SharedPreferences不保存/持续

Question

我不明白为什么我的复选框首选项未保存或未正确读取。我有下面的代码在AndroidManifest.xml：

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

然后在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 /价值/ strings.xml中

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

然后我有一个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; 
     } 
    }); 
} 
} 

然后我在MainActivity.java在测试按钮，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()); 

和输出始终是：

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: {} 

不管复选框是否被选中与否。

Answer 1

我认为你的问题是，你从一个不同的偏好文件读取，而不是你写的。您按名称阅读，但写入默认值。

尝试在MainActivity分配改为

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

Answer 2

您忘记使用SharedPreference的编辑器并调用编辑器对象的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; 

     } 
    });