenceActivity。 Navigation Drawer 代码或布局是搞乱它的代码。我得到了 listview.onclick(adapter) NPE，因为我的列表项点击父 Activity 转到空引用，在本例中它是 PreferenceActivity 本身。调试也没有在 PreferenceActivity 的 onCreate 中显示任何 null，除了 savedInstanceState。

Answer 1

我能够使用您的代码重现相同的 NPE，并通过使用 fragment 代替 addPreferencesFromResource 调用(注意它已被弃用)来修复它，如这些线程中所述:

Android: Preference Fragment with a Navigation Drawer's Fragment

What to use instead of "addPreferencesFromResource" in a PreferenceActivity?

尽管在我的版本中，首选项 View 与工具栏重叠，而且我不确定应该使用什么 Activity 布局来解决这个问题，但也许在您的版本中就可以了。