android–SharedPreferences ListPreference NullPointerException

概述我正在尝试在我的首选项xml中设置频率列表,但我一直收到此错误.我也附上了所有相关文件.我相信我正确设置了值,但我找不到我的错误当前的位置.另外,当我使用SharedPreferences.getString(key,defaultValue)时返回什么值？ENTRY或ENTRYVALUE？我的错误：08-2000:14:25.195:E/Android

我正在尝试在我的首选项xml中设置频率列表,但我一直收到此错误.我也附上了所有相关文件.我相信我正确设置了值,但我找不到我的错误当前的位置.另外,当我使用SharedPreferences.getString(key,defaultValue)时返回什么值？ ENTRY或ENTRYVALUE？

我的错误：

08-20 00:14:25.195: E/AndroIDRuntime(1260): FATAL EXCEPTION: main08-20 00:14:25.195: E/AndroIDRuntime(1260): java.lang.NullPointerException08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.preference.ListPreference.findindexOfValue(ListPreference.java:215)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.preference.ListPreference.getValueIndex(ListPreference.java:224)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.preference.ListPreference.getEntry(ListPreference.java:202)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.preference.ListPreference.getSummary(ListPreference.java:148)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.preference.Preference.onBindVIEw(Preference.java:515)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.preference.Preference.getVIEw(Preference.java:453)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.preference.PreferenceGroupAdapter.getVIEw(PreferenceGroupAdapter.java:222)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.AbsListVIEw.obtainVIEw(AbsListVIEw.java:2461)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.ListVIEw.makeAndAddVIEw(ListVIEw.java:1775)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.ListVIEw.fillDown(ListVIEw.java:678)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.ListVIEw.fillFromtop(ListVIEw.java:739)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.ListVIEw.layoutChildren(ListVIEw.java:1628)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.AbsListVIEw.onLayout(AbsListVIEw.java:2296)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEw.layout(VIEw.java:14063)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwGroup.layout(VIEwGroup.java:4603)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.linearLayout.setChildFrame(linearLayout.java:1655)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.linearLayout.layoutVertical(linearLayout.java:1513)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.linearLayout.onLayout(linearLayout.java:1426)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEw.layout(VIEw.java:14063)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwGroup.layout(VIEwGroup.java:4603)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.FrameLayout.onLayout(FrameLayout.java:448)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEw.layout(VIEw.java:14063)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwGroup.layout(VIEwGroup.java:4603)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.linearLayout.setChildFrame(linearLayout.java:1655)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.linearLayout.layoutVertical(linearLayout.java:1513)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.linearLayout.onLayout(linearLayout.java:1426)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEw.layout(VIEw.java:14063)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwGroup.layout(VIEwGroup.java:4603)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.Widget.FrameLayout.onLayout(FrameLayout.java:448)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEw.layout(VIEw.java:14063)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwGroup.layout(VIEwGroup.java:4603)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwRootImpl.performlayout(VIEwRootImpl.java:1994)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwRootImpl.performTraversals(VIEwRootImpl.java:1815)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwRootImpl.doTraversal(VIEwRootImpl.java:1112)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.VIEwRootImpl$TraversalRunnable.run(VIEwRootImpl.java:4518)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.Choreographer$CallbackRecord.run(Choreographer.java:725)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.Choreographer.doCallbacks(Choreographer.java:555)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.Choreographer.doFrame(Choreographer.java:525)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.vIEw.Choreographer$FramedisplayEventReceiver.run(Choreographer.java:711)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.os.Handler.handleCallback(Handler.java:615)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.os.Handler.dispatchMessage(Handler.java:92)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.os.Looper.loop(Looper.java:137)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at androID.app.ActivityThread.main(ActivityThread.java:4898)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at java.lang.reflect.Method.invokeNative(Native Method)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at java.lang.reflect.Method.invoke(Method.java:511)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:773)08-20 00:14:25.195: E/AndroIDRuntime(1260):     at dalvik.system.NativeStart.main(Native Method)

xml布局：

<ListPreference         androID:key="frequency_key"        androID:title="Sample Rate"        androID:defaultValue="8000"        androID:entrIEs="@array/freq_Titles"        androID:entryValues="@array/freq_values"        />

xml数组：

<?xml version="1.0" enCoding="utf-8"?><resources><string-array name="freq_Titles">    <item name="8000">8k Hz</item>    <item name="16000">16k Hz</item>    <item name="22050">22.05k Hz</item>    <item name="44100">44.1k Hz</item>    <item name="48000">48k Hz</item></string-array><array name="freq_values">    <item name="8000">8000</item>    <item name="16000">16000</item>    <item name="22050">22050</item>    <item name="44100">44100</item>    <item name="48000">48000</item></array></resources>

更新：即使我从默认的共享首选项中执行getAll(),它也很奇怪,它向我显示“frequency_key = 8k Hz”.所以它已经初始化了.

来自我的偏好类的更多代码：

public class Settings_ActivityAH extends PreferenceFragment implements OnSharedPreferencechangelistener{private SharedPreferences prefs;private Preference myAccountname;private Preference myGoogleUsername;private Preference myGooglePassword;private static Context context;public voID onCreate(Bundle savedInstanceState){    super.onCreate(savedInstanceState);    addPreferencesFromresource(R.xml.preferences);    context = getActivity();    if (context == null){        Log.e("error","context is null");    }    prefs = PreferenceManager.getDefaultSharedPreferences(context);    myAccountname = (Preference) findPreference("account_name_Title_key");    myGoogleUsername = (Preference) findPreference("Googleusername_key");    myGooglePassword = (Preference) findPreference("Googlepassword_key");    myAccountname.setSummary(prefs.getString("account_name_Title_key", "none"));    myGoogleUsername.setTitle("username: "+prefs.getString("Googleusername_key", "none"));    myGooglePassword.setTitle("password: "+prefs.getString("Googlepassword_key", "none"));    Log.e("Check prefs",prefs.getAll().toString());    prefs.registerOnSharedPreferencechangelistener(this);}@OverrIDepublic voID onSharedPreferenceChanged(SharedPreferences sharedPreferences,        String key) {    Log.e("in onSharedPref","yea");    Preference preference = findPreference(key);    if (preference.getClass() == EditTextPreference.class){        Log.e("in editText Pref", "yeah");        if( key.equals("account_name_Title_key")){            myAccountname.setSummary(sharedPreferences.getString("account_name_key","none"));            Log.e("accountname prefs",sharedPreferences.getString("account_name_key","none"));    }        if( key.equals("account_name_key")){            myAccountname.setSummary(sharedPreferences.getString("account_name_key","none"));            Log.e("accountname prefs",sharedPreferences.getString("account_name_key","none"));    }    else if (preference.getClass() == Preferencecategory.class){        Log.e("in category Pref", "yeah");        if (key.equals("Googleusername_key")){            myGoogleUsername.setTitle("Username: "+sharedPreferences.getString(key, "none"));            Log.e("Googleusername prefs",sharedPreferences.getString(key, "none"));        }        else if( key.equals("Googlepassword_key")){            myGooglePassword.setTitle("Password: "+sharedPreferences.getString(key, "none"));            Log.e("Googlepassword prefs",sharedPreferences.getString(key, "none"));        }    }}else{    Log.e("insufficIEnt key called","onSharedPreferenceChanged AH");}}

}

解决方法:

似乎AndroID只接受字符串数组作为ListPreference XML属性androID：entryValues的参数.这与所有XML属性仅采用具有一种特定的预定类型(即int,bool,string等)的参数一致.请参阅以下问题：ListPreference: use string-array as Entry and integer-array as Entry Values doesn’t work

关于你的问题,getString()将返回与被点击的条目对应的androID：entryValues数组的元素. androID：entrIEs数组仅用作用户的一系列显示字符串,并且在代码中没有其他影响,而androID：entryValues中的值用于应用程序中的持久存储.

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