java - EditTextPreference 不适用于字符串

Question

我使用 Android 模板创建了一个设置 Activity 。 首先，一切正常，但现在我想从 EditTextPreference 获取 String。但是当我开始运行它时，它因以下错误而崩溃:

java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String

我使用了正确的 Key 和 getString 方法。 由于每次我想打开“设置”时都会发生这种情况，我的应用程序崩溃并且出现错误:

2020-02-01 17:22:55.260 24468-24468/de.fabipfolix.vertretungsplan E/AndroidRuntime: FATAL EXCEPTION: main
Process: de.fabipfolix.vertretungsplan, PID: 24468
java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
    at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:288)
    at androidx.preference.Preference.getPersistedString(Preference.java:1686)
    at androidx.preference.EditTextPreference.onSetInitialValue(EditTextPreference.java:106)
    at androidx.preference.Preference.onSetInitialValue(Preference.java:1614)
    at androidx.preference.Preference.dispatchSetInitialValue(Preference.java:1587)
    at androidx.preference.Preference.onAttachedToHierarchy(Preference.java:1311)
    at androidx.preference.Preference.onAttachedToHierarchy(Preference.java:1326)
    at androidx.preference.PreferenceGroup.addPreference(PreferenceGroup.java:249)
    at androidx.preference.PreferenceGroup.addItemFromInflater(PreferenceGroup.java:170)
    at androidx.preference.PreferenceInflater.rInflate(PreferenceInflater.java:345)
    at androidx.preference.PreferenceInflater.rInflate(PreferenceInflater.java:346)
    at androidx.preference.PreferenceInflater.inflate(PreferenceInflater.java:157)
    at androidx.preference.PreferenceInflater.inflate(PreferenceInflater.java:109)
    at androidx.preference.PreferenceManager.inflateFromResource(PreferenceManager.java:216)
    at androidx.preference.PreferenceFragmentCompat.setPreferencesFromResource(PreferenceFragmentCompat.java:377)
    at de.fabipfolix.vertretungsplan.SettingsActivity$SettingsFragment.onCreatePreferences(SettingsActivity.java:42)
    at androidx.preference.PreferenceFragmentCompat.onCreate(PreferenceFragmentCompat.java:160)
    at androidx.fragment.app.Fragment.performCreate(Fragment.java:2586)
    at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:838)
    at androidx.fragment.app.FragmentTransition.addToFirstInLastOut(FragmentTransition.java:1197)
    at androidx.fragment.app.FragmentTransition.calculateFragments(FragmentTransition.java:1080)
    at androidx.fragment.app.FragmentTransition.startTransitions(FragmentTransition.java:119)
    at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1866)
    at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
    at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
    at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2663)
    at androidx.fragment.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManagerImpl.java:2613)
    at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:246)
    at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:542)
    at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:201)
    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1425)
    at android.app.Activity.performStart(Activity.java:7825)
    at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3294)
    at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
    at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
    at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

我已经评论了我今天所做的一切，但我不知道问题是什么。 XML 文件的设计窗口显示我必须输入一个 boolean 值。 有谁知道如何解决这个问题吗？

这是我的文件:

root_preferences.xml:

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">

<PreferenceCategory app:title="Login Daten">

    <EditTextPreference
        android:ems="10"
        android:inputType="text"
        android:key="pref_username"
        android:title="BenutzernameEditText"
        app:title="Benutzername"
        app:useSimpleSummaryProvider="true" />

    <EditTextPreference
        android:dialogTitle="Passwort"
        android:inputType="text"
        android:key="pref_password"
        android:title="Passwort" />

</PreferenceCategory>
<PreferenceCategory app:title="Benachrichtigungen">

    <SwitchPreference
        android:defaultValue="true"
        android:key="switchNotifications"
        android:summary="@string/summarySwitchNotifications"
        android:title="NotificationSwitch" />

</PreferenceCategory>

<PreferenceCategory app:title="Hintergrundaktivität">
</PreferenceCategory>
<PreferenceCategory app:title="Oberstufe">

    <SwitchPreference
        android:contentDescription="Kursbezeichnungen mit  Komma trennen"
        android:defaultValue="false"
        android:key="switchKurse"
        android:title="Kurse filtern" />

    <EditTextPreference
        android:dialogMessage="Kursnamen mit Komma trennen "
        android:key="pref_kurse"
        android:summary="Kursnamen mit Komma trennen "
        android:title="Kursbezeichnungen"
        android:inputType="text"
        app:dialogTitle="Kursbezeichnungen" />

</PreferenceCategory>

主要 Activity :

public class MainActivity extends AppCompatActivity {


FloatingActionButton fabRefresh;

RecyclerView recyclerView;
RecyclerView.Adapter adapter;
RecyclerView.LayoutManager layoutManager;
ArrayList<Vertretungsstunde> vertretungen;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    SharedPreferences sharedPref =PreferenceManager.getDefaultSharedPreferences(this);
    Boolean notifications = sharedPref.getBoolean(SettingsActivity.KEY_PREF_NOTIFICATIONS_SWITCH, false);
    String username = sharedPref.getString(SettingsActivity.KEY_PREF_USERNAME_TEXT, "");


    ArrayList<Vertretungsstunde> list = ...;

    //RECYCLERVIEW
    recyclerView = findViewById(R.id.rv_VertretungenHeute);
    recyclerView.setHasFixedSize(false);
    layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
    recyclerView.setLayoutManager(layoutManager);
    ((SimpleItemAnimator) recyclerView.getItemAnimator()).setSupportsChangeAnimations(false);
    adapter = new VertretungsAdapter(this, list);
    recyclerView.setAdapter(adapter);


    //TOOLBAR
    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    //REFRESH BUTTON
    fabRefresh = findViewById(R.id.fabRefresh);
    fabRefresh.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {                                                //FABRefresh OnClickListener
            Toast.makeText(MainActivity.this, "Refreshing...", Toast.LENGTH_SHORT).show();
            //...               
        }
    });


}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        Intent intent = new Intent(MainActivity.this, de.fabipfolix.vertretungsplan.SettingsActivity.class);
        startActivity(intent);
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

设置 Activity :

public class SettingsActivity extends AppCompatActivity {

public static final String KEY_PREF_NOTIFICATIONS_SWITCH = "switchNotifications";
public static final String KEY_PREF_FILTER_SWITCH = "switchKurse";
public static final String KEY_PREF_KURSE_TEXT ="pref_kurse";
public static final String KEY_PREF_PASSWORD_TEXT = "pref_password";
public static final String KEY_PREF_USERNAME_TEXT = "pref_username";




@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.settings_activity);
    getSupportFragmentManager()
            .beginTransaction()
            .replace(R.id.settings, new SettingsFragment())
            .commit();
    ActionBar actionBar = getSupportActionBar();
    if (actionBar != null) {
        actionBar.setDisplayHomeAsUpEnabled(true);
    }
}

public static class SettingsFragment extends PreferenceFragmentCompat {
    @Override
    public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
        setPreferencesFromResource(R.xml.root_preferences, rootKey);
    }
}
}

Answer 1

根据评论:

您之前保存的数据可能会破坏当前的实现。如果是这种情况，清洁存储应该可以做到