Android example source code file (SettingsBackupAgent.java)

This example Android source code file (SettingsBackupAgent.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, app, application, bufferedreader, couldn't, crc32, dataoutputstream, debug, empty_data, file, io, ioexception, network, os, parcelfiledescriptor, projection, settingshelper, state_size, state_version, string

The SettingsBackupAgent.java Android example source code

/*
 * Copyright (C) 2008 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 com.android.providers.settings;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Arrays;
import java.util.zip.CRC32;

import android.app.backup.BackupDataInput;
import android.app.backup.BackupDataOutput;
import android.app.backup.BackupAgentHelper;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.net.wifi.WifiManager;
import android.os.FileUtils;
import android.os.ParcelFileDescriptor;
import android.os.Process;
import android.provider.Settings;
import android.text.TextUtils;
import android.util.Log;

/**
 * Performs backup and restore of the System and Secure settings.
 * List of settings that are backed up are stored in the Settings.java file
 */
public class SettingsBackupAgent extends BackupAgentHelper {
    private static final boolean DEBUG = false;

    private static final String KEY_SYSTEM = "system";
    private static final String KEY_SECURE = "secure";
    private static final String KEY_LOCALE = "locale";

    // Versioning of the state file.  Increment this version
    // number any time the set of state items is altered.
    private static final int STATE_VERSION = 1;

    private static final int STATE_SYSTEM = 0;
    private static final int STATE_SECURE = 1;
    private static final int STATE_LOCALE = 2;
    private static final int STATE_WIFI   = 3;
    private static final int STATE_SIZE   = 4; // The number of state items

    private static String[] sortedSystemKeys = null;
    private static String[] sortedSecureKeys = null;

    private static final byte[] EMPTY_DATA = new byte[0];

    private static final String TAG = "SettingsBackupAgent";

    private static final int COLUMN_NAME = 1;
    private static final int COLUMN_VALUE = 2;

    private static final String[] PROJECTION = {
        Settings.NameValueTable._ID,
        Settings.NameValueTable.NAME,
        Settings.NameValueTable.VALUE
    };

    private static final String FILE_WIFI_SUPPLICANT = "/data/misc/wifi/wpa_supplicant.conf";
    private static final String FILE_WIFI_SUPPLICANT_TEMPLATE =
            "/system/etc/wifi/wpa_supplicant.conf";

    // the key to store the WIFI data under, should be sorted as last, so restore happens last.
    // use very late unicode character to quasi-guarantee last sort position.
    private static final String KEY_WIFI_SUPPLICANT = "\uffedWIFI";

    private SettingsHelper mSettingsHelper;

    public void onCreate() {
        mSettingsHelper = new SettingsHelper(this);
        super.onCreate();
    }

    @Override
    public void onBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
            ParcelFileDescriptor newState) throws IOException {

        byte[] systemSettingsData = getSystemSettings();
        byte[] secureSettingsData = getSecureSettings();
        byte[] locale = mSettingsHelper.getLocaleData();
        byte[] wifiData = getWifiSupplicant(FILE_WIFI_SUPPLICANT);

        long[] stateChecksums = readOldChecksums(oldState);

        stateChecksums[STATE_SYSTEM] =
                writeIfChanged(stateChecksums[STATE_SYSTEM], KEY_SYSTEM, systemSettingsData, data);
        stateChecksums[STATE_SECURE] =
                writeIfChanged(stateChecksums[STATE_SECURE], KEY_SECURE, secureSettingsData, data);
        stateChecksums[STATE_LOCALE] =
                writeIfChanged(stateChecksums[STATE_LOCALE], KEY_LOCALE, locale, data);
        stateChecksums[STATE_WIFI] =
                writeIfChanged(stateChecksums[STATE_WIFI], KEY_WIFI_SUPPLICANT, wifiData, data);

        writeNewChecksums(stateChecksums, newState);
    }

    @Override
    public void onRestore(BackupDataInput data, int appVersionCode,
            ParcelFileDescriptor newState) throws IOException {

        while (data.readNextHeader()) {
            final String key = data.getKey();
            final int size = data.getDataSize();
            if (KEY_SYSTEM.equals(key)) {
                restoreSettings(data, Settings.System.CONTENT_URI);
                mSettingsHelper.applyAudioSettings();
            } else if (KEY_SECURE.equals(key)) {
                restoreSettings(data, Settings.Secure.CONTENT_URI);
            } else if (KEY_WIFI_SUPPLICANT.equals(key)) {
                int retainedWifiState = enableWifi(false);
                restoreWifiSupplicant(FILE_WIFI_SUPPLICANT, data);
                FileUtils.setPermissions(FILE_WIFI_SUPPLICANT,
                        FileUtils.S_IRUSR | FileUtils.S_IWUSR |
                        FileUtils.S_IRGRP | FileUtils.S_IWGRP,
                        Process.myUid(), Process.WIFI_UID);
                // retain the previous WIFI state.
                enableWifi(retainedWifiState == WifiManager.WIFI_STATE_ENABLED ||
                        retainedWifiState == WifiManager.WIFI_STATE_ENABLING);
            } else if (KEY_LOCALE.equals(key)) {
                byte[] localeData = new byte[size];
                data.readEntityData(localeData, 0, size);
                mSettingsHelper.setLocaleData(localeData);
            } else {
                data.skipEntityData();
            }
        }
    }

    private long[] readOldChecksums(ParcelFileDescriptor oldState) throws IOException {
        long[] stateChecksums = new long[STATE_SIZE];

        DataInputStream dataInput = new DataInputStream(
                new FileInputStream(oldState.getFileDescriptor()));

        try {
            int stateVersion = dataInput.readInt();
            if (stateVersion == STATE_VERSION) {
                for (int i = 0; i < STATE_SIZE; i++) {
                    stateChecksums[i] = dataInput.readLong();
                }
            }
        } catch (EOFException eof) {
            // With the default 0 checksum we'll wind up forcing a backup of
            // any unhandled data sets, which is appropriate.
        }
        dataInput.close();
        return stateChecksums;
    }

    private void writeNewChecksums(long[] checksums, ParcelFileDescriptor newState)
            throws IOException {
        DataOutputStream dataOutput = new DataOutputStream(
                new FileOutputStream(newState.getFileDescriptor()));

        dataOutput.writeInt(STATE_VERSION);
        for (int i = 0; i < STATE_SIZE; i++) {
            dataOutput.writeLong(checksums[i]);
        }
        dataOutput.close();
    }

    private long writeIfChanged(long oldChecksum, String key, byte[] data,
            BackupDataOutput output) {
        CRC32 checkSummer = new CRC32();
        checkSummer.update(data);
        long newChecksum = checkSummer.getValue();
        if (oldChecksum == newChecksum) {
            return oldChecksum;
        }
        try {
            output.writeEntityHeader(key, data.length);
            output.writeEntityData(data, data.length);
        } catch (IOException ioe) {
            // Bail
        }
        return newChecksum;
    }

    private byte[] getSystemSettings() {
        Cursor sortedCursor = getContentResolver().query(Settings.System.CONTENT_URI, PROJECTION,
                null, null, Settings.NameValueTable.NAME);
        // Copy and sort the array
        if (sortedSystemKeys == null) {
            sortedSystemKeys = copyAndSort(Settings.System.SETTINGS_TO_BACKUP);
        }
        byte[] result = extractRelevantValues(sortedCursor, sortedSystemKeys);
        sortedCursor.close();
        return result;
    }

    private byte[] getSecureSettings() {
        Cursor sortedCursor = getContentResolver().query(Settings.Secure.CONTENT_URI, PROJECTION,
                null, null, Settings.NameValueTable.NAME);
        // Copy and sort the array
        if (sortedSecureKeys == null) {
            sortedSecureKeys = copyAndSort(Settings.Secure.SETTINGS_TO_BACKUP);
        }
        byte[] result = extractRelevantValues(sortedCursor, sortedSecureKeys);
        sortedCursor.close();
        return result;
    }

    private void restoreSettings(BackupDataInput data, Uri contentUri) {
        if (DEBUG) Log.i(TAG, "restoreSettings: " + contentUri);
        String[] whitelist = null;
        if (contentUri.equals(Settings.Secure.CONTENT_URI)) {
            whitelist = Settings.Secure.SETTINGS_TO_BACKUP;
        } else if (contentUri.equals(Settings.System.CONTENT_URI)) {
            whitelist = Settings.System.SETTINGS_TO_BACKUP;
        }

        ContentValues cv = new ContentValues(2);
        byte[] settings = new byte[data.getDataSize()];
        try {
            data.readEntityData(settings, 0, settings.length);
        } catch (IOException ioe) {
            Log.e(TAG, "Couldn't read entity data");
            return;
        }
        int pos = 0;
        while (pos < settings.length) {
            int length = readInt(settings, pos);
            pos += 4;
            String settingName = length > 0? new String(settings, pos, length) : null;
            pos += length;
            length = readInt(settings, pos);
            pos += 4;
            String settingValue = length > 0? new String(settings, pos, length) : null;
            pos += length;
            if (!TextUtils.isEmpty(settingName) && !TextUtils.isEmpty(settingValue)) {
                //Log.i(TAG, "Restore " + settingName + " = " + settingValue);

                // Only restore settings in our list of known-acceptable data
                if (invalidSavedSetting(whitelist, settingName)) {
                    continue;
                }

                if (mSettingsHelper.restoreValue(settingName, settingValue)) {
                    cv.clear();
                    cv.put(Settings.NameValueTable.NAME, settingName);
                    cv.put(Settings.NameValueTable.VALUE, settingValue);
                    getContentResolver().insert(contentUri, cv);
                }
            }
        }
    }

    // Returns 'true' if the given setting is one that we refuse to restore
    private boolean invalidSavedSetting(String[] knownNames, String candidate) {
        // no filter? allow everything
        if (knownNames == null) {
            return false;
        }

        // whitelisted setting?  allow it
        for (String name : knownNames) {
            if (name.equals(candidate)) {
                return false;
            }
        }

        // refuse everything else
        if (DEBUG) Log.v(TAG, "Ignoring restore datum: " + candidate);
        return true;
    }

    private String[] copyAndSort(String[] keys) {
        String[] sortedKeys = new String[keys.length];
        System.arraycopy(keys, 0, sortedKeys, 0, keys.length);
        Arrays.sort(sortedKeys);
        return sortedKeys;
    }

    /**
     * Given a cursor sorted by key name and a set of keys sorted by name,
     * extract the required keys and values and write them to a byte array.
     * @param sortedCursor
     * @param sortedKeys
     * @return
     */
    byte[] extractRelevantValues(Cursor sortedCursor, String[] sortedKeys) {
        byte[][] values = new byte[sortedKeys.length * 2][]; // keys and values
        if (!sortedCursor.moveToFirst()) {
            Log.e(TAG, "Couldn't read from the cursor");
            return new byte[0];
        }
        int keyIndex = 0;
        int totalSize = 0;
        while (!sortedCursor.isAfterLast()) {
            String name = sortedCursor.getString(COLUMN_NAME);
            while (sortedKeys[keyIndex].compareTo(name.toString()) < 0) {
                keyIndex++;
                if (keyIndex == sortedKeys.length) break;
            }
            if (keyIndex < sortedKeys.length && name.equals(sortedKeys[keyIndex])) {
                String value = sortedCursor.getString(COLUMN_VALUE);
                byte[] nameBytes = name.toString().getBytes();
                totalSize += 4 + nameBytes.length;
                values[keyIndex * 2] = nameBytes;
                byte[] valueBytes;
                if (TextUtils.isEmpty(value)) {
                    valueBytes = null;
                    totalSize += 4;
                } else {
                    valueBytes = value.toString().getBytes();
                    totalSize += 4 + valueBytes.length;
                    //Log.i(TAG, "Backing up " + name + " = " + value);
                }
                values[keyIndex * 2 + 1] = valueBytes;
                keyIndex++;
            }
            if (keyIndex == sortedKeys.length || !sortedCursor.moveToNext()) {
                break;
            }
        }

        byte[] result = new byte[totalSize];
        int pos = 0;
        for (int i = 0; i < sortedKeys.length * 2; i++) {
            if (values[i] != null) {
                pos = writeInt(result, pos, values[i].length);
                pos = writeBytes(result, pos, values[i]);
            }
        }
        return result;
    }

    private byte[] getWifiSupplicant(String filename) {
        try {
            File file = new File(filename);
            if (file.exists()) {
                BufferedReader br = new BufferedReader(new FileReader(file));
                StringBuffer relevantLines = new StringBuffer();
                boolean started = false;
                String line;
                while ((line = br.readLine()) != null) {
                    if (!started && line.startsWith("network")) {
                        started = true;
                    }
                    if (started) {
                        relevantLines.append(line).append("\n");
                    }
                }
                if (relevantLines.length() > 0) {
                    return relevantLines.toString().getBytes();
                } else {
                    return EMPTY_DATA;
                }
            } else {
                return EMPTY_DATA;
            }
        } catch (IOException ioe) {
            Log.w(TAG, "Couldn't backup " + filename);
            return EMPTY_DATA;
        }
    }

    private void restoreWifiSupplicant(String filename, BackupDataInput data) {
        byte[] bytes = new byte[data.getDataSize()];
        if (bytes.length <= 0) return;
        try {
            data.readEntityData(bytes, 0, bytes.length);
            File supplicantFile = new File(FILE_WIFI_SUPPLICANT);
            if (supplicantFile.exists()) supplicantFile.delete();
            copyWifiSupplicantTemplate();

            FileOutputStream fos = new FileOutputStream(filename, true);
            fos.write("\n".getBytes());
            fos.write(bytes);
        } catch (IOException ioe) {
            Log.w(TAG, "Couldn't restore " + filename);
        }
    }

    private void copyWifiSupplicantTemplate() {
        try {
            BufferedReader br = new BufferedReader(new FileReader(FILE_WIFI_SUPPLICANT_TEMPLATE));
            BufferedWriter bw = new BufferedWriter(new FileWriter(FILE_WIFI_SUPPLICANT));
            char[] temp = new char[1024];
            int size;
            while ((size = br.read(temp)) > 0) {
                bw.write(temp, 0, size);
            }
            bw.close();
            br.close();
        } catch (IOException ioe) {
            Log.w(TAG, "Couldn't copy wpa_supplicant file");
        }
    }

    /**
     * Write an int in BigEndian into the byte array.
     * @param out byte array
     * @param pos current pos in array
     * @param value integer to write
     * @return the index after adding the size of an int (4)
     */
    private int writeInt(byte[] out, int pos, int value) {
        out[pos + 0] = (byte) ((value >> 24) & 0xFF);
        out[pos + 1] = (byte) ((value >> 16) & 0xFF);
        out[pos + 2] = (byte) ((value >>  8) & 0xFF);
        out[pos + 3] = (byte) ((value >>  0) & 0xFF);
        return pos + 4;
    }

    private int writeBytes(byte[] out, int pos, byte[] value) {
        System.arraycopy(value, 0, out, pos, value.length);
        return pos + value.length;
    }

    private int readInt(byte[] in, int pos) {
        int result =
                ((in[pos    ] & 0xFF) << 24) |
                ((in[pos + 1] & 0xFF) << 16) |
                ((in[pos + 2] & 0xFF) <<  8) |
                ((in[pos + 3] & 0xFF) <<  0);
        return result;
    }

    private int enableWifi(boolean enable) {
        WifiManager wfm = (WifiManager) getSystemService(Context.WIFI_SERVICE);
        if (wfm != null) {
            int state = wfm.getWifiState();
            wfm.setWifiEnabled(enable);
            return state;
        }
        return WifiManager.WIFI_STATE_UNKNOWN;
    }
}