【Android】一种提高Android应用进程存活率新方法
【Android】一种提高Android应用进程存活率新方法
SkySeraph Jun. 19st 2016
Email:skyseraph00@163.com
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一、基础知识
1.Android 进程优先级
1.1 进程优先级等级一般分法:
- Activte process
- Visible Process
- Service process
- Background process
- Empty process
1.2 进程优先级号
ProcessList.java
1 // Adjustment used in certain places where we don't know it yet. 2 // (Generally this is something that is going to be cached, but we 3 // don't know the exact value in the cached range to assign yet.) 4 static final int UNKNOWN_ADJ = 16; 5 6 // This is a process only hosting activities that are not visible, 7 // so it can be killed without any disruption. 8 static final int CACHED_APP_MAX_ADJ = 15; 9 static final int CACHED_APP_MIN_ADJ = 9;10 11 // The B list of SERVICE_ADJ -- these are the old and decrepit12 // services that aren't as shiny and interesting as the ones in the A list.13 static final int SERVICE_B_ADJ = 8;14 15 // This is the process of the previous application that the user was in.16 // This process is kept above other things, because it is very common to17 // switch back to the previous app. This is important both for recent18 // task switch (toggling between the two top recent apps) as well as normal19 // UI flow such as clicking on a URI in the e-mail app to view in the browser,20 // and then pressing back to return to e-mail.21 static final int PREVIOUS_APP_ADJ = 7;22 23 // This is a process holding the home application -- we want to try24 // avoiding killing it, even if it would normally be in the background,25 // because the user interacts with it so much.26 static final int HOME_APP_ADJ = 6;27 28 // This is a process holding an application service -- killing it will not29 // have much of an impact as far as the user is concerned.30 static final int SERVICE_ADJ = 5;31 32 // This is a process with a heavy-weight application. It is in the33 // background, but we want to try to avoid killing it. Value set in34 // system/rootdir/init.rc on startup.35 static final int HEAVY_WEIGHT_APP_ADJ = 4;36 37 // This is a process currently hosting a backup operation. Killing it38 // is not entirely fatal but is generally a bad idea.39 static final int BACKUP_APP_ADJ = 3;40 41 // This is a process only hosting components that are perceptible to the42 // user, and we really want to avoid killing them, but they are not43 // immediately visible. An example is background music playback.44 static final int PERCEPTIBLE_APP_ADJ = 2;45 46 // This is a process only hosting activities that are visible to the47 // user, so we'd prefer they don't disappear.48 static final int VISIBLE_APP_ADJ = 1;49 50 // This is the process running the current foreground app. We'd really51 // rather not kill it!52 static final int FOREGROUND_APP_ADJ = 0;53 54 // This is a process that the system or a persistent process has bound to,55 // and indicated it is important.56 static final int PERSISTENT_SERVICE_ADJ = -11;57 58 // This is a system persistent process, such as telephony. Definitely59 // don't want to kill it, but doing so is not completely fatal.60 static final int PERSISTENT_PROC_ADJ = -12;61 62 // The system process runs at the default adjustment.63 static final int SYSTEM_ADJ = -16;64 65 // Special code for native processes that are not being managed by the system (so66 // don't have an oom adj assigned by the system).67 static final int NATIVE_ADJ = -17;View Code
2. Android Low Memory Killer
Android系统内存不足时,系统会杀掉一部分进程以释放空间,谁生谁死的这个生死大权就是由LMK所决定的,这就是Android系统中的Low Memory Killer,其基于Linux的OOM机制,其阈值定义如下面所示的lowmemorykiller文件中,当然也可以通过系统的init.rc实现自定义。
lowmemorykiller.c
1 static uint32_t lowmem_debug_level = 1; 2 static int lowmem_adj[6] = { 3 0, 4 1, 5 6, 6 12, 7 }; 8 static int lowmem_adj_size = 4; 9 static int lowmem_minfree[6] = {10 3 * 512, /* 6MB */11 2 * 1024, /* 8MB */12 4 * 1024, /* 16MB */13 16 * 1024, /* 64MB */14 };15 static int lowmem_minfree_size = 4;View Code
① 在Low Memory Killer中通过进程的oom_adj与占用内存的大小决定要杀死的进程,oom_adj值越小越不容易被杀死。其中,lowmem_minfree是杀进程的时机,谁被杀,则取决于lowmem_adj,具体值得含义参考上面 Android进程优先级 所述.
② 在init.rc中定义了init进程(系统进程)的oom_adj为-16,其不可能会被杀死(init的PID是1),而前台进程是0(这里的前台进程是指用户正在使用的Activity所在的进程),用户按Home键回到桌面时的优先级是6,普通的Service的进程是8.
init.rc
1 # Set init and its forked children's oom_adj.2 write /proc/1/oom_adj -16View Code
关于Low Memory Killer的具体实现原理可参考Ref-2.
3. 查看某个App的进程
步骤(手机与PC连接)
1. adb shell
2. ps | grep 进程名
3. cat /proc/pid/oom_adj //其中pid是上述grep得到的进程号
4. Android账号和同步机制
属于Android中较偏冷的知识,具体参考 Ref 3/4/5
二、现有方法
1. 网络连接保活方法
a. GCM
b. 公共的第三方push通道(信鸽等)
c. 自身跟服务器通过轮询,或者长连接
具体实现请参考 微信架构师杨干荣的"微信Android客户端后台保活经验分享" (Ref-1).
2. 双service 提高进程优先级
思路:(API level > 18 )
① 应用启动时启动一个假的Service(FakeService), startForeground(),传一个空的Notification
② 启动真正的Service(AlwaysLiveService),startForeground(),注意必须相同Notification ID
③ FakeService stopForeground()
效果:通过adb查看,运行在后台的服务其进程号变成了1(优先级仅次于前台进程)
风险:Android系统前台service的一个漏洞,可能在6.0以上系统中修复
实现:核心代码如下
AlwaysLiveService 常驻内存服务
1 @Override2 public int onStartCommand(Intent intent, int flags, int startId) {3 startForeground(R.id.notify, new Notification());4 startService(new Intent(this, FakeService.class));5 return super.onStartCommand(intent, flags, startId);6 }View Code
FakeService 临时服务
1 public class FakeService extends Service { 2 @Nullable 3 @Override 4 public IBinder onBind(Intent intent) { 5 return null; 6 } 7 8 @Override 9 public int onStartCommand(Intent intent, int flags, int startId) {10 startForeground(R.id.notify, new Notification());11 stopSelf();12 return super.onStartCommand(intent, flags, startId);13 }14 15 @Override16 public void onDestroy() {17 stopForeground(true);18 super.onDestroy();19 }20 }View Code
3. 守护进程及时拉起
AlarmReceiver, ConnectReceiver,BootReceiver等
三、新方法(AccountSyncAdapter)
1. 思路:
利用Android系统提供的账号和同步机制实现
2. 效果:
① 通过adb查看,运行在后台的服务其进程号变成了1(优先级仅次于前台进程),能提高进程优先级,对比如下图
正常情况
采用AccountSyncAdapter方法后
② 进程被系统kill后,可以由syn拉起
3. 风险:
①SyncAdapter时间进度不高,往往会因为手机处于休眠状态,而时间往后调整,同步间隔最低为1分钟
②用户可以单独停止或者删除,有些手机账号默认是不同步的,需要手动开启
4. 实现:核心代码如下
① 建立数据同步系统(ContentProvider)
通过一个ContentProvider用来作数据同步,由于并没有实际数据同步,所以此处就直接建立一个空的ContentProvider即可
1 public class XXAccountProvider extends ContentProvider { 2 public static final String AUTHORITY = "包名.provider"; 3 public static final String CONTENT_URI_BASE = "content://" + AUTHORITY; 4 public static final String TABLE_NAME = "data"; 5 public static final Uri CONTENT_URI = Uri.parse(CONTENT_URI_BASE + "/" + TABLE_NAME); 6 7 @Override 8 public boolean onCreate() { 9 return true;10 }11 12 @Nullable13 @Override14 public Cursor query(Uri uri, String[] projection, String selection,15 String[] selectionArgs, String sortOrder) {16 return null;17 }18 19 @Nullable20 @Override21 public String getType(Uri uri) {22 return new String();23 }24 25 @Nullable26 @Override27 public Uri insert(Uri uri, ContentValues values) {28 return null;29 }30 31 @Override32 public int delete(Uri uri, String selection, String[] selectionArgs) {33 return 0;34 }35 36 @Override37 public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {38 return 0;39 }40 }View Code
然后再Manifest中声明
<provider android:name="**.XXAccountProvider" android:authorities="@string/account_auth_provider" android:exported="false" android:syncable="true"/>View Code
② 建立Sync系统 (SyncAdapter)
通过实现SyncAdapter这个系统服务后, 利用系统的定时器对程序数据ContentProvider进行更新,具体步骤为:
- 创建Sync服务
1 public class XXSyncService extends Service { 2 private static final Object sSyncAdapterLock = new Object(); 3 private static XXSyncAdapter sSyncAdapter = null; 4 @Override 5 public void onCreate() { 6 synchronized (sSyncAdapterLock) { 7 if (sSyncAdapter == null) { 8 sSyncAdapter = new XXSyncAdapter(getApplicationContext(), true); 9 }10 }11 }12 13 @Override14 public IBinder onBind(Intent intent) {15 return sSyncAdapter.getSyncAdapterBinder();16 }17 18 static class XXSyncAdapter extends AbstractThreadedSyncAdapter {19 public XXSyncAdapter(Context context, boolean autoInitialize) {20 super(context, autoInitialize);21 }22 @Override23 public void onPerformSync(Account account, Bundle extras, String authority, ContentProviderClient provider, SyncResult syncResult) {24 getContext().getContentResolver().notifyChange(XXAccountProvider.CONTENT_URI, null, false);25 }26 }27 }View Code
- 声明Sync服务
1 <service 2 android:name="**.XXSyncService" 3 android:exported="true" 4 android:process=":core"> 5 <intent-filter> 6 <action 7 android:name="android.content.SyncAdapter"/> 8 </intent-filter> 9 <meta-data10 android:name="android.content.SyncAdapter"11 android:resource="@xml/sync_adapter"/>12 </service>View Code
其中sync_adapter为:
1 <sync-adapter xmlns:android="http://schemas.android.com/apk/res/android"2 android:accountType="@string/account_auth_type"3 android:allowParallelSyncs="false"4 android:contentAuthority="@string/account_auth_provide"5 android:isAlwaysSyncable="true"6 android:supportsUploading="false"7 android:userVisible="true"/>View Code
参数说明:
android:contentAuthority 指定要同步的ContentProvider在其AndroidManifest.xml文件中有个android:authorities属性。
android:accountType 表示进行同步的账号的类型。
android:userVisible 设置是否在“设置”中显示
android:supportsUploading 设置是否必须notifyChange通知才能同步
android:allowParallelSyncs 是否支持多账号同时同步
android:isAlwaysSyncable 设置所有账号的isSyncable为1
android:syncAdapterSettingsAction 指定一个可以设置同步的activity的Action。
- 账户调用Sync服务
首先配置好Account(第三步),然后再通过ContentProvider实现
手动更新
1 public void triggerRefresh() {2 Bundle b = new Bundle();3 b.putBoolean(ContentResolver.SYNC_EXTRAS_MANUAL, true);4 b.putBoolean(ContentResolver.SYNC_EXTRAS_EXPEDITED, true);5 ContentResolver.requestSync(6 account,7 CONTENT_AUTHORITY,8 b);9 }View Code
添加账号
1 Account account = AccountService.GetAccount(); 2 AccountManager accountManager = (AccountManager) context.getSystemService(Context.ACCOUNT_SERVICE);3 accountManager.addAccountExplicitly(...)View Code
同步周期设置
1 ContentResolver.setIsSyncable(account, CONTENT_AUTHORITY, 1);2 ContentResolver.setSyncAutomatically(account, CONTENT_AUTHORITY, true);3 ContentResolver.addPeriodicSync(account, CONTENT_AUTHORITY, new Bundle(), SYNC_FREQUENCY);View Code
③ 建立账号系统 (Account Authenticator)
通过建立Account账号,并关联SyncAdapter服务实现同步
- 创建Account服务
1 public class XXAuthService extends Service { 2 private XXAuthenticator mAuthenticator; 3 4 @Override 5 public void onCreate() { 6 mAuthenticator = new XXAuthenticator(this); 7 } 8 9 private XXAuthenticator getAuthenticator() {10 if (mAuthenticator == null)11 mAuthenticator = new XXAuthenticator(this);12 return mAuthenticator;13 }14 15 @Override16 public IBinder onBind(Intent intent) {17 return getAuthenticator().getIBinder();18 }19 20 class XXAuthenticator extends AbstractAccountAuthenticator {21 private final Context context;22 private AccountManager accountManager;23 public XXAuthenticator(Context context) {24 super(context);25 this.context = context;26 accountManager = AccountManager.get(context);27 }28 29 @Override30 public Bundle addAccount(AccountAuthenticatorResponse response, String accountType, String authTokenType, String[] requiredFeatures, Bundle options)31 throws NetworkErrorException {32 // 添加账号 示例代码33 final Bundle bundle = new Bundle();34 final Intent intent = new Intent(context, AuthActivity.class);35 intent.putExtra(AccountManager.KEY_ACCOUNT_AUTHENTICATOR_RESPONSE, response);36 bundle.putParcelable(AccountManager.KEY_INTENT, intent);37 return bundle;38 }39 40 @Override41 public Bundle getAuthToken(AccountAuthenticatorResponse response, Account account, String authTokenType, Bundle options)42 throws NetworkErrorException {43 // 认证 示例代码44 String authToken = accountManager.peekAuthToken(account, getString(R.string.account_token_type));45 //if not, might be expired, register again46 if (TextUtils.isEmpty(authToken)) {47 final String password = accountManager.getPassword(account);48 if (password != null) {49 //get new token50 authToken = account.name + password;51 }52 }53 //without password, need to sign again54 final Bundle bundle = new Bundle();55 if (!TextUtils.isEmpty(authToken)) {56 bundle.putString(AccountManager.KEY_ACCOUNT_NAME, account.name);57 bundle.putString(AccountManager.KEY_ACCOUNT_TYPE, account.type);58 bundle.putString(AccountManager.KEY_AUTHTOKEN, authToken);59 return bundle;60 }61 62 //no account data at all, need to do a sign63 final Intent intent = new Intent(context, AuthActivity.class);64 intent.putExtra(AccountManager.KEY_ACCOUNT_AUTHENTICATOR_RESPONSE, response);65 intent.putExtra(AuthActivity.ARG_ACCOUNT_NAME, account.name);66 bundle.putParcelable(AccountManager.KEY_INTENT, intent);67 return bundle;68 }69 70 @Override71 public String getAuthTokenLabel(String authTokenType) {72 // throw new UnsupportedOperationException();73 return null;74 }75 76 @Override77 public Bundle editProperties(AccountAuthenticatorResponse response, String accountType) {78 return null;79 }80 81 @Override82 public Bundle confirmCredentials(AccountAuthenticatorResponse response, Account account, Bundle options)83 throws NetworkErrorException {84 return null;85 }86 87 @Override88 public Bundle updateCredentials(AccountAuthenticatorResponse response, Account account, String authTokenType, Bundle options)89 throws NetworkErrorException {90 return null;91 }92 93 @Override94 public Bundle hasFeatures(AccountAuthenticatorResponse response, Account account, String[] features)95 throws NetworkErrorException {96 return null;97 }98 }99 }View Code
- 声明Account服务
1 <service 2 android:name="**.XXAuthService" 3 android:exported="true" 4 android:process=":core"> 5 <intent-filter> 6 <action 7 android:name="android.accounts.AccountAuthenticator"/> 8 </intent-filter> 9 <meta-data10 android:name="android.accounts.AccountAuthenticator"11 android:resource="@xml/authenticator"/>12 </service>View Code
其中authenticator为:
1 <?xml version="1.0" encoding="utf-8"?>2 <account-authenticator xmlns:android="http://schemas.android.com/apk/res/android"3 android:accountType="@string/account_auth_type"4 android:icon="@drawable/icon"5 android:smallIcon="@drawable/icon"6 android:label="@string/app_name"7 />View Code
- 使用Account服务
同SyncAdapter,通过AccountManager使用
- 申请Token主要是通过 [AccountManager.getAuthToken]系列方法
- 添加账号则通过 [AccountManager.addAccount]
- 查看是否存在账号通过 [AccountManager.getAccountsByType]
Refs
1. [微信Android客户端后台保活经验分享]
2. [Android Low Memory Killer原理]
3. [stackOverflow 上介绍的双Service方法]
4. [Write your own Android Sync Adapter]
5. [Write your own Android Authenticator]
6. Android developer
- [android.accounts]
- [AccountManager]
- [AbstractAccountAuthenticator]
- [AccountAuthenticatorActivity]
- [Creating a Sync Adapter]
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By SkySeraph-2016 www.skyseraph.com
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