addPreferencesFromResource 上的 java.lang.Integer 无法转换为 java.lang.String

Question

我有一个关于首选项的示例，如下所示:

public class UserPreferences extends PreferenceActivity {
    @Override
    public void onCreate(Bundle saveInstanceState){
        super.onCreate(saveInstanceState);
        getFragmentManager().beginTransaction().replace(android.R.id.content, new MynewFracment()).commit();
    }
    public static class MynewFracment extends PreferenceFragment{
        @Override
        public void onCreate(Bundle saveInstanceState){
            super.onCreate(saveInstanceStates);
            addPreferencesFromResource(R.xml.userpreference);
        }
    }
}

但是返回的结果是 addPreferencesFromResource(R.xml.userpreferences); 行上的 java.lang.Integer Cannot be Cast to java.lang.String 。我真的不知道我在这里做错了什么？

<小时/>

更新 1

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <CheckBoxPreference
        android:key="PREF_AUTO_UPDATE"
        android:title="Auto refresh"
        android:summary="Select to turn on automatic updateing"
        android:defaultValue="true"
        ></CheckBoxPreference>
    <ListPreference
        android:key="PREF_UPDATE_FREQ"
        android:title="Refresh frequency"
        android:summary="Frequency at which to refresh earthquake list"
        android:entries="@array/update_freq_option"
        android:entryValues="@array/update_freq_values"
        android:dialogTitle="Refresh frequency"
        android:defaultValue="60"
        ></ListPreference>
    <ListPreference
        android:key="PREF_MIN_MAG"
        android:title="Minimum magnitude"
        android:summary="Select the minimum magnitude earthquake to report"
        android:entries="@array/magnitude_options"
        android:entryValues="@array/magnitude"
        android:dialogTitle="Magnitude"
        android:defaultValue="3"
        ></ListPreference>
</PreferenceScreen>

<小时/>

更新2

我的 R 值

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="update_freq_option">
        <item>Every Minutes</item>
        <item>5 mins</item>
        <item>10 mins</item>
        <item>15 mins</item>
        <item>Every Hours</item>
    </string-array>

    <array name="magnitude">
        <item>3</item>
        <item>5</item>
        <item>6</item>
        <item>7</item>
        <item>8</item>
    </array>

    <string-array name="magnitude_options">
        <item>3</item>
        <item>5</item>
        <item>6</item>
        <item>7</item>
        <item>8</item>
    </string-array>

    <array name="update_freq_values">
        <item>1</item>
        <item>5</item>
        <item>10</item>
        <item>15</item>
        <item>60</item>
    </array>
</resources>

还有我的堆栈跟踪

E/AndroidRuntime: FATAL EXCEPTION: main
                                                                     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.begood.earthquake/com.begood.earthquake.UserPreferences}: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
                                                                         at android.app.ActivityThread.access$600(ActivityThread.java:130)
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
                                                                         at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                         at android.os.Looper.loop(Looper.java:137)
                                                                         at android.app.ActivityThread.main(ActivityThread.java:4745)
                                                                         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:786)
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
                                                                         at dalvik.system.NativeStart.main(Native Method)
                                                                      Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
                                                                         at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:205)
                                                                         at android.preference.Preference.getPersistedString(Preference.java:1399)
                                                                         at android.preference.ListPreference.onSetInitialValue(ListPreference.java:278)
                                                                         at android.preference.Preference.dispatchSetInitialValue(Preference.java:1315)
                                                                         at android.preference.Preference.onAttachedToHierarchy(Preference.java:1127)
                                                                         at android.preference.PreferenceGroup.addPreference(PreferenceGroup.java:156)
                                                                         at android.preference.PreferenceGroup.addItemFromInflater(PreferenceGroup.java:97)
                                                                         at android.preference.PreferenceGroup.addItemFromInflater(PreferenceGroup.java:38)
                                                                         at android.preference.GenericInflater.rInflate(GenericInflater.java:488)
                                                                         at android.preference.GenericInflater.inflate(GenericInflater.java:326)
                                                                         at android.preference.GenericInflater.inflate(GenericInflater.java:263)
                                                                         at android.preference.PreferenceManager.inflateFromResource(PreferenceManager.java:269)
                                                                         at android.preference.PreferenceFragment.addPreferencesFromResource(PreferenceFragment.java:278)
                                                                         at com.begood.earthquake.UserPreferences$MynewFracment.onCreate(UserPreferences.java:20)
                                                                         at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:796)
                                                                         at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1035)
                                                                         at android.app.BackStackRecord.run(BackStackRecord.java:635)
                                                                         at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1397)
                                                                         at android.app.Activity.performStart(Activity.java:5017)
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2032)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
                                                                         at android.app.ActivityThread.access$600(ActivityThread.java:130) 
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
                                                                         at android.os.Handler.dispatchMessage(Handler.java:99) 
                                                                         at android.os.Looper.loop(Looper.java:137) 
                                                                         at android.app.ActivityThread.main(ActivityThread.java:4745) 
                                                                         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:786) 
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
                                                                         at dalvik.system.NativeStart.main(Native Method) 

Answer 1

正如您从堆栈跟踪中看到的，当您调用 addPreferencesFromResource 时，会加载首选项，并调用 onSetInitialValue 将首选项的值设置为保存的值之前，如果有的话。

因为它是一个 ListPreference，所以它使用 getPersistedString，它会尝试加载 String。

这会引发 ClassCastException，因为 pref 曾经是 Integer 类型，并且是这样保存的。

您知道设备上现有的首选项版本与新版本的应用程序不兼容。

要解决此问题，请清除应用数据，或直接将其卸载。

如果您无法做到这一点(如果您的用户拥有该应用的先前版本)，则您需要一个迁移策略，并且可能需要更改新首选项的名称以避免像这样的冲突。