CollapsiblePreferenceGroupController.java
/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.preference;
import android.content.Context;
import android.text.TextUtils;
import java.util.ArrayList;
import java.util.List;
/**
* A controller to handle child visibility logic when dealing with expandable preferences.
*/
final class CollapsiblePreferenceGroupController {
@SuppressWarnings("WeakerAccess") /* synthetic access */
final PreferenceGroupAdapter mPreferenceGroupAdapter;
private final Context mContext;
/**
* Whether there is a child {@link PreferenceGroup} that has an expandable preference. This
* is used to avoid unnecessary preference tree rebuilds when no such group exists.
*/
private boolean mHasExpandablePreference = false;
CollapsiblePreferenceGroupController(PreferenceGroup preferenceGroup,
PreferenceGroupAdapter preferenceGroupAdapter) {
mPreferenceGroupAdapter = preferenceGroupAdapter;
mContext = preferenceGroup.getContext();
}
/**
* Generates the visible section of the {@link PreferenceGroup}.
*
* @param group The root preference group to be processed
* @return The flattened and visible section of the preference group
*/
public List<Preference> createVisiblePreferencesList(PreferenceGroup group) {
return createInnerVisiblePreferencesList(group);
}
private List<Preference> createInnerVisiblePreferencesList(PreferenceGroup group) {
mHasExpandablePreference = false;
int visiblePreferenceCount = 0;
final boolean hasExpandablePreference =
group.getInitialExpandedChildrenCount() != Integer.MAX_VALUE;
final List<Preference> visiblePreferences = new ArrayList<>();
final List<Preference> collapsedPreferences = new ArrayList<>();
final int groupSize = group.getPreferenceCount();
for (int i = 0; i < groupSize; i++) {
final Preference preference = group.getPreference(i);
if (!preference.isVisible()) {
continue;
}
if (!hasExpandablePreference
|| visiblePreferenceCount < group.getInitialExpandedChildrenCount()) {
visiblePreferences.add(preference);
} else {
collapsedPreferences.add(preference);
}
// PreferenceGroups do not count towards the maximal number of preferences to show
if (!(preference instanceof PreferenceGroup)) {
visiblePreferenceCount++;
continue;
}
PreferenceGroup innerGroup = (PreferenceGroup) preference;
if (!innerGroup.isOnSameScreenAsChildren()) {
continue;
}
// Recursively generate nested list of visible preferences
final List<Preference> innerList = createInnerVisiblePreferencesList(innerGroup);
if (hasExpandablePreference && mHasExpandablePreference) {
throw new IllegalArgumentException("Nested expand buttons are not supported!");
}
for (Preference inner : innerList) {
if (!hasExpandablePreference
|| visiblePreferenceCount < group.getInitialExpandedChildrenCount()) {
visiblePreferences.add(inner);
} else {
collapsedPreferences.add(inner);
}
visiblePreferenceCount++;
}
}
// If there are any visible preferences being hidden, add an expand button to show the rest
// of the preferences. Clicking the expand button will show all the visible preferences.
if (hasExpandablePreference
&& visiblePreferenceCount > group.getInitialExpandedChildrenCount()) {
final ExpandButton expandButton = createExpandButton(group, collapsedPreferences);
visiblePreferences.add(expandButton);
}
mHasExpandablePreference |= hasExpandablePreference;
return visiblePreferences;
}
private ExpandButton createExpandButton(final PreferenceGroup group,
List<Preference> collapsedPreferences) {
final ExpandButton preference = new ExpandButton(mContext, collapsedPreferences,
group.getId());
preference.setOnPreferenceClickListener(new Preference.OnPreferenceClickListener() {
@Override
public boolean onPreferenceClick(Preference preference) {
group.setInitialExpandedChildrenCount(Integer.MAX_VALUE);
mPreferenceGroupAdapter.onPreferenceHierarchyChange(preference);
final PreferenceGroup.OnExpandButtonClickListener listener =
group.getOnExpandButtonClickListener();
if (listener != null) {
listener.onExpandButtonClick();
}
return true;
}
});
return preference;
}
/**
* A {@link Preference} that expands the collapsed items in the {@link PreferenceGroup}.
*/
static class ExpandButton extends Preference {
private long mId;
ExpandButton(Context context, List<Preference> collapsedPreferences, long parentId) {
super(context);
initLayout();
setSummary(collapsedPreferences);
// Since IDs are unique, using the parentId as a reference ensures that this expand
// button will have a unique ID and hence transitions will be correctly animated by
// RecyclerView when there are multiple expand buttons.
mId = parentId + 1000000;
}
private void initLayout() {
setLayoutResource(R.layout.expand_button);
setIcon(R.drawable.ic_arrow_down_24dp);
setTitle(R.string.expand_button_title);
// Sets a high order so that the expand button will be placed at the bottom of the group
setOrder(999);
}
/*
* Sets the summary of the expand button to a list containing the titles of the collapsed
* preferences. If there are any nested groups with titles, only add the group's title
* and not the titles of the group's children.
*/
private void setSummary(List<Preference> collapsedPreferences) {
CharSequence summary = null;
final List<PreferenceGroup> parents = new ArrayList<>();
for (Preference preference : collapsedPreferences) {
final CharSequence title = preference.getTitle();
if (preference instanceof PreferenceGroup && !TextUtils.isEmpty(title)) {
parents.add((PreferenceGroup) preference);
}
if (parents.contains(preference.getParent())) {
if (preference instanceof PreferenceGroup) {
parents.add((PreferenceGroup) preference);
}
continue;
}
if (!TextUtils.isEmpty(title)) {
if (summary == null) {
summary = title;
} else {
summary = getContext().getString(
R.string.summary_collapsed_preference_list, summary, title);
}
}
}
setSummary(summary);
}
@Override
public void onBindViewHolder(PreferenceViewHolder holder) {
super.onBindViewHolder(holder);
holder.setDividerAllowedAbove(false);
}
@Override
public long getId() {
return mId;
}
}
}