Android example source code file (PreferenceGroupAdapter.java)

This example Android source code file (PreferenceGroupAdapter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, arraylist, baseadapter, comparable, handler, ignore_item_view_type, os, override, preference, preferencegroup, preferencegroupadapter, preferencelayout, runnable, string, tag, ui, util, view, viewgroup, widget

The PreferenceGroupAdapter.java Android example source code

/*
 * Copyright (C) 2007 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 android.preference;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import android.os.Handler;
import android.preference.Preference.OnPreferenceChangeInternalListener;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Adapter;
import android.widget.BaseAdapter;
import android.widget.ListView;

/**
 * An adapter that returns the {@link Preference} contained in this group.
 * In most cases, this adapter should be the base class for any custom
 * adapters from {@link Preference#getAdapter()}.
 * <p>
 * This adapter obeys the
 * {@link Preference}'s adapter rule (the
 * {@link Adapter#getView(int, View, ViewGroup)} should be used instead of
 * {@link Preference#getView(ViewGroup)} if a {@link Preference} has an
 * adapter via {@link Preference#getAdapter()}).
 * <p>
 * This adapter also propagates data change/invalidated notifications upward.
 * <p>
 * This adapter does not include this {@link PreferenceGroup} in the returned
 * adapter, use {@link PreferenceCategoryAdapter} instead.
 * 
 * @see PreferenceCategoryAdapter
 */
class PreferenceGroupAdapter extends BaseAdapter implements OnPreferenceChangeInternalListener {
    
    private static final String TAG = "PreferenceGroupAdapter";

    /**
     * The group that we are providing data from.
     */
    private PreferenceGroup mPreferenceGroup;
    
    /**
     * Maps a position into this adapter -> {@link Preference}. These
     * {@link Preference}s don't have to be direct children of this
     * {@link PreferenceGroup}, they can be grand children or younger)
     */
    private List<Preference> mPreferenceList;
    
    /**
     * List of unique Preference and its subclasses' names. This is used to find
     * out how many types of views this adapter can return. Once the count is
     * returned, this cannot be modified (since the ListView only checks the
     * count once--when the adapter is being set). We will not recycle views for
     * Preference subclasses seen after the count has been returned.
     */
    private ArrayList<PreferenceLayout> mPreferenceLayouts;

    private PreferenceLayout mTempPreferenceLayout = new PreferenceLayout();

    /**
     * Blocks the mPreferenceClassNames from being changed anymore.
     */
    private boolean mHasReturnedViewTypeCount = false;
    
    private volatile boolean mIsSyncing = false;
    
    private Handler mHandler = new Handler(); 
    
    private Runnable mSyncRunnable = new Runnable() {
        public void run() {
            syncMyPreferences();
        }
    };

    private static class PreferenceLayout implements Comparable<PreferenceLayout> {
        private int resId;
        private int widgetResId;
        private String name;

        public int compareTo(PreferenceLayout other) {
            int compareNames = name.compareTo(other.name);
            if (compareNames == 0) {
                if (resId == other.resId) {
                    if (widgetResId == other.widgetResId) {
                        return 0;
                    } else {
                        return widgetResId - other.widgetResId;
                    }
                } else {
                    return resId - other.resId;
                }
            } else {
                return compareNames;
            }
        }
    }

    public PreferenceGroupAdapter(PreferenceGroup preferenceGroup) {
        mPreferenceGroup = preferenceGroup;
        // If this group gets or loses any children, let us know
        mPreferenceGroup.setOnPreferenceChangeInternalListener(this);

        mPreferenceList = new ArrayList<Preference>();
        mPreferenceLayouts = new ArrayList<PreferenceLayout>();

        syncMyPreferences();
    }

    private void syncMyPreferences() {
        synchronized(this) {
            if (mIsSyncing) {
                return;
            }

            mIsSyncing = true;
        }

        List<Preference> newPreferenceList = new ArrayList(mPreferenceList.size());
        flattenPreferenceGroup(newPreferenceList, mPreferenceGroup);
        mPreferenceList = newPreferenceList;
        
        notifyDataSetChanged();

        synchronized(this) {
            mIsSyncing = false;
            notifyAll();
        }
    }
    
    private void flattenPreferenceGroup(List<Preference> preferences, PreferenceGroup group) {
        // TODO: shouldn't always?
        group.sortPreferences();

        final int groupSize = group.getPreferenceCount();
        for (int i = 0; i < groupSize; i++) {
            final Preference preference = group.getPreference(i);
            
            preferences.add(preference);
            
            if (!mHasReturnedViewTypeCount && !preference.hasSpecifiedLayout()) {
                addPreferenceClassName(preference);
            }
            
            if (preference instanceof PreferenceGroup) {
                final PreferenceGroup preferenceAsGroup = (PreferenceGroup) preference;
                if (preferenceAsGroup.isOnSameScreenAsChildren()) {
                    flattenPreferenceGroup(preferences, preferenceAsGroup);
                }
            }

            preference.setOnPreferenceChangeInternalListener(this);
        }
    }

    /**
     * Creates a string that includes the preference name, layout id and widget layout id.
     * If a particular preference type uses 2 different resources, they will be treated as
     * different view types.
     */
    private PreferenceLayout createPreferenceLayout(Preference preference, PreferenceLayout in) {
        PreferenceLayout pl = in != null? in : new PreferenceLayout();
        pl.name = preference.getClass().getName();
        pl.resId = preference.getLayoutResource();
        pl.widgetResId = preference.getWidgetLayoutResource();
        return pl;
    }

    private void addPreferenceClassName(Preference preference) {
        final PreferenceLayout pl = createPreferenceLayout(preference, null);
        int insertPos = Collections.binarySearch(mPreferenceLayouts, pl);

        // Only insert if it doesn't exist (when it is negative).
        if (insertPos < 0) {
            // Convert to insert index
            insertPos = insertPos * -1 - 1;
            mPreferenceLayouts.add(insertPos, pl);
        }
    }
    
    public int getCount() {
        return mPreferenceList.size();
    }

    public Preference getItem(int position) {
        if (position < 0 || position >= getCount()) return null;
        return mPreferenceList.get(position);
    }

    public long getItemId(int position) {
        if (position < 0 || position >= getCount()) return ListView.INVALID_ROW_ID;
        return this.getItem(position).getId();
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        final Preference preference = this.getItem(position);
        // Build a PreferenceLayout to compare with known ones that are cacheable.
        mTempPreferenceLayout = createPreferenceLayout(preference, mTempPreferenceLayout);

        // If it's not one of the cached ones, set the convertView to null so that 
        // the layout gets re-created by the Preference.
        if (Collections.binarySearch(mPreferenceLayouts, mTempPreferenceLayout) < 0) {
            convertView = null;
        }

        return preference.getView(convertView, parent);
    }

    @Override
    public boolean isEnabled(int position) {
        if (position < 0 || position >= getCount()) return true;
        return this.getItem(position).isSelectable();
    }

    @Override
    public boolean areAllItemsEnabled() {
        // There should always be a preference group, and these groups are always
        // disabled
        return false;
    }

    public void onPreferenceChange(Preference preference) {
        notifyDataSetChanged();
    }

    public void onPreferenceHierarchyChange(Preference preference) {
        mHandler.removeCallbacks(mSyncRunnable);
        mHandler.post(mSyncRunnable);
    }

    @Override
    public boolean hasStableIds() {
        return true;
    }

    @Override
    public int getItemViewType(int position) {
        if (!mHasReturnedViewTypeCount) {
            mHasReturnedViewTypeCount = true;
        }
        
        final Preference preference = this.getItem(position);
        if (preference.hasSpecifiedLayout()) {
            return IGNORE_ITEM_VIEW_TYPE;
        }

        mTempPreferenceLayout = createPreferenceLayout(preference, mTempPreferenceLayout);

        int viewType = Collections.binarySearch(mPreferenceLayouts, mTempPreferenceLayout);
        if (viewType < 0) {
            // This is a class that was seen after we returned the count, so
            // don't recycle it.
            return IGNORE_ITEM_VIEW_TYPE;
        } else {
            return viewType;
        }
    }

    @Override
    public int getViewTypeCount() {
        if (!mHasReturnedViewTypeCount) {
            mHasReturnedViewTypeCount = true;
        }
        
        return Math.max(1, mPreferenceLayouts.size());
    }

}