Android example source code file (History.java)

This example Android source code file (History.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, committing, comparator, content, editor, history, historyrecord, language_comparator, list, map, most_recent_comparator, removing, sharedpreferences, string, util, utilities, utils

The History.java Android example source code

/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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 com.beust.android.translate;

import com.beust.android.translate.Languages.Language;

import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.util.Log;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Map;

/**
 * This class handles the history of past translations.
 */
public class History {
    private static final String HISTORY = "history";

    /**
     * Sort the translations by timestamp.
     */
    private static final Comparator<HistoryRecord> MOST_RECENT_COMPARATOR
             = new Comparator<HistoryRecord>() {

        public int compare(HistoryRecord object1, HistoryRecord object2) {
            return (int) (object2.when - object1.when);
        }
    };

    /**
     * Sort the translations by destination language and then by input.
     */
    private static final Comparator<HistoryRecord> LANGUAGE_COMPARATOR
            = new Comparator<HistoryRecord>() {

        public int compare(HistoryRecord object1, HistoryRecord object2) {
            int result = object1.to.getLongName().compareTo(object2.to.getLongName());
            if (result == 0) {
                result = object1.input.compareTo(object2.input);
            }
            return result;
        }
    };

    private List<HistoryRecord> mHistoryRecords = Lists.newArrayList();
    
    public History(SharedPreferences prefs) {
        mHistoryRecords = restoreHistory(prefs);
    }

    public static List<HistoryRecord> restoreHistory(SharedPreferences prefs) {
        List<HistoryRecord> result = Lists.newArrayList();
        boolean done = false;
        int i = 0;
        Map<String, ?> allKeys = prefs.getAll();
        for (String key : allKeys.keySet()) {
            if (key.startsWith(HISTORY)) {
                String value = (String) allKeys.get(key);
                result.add(HistoryRecord.decode(value));
            }
        }
//        while (! done) {
//            String history = prefs.getString(HISTORY + "-" + i++, null);
//            if (history != null) {
//                result.add(HistoryRecord.decode(history));
//            } else {
//                done = true;
//            }
//        }

        return result;
    }

//    public void saveHistory(Editor edit) {
//        log("Saving history");
//        for (int i = 0; i < mHistoryRecords.size(); i++) {
//            HistoryRecord hr = mHistoryRecords.get(i);
//            edit.putString(HISTORY + "-" + i, hr.encode());
//        }
//    }
    
    public static void addHistoryRecord(Context context,
        Language from, Language to, String input, String output) {
        History historyRecord = new History(TranslateActivity.getPrefs(context));
        HistoryRecord hr = new HistoryRecord(from, to, input, output, System.currentTimeMillis());
        
        // Find an empty key to add this history record
        SharedPreferences prefs = TranslateActivity.getPrefs(context);
        int i = 0;
        while (true) {
            String key = HISTORY + "-" + i; 
            if (!prefs.contains(key)) {
                Editor edit = prefs.edit();
                edit.putString(key, hr.encode());
                log("Committing " + key + " " + hr.encode());
                edit.commit();
                return;
            } else {
                i++;
            }
        }
    }
    
//    public static void addHistoryRecord(Context context, List<HistoryRecord> result, HistoryRecord hr) {
//        if (! result.contains(hr)) {
//            result.add(hr);
//        }
//        Editor edit = getPrefs(context).edit();
//    }

    private static void log(String s) {
        Log.d(TranslateActivity.TAG, "[History] " + s);
    }
    
    
    public List<HistoryRecord> getHistoryRecordsMostRecentFirst() {
        Collections.sort(mHistoryRecords, MOST_RECENT_COMPARATOR);
        return mHistoryRecords;
    }
    
    public List<HistoryRecord> getHistoryRecordsByLanguages() {
        Collections.sort(mHistoryRecords, LANGUAGE_COMPARATOR);
        return mHistoryRecords;
    }

    public List<HistoryRecord> getHistoryRecords(Comparator comparator) {
        if (comparator != null) {
            Collections.sort(mHistoryRecords, comparator);
        }
        return mHistoryRecords;
    }

    public void clear(Context context) {
        int size = mHistoryRecords.size();
        mHistoryRecords = Lists.newArrayList();
        Editor edit = TranslateActivity.getPrefs(context).edit();
        for (int i = 0; i < size; i++) {
            String key = HISTORY + "-" + i;
            log("Removing key " + key);
            edit.remove(key);
        }
        edit.commit();
    }


}