在同步完成后,我正在更改SyncAdapter中的SharedPreference,但是当我访问我的活动中的首选项时,我没有看到更新的值(而是看到旧的值).我究竟做错了什么？不同的语境
我的SyncAdapter更新优先级：
class SyncAdapter extends AbstractThreadedSyncAdapter {
private int PARTICIPANT_ID;
private final Context mContext;
private final ContentResolver mContentResolver;
public SyncAdapter(Context context,boolean autoInitialize) {
super(context,autoInitialize);
mContext = context;
mContentResolver = context.getContentResolver();
}
public SyncAdapter(Context context,boolean autoInitialize,boolean allowParallelSyncs) {
super(context,autoInitialize,allowParallelSyncs);
mContext = context;
mContentResolver = context.getContentResolver();
}
@Override
public void onPerformSync(Account account,Bundle extras,String authority,ContentProviderClient provider,SyncResult syncResult) {
final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
PARTICIPANT_ID = Integer.parseInt(prefs.getString("participant_id","0"));
if (success) {
// save and set the new participant id
PARTICIPANT_ID = newParticipantId;
prefs.edit().putString("participant_id",String.valueOf(newParticipantId)).commit();
}
}
}
该服务使用ApplicationContext初始化SyncAdapter：
public class SyncService extends Service {
private static final Object sSyncAdapterLock = new Object();
private static SyncAdapter sSyncAdapter = null;
@Override
public void onCreate() {
synchronized (sSyncAdapterLock) {
if (sSyncAdapter == null) {
sSyncAdapter = new SyncAdapter(getApplicationContext(),false);
}
}
}
@Override
public IBinder onBind(Intent intent) {
return sSyncAdapter.getSyncAdapterBinder();
}
}
Activity中的一个静态函数,由Activity检查SharedPreference.这不返回在SyncAdapter中提交的值,而是返回旧值. (我的设置活动和其他活动也使用旧值.)：
public static boolean isUserLoggedIn(Context ctx) {
final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(ctx);
int participantId = Integer.parseInt(prefs.getString("participant_id","0"));
LOGD("dg_Utils","isUserLoggedIn.participantId: " + participantId);// TODO
if (participantId <= 0) {
ctx.startActivity(new Intent(ctx,LoginActivity.class).addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
return false;
}
return true;
}
更新：当我完全关闭应用程序(从运行的应用程序中滑动)时,我获得了新的值.我还有一个SharedPreferenceChangeListener,当更改首选项时,它不会被触发.
private final SharedPreferences.OnSharedPreferenceChangeListener mParticipantIDPrefChangeListener = new SharedPreferences.OnSharedPreferenceChangeListener() {
public void onSharedPreferenceChanged(SharedPreferences prefs,String key) {
if (key.equals("participant_id")) {
LOGI(TAG,"participant_id has changed,requesting to restart the loader.");
mRestartLoader = true;
}
}
};
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// subscribe to the participant_id change lister
final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
PARTICIPANT_ID = Integer.parseInt(prefs.getString("participant_id","0"));
prefs.registerOnSharedPreferenceChangeListener(mParticipantIDPrefChangeListener);
}
解决方法
好的,我通过@Titus的帮助,经过一些研究,拼凑了一个解决我的问题的自己.
没有更新相同上下文的DefaultSharedPreferences的原因是我已经指定了SyncService在AndroidManifest.xml中的自己的进程中运行(见下文).因此,从Android 2.3开始,其他进程被阻止访问更新的SharedPreferences文件(参见this answer和Context.MODE_MULTI_PROCESS上的Android文档).
<service
android:name=".sync.SyncService"
android:exported="true"
android:process=":sync"
tools:ignore="ExportedService" >
<intent-filter>
<action android:name="android.content.SyncAdapter" />
</intent-filter>
<Meta-data
android:name="android.content.SyncAdapter"
android:resource="@xml/syncadapter" />
</service>
所以在SyncAdapter和我的应用程序的UI进程中访问SharedPreferences时,我必须设置MODE_MULTI_PROCESS.因为我在整个应用程序中广泛使用了PreferenceManager.getDefaultSharedPreferences(Context),所以我编写了一个实用程序方法,并用此方法替换了PreferenceManager.getDefaultSharedPreferences(Context)的所有调用(见下文).首选项文件的默认名称是硬编码的,并从the Android source code和this answer派生.
public static SharedPreferences getDefaultSharedPreferencesMultiProcess(
Context context) {
return context.getSharedPreferences(
context.getPackageName() + "_preferences",Context.MODE_PRIVATE | Context.MODE_MULTI_PROCESS);
}
