至於爲何要在這裏講解android系統源碼中的系統更新，我已經在上一篇《 CM android的CMUpdater分析(一)》中介紹了。在上一篇中，主要講解了在eclipse中如何搭建系統應用的開發環境，現在我們就使用eclipse來分析CMUpdater源碼。該系統更新是CM修改原生android的基礎上實現的。通過分析android系統的應用源碼，可以學到一些很好的思想和編程方法學。好了，廢話少說，現在就開始我們的學習之旅。
首先，在開始介紹之前，我先把之前根據CMUpdater源碼分析來的框圖放到上來，大家先看框圖，把系統更新的整體流程大體瞭解一下。
通過這個框圖，看上去挺複雜，其實是挺簡單的，就是Service檢查更新，後臺下載更新，包括全安裝包或者是增量更新包，下載完成之後，安裝更新，重啓，安裝完成。
現在我們從代碼開始，進行分析。
首先，我們先來看一個app項目中，所有的activity和service,就是要查看AndroidManifest.xml文件。通過分析該代碼，我們看到，在CMUpdater中的入口Activity是UpdatesSettings，同時在
AndroidManifest.xml文件中，還靜態註冊了四個receiver，其中包括：
- UpdateCheckReceiver : 在該receiver中註冊了兩個action，其中包括BOOT_COMPLETED和CONNECTIVITY_CHANGE，該receiver用於在系統啓動後或者是網絡連接發生變化的時候，進行檢查系統更新。
- DownloadReceiver : 該receiver也註冊了兩個action，包括DOWNLOAD_COMPLETE和START_DOWNLOAD，當下載完成和開始下載廣播發出之後，進行相應的操作。
- NotificationClickReceiver，該廣播接收器註冊了一個DOWNLOAD_NOTIFICATION_CLICKED廣播，當接收到下載提醒框被點擊的時候，進行更新操作。
- CheckFinishReceiver : 該廣播接收器用於接收UPDATE_CHECK_FINISHED廣播，當檢查更新完成之後，刷新列表。
同時，在該xml文件中，也註冊了幾個Service：
- CMDashClockExtension : 該服務用於檢查時間，用戶可以選擇某個時間點，進行檢查更新。
- UpdateCheckService : 該服務的操作就是用於檢查更新，檢查更新完成之後，發出檢查更新完成的廣播。
- DownloadService : 顧名思義，下載服務，也就是說該服務是用來下載系統更新的。
- DownloadCompleteIntentService : 下載完成服務，當下載完成之後，發出下載完成廣播。
好了，現在我們先進入入口Activity來看一下。
進入到UpdateSettings.java文件，可以看到，該類中註冊了一個Receiver，該接收器的實現爲：
private BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
//如果Action爲ACTION_DOWNLOAD_STARTED,即爲下載開始
if (DownloadReceiver.ACTION_DOWNLOAD_STARTED.equals(action)) {
mDownloadId = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
mUpdateHandler.post(mUpdateProgress); //更新ProgressBar
//如果Action爲ACTION_CHECK_FINISHED，即爲檢查更新完成
} else if (UpdateCheckService.ACTION_CHECK_FINISHED.equals(action)) {
if (mProgressDialog != null) {
mProgressDialog.dismiss();
mProgressDialog = null;
//獲取系統更新的條數
int count = intent.getIntExtra(UpdateCheckService.EXTRA_NEW_UPDATE_COUNT, -1);
if (count == 0) { // 如果爲0，提醒用戶未找到
Toast.makeText(UpdatesSettings.this, R.string.no_updates_found,
Toast.LENGTH_SHORT).show();
} else if (count < 0) { //如果小於0，則表示檢查更新失敗
Toast.makeText(UpdatesSettings.this, R.string.update_check_failed,
Toast.LENGTH_LONG).show();
}
}
//如果其他都不是，表示更新完成，並且有更新，則刷新UI
updateLayout();
}
}
};
當用戶點擊item(MENU_REFRESH)之後，手動進行更新檢查，即爲checkForUpdates()。
private void checkForUpdates() {
if (mProgressDialog != null) {
return;
}
// 未連接網絡，提示用戶並返回
if (!Utils.isOnline(this)) {
Toast.makeText(this, R.string.data_connection_required, Toast.LENGTH_SHORT).show();
return;
}
//彈出進度條，用戶提示用戶正在檢查更新
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setTitle(R.string.checking_for_updates);
mProgressDialog.setMessage(getString(R.string.checking_for_updates));
mProgressDialog.setIndeterminate(true);
mProgressDialog.setCancelable(true);
mProgressDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
@Override
public void onCancel(DialogInterface dialog) {
//當用戶點擊取消後，提醒服務程序，取消檢查更新操作
Intent cancelIntent = new Intent(UpdatesSettings.this, UpdateCheckService.class);
cancelIntent.setAction(UpdateCheckService.ACTION_CANCEL_CHECK);
startService(cancelIntent);
mProgressDialog = null;
}
});
//開啓服務程序進行檢查更新
Intent checkIntent = new Intent(UpdatesSettings.this, UpdateCheckService.class);
checkIntent.setAction(UpdateCheckService.ACTION_CHECK);
startService(checkIntent);
mProgressDialog.show();
}
現在我們進入檢查更新服務程序，即UpdateCheckService。在服務程序的啓動方法onStartCommand()檢查用戶的操作是取消檢查還是檢查更新，如果是取消檢查，就將位於請求列表中的請求刪除掉。
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
//取消檢查更新
if (TextUtils.equals(intent.getAction(), ACTION_CANCEL_CHECK)) {
((UpdateApplication) getApplicationContext()).getQueue().cancelAll(TAG);
return START_NOT_STICKY;
}
return super.onStartCommand(intent, flags, startId);
}
接着，服務程序調用getAvailableUpdates()來檢查可用更新，我們來看一下這個方法：
private void getAvailableUpdates() {
// Get the type of update we should check for
int updateType = Utils.getUpdateType();
// Get the actual ROM Update Server URL
URI updateServerUri = getServerURI();
Log.e(TAG, updateServerUri.toString());
UpdatesJsonObjectRequest request;
try {
request = new UpdatesJsonObjectRequest(updateServerUri.toASCIIString(),
Utils.getUserAgentString(this), buildUpdateRequest(updateType), this, this);
// Set the tag for the request, reuse logging tag
request.setTag(TAG);
} catch (JSONException e) {
Log.e(TAG, "Could not build request", e);
return;
}
((UpdateApplication) getApplicationContext()).getQueue().add(request);
}
這個代碼很好理解，就是封裝一下請求信息，封裝爲請求對象，將該請求對象添加到請求隊列中，等待從服務器中獲取信息。請求對象的封裝是通過buildUpdateRequest()方法來實現的。
接着，服務程序通過回調函數onResponse()來獲取相應的服務器反饋信息。
@Override
public void onResponse(JSONObject jsonObject) {
int updateType = Utils.getUpdateType();
LinkedList<UpdateInfo> lastUpdates = State.loadState(this);
LinkedList<UpdateInfo> updates = parseJSON(jsonObject.toString(), updateType);
int newUpdates = 0, realUpdates = 0;
for (UpdateInfo ui : updates) {
if (!lastUpdates.contains(ui)) {
newUpdates++;
}
if (ui.isNewerThanInstalled()) {
realUpdates++;
}
}
Intent intent = new Intent(ACTION_CHECK_FINISHED);
intent.putExtra(EXTRA_UPDATE_COUNT, updates.size());
intent.putExtra(EXTRA_REAL_UPDATE_COUNT, realUpdates);
intent.putExtra(EXTRA_NEW_UPDATE_COUNT, newUpdates);
recordAvailableUpdates(updates, intent);
State.saveState(this, updates);
}
在該回調函數中，將更新信息放到更新列表中，同時通過調用recordAvailableUpdates()發送actionACTION_CHECK_FINISHED的廣播給UpdateSettings中。接着UpdateSettings調用updateLayout()更新UI，同時調用refreshPreferences()接着調用回調函數onStartDownload()來通知DownloadReceiver進行下載。
我們先來看一下recordAvailableUpdates()函數的實現：
private void recordAvailableUpdates(LinkedList<UpdateInfo> availableUpdates,
Intent finishedIntent) {
if (availableUpdates == null) {
sendBroadcast(finishedIntent);
return;
}
//保存上次更新時間，然後確保啓動檢查更新完成是正確的
Date d = new Date();
PreferenceManager.getDefaultSharedPreferences(UpdateCheckService.this).edit()
.putLong(Constants.LAST_UPDATE_CHECK_PREF, d.getTime())
.putBoolean(Constants.BOOT_CHECK_COMPLETED, true)
.apply();
int realUpdateCount = finishedIntent.getIntExtra(EXTRA_REAL_UPDATE_COUNT, 0);
UpdateApplication app = (UpdateApplication) getApplicationContext();
// Write to log
Log.i(TAG, "The update check successfully completed at " + d + " and found "
+ availableUpdates.size() + " updates ("
+ realUpdateCount + " newer than installed)");
//如果程序被關掉了，則在提醒框中顯示更新信息
if (realUpdateCount != 0 && !app.isMainActivityActive()) {
// There are updates available
// The notification should launch the main app
Intent i = new Intent(this, UpdatesSettings.class);
i.putExtra(UpdatesSettings.EXTRA_UPDATE_LIST_UPDATED, true);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, i,
PendingIntent.FLAG_ONE_SHOT);
Resources res = getResources();
String text = res.getQuantityString(R.plurals.not_new_updates_found_body,
realUpdateCount, realUpdateCount);
// Get the notification ready
Notification.Builder builder = new Notification.Builder(this)
.setSmallIcon(R.drawable.cm_updater)
.setWhen(System.currentTimeMillis())
.setTicker(res.getString(R.string.not_new_updates_found_ticker))
.setContentTitle(res.getString(R.string.not_new_updates_found_title))
.setContentText(text)
.setContentIntent(contentIntent)
.setAutoCancel(true);
LinkedList<UpdateInfo> realUpdates = new LinkedList<UpdateInfo>();
for (UpdateInfo ui : availableUpdates) {
if (ui.isNewerThanInstalled()) {
realUpdates.add(ui);
}
}
Collections.sort(realUpdates, new Comparator<UpdateInfo>() {
@Override
public int compare(UpdateInfo lhs, UpdateInfo rhs) {
/* sort by date descending */
long lhsDate = lhs.getDate();
long rhsDate = rhs.getDate();
if (lhsDate == rhsDate) {
return 0;
}
return lhsDate < rhsDate ? 1 : -1;
}
});
Notification.InboxStyle inbox = new Notification.InboxStyle(builder)
.setBigContentTitle(text);
int added = 0, count = realUpdates.size();
for (UpdateInfo ui : realUpdates) {
if (added < EXPANDED_NOTIF_UPDATE_COUNT) {
inbox.addLine(ui.getName());
added++;
}
}
if (added != count) {
inbox.setSummaryText(res.getQuantityString(R.plurals.not_additional_count,
count - added, count - added));
}
builder.setStyle(inbox);
builder.setNumber(availableUpdates.size());
//如果更新條數爲1 ，則直接發送開始下載更新的廣播
if (count == 1) {
i = new Intent(this, DownloadReceiver.class);
i.setAction(DownloadReceiver.ACTION_START_DOWNLOAD);
i.putExtra(DownloadReceiver.EXTRA_UPDATE_INFO, (Parcelable) realUpdates.getFirst());
PendingIntent downloadIntent = PendingIntent.getBroadcast(this, 0, i,
PendingIntent.FLAG_ONE_SHOT | PendingIntent.FLAG_UPDATE_CURRENT);
builder.addAction(R.drawable.ic_tab_download,
res.getString(R.string.not_action_download), downloadIntent);
}
// Trigger the notification
NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
nm.notify(R.string.not_new_updates_found_title, builder.build());
}
//發送廣播，提醒UpdateSettings類
sendBroadcast(finishedIntent);
}
在updateLayout()函數中會更新UI,用戶可以點擊下載按鈕進行更新下載。
當下載開始之後，會廣播給`DownloadReceiver’接收器。
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (ACTION_START_DOWNLOAD.equals(action)) {
UpdateInfo ui = (UpdateInfo) intent.getParcelableExtra(EXTRA_UPDATE_INFO);
handleStartDownload(context, ui);
} else if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
long id = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
handleDownloadComplete(context, id);
} else if (ACTION_INSTALL_UPDATE.equals(action)) {
StatusBarManager sb = (StatusBarManager) context.getSystemService(Context.STATUS_BAR_SERVICE);
sb.collapsePanels();
String fileName = intent.getStringExtra(EXTRA_FILENAME);
try {
Utils.triggerUpdate(context, fileName);
} catch (IOException e) {
Log.e(TAG, "Unable to reboot into recovery mode", e);
Toast.makeText(context, R.string.apply_unable_to_reboot_toast,
Toast.LENGTH_SHORT).show();
Utils.cancelNotification(context);
}
}
}
在該接收器中，如果action爲ACTION_START_DOWNLOAD，則進行handleStartDownload()操作。
private void handleStartDownload(Context context, UpdateInfo ui) {
DownloadService.start(context, ui);
}
啓動DownloadService開始操作。
public static void start(Context context, UpdateInfo ui) {
Intent intent = new Intent(context, DownloadService.class);
intent.putExtra(EXTRA_UPDATE_INFO, (Parcelable) ui);
context.startService(intent);
}
靜態方法，啓動DownloadService服務。
@Override
protected void onHandleIntent(Intent intent) {
mPrefs = PreferenceManager.getDefaultSharedPreferences(this);
mInfo = intent.getParcelableExtra(EXTRA_UPDATE_INFO);
if (mInfo == null) {
Log.e(TAG, "Intent UpdateInfo extras were null");
return;
}
try {
getIncremental();
} catch (IOException e) {
downloadFullZip();
}
}
嘗試下載增量更新包，如果增量更新包報出異常，則下載全更新包。
private void downloadFullZip() {
Log.v(TAG, "Downloading full zip");
// Build the name of the file to download, adding .partial at the end. It will get
// stripped off when the download completes
String fullFilePath = "file://" + getUpdateDirectory().getAbsolutePath() +
"/" + mInfo.getFileName() + ".partial";
long downloadId = enqueueDownload(mInfo.getDownloadUrl(), fullFilePath);
// Store in shared preferences
mPrefs.edit()
.putLong(Constants.DOWNLOAD_ID, downloadId)
.putString(Constants.DOWNLOAD_MD5, mInfo.getMD5Sum())
.apply();
Utils.cancelNotification(this);
Intent intent = new Intent(DownloadReceiver.ACTION_DOWNLOAD_STARTED);
intent.putExtra(DownloadManager.EXTRA_DOWNLOAD_ID, downloadId);
sendBroadcast(intent);
}
調用enqueueDownload()函數來獲取該下載在下載隊列中的id:
private long enqueueDownload(String downloadUrl, String localFilePath) {
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(downloadUrl));
String userAgent = Utils.getUserAgentString(this);
if (userAgent != null) {
request.addRequestHeader("User-Agent", userAgent);
}
request.setTitle(getString(R.string.app_name));
request.setDestinationUri(Uri.parse(localFilePath));
request.setAllowedOverRoaming(false);
request.setVisibleInDownloadsUi(false);
// TODO: this could/should be made configurable
request.setAllowedOverMetered(true);
final DownloadManager dm = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
return dm.enqueue(request);
}
該操作相當於封裝請求服務器的信息，將該信息放到DownloadManager中，獲取id。
接着，向DownloadReceiver發送ACTION_DOWNLOAD_STARTED廣播。
當下載完成之後，會向DownloadReceiver發送廣播ACTION_DOWNLOAD_COMPLET，當接收器接到該廣播之後，則調用handleDownloadComplete(context, id)函數來處理下載完成的安裝包。
private void handleDownloadComplete(Context context, long id) {
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
long enqueued = prefs.getLong(Constants.DOWNLOAD_ID, -1);
if (enqueued < 0 || id < 0 || id != enqueued) {
return;
}
String downloadedMD5 = prefs.getString(Constants.DOWNLOAD_MD5, "");
String incrementalFor = prefs.getString(Constants.DOWNLOAD_INCREMENTAL_FOR, null);
// Send off to DownloadCompleteIntentService
Intent intent = new Intent(context, DownloadCompleteIntentService.class);
intent.putExtra(Constants.DOWNLOAD_ID, id);
intent.putExtra(Constants.DOWNLOAD_MD5, downloadedMD5);
intent.putExtra(Constants.DOWNLOAD_INCREMENTAL_FOR, incrementalFor);
context.startService(intent);
// Clear the shared prefs
prefs.edit()
.remove(Constants.DOWNLOAD_MD5)
.remove(Constants.DOWNLOAD_ID)
.remove(Constants.DOWNLOAD_INCREMENTAL_FOR)
.apply();
}
通過md5檢查完整性，接着啓動DownloadCompleteIntentService服務來安裝更新。
@Override
protected void onHandleIntent(Intent intent) {
if (!intent.hasExtra(Constants.DOWNLOAD_ID) ||
!intent.hasExtra(Constants.DOWNLOAD_MD5)) {
return;
}
long id = intent.getLongExtra(Constants.DOWNLOAD_ID, -1);
String downloadedMD5 = intent.getStringExtra(Constants.DOWNLOAD_MD5);
String incrementalFor = intent.getStringExtra(Constants.DOWNLOAD_INCREMENTAL_FOR);
Intent updateIntent = new Intent(this, UpdatesSettings.class);
updateIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
int status = fetchDownloadStatus(id);
if (status == DownloadManager.STATUS_SUCCESSFUL) {
// Get the full path name of the downloaded file and the MD5
// Strip off the .partial at the end to get the completed file
String partialFileFullPath = fetchDownloadPartialPath(id);
if (partialFileFullPath == null) {
displayErrorResult(updateIntent, R.string.unable_to_download_file);
}
String completedFileFullPath = partialFileFullPath.replace(".partial", "");
File partialFile = new File(partialFileFullPath);
File updateFile = new File(completedFileFullPath);
partialFile.renameTo(updateFile);
// Start the MD5 check of the downloaded file
if (MD5.checkMD5(downloadedMD5, updateFile)) {
// We passed. Bring the main app to the foreground and trigger download completed
updateIntent.putExtra(UpdatesSettings.EXTRA_FINISHED_DOWNLOAD_ID, id);
updateIntent.putExtra(UpdatesSettings.EXTRA_FINISHED_DOWNLOAD_PATH,
completedFileFullPath);
updateIntent.putExtra(UpdatesSettings.EXTRA_FINISHED_DOWNLOAD_INCREMENTAL_FOR,
incrementalFor);
displaySuccessResult(updateIntent, updateFile);
} else {
// We failed. Clear the file and reset everything
mDm.remove(id);
if (updateFile.exists()) {
updateFile.delete();
}
displayErrorResult(updateIntent, R.string.md5_verification_failed);
}
} else if (status == DownloadManager.STATUS_FAILED) {
// The download failed, reset
mDm.remove(id);
displayErrorResult(updateIntent, R.string.unable_to_download_file);
}
}
該服務通過封裝Intent來返回UpdateSettings中的onNewIntent()函數來進行處理。
@Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
// Check if we need to refresh the screen to show new updates
if (intent.getBooleanExtra(EXTRA_UPDATE_LIST_UPDATED, false)) {
updateLayout();
}
//檢查下載完成
checkForDownloadCompleted(intent);
}
我們來看一下checkForDownloadCompleted()函數的實現：
private void checkForDownloadCompleted(Intent intent) {
if (intent == null) {
return;
}
long downloadId = intent.getLongExtra(EXTRA_FINISHED_DOWNLOAD_ID, -1);
if (downloadId < 0) {
return;
}
String fullPathName = intent.getStringExtra(EXTRA_FINISHED_DOWNLOAD_PATH);
if (fullPathName == null) {
return;
}
String fileName = new File(fullPathName).getName();
// If this is an incremental, find matching target and mark it as downloaded.
String incrementalFor = intent.getStringExtra(EXTRA_FINISHED_DOWNLOAD_INCREMENTAL_FOR);
if (incrementalFor != null) {
UpdatePreference pref = (UpdatePreference) mUpdatesList.findPreference(incrementalFor);
if (pref != null) {
pref.setStyle(UpdatePreference.STYLE_DOWNLOADED);
pref.getUpdateInfo().setFileName(fileName);
//調用更新安裝
onStartUpdate(pref);
}
} else {
// Find the matching preference so we can retrieve the UpdateInfo
UpdatePreference pref = (UpdatePreference) mUpdatesList.findPreference(fileName);
if (pref != null) {
pref.setStyle(UpdatePreference.STYLE_DOWNLOADED);
onStartUpdate(pref);
}
}
resetDownloadState();
}
該函數通過調用onStartUpdate(pref)來安裝更新：
@Override
public void onStartUpdate(UpdatePreference pref) {
final UpdateInfo updateInfo = pref.getUpdateInfo();
// Prevent the dialog from being triggered more than once
if (mStartUpdateVisible) {
return;
}
mStartUpdateVisible = true;
// Get the message body right
String dialogBody = getString(R.string.apply_update_dialog_text, updateInfo.getName());
// Display the dialog
new AlertDialog.Builder(this)
.setTitle(R.string.apply_update_dialog_title)
.setMessage(dialogBody)
.setPositiveButton(R.string.dialog_update, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
try {
//提醒用戶是否安裝，用戶點擊確定之後，triggerUpdate()
Utils.triggerUpdate(UpdatesSettings.this, updateInfo.getFileName());
} catch (IOException e) {
Log.e(TAG, "Unable to reboot into recovery mode", e);
Toast.makeText(UpdatesSettings.this, R.string.apply_unable_to_reboot_toast,
Toast.LENGTH_SHORT).show();
}
}
})
.setNegativeButton(R.string.dialog_cancel, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
mStartUpdateVisible = false;
}
})
.show();
}
提醒用戶是否安裝，用戶點擊安裝之後，激發triggerUpdate()函數進行安裝：
public static void triggerUpdate(Context context, String updateFileName) throws IOException {
/*
* Should perform the following steps.
* 1.- mkdir -p /cache/recovery
* 2.- echo 'boot-recovery' > /cache/recovery/command
* 3.- if(mBackup) echo '--nandroid' >> /cache/recovery/command
* 4.- echo '--update_package=SDCARD:update.zip' >> /cache/recovery/command
* 5.- reboot recovery
*/
// Set the 'boot recovery' command
Process p = Runtime.getRuntime().exec("sh");
OutputStream os = p.getOutputStream();
os.write("mkdir -p /cache/recovery/\n".getBytes());
os.write("echo 'boot-recovery' >/cache/recovery/command\n".getBytes());
// See if backups are enabled and add the nandroid flag
/* TODO: add this back once we have a way of doing backups that is not recovery specific
if (mPrefs.getBoolean(Constants.BACKUP_PREF, true)) {
os.write("echo '--nandroid' >> /cache/recovery/command\n".getBytes());
}
*/
// Add the update folder/file name
// Emulated external storage moved to user-specific paths in 4.2
String userPath = Environment.isExternalStorageEmulated() ? ("/" + UserHandle.myUserId()) : "";
String cmd = "echo '--update_package=" + getStorageMountpoint(context) + userPath
+ "/" + Constants.UPDATES_FOLDER + "/" + updateFileName
+ "' >> /cache/recovery/command\n";
os.write(cmd.getBytes());
os.flush();
// Trigger the reboot
PowerManager powerManager = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
powerManager.reboot("recovery");
}
/*
* Should perform the following steps.
* 1.- mkdir -p /cache/recovery
* 2.- echo ‘boot-recovery’ > /cache/recovery/command
* 3.- if(mBackup) echo ‘–nandroid’ >> /cache/recovery/command
* 4.- echo ‘–update_package=SDCARD:update.zip’ >> /cache/recovery/command
* 5.- reboot recovery
*/
在註釋中，說明了必須運行下面步驟：
- mkdir -p /cache/recovery //創建文件夾
- echo ‘boot-recovery’ > /cache/recovery/command
- if(mBackup) echo ‘–nandroid’ >> /cache/recovery/command
- echo ‘–update_package=SDCARD:update.zip’ >> /cache/recovery/command
- reboot recovery
這五個命令運行完成之後，便會重啓安裝系統更新了。