Android4_SRC_分析~ActivityManagerService~图解（一）

OK,从现在开始，我们会一个要点一个要点的把Android目前在开发上比较中要的几个知识点从源码开始详细分析，当然，在这里，我主要的是分析framework层下的代码,今天我给分析是关于ActivityManagerService.java这个类，分析内容主要为其内部原理，由于本类代码比较多，所以我不可能在一个篇幅中全部给细细分析与展示出来，所以我主要分析其内部原理：

好了先看下面:

package com.android.server.am;

18

19 import com.android.internal.R;

20 import com.android.internal.os.BatteryStatsImpl;

21 import com.android.internal.os.ProcessStats;

22 import com.android.server.AttributeCache;

23 import com.android.server.IntentResolver;

24 import com.android.server.ProcessMap;

25 import com.android.server.SystemServer;

26 import com.android.server.Watchdog;

27 import com.android.server.am.ActivityStack.ActivityState;

28 import com.android.server.wm.WindowManagerService;

30 import dalvik.system.Zygote;

32 import android.app.Activity;

33 import android.app.ActivityManager;

34 import android.app.ActivityManagerNative;

35 import android.app.ActivityThread;

36 import android.app.AlertDialog;

37 import android.app.AppGlobals;

38 import android.app.ApplicationErrorReport;

39 import android.app.Dialog;

40 import android.app.IActivityController;

41 import android.app.IActivityWatcher;

42 import android.app.IApplicationThread;

43 import android.app.IInstrumentationWatcher;

44 import android.app.INotificationManager;

45 import android.app.IProcessObserver;

46 import android.app.IServiceConnection;

47 import android.app.IThumbnailReceiver;

48 import android.app.Instrumentation;

49 import android.app.Notification;

50 import android.app.NotificationManager;

51 import android.app.PendingIntent;

52import android.app.Service;

53 import android.app.backup.IBackupManager;

54 import android.content.ActivityNotFoundException;

55 import android.content.BroadcastReceiver;

56 import android.content.ComponentCallbacks2;

57 import android.content.ComponentName;

58 import android.content.ContentResolver;

59 import android.content.Context;

60 import android.content.DialogInterface;

61 import android.content.Intent;

62 import android.content.IntentFilter;

63 import android.content.IIntentReceiver;

64 import android.content.IIntentSender;

65 import android.content.IntentSender;

66 import android.content.pm.ActivityInfo;

67 import android.content.pm.ApplicationInfo;

68 import android.content.pm.ConfigurationInfo;

69 import android.content.pm.IPackageDataObserver;

70 import android.content.pm.IPackageManager;

71 import android.content.pm.InstrumentationInfo;

72 import android.content.pm.PackageInfo;

73 import android.content.pm.PackageManager;

74 import android.content.pm.PathPermission;

75 import android.content.pm.ProviderInfo;

76 import android.content.pm.ResolveInfo;

77 import android.content.pm.ServiceInfo;

78 import android.content.pm.PackageManager.NameNotFoundException;

79 import android.content.res.CompatibilityInfo;

80 import android.content.res.Configuration;

81 import android.graphics.Bitmap;

82 import android.net.Proxy;

83 import android.net.ProxyProperties;

84 import android.net.Uri;

85 import android.os.Binder;

86 import android.os.Build;

87 import android.os.Bundle;

88 import android.os.Debug;

89 import android.os.DropBoxManager;

90 import android.os.Environment;

91 import android.os.FileObserver;

92 import android.os.FileUtils;

93 import android.os.Handler;

94 import android.os.IBinder;

95 import android.os.IPermissionController;

96 import android.os.Looper;

97 import android.os.Message;

98 import android.os.Parcel;

99 import android.os.ParcelFileDescriptor;

100 import android.os.Process;

101 import android.os.RemoteCallbackList;

102 import android.os.RemoteException;

103 import android.os.ServiceManager;

104 import android.os.StrictMode;

105 import android.os.SystemClock;

106 import android.os.SystemProperties;

107 import android.provider.Settings;

108 import android.text.format.Time;

109 import android.util.EventLog;

110 import android.util.Pair;

111 import android.util.Slog;

112 import android.util.Log;

113 import android.util.PrintWriterPrinter;

114 import android.util.SparseArray;

115 import android.util.TimeUtils;

116 import android.view.Gravity;

117 import android.view.LayoutInflater;

118 import android.view.View;

119 import android.view.WindowManager;

120 import android.view.WindowManagerPolicy;

121

122 import java.io.BufferedInputStream;

123 import java.io.BufferedOutputStream;

124 import java.io.BufferedReader;

125 import java.io.DataInputStream;

126 import java.io.DataOutputStream;

127 import java.io.File;

128 import java.io.FileDescriptor;

129 import java.io.FileInputStream;

91 import android.os.FileObserver;

92 import android.os.FileUtils;

93 import android.os.Handler;

94 import android.os.IBinder;

95 import android.os.IPermissionController;

96 import android.os.Looper;

97 import android.os.Message;

98 import android.os.Parcel;

99 import android.os.ParcelFileDescriptor;

100 import android.os.Process;

101 import android.os.RemoteCallbackList;

102 import android.os.RemoteException;

103 import android.os.ServiceManager;

104 import android.os.StrictMode;

105 import android.os.SystemClock;

106 import android.os.SystemProperties;

107 import android.provider.Settings;

108 import android.text.format.Time;

109 import android.util.EventLog;

110 import android.util.Pair;

111 import android.util.Slog;

112 import android.util.Log;

113 import android.util.PrintWriterPrinter;

114 import android.util.SparseArray;

115 import android.util.TimeUtils;

116 import android.view.Gravity;

117 import android.view.LayoutInflater;

118 import android.view.View;

119 import android.view.WindowManager;

120 import android.view.WindowManagerPolicy;

121

122 import java.io.BufferedInputStream;

123 import java.io.BufferedOutputStream;

124 import java.io.BufferedReader;

125 import java.io.DataInputStream;

126 import java.io.DataOutputStream;

127 import java.io.File;

128 import java.io.FileDescriptor;

129 import java.io.FileInputStream;

根据上面，就可以看出，此类在是server层下的，当然，也是属于framework层下的，上面导入来哪些类来实现呢，从导入的情况可以发现有电池状态实现(BatteryStatesImpl)，R,进程状态(ProcessState)，属性缓存(AttributeCache)，意图接收(IntentResolver)，进程哈系(ProcessMap)，系统服务(SystemService)，观察狗(WatchDog)，Activity栈状态(ActivityState)，窗口管理服务(WindowManagerService)，卵化器(Zygote)，Activity,Activity管理(ActivityManager)，Activity管理本地类(ActivityManagerNative)，Activity线程(ActivityThread)，警告对话框(AlertDialog)，App全局(AppGlobals)，应用错误报告(ApplicationErrorReport)，对话框(Dialog)，Activity控制接口(IActivityController)，Activity观察接口(IActivityWather)，应用线程接口(IApplicationThread),仪器观察接口(IStrumentationObserver)，通知管理接口(INotificationManager)，进程关注接口(IProcessObserver)，服务链接接口(IServerConnection)，缩略图接收器接口(IThumbnailReceiver)，仪器(Instrumentation)，通知(Notification)，通知管理(NotificationManager)，有待意图(PindingINtent)，服务(Service),备份管理接口(IBackupManager),Activity没有找到异常(ActivityNotFoundException),广播接收者(BroadcastReceiver),组建回调2(ComponentCallbacks2),组建名称(ComponentName),内容分解(ContentResolver),上下文(Context),对话框接口(DialogInterface),意图(Intent),意图过滤器(IntentFilter),意图接收接口(IIntentReceiver),意图发送接口(IIntentSender),意图发送(IntentSender),Activity信息(ActivityInfo),应用信息(ApplicationInfo),配置信息(ConfigurationInfo),包数据关注接口(IPackageDataObserver),包管理接口(IPackageManager),仪器信息(InstrmatationInfo),包信息(PackageInfo),包管理(PackageManager),路径权限(PathPermission),提供者信息(ProviderInfo),解析器信息(ResolveInfo),服务信息(ServiceInfo),名称没有发现异常(NameNotFoundException),兼容性信息(CompatibilityInfo),配置(Configuration),位图(Bitmap),代理(Proxy),代理属性(ProxyProperties),统一资源标志符(Uri),帮第器(binder),建立(Build),捆(Bundle),调试(Debug),下拉框管理器(DropBoxManager),环境变量(Environment),文件关注(FileObserver),文件单元(FileUtils),处理器(Handler),捆绑器接口(IBinder),权限控制接口(IPermissionController),论寻(Looper),消息(Message),邮包(Parcel),邮包文件描述(ParcelFileDescript),进程(Process),远程回调列表(RemoteCallBackList),远程异常(RemoteException),服务管理(ServiceManager),严格模式(StrictMode),SystemClock(系统时钟),系统属性(SystemProperties),设置(Settings),时间(Time),事件日志(EventLog),一对(Pair),系统日志(SLog),日志(Log),输入打印(PrintWriterPrinter),数组解析(ParseArray),时间单元(TImeUtils),重力(Gravity),布局填充(LayoutInfalter),视图(View),窗口管理(WindowManager),窗口管理策略(WindowManagerPolicy),输入流缓冲(BufferedInputStream)，输出流缓冲(BufferedOutputStream),缓冲读取(BufferedReader),数据输入流(DataInputStream),数据输出流(DataOutputStream),文件(File),文件描述(FileDescriptor),文件输入流(FileInputStream),文件没有发现异常(FileNotFoundException),文件输出流(FileOutputStream),IO异常(IOException),读取输入流(InputStreamReader),输入打印(PrintWriter),字符串写入(StringWriter)，非状态异常(IllegalStateException),弱引用(WeakReference),数组列表(ArrayList),集合(Collections),比较(Comparator),哈系映射(HashMap),哈系集合(HashSet),迭代(Iterator),列表(List),语言环境(Locale),映射(Map),集合(Set),原子布尔(AtomicBoolean),原子长(AtimicLong).

OK,以上就是需要导入的相关类，可能有的人看到这里就有点晕了，其实际你看到这里并能很清晰的知道相干类的话，那说明你真的很懂了，毕竟这个类是一个重量级的类，容量达到了608k,代码标准行数达到来14382行，看看上面导入的类就知道这个类不可忽视，好来我们知道了上面，现在来具体分析下它的内部运行原理吧，在这里需要注意：

public class ActivityManagerService extends ActivityManagerNative implements Watchdog.Monitor,BatteryStatesImpl.BatteryCallBack{},这里它继承了本地窗口管理类，并且同时实现了观察狗的监听器与电池状态的实现回调，接下来，看首先声明的一些相关变量：

static final String TAG = "ActivityManager";

154 static final boolean DEBUG = false;

155 static final boolean localLOGV = DEBUG;

156 static final boolean DEBUG_SWITCH = localLOGV || false;

157 static final boolean DEBUG_TASKS = localLOGV || false;

158 static final boolean DEBUG_PAUSE = localLOGV || false;

159 static final boolean DEBUG_OOM_ADJ = localLOGV || false;

160 static final boolean DEBUG_TRANSITION = localLOGV || false;

161 static final boolean DEBUG_BROADCAST = localLOGV || false;

162 static final boolean DEBUG_BROADCAST_LIGHT = DEBUG_BROADCAST || false;

163 static final boolean DEBUG_SERVICE = localLOGV || false;

164 static final boolean DEBUG_SERVICE_EXECUTING = localLOGV || false;

165 static final boolean DEBUG_VISBILITY = localLOGV || false;

166 static final boolean DEBUG_PROCESSES = localLOGV || false;

167 static final boolean DEBUG_PROVIDER = localLOGV || false;

168 static final boolean DEBUG_URI_PERMISSION = localLOGV || false;

169 static final boolean DEBUG_USER_LEAVING = localLOGV || false;

170 static final boolean DEBUG_RESULTS = localLOGV || false;

171 static final boolean DEBUG_BACKUP = localLOGV || false;

172 static final boolean DEBUG_CONFIGURATION = localLOGV || false;

173 static final boolean DEBUG_POWER = localLOGV || false;

174 static final boolean DEBUG_POWER_QUICK = DEBUG_POWER || false;

175 static final boolean VALIDATE_TOKENS = false;

176 static final boolean SHOW_ACTIVITY_START_TIME = true;

177

178 // Control over CPU and battery monitoring.

179 static final long BATTERY_STATS_TIME = 30*60*1000; // write battery stats every 30 minutes.

180 static final boolean MONITOR_CPU_USAGE = true;

181 static final long MONITOR_CPU_MIN_TIME = 5*1000; // don't sample cpu less than every 5 seconds.

182 static final long MONITOR_CPU_MAX_TIME = 0x0fffffff; // wait possibly forever for next cpu sample.

183 static final boolean MONITOR_THREAD_CPU_USAGE = false;

// The flags that are set for all calls we make to the package manager.

186 static final int STOCK_PM_FLAGS = PackageManager.GET_SHARED_LIBRARY_FILES;

187

188 private static final String SYSTEM_DEBUGGABLE = "ro.debuggable";

189

190 static final boolean IS_USER_BUILD = "user".equals(Build.TYPE);

191

192 // Maximum number of recent tasks that we can remember.

193 static final int MAX_RECENT_TASKS = 20;

194

195 // Amount of time after a call to stopAppSwitches() during which we will

196 // prevent further untrusted switches from happening.

197 static final long APP_SWITCH_DELAY_TIME = 5*1000;

198

199 // How long we wait for a launched process to attach to the activity manager

200 // before we decide it's never going to come up for real.

201 static final int PROC_START_TIMEOUT = 10*1000;

202

203 // How long we wait for a launched process to attach to the activity manager

204 // before we decide it's never going to come up for real, when the process was

205 // started with a wrapper for instrumentation (such as Valgrind) because it

206 // could take much longer than usual.

207 static final int PROC_START_TIMEOUT_WITH_WRAPPER = 300*1000;

208

209 // How long to wait after going idle before forcing apps to GC.

210 static final int GC_TIMEOUT = 5*1000;

211

212 // The minimum amount of time between successive GC requests for a process.

213 static final int GC_MIN_INTERVAL = 60*1000;

214

215 // The rate at which we check for apps using excessive power -- 15 mins.

216 static final int POWER_CHECK_DELAY = (DEBUG_POWER_QUICK ? 2 : 15) * 60*1000;

217

218 // The minimum sample duration we will allow before deciding we have

219 // enough data on wake locks to start killing things.

220 static final int WAKE_LOCK_MIN_CHECK_DURATION = (DEBUG_POWER_QUICK ? 1 : 5) * 60*1000;

// The minimum sample duration we will allow before deciding we have

223 // enough data on CPU usage to start killing things.

224 static final int CPU_MIN_CHECK_DURATION = (DEBUG_POWER_QUICK ? 1 : 5) * 60*1000;

225

226 // How long we allow a receiver to run before giving up on it.

227 static final int BROADCAST_TIMEOUT = 10*1000;

228

229 // How long we wait for a service to finish executing.

230 static final int SERVICE_TIMEOUT = 20*1000;

231

232 // How long a service needs to be running until restarting its process

233 // is no longer considered to be a relaunch of the service.

234 static final int SERVICE_RESTART_DURATION = 5*1000;

235

236 // How long a service needs to be running until it will start back at

237 // SERVICE_RESTART_DURATION after being killed.

238 static final int SERVICE_RESET_RUN_DURATION = 60*1000;

239

240 // Multiplying factor to increase restart duration time by, for each time

241 // a service is killed before it has run for SERVICE_RESET_RUN_DURATION.

242 static final int SERVICE_RESTART_DURATION_FACTOR = 4;

243

244 // The minimum amount of time between restarting services that we allow.

245 // That is, when multiple services are restarting, we won't allow each

246 // to restart less than this amount of time from the last one.

247 static final int SERVICE_MIN_RESTART_TIME_BETWEEN = 10*1000;

248

249 // Maximum amount of time for there to be no activity on a service before

250 // we consider it non-essential and allow its process to go on the

251 // LRU background list.

252 static final int MAX_SERVICE_INACTIVITY = 30*60*1000;

253

254 // How long we wait until we timeout on key dispatching.

255 static final int KEY_DISPATCHING_TIMEOUT = 5*1000;

// How long we wait until we timeout on key dispatching during instrumentation.

258 static final int INSTRUMENTATION_KEY_DISPATCHING_TIMEOUT = 60*1000;

259

260 static final int MY_PID = Process.myPid();

261

262 static final String[] EMPTY_STRING_ARRAY = new String[0];

263

264 public ActivityStack mMainStack;

上面是相关的一些前奏变量声明，看声明良不小哦，毕竟ActivityManagerService为Android内核的三大核心功能之一，Android内核的三大核心功能分别是:ActivityManagerService,WindowManagerService,View. 我从功能的角度可以知道ActivityManagerService主要有三大功能，即对应用程序的Activity作统一调度，内存管理与进程管理这三大主要功能，我们分析下，应用程序需要运行Activity,首先会通过ActivityManagerService来决定是否启动该Activity,再就是Activity退出后，所在的进程并不会立即被杀死，而会短时间存活在内存里，以便在下次启动时来提升其速度，当然在内存紧张时会对其杀死，这是由ActivityManagerService来完成的，应用程序并不需要对其管理，再就是进程管理，对其进程运行的API信息进行查询。

下面我们就单一来讲下，Activity调度：

思路：对其应用要启动的Activity必须通过ActivityManagerService来对记录的指示启动，当遇到其Activity停止或者启动需求时，它都会对其记录进行更新，从而掌握了Activity的启动与否的状态信息，在这里顺便来举一个Activity启动的几种方式:一般有四种：1.可在应用程序中调用this.startActivity()来启动指定的Activity,2.在Home程序中单击一个图标来启动新的Activity,3.按"Back(回退键)"来结束当前Activity,从而自动启动上一个Activity,4.长按Home键，显示出当前列表，从中选择一个启动。从上面可知，启动可分为顺序启动与前端处理启动，后面三种分为前端处理启动，看来要讲的还很多，今天就讲到这里吧，明天继续。。。