SharedPreferences不保存/持續

Question

我不明白爲什麼我的複選框首選項未保存或未正確讀取。我有下面的代碼在AndroidManifest.xml：

<activity android:name=".Preferences" /> 

然後在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="Preferences"> 
    <CheckBoxPreference 
     android:title="Always Run" 
     android:key="@string/pref_always_run_key" 
     android:summary="Always run it" /> 
</PreferenceCategory> 

而在RES /價值/ strings.xml中

<string name="pref_always_run_key">always_run_default</string> 

然後我有一個src/com.name/Preferences.java文件

public class Preferences extends PreferenceActivity 
{ 
private static final String LOG_TAG = Preferences.class.getSimpleName() + "_LOG"; 

@SuppressWarnings("deprecation") 
@Override 
protected void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
    addPreferencesFromResource(R.xml.preferences); //5 

    //getPreferenceManager().setSharedPreferencesName(); 

    CheckBoxPreference alwaysRunCheckBox = (CheckBoxPreference)findPreference(getString(R.string.pref_always_run_key));// 8 

    alwaysRunCheckBox.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() 
    { 

     @Override 
     public boolean onPreferenceChange(Preference preference, Object newValue) 
     { 

      Log.d(LOG_TAG, "User set always run to " + newValue.toString().equals("true")); 
      return true; 
     } 
    }); 
} 
} 

然後我在MainActivity.java在測試按鈕，我有

SharedPreferences prefs = MainActivity.this.getSharedPreferences("com.projname.Preferences", Context.MODE_PRIVATE); 
      String defaultAlwaysRunKey = MainActivity.this.getResources().getString(R.string.pref_always_run_key); 
      Log.d(LOG_TAG, "Always run key is " + defaultAlwaysRunKey); 
      boolean run = prefs.getBoolean(defaultAlwaysRunKey, false); 
          Log.d(LOG_TAG, "It contains the key: " + prefs.contains(defaultAlwaysRunKey)); 
      Log.d(LOG_TAG, "Always run set to " + run); 
Log.d(LOG_TAG, "All the preferences saved are: " + prefs.getAll().toString()); 

和輸出始終是：

10-25 16:15:50.844: D/MainActivity_LOG(1219): Clicked on test... 
10-25 16:15:50.844: D/MainActivity_LOG(1219): Always run key is always_run_default 
10-25 16:15:50.844: D/MainActivity_LOG(1219): It contains the key: false 
10-25 16:15:50.844: D/MainActivity_LOG(1219): Always run set to false 
10-25 16:15:50.855: D/MainActivity_LOG(1219): All the preferences saved are: {} 

不管複選框是否被選中與否。

Answer 1

我認爲你的問題是，你從一個不同的偏好文件讀取，而不是你寫的。您按名稱閱讀，但寫入默認值。

嘗試在MainActivity分配改爲

SharedPreferences prefs = 
    PreferenceManager.getDefaultSharedPreferences(MainActivity.this); 

Answer 2

您忘記使用SharedPreference的編輯器並調用編輯器對象的commit();方法。

CheckBoxPreference alwaysRunCheckBox = (CheckBoxPreference)findPreference(getString(R.string.pref_always_run_key));// 8 

    alwaysRunCheckBox.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() 
    { 

     @Override 
     public boolean onPreferenceChange(Preference preference, Object newValue) 
     { 

      boolean val = Boolean.parseBoolean(newValue.toString()); 

      Editor e = preference.getEditor(); 
      e.putBoolean(getString(R.string.pref_always_run_key), val); 
      e.commit(); 
      Log.d(LOG_TAG, "User set always run to " + String.valueOf(val)); 

      return true; 

     } 
    });