Because MODE_MULTI_PROCESS is not currently supported, I haven't found any way to work with Shared Preferences between processes other than working around it.
I know people are sharing the libraries they wrote to address this, but I actually used a third-party library I found on another thread that implements SQLLite in lieu of the Shared Preferences:
https://github.com/hamsterready/dbpreferences
However, what was important to me that I haven't found addressed in other solutions was maintaining the automatic UI generation already built into Preference Fragment - better to be able to specify your elements in XML and call addPreferencesFromResource(R.xml.preferences) than have to build your UI from scratch.
So, to make this work, I subclassed each of the Preference elements I needed (in my case just Preference, SwitchPreference, and EditTextPreference), and overrode a few methods from the base classes to include saving to an instance of DatabaseSharedPreferences taken from the above library.
For example, below I subclass EditTextPreference and get the preference key from the base class. I then override the persist and getPersisted methods in Preference base class. I then override onSetInitialValue, setText, and getText in the EditText base class.
public class EditTextDBPreference extends EditTextPreference {
private DatabaseBasedSharedPreferences mDBPrefs;
private String mKey;
private String mText;
public EditTextDBPreference(Context context) {
super(context);
init(context);
}
public EditTextDBPreference(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public EditTextDBPreference(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
public EditTextDBPreference(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init(context);
}
private void init(Context context)
{
mDBPrefs = new DatabaseBasedSharedPreferences(context);
mKey = super.getKey();
}
public DatabaseBasedSharedPreferences getSharedDBPreferences()
{
if (mDBPrefs == null) {
return null;
}
return mDBPrefs;
}
@Override
protected boolean persistBoolean(boolean value) {
if (mKey != null)
mDBPrefs.putBoolean(mKey,value);
return super.persistBoolean(value);
}
@Override
protected boolean persistFloat(float value) {
if (mKey != null)
mDBPrefs.putFloat(mKey, value);
return super.persistFloat(value);
}
@Override
protected boolean persistInt(int value) {
if (mKey != null)
mDBPrefs.putInt(mKey, value);
return super.persistInt(value);
}
@Override
protected boolean persistLong(long value) {
if (mKey != null)
mDBPrefs.putLong(mKey, value);
return super.persistLong(value);
}
@Override
protected boolean persistString(String value) {
if (mKey != null)
mDBPrefs.putString(mKey, value);
return super.persistString(value);
}
@Override
protected boolean getPersistedBoolean(boolean defaultReturnValue) {
if (mKey == null)
return false;
return mDBPrefs.getBoolean(mKey, defaultReturnValue);
}
@Override
protected float getPersistedFloat(float defaultReturnValue) {
if (mKey == null)
return -1f;
return mDBPrefs.getFloat(mKey, defaultReturnValue);
}
@Override
protected int getPersistedInt(int defaultReturnValue) {
if (mKey == null)
return -1;
return mDBPrefs.getInt(mKey, defaultReturnValue);
}
@Override
protected long getPersistedLong(long defaultReturnValue) {
if (mKey == null)
return (long)-1.0;
return mDBPrefs.getLong(mKey, defaultReturnValue);
}
@Override
protected String getPersistedString(String defaultReturnValue) {
if (mKey == null)
return null;
return mDBPrefs.getString(mKey, defaultReturnValue);
}
@Override
public void setKey(String key) {
super.setKey(key);
mKey = key;
}
@Override
protected void onSetInitialValue(boolean restoreValue, Object defaultValue) {
setText(restoreValue ? getPersistedString(mText) : (String) defaultValue);
}
@Override
public void setText(String text) {
final boolean wasBlocking = shouldDisableDependents();
boolean textChanged = false;
if (mText != null && !mText.equals(text))
textChanged = true;
mText = text;
persistString(text);
if (textChanged) {
// NOTE: This is a an external class in my app that I use to send a broadcast to other processes that preference settings have changed
BASettingsActivity.SendSettingsUpdate(getContext());
}
final boolean isBlocking = shouldDisableDependents();
if (isBlocking != wasBlocking) {
notifyDependencyChange(isBlocking);
}
}
@Override
public String getText() {
return mText;
}
Then you simply specify the new element in your preferences.xml file, and voila!
You now get the process interoperability of SQLLite and the UI auto-generation of PreferenceFragment!
<com.sampleproject.EditTextDBPreference
android:key="@string/pref_key_build_number"
android:title="@string/build_number"
android:enabled="false"
android:selectable="false"
android:persistent="false"
android:shouldDisableView="false"/>
android:processelement. I'm less certain about not using the shared prefs; the subprocess is running a third party native lib. – Figureground