我目前正在使用SharedPreferences开发应用程序，我正在尝试动态更改Prefs活动屏幕上显示的值。 在屏幕上，我有一个preferencelistview，其中包含一年中的几个月和两个编辑框，用于存储与所选月份相关的信息。选择一个月后，我想要做一些事情：
所以，基本上，我的问题是第2项。我有一个函数来检查从列表中选择新月份的时间：
public void setMonth(SharedPreferences sp) {
ContentValues cv = new ContentValues();
cv.clear();
int sel_month = Integer.valueOf(sp.getString("pActivityMonth", String.valueOf(this.month))); //listvew works with strings, convert to int
int stored_new = 0; //default value
int stored_ren = 0; //default value
Log.d(TAG, String.valueOf(sel_month));
String[] col = { Database.C_MONTH, Database.C_QNEW, Database.C_QRENEW };
String[] arg = { String.valueOf(sel_month) };
Cursor c = db.query(Database.RR_TABLE, col, Database.C_MONTH + "=?", arg, null, null, null);
if (c.getCount()<1) { //New month, insert row
cv.put(Database.C_MONTH, sel_month);
db.insertWithOnConflict(Database.RR_TABLE, null, cv, SQLiteDatabase.CONFLICT_IGNORE);
} else { //row exists, get stored values
Log.d(TAG, "cursor count: " + String.valueOf(c.getCount()));
c.moveToFirst();
stored_new = c.getInt(c.getColumnIndex(Database.C_QNEW));
stored_ren = c.getInt(c.getColumnIndex(Database.C_QRENEW));
Log.d(TAG, "stored_new: " + String.valueOf(stored_new));
}
//Change edittext preferences to stored values
editor.putString("pNewQuota", String.valueOf(stored_new));
editor.putString("pRenewQuota", String.valueOf(stored_ren));
editor.apply();
editor.commit();
}
所以，我选择一个新的月份（7月），点击其中一个edittext选项来更新信息（假设我输入了20），然后选择不同的月份（8月），默认值为0。然后我再次单击edittext，对话框继续显示20而不是0.如果我将此0更改为其他内容，它将存储在数据库的正确行中，但此值在更改为另一个月后继续保持（比如说，回到7月）。 我的Logcat显示该函数正在获取正确的值，并且正在运行putString。 PreferenceScreen是否无法自行刷新？谢谢你的帮助。
答案 0 :(得分：1)
如果我理解正确，您似乎有一个PreferenceActivity，它使用SharedPreferences和SQLiteDatabase来持久保存/保存相同的数据。虽然PreferenceActivity看起来像是为数据输入而设计的预构建ListView，但它实际上还有很多：PreferenceActivity会自动保存并加载Preferences到SharedPreferences，这是一个分配给您的应用程序并由Android OS管理的特殊数据存储。 / p>
虽然打算存储首选项，但如果需要，可以使用SharedPreferences来保存某些数据;要么自动通过“首选项”，要么通过调用编辑器手动进行。您可以通过多种方式中断和/或修改此持久性，例如创建首选项子类以替换行为，使用OnPreferenceChangeListener修改行为，或通过调用setPersistent（boolean）来切换持久性。
以这种方式使用PreferenceActivity的另一种方法是使用AdapterView或ListActivity创建一个Activity，并使用SimpleCursorAdapter自动将数据绑定到视图。
要回答有关在PreferenceActivity中持续更改SharedPreferences的问题，我在上下文中提供了一些粗略概述的示例代码，并概述了几个潜在的问题点。它并不打算代表一个可用的解决方案，而是想知道你需要什么，在哪里，我希望是一种清晰（如果详细）的方式，不应该太难以适应你的项目。 / p>
/* Preference value modification example.
* This is a code sample with some context, not a solution.
* @author codeshane.com
* */
public class StackOverflow_Question_11513113 extends PreferenceActivity {
/*
*/
class MyPreferenceActivity extends PreferenceActivity {
//Preference keys that were either set in xml, or possibly in source via .setKey():
private final String pref_group_key = "some_prefs_key";
private final String list_pref_key = "some_list_key";
private final String edittext_pref_key = "some_edittext_key";
private PreferenceActivity mPreferenceActivity; /* the activity */
private SharedPreferences mSharedPreferences; /* auto-saving preferences */
private Editor mEdit;
private PreferenceScreen mPreferenceScreen; /* root of the preference hierarchy */
private PreferenceGroup mPreferenceGroup; /* optional grouping of preferences */
private ListPreference mListPreference; /* a pop-up selectable-items-list */
private EditTextPreference mEditTextPreference; /* a pop-up text entry box */
private int stored_new;
private int stored_ren;
/* ... */
public void setMonth() { /*SharedPreferences sp*/
/* ... */
//int stored_new = 0; //default value
//int stored_ren = 0; //default value
/* ... */
/* Should only call either apply() or commit(), not both; calling a .commit() after an .apply() can block the thread (always fun),
* not to mention they essentially do the same thing, just synchronously vs asynchronously.
* http://developer.android.com/reference/android/content/SharedPreferences.Editor.html#apply()
* */
// mEdit.apply(); //API level 9+, void, asynchronous.
// mEdit.commit(); //API level 1+, returns boolean, synchronous.
}
/* ... */
@Override
public void onCreate(Bundle savedInstanceState) {
/* Called once when the Activity is created. */
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.affirm_prefs);
/* ... */
}
@Override
protected void onResume() {
super.onResume();
/* Called when the Activity is created or comes to foreground. */
if (null==mSharedPreferences){init(this);}
mSharedPreferences.registerOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener);
/* manually load data from shared preferences that IS NOT REPRESENTED
* by a Preference already, or for which Persistent has been manually
* set to false. */
stored_new = mSharedPreferences.getInt("stored_new", 0); //If not found, assigns a default value of 0.
stored_ren = mSharedPreferences.getInt("stored_ren", 0); //If not found, assigns a default value of 0.
}
@Override
protected void onPause() { /* Called when the Activity goes to background. */
super.onPause();
mSharedPreferences.unregisterOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener);
/* manually save data to shared preferences that IS NOT REPRESENTED
* by a Preference already, or for which Persistent has been manually
* set to false. */
mEdit.putInt("stored_new", stored_new);
mEdit.putInt("stored_ren", stored_ren);
mEdit.commit();
}
private boolean init(PreferenceActivity activity){
mPreferenceActivity = activity; // or PreferenceActivity.this;
mSharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
mPreferenceScreen = mPreferenceActivity.getPreferenceScreen();
mPreferenceGroup = (PreferenceGroup)mPreferenceScreen.findPreference(pref_group_key);
mListPreference = (ListPreference)mPreferenceScreen.findPreference(list_pref_key);
mEditTextPreference = (EditTextPreference)mPreferenceScreen.findPreference(edittext_pref_key);
return true;
}
/* When registered to a preference, this listener is notified of changes before saving.
* */
OnPreferenceChangeListener onPreferenceChangeListener = new OnPreferenceChangeListener(){
public boolean onPreferenceChange(Preference preference, Object newValue) {
boolean persistNewValue = true;
/* This occurs when a user has changed a preference, but before it is persisted */
/* this is a good place for your "setMonth" logic,
* at least in a PreferenceActivity*/
updateElement(preference, newValue);
changeMoreStuffBonusMethod(preference);
return persistNewValue;
}};
/* When registered to SharedPreferences, this listener is notified of all saves to SharedPreferences, even if the data is the same
* */
OnSharedPreferenceChangeListener onSharedPreferenceChangeListener = new OnSharedPreferenceChangeListener(){
public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
}
};
private boolean updateElement(Preference prefUpdating, Object value){
if (null==prefUpdating) return false;
/* This function is for manually changing the value before it
* is saved by the PreferenceActivity. */
/* ... */
/* Can match exact instances, such as our mListPreference */
if (mListPreference.equals(prefUpdating)) {
/* set selected item by item's index id */
mListPreference.setValueIndex(0);
/* or set selected item by item's key*/
mListPreference.setValue("item_key");
}
/* Can also match by Class, such as any EditTextPreference */
if (prefUpdating instanceof EditTextPreference){
EditTextPreference etp = (EditTextPreference)prefUpdating;
String oldText = etp.getText();
etp.setText("Some new text in edit text box"); /* or */
etp.setText(String.valueOf(stored_new)); /* or */
etp.setText(oldText.trim()); /* remove leading/trailing whitespace */
etp.setText(dataModel.get(prefUpdating.getKey())); /* if you use a model.. */
}
/* ... */
}
private void changeMoreStuffBonusMethod(Preference prefUpdating){
/* Change the preference text */
prefUpdating.setTitle("Click Me!");
prefUpdating.setSummary("I am a cool preference widget!");
/* Change the pop-up list (not items) text */
if (prefUpdating instanceof ListPreference){
ListPreference lp = (ListPreference)prefUpdating;
lp.setDialogTitle("I am the pop-up.");
lp.setDialogMessage("Select something from my list.");
}
/* If persistent, PreferenceActivity should handle saving: */
Log.v(TAG,prefUpdating.getClass().getSimpleName()+".isPersistent="+String.valueOf(mListPreference.isPersistent()));
}
}
}