Preference状态恢复原理
0. 入口：PreferenceFragment.java
public void addPreferencesFromResource(@XmlRes int preferencesResId) {
requirePreferenceManager();
setPreferenceScreen(mPreferenceManager.inflateFromResource(getActivity(),
preferencesResId, getPreferenceScreen()));
}
1. PreferenceManager.java
public PreferenceScreen inflateFromResource(Context context, @XmlRes int resId,
PreferenceScreen rootPreferences) {
// Block commits
setNoCommit(true);
final PreferenceInflater inflater = new PreferenceInflater(context, this);
rootPreferences = (PreferenceScreen) inflater.inflate(resId, rootPreferences, true);
rootPreferences.onAttachedToHierarchy(this);
// Unblock commits
setNoCommit(false);
return rootPreferences;
}
2. GenericInflater(PreferenceInflater的父类)
private void rInflate(XmlPullParser parser, T parent, final AttributeSet attrs)
throws XmlPullParserException, IOException {
.......
if (onCreateCustomFromTag(parser, parent, attrs)) {
.......
}
if (DEBUG) {
((P) parent).addItemFromInflater(item);
......
}
其中parent就是PreferenceGroup
3. PreferenceGroup.java
public boolean addPreference(Preference preference) {
synchronized(this) {
mPreferenceList.add(insertionIndex, preference);
}
preference.onAttachedToHierarchy(getPreferenceManager());
if (mAttachedToActivity) {
preference.onAttachedToActivity();
}
4. Preference.java
protected void onAttachedToHierarchy(PreferenceManager preferenceManager) {
mPreferenceManager = preferenceManager;
mId = preferenceManager.getNextId();
dispatchSetInitialValue();
}
private void dispatchSetInitialValue() {
// By now, we know if we are persistent.
final boolean shouldPersist = shouldPersist();
if (!shouldPersist || !getSharedPreferences().contains(mKey)) {
if (mDefaultValue != null) {
onSetInitialValue(false, mDefaultValue);
}
} else {
onSetInitialValue(true, null);
}
}
TwoStatePreference/MultiSelectListPreference/SeekBarPreference/YesNoPreference/EditTextPreference等都有onSetInitialValue的实现,比如：TwoStatePreference
@Override
protected void onSetInitialValue(boolean restoreValue, Object defaultValue) {
setChecked(restoreValue ?getPersistedBoolean(mChecked)
: (Boolean) defaultValue);
}
protected boolean getPersistedBoolean(boolean defaultReturnValue) {
if (!shouldPersist()) {
return defaultReturnValue;
}
return mPreferenceManager.getSharedPreferences().getBoolean(mKey, defaultReturnValue);
}
至此，数据恢复了。
