如何按显示值对ListPreference进行排序

Question

我正在从XML文件创建首选项。从首选项活动的onCreate()调用的以下代码应根据向用户显示的标签按字母顺序对显示项进行排序。

private void sortListPreferenceByEntries(String preferenceKey) {
  ListPreference preference = (ListPreference) findPreference(preferenceKey);
  Iterator<CharSequence> labels = Arrays.asList(preference.getEntries()).iterator();
  Iterator<CharSequence> keys = Arrays.asList(preference.getEntryValues()).iterator();
  Collator sortRules = Collator.getInstance(getResources().getConfiguration().locale);
  sortRules.setStrength(Collator.PRIMARY);
  TreeMap<CharSequence, CharSequence> sorter = new TreeMap<>(sortRules);
  int size = 0;
  while (labels.hasNext() && keys.hasNext()) {
    sorter.put(labels.next(), keys.next());
    size++;
  }
  CharSequence[] sortedLabels = new CharSequence[size];
  CharSequence[] sortedValues = new CharSequence[size];
  Iterator<Map.Entry<CharSequence, CharSequence>> entryIterator = sorter.entrySet().iterator();
  if (entryIterator.hasNext()) {
    Map.Entry<CharSequence, CharSequence> entry = entryIterator.next();
    for (int i = 0; entryIterator.hasNext() && i < size; entry = entryIterator.next(), i++) {
      sortedLabels[i] = entry.getKey();
      sortedValues[i] = entry.getValue();
    }
  }
  preference.setEntries(sortedLabels);
  preference.setEntryValues(sortedValues);
}

代码在调试器中运行正常，结果数组sortedLabels和sortedValues正在创建，手动检查显示它们是我所期望的。选项也以所需的排序方式呈现给用户。只要列表中没有选择任何项目，一切正常，但只要我从列表中选择一个项目，就会抛出NullPointerException。我编写的代码行中没有一行是堆栈跟踪的一部分。

07-27 16:37:19.343    7589-7589/org.example.appName E/App-Name﹕ null
java.lang.NullPointerException
        at android.preference.ListPreference.findIndexOfValue(ListPreference.java:215)
        at android.preference.ListPreference.getValueIndex(ListPreference.java:224)
        at android.preference.ListPreference.getEntry(ListPreference.java:202)
        at android.preference.ListPreference.getSummary(ListPreference.java:148)
        at android.preference.Preference.onBindView(Preference.java:542)
        at android.preference.Preference.getView(Preference.java:472)
        at android.preference.PreferenceGroupAdapter.getView(PreferenceGroupAdapter.java:222)
        at android.widget.AbsListView.obtainView(AbsListView.java:2588)
        at android.widget.ListView.makeAndAddView(ListView.java:1840)
        at android.widget.ListView.fillDown(ListView.java:681)
        at android.widget.ListView.fillGap(ListView.java:645)
        at android.widget.AbsListView.trackMotionScroll(AbsListView.java:6535)
        at android.widget.AbsListView.scrollIfNeeded(AbsListView.java:3664)
        at android.widget.AbsListView.onTouchEvent(AbsListView.java:4492)
        at android.view.View.dispatchTouchEvent(View.java:7690)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2395)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2119)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2401)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2134)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2401)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2134)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2401)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2134)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2401)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2134)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2401)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2134)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2401)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2134)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2306)
        at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1575)
        at android.app.Activity.dispatchTouchEvent(Activity.java:2470)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2254)
        at android.view.View.dispatchPointerEvent(View.java:7888)
        at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3977)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3861)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5101)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5080)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5179)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
        at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
        at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:174)
        at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:5151)
        at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:5198)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:791)
        at android.view.Choreographer.doCallbacks(Choreographer.java:591)
        at android.view.Choreographer.doFrame(Choreographer.java:559)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:777)
        at android.os.Handler.handleCallback(Handler.java:725)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:176)
        at android.app.ActivityThread.main(ActivityThread.java:5365)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.jav

在不对元素进行排序的情况下，应用程序完全稳定。与我在可能的堆栈跟踪中找到的其他情况不同，我不会尝试将int s用作条目值。有什么不对？我还可以验证回写的新数组与最初从getter中检索的数组长度相同（在我的情况下为118个条目）。我还尝试将新的显示顺序压缩回原始数组，如下所示：

System.arraycopy(sortedLabels, 0, preference.getEntries(), 0, sortedLabels.length);
System.arraycopy(sortedValues, 0, preference.getEntryValues(), 0, sortedValues.length);

但结果相同。我真的不明白我错过了什么。任何帮助将不胜感激。

可能this question可能有关系，但也没有答案。

编辑：根据要求，这是一个完整的应用程序，它会重现错误：

的AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="org.example.appName">

    <application android:allowBackup="true" android:label="App-Name"
        android:icon="@mipmap/ic_launcher" android:theme="@android:style/Theme.Black">

        <activity
            android:name="org.example.appName.SettingsActivity"
            android:theme="@android:style/Theme.Black.NoTitleBar" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>

</manifest>

的java /组织/示例/ APPNAME / SettingsActivity.java

package org.example.appName;

import android.os.Bundle;
import android.preference.ListPreference;
import android.preference.PreferenceActivity;
import android.util.Log;

import java.text.Collator;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;

public class SettingsActivity extends PreferenceActivity {

  @Override
  @SuppressWarnings("deprecation")
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
      @Override
      public void uncaughtException(Thread t, Throwable e) {
        Log.e("App-Name", e.getMessage(), e);
      }
    });
    addPreferencesFromResource(R.xml.preferences);
    sortListPreferenceByEntries("language");
  }

  private void sortListPreferenceByEntries(String preferenceKey) {
    ListPreference preference = (ListPreference) findPreference(preferenceKey);
    Iterator<CharSequence> labels = Arrays.asList(preference.getEntries()).iterator();
    Iterator<CharSequence> keys = Arrays.asList(preference.getEntryValues()).iterator();
    Collator sortRules = Collator.getInstance(getResources().getConfiguration().locale);
    sortRules.setStrength(Collator.PRIMARY);
    TreeMap<CharSequence, CharSequence> sorter = new TreeMap<>(sortRules);
    int size = 0;
    while (labels.hasNext() && keys.hasNext()) {
      sorter.put(labels.next(), keys.next());
      size++;
    }
    CharSequence[] sortedLabels = new CharSequence[size];
    CharSequence[] sortedValues = new CharSequence[size];
    Iterator<Map.Entry<CharSequence, CharSequence>> entryIterator = sorter.entrySet().iterator();
    if (entryIterator.hasNext()) {
      Map.Entry<CharSequence, CharSequence> entry = entryIterator.next();
      for (int i = 0; entryIterator.hasNext() && i < size; entry = entryIterator.next(), i++) {
        sortedLabels[i] = entry.getKey();
        sortedValues[i] = entry.getValue();
      }
    }
    preference.setEntries(sortedLabels);
    preference.setEntryValues(sortedValues);
  }
}

RES / XML /的preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory android:title="caption">
        <ListPreference
            android:entries="@array/mode1_options"
            android:entryValues="@array/mode1_values"
            android:key="mode1"
            android:summary="Change mode 1"
            android:title="Mode 1" />
        <ListPreference
            android:entries="@array/mode2_options"
            android:entryValues="@array/mode2_values"
            android:key="mode2"
            android:summary="Change mode 2"
            android:title="Mode 2" />
        <ListPreference
            android:entries="@array/mode3_options"
            android:entryValues="@array/mode3_values"
            android:key="mode3"
            android:summary="Change mode 3"
            android:title="Mode 3" />
        <ListPreference
            android:entries="@array/mode4_options"
            android:entryValues="@array/mode4_values"
            android:key="mode4"
            android:summary="Change mode 4"
            android:title="Mode 4" />
        <ListPreference
            android:entries="@array/mode5_options"
            android:entryValues="@array/mode5_values"
            android:key="mode5"
            android:summary="Change mode 5"
            android:title="Mode 5" />
    </PreferenceCategory>
    <PreferenceCategory android:title="caption">
        <EditTextPreference
            android:key="input1"
            android:title="Input text" />
        <ListPreference
            android:entries="@array/mode6_options"
            android:entryValues="@array/mode6_values"
            android:key="mode6"
            android:summary="Change mode 6"
            android:title="Mode 6" />
        <CheckBoxPreference
            android:key="option1"
            android:summary="Change option 1"
            android:title="Option 1" />
        <CheckBoxPreference
            android:key="option2"
            android:summary="Change option 2"
            android:title="Option 2" />
        <ListPreference
            android:entries="@array/language_options"
            android:entryValues="@array/language_values"
            android:key="language"
            android:summary="To demonstrate the problem"
            android:title="Use this menu" />
        <CheckBoxPreference
            android:key="option3"
            android:summary="Change option 3"
            android:title="Option 3" />
    </PreferenceCategory>
    <PreferenceCategory android:title="caption">
        <CheckBoxPreference
            android:defaultValue="true"
            android:key="option4"
            android:summary="Change option 4"
            android:title="Option 4" />
        <CheckBoxPreference
            android:defaultValue="false"
            android:key="option5"
            android:summary="Change option 5"
            android:title="Option 5" />
    </PreferenceCategory>
</PreferenceScreen>

RES /值/ array.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="mode1_options">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode1_values" translatable="false">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode2_options">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode2_values" translatable="false">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode3_options">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode3_values" translatable="false">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode4_options">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode4_values" translatable="false">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode5_options">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode5_values" translatable="false">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="language_options">
        <item>Oromo</item>
        <item>Afrikaans</item>
        <item>Albanian</item>
        <item>Asturian</item>
        <item>Aymara</item>
        <item>Azerbaijani, Latin script</item>
        <item>Balinese</item>
        <item>Basque</item>
        <item>Belarusian</item>
        <item>Bemba</item>
        <item>Bikol</item>
        <item>Bislama</item>
        <item>Bosnian, Cyrillic script</item>
        <item>Bosnian, Latin script</item>
        <item>Brazilian Portuguese</item>
        <item>Breton</item>
        <item>Bulgarian</item>
        <item>Catalan</item>
        <item>Chamorro</item>
        <item>Corsican</item>
        <item>Croatian</item>
        <item>Czech</item>
        <item>Danish</item>
        <item>Dutch</item>
        <item>English</item>
        <item>Esperanto</item>
        <item>Estonian</item>
        <item>Faeroese</item>
        <item>Fijian</item>
        <item>Finnish</item>
        <item>French</item>
        <item>Frisian</item>
        <item>Friulian</item>
        <item>Galician</item>
        <item>Luganda</item>
        <item>German</item>
        <item>Greek</item>
        <item>Greenlandic</item>
        <item>Haitian Creole</item>
        <item>Hani</item>
        <item>Hiligaynon</item>
        <item>Hungarian</item>
        <item>Icelandic</item>
        <item>Ido</item>
        <item>Ilocano</item>
        <item>Indonesian</item>
        <item>Interlingua</item>
        <item>Irish</item>
        <item>Italian</item>
        <item>Javanese</item>
        <item>Kapampangan</item>
        <item>Kazakh</item>
        <item>Kongo</item>
        <item>Kinyarwanda</item>
        <item>Kurdish</item>
        <item>Latin</item>
        <item>Latvian</item>
        <item>Lithuanian</item>
        <item>Luba-Kasai</item>
        <item>Luxembourgish</item>
        <item>Macedonian</item>
        <item>Madurese</item>
        <item>Malagasy</item>
        <item>Malay</item>
        <item>Maltese</item>
        <item>Manx</item>
        <item>Maori</item>
        <item>Mayan</item>
        <item>Mexican Spanish</item>
        <item>Minangkabau</item>
        <item>Mongolian</item>
        <item>Nahuatl</item>
        <item>none</item>
        <item>Norwegian</item>
        <item>Nyanja</item>
        <item>Nynorsk</item>
        <item>Papiamento</item>
        <item>Nigerian Pidgin</item>
        <item>English-based pidgin</item>
        <item>Polish</item>
        <item>Portuguese</item>
        <item>Provençal</item>
        <item>Quechua</item>
        <item>Rhaeto-Romance</item>
        <item>Romanian</item>
        <item>Rundi</item>
        <item>Russian</item>
        <item>Samoan</item>
        <item>Sardinian</item>
        <item>Scottish Gaelic</item>
        <item>Serbian, Cyrillic script</item>
        <item>Serbian, Latin script</item>
        <item>Shona</item>
        <item>Slovak</item>
        <item>Slovene</item>
        <item>Somali</item>
        <item>Sotho</item>
        <item>Spanish</item>
        <item>Sundanese</item>
        <item>Swahili</item>
        <item>Swedish</item>
        <item>Swiss German</item>
        <item>Tagalog</item>
        <item>Tahitian</item>
        <item>Tatar</item>
        <item>Tetum</item>
        <item>Tongan</item>
        <item>Tswana</item>
        <item>Turkish</item>
        <item>Turkmen</item>
        <item>Ukrainian</item>
        <item>Uzbek, Latin script</item>
        <item>Waray-Waray</item>
        <item>Welsh</item>
        <item>Wolof</item>
        <item>Xhosa</item>
        <item>Zapotec</item>
        <item>Zulu</item>
    </string-array>
    <string-array name="language_values" translatable="false">
        <item>Afaan</item>
        <item>Afrikaans</item>
        <item>Albanian</item>
        <item>Asturian</item>
        <item>Aymara</item>
        <item>Azeri_Latin</item>
        <item>Balines</item>
        <item>Basque</item>
        <item>Belrusian</item>
        <item>Bemba</item>
        <item>Bikol</item>
        <item>Bislama</item>
        <item>Bosnian_Cyrillic</item>
        <item>Bosnian_Latin</item>
        <item>Brazilian</item>
        <item>Breton</item>
        <item>Bulgarian</item>
        <item>Catalan</item>
        <item>Chamorro</item>
        <item>Corsican</item>
        <item>Croatian</item>
        <item>Czech</item>
        <item>Danish</item>
        <item>Dutch</item>
        <item>English</item>
        <item>Esperanto</item>
        <item>Estonian</item>
        <item>Faeroese</item>
        <item>Fijian</item>
        <item>Finnish</item>
        <item>French</item>
        <item>Frisian</item>
        <item>Friulian</item>
        <item>Galician</item>
        <item>Ganda</item>
        <item>German</item>
        <item>Greek</item>
        <item>Greenlandic</item>
        <item>Haitian_Creole</item>
        <item>Hani</item>
        <item>Hiligaynon</item>
        <item>Hungarian</item>
        <item>Icelandic</item>
        <item>Ido</item>
        <item>Ilocano</item>
        <item>Indonesian</item>
        <item>Interlingua</item>
        <item>Irish_Gaelic</item>
        <item>Italian</item>
        <item>Javanese</item>
        <item>Kapampangan</item>
        <item>Kazakh</item>
        <item>Kicongo</item>
        <item>Kinyarwanda</item>
        <item>Kurdish</item>
        <item>Latin</item>
        <item>Latvian</item>
        <item>Lithuanian</item>
        <item>Luba</item>
        <item>Luxemb</item>
        <item>Macedonian</item>
        <item>Madurese</item>
        <item>Malagasy</item>
        <item>Malay</item>
        <item>Maltese</item>
        <item>Manx</item>
        <item>Maori</item>
        <item>Mayan</item>
        <item>Mexican</item>
        <item>Minankabaw</item>
        <item>Mongol</item>
        <item>Nahuatl</item>
        <item>None</item>
        <item>Norwegian</item>
        <item>Nyanja</item>
        <item>Nynorsk</item>
        <item>Papiamento</item>
        <item>Pidgin_nigeria</item>
        <item>PidginEnglish</item>
        <item>Polish</item>
        <item>Portuguese</item>
        <item>Provencal</item>
        <item>Quechua</item>
        <item>Rhaeto_Roman</item>
        <item>Romanian</item>
        <item>Rundi</item>
        <item>Russian</item>
        <item>Samoan</item>
        <item>Sardinian</item>
        <item>Scottish_Gaelic</item>
        <item>Serbian</item>
        <item>Serbian_Latin</item>
        <item>Shona</item>
        <item>Slovak</item>
        <item>Slovenian</item>
        <item>Somali</item>
        <item>Sotho</item>
        <item>Spanish</item>
        <item>Sundanese</item>
        <item>Swahili</item>
        <item>Swedish</item>
        <item>Swiss_German</item>
        <item>Tagalog</item>
        <item>Tahitian</item>
        <item>Tatar</item>
        <item>Tetum</item>
        <item>Tongan</item>
        <item>Tswana</item>
        <item>Turkish</item>
        <item>Turkmen</item>
        <item>Ukrainian</item>
        <item>Uzbek_Latin</item>
        <item>Waray</item>
        <item>Welsh</item>
        <item>Wolof</item>
        <item>Xhosa</item>
        <item>Zapotec</item>
        <item>Zulu</item>
    </string-array>
    <string-array name="mode6_options">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="mode6_values" translatable="false">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
</resources>

应用启动后，向下滚动到菜单条目“使用此菜单”。如你所见，排序工作，首先是“南非荷兰语”（不是“奥罗莫”）。选择您选择的任何选项，然后滚动菜单或尝试再次打开相同的菜单项：Stacktrace出现。如果您注释掉排序功能

// sortListPreferenceByEntries("language");

菜单按预期工作，不会崩溃。所以问题仍然存在：如何以应用程序继续工作的方式对菜单进行排序（与未分类的菜单一样）？

Answer 1

您的i在

for (int i = 0; entryIterator.hasNext() && i < size; entry = entryIterator.next(), i++) {

是错误的。如果您有size中的15，实际上您遍历了0到 13 ，最后一个（{{1} }）留在14。