Android开机向导启动流程分析
Android开机向导启动流程
首先来看Android启动流程:
1、Bootloader(系统启动加载器,将Linux加载到RAM);
2、Kernel
3、init进程
4、Zygote(Zygote进程是整个android系统的根进程,fork出System server进程);
5、system_server(Android系统的核心进程,负责启动各种系统服务);
6、System Services(由system_server调用startBootstrapServices()、startCoreServices()、startOtherServices()三个方法启动各种服务,其中重要的服务启动顺序如下:
ActivityManagerService
PowerManagerService
PackageManagerService
WindowManagerService
StorageManagerService);
接下来就是开机向导的启动过程。
一、在SystemServer类的startOtherServices()方法中,当启动了所有需要的服务后,会调用ActivityManagerService类的systemReady()方法,代码如下:
private void startOtherServices() { final Context context = mSystemContext; VibratorService vibrator = null; ... // We now tell the activity manager it is okay to run third party // code. It will call back into us once it has gotten to the state // where third party code can really run (but before it has actually // started launching the initial applications), for us to complete our // initialization. mActivityManagerService.systemReady(() -> { Slog.i(TAG, "Making services ready"); traceBeginAndSlog("StartActivityManagerReadyPhase"); mSystemServiceManager.startBootPhase( SystemService.PHASE_ACTIVITY_MANAGER_READY); traceEnd(); traceBeginAndSlog("StartObservingNativeCrashes"); ...}
二、ActivityManagerService类的systemReady()方法会调用startHomeActivityLocked()方法,开始执行启动HomeActivity的操作。
public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) { ...startHomeActivityLocked(currentUserId, "systemReady");...}
我们来看startHomeActivityLocked()方法:
Intent getHomeIntent() { Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null); intent.setComponent(mTopComponent); intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING); if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) { intent.addCategory(Intent.CATEGORY_HOME); } return intent; } boolean startHomeActivityLocked(int userId, String reason) { if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL && mTopAction == null) { // We are running in factory test mode, but unable to find // the factory test app, so just sit around displaying the // error message and don't try to start anything. return false; } Intent intent = getHomeIntent(); ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId); if (aInfo != null) { intent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name)); // Don't do this if the home app is currently being // instrumented. aInfo = new ActivityInfo(aInfo); aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId); ProcessRecord app = getProcessRecordLocked(aInfo.processName, aInfo.applicationInfo.uid, true); if (app == null || app.instr == null) { intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK); final int resolvedUserId = UserHandle.getUserId(aInfo.applicationInfo.uid); // For ANR debugging to verify if the user activity is the one that actually // launched. final String myReason = reason + ":" + userId + ":" + resolvedUserId; mActivityStarter.startHomeActivityLocked(intent, aInfo, myReason); } } else { Slog.wtf(TAG, "No home screen found for " + intent, new Throwable()); } return true; }
首先调用getHomeIntent()方法,该方法为Intent对象添加了Intent.CATEGORY_HOME常量,之后调用了ActivityStarter类的startHomeActivityLocked()方法,然后就是Activity的启动流程啦,关于Activity的启动流程请看我上一篇博客Activity启动流程分析。最后响应android.intent.category.HOME属性的应用就被启动了。
三、通过上面的流程,我们知道,Android通过ActivityManagerService类中的startHomeActivityLocked方法,发送一个带有android.intent.category.HOME的intent来启动响应该属性的应用。一般Launcher的AndroidManifest配置文件中都会有该属性,所以系统的Launcher就是这样被启动了。
再来看Android中的Provision应用(/packages/apps/provision),Provision其实就是类似刚出厂时或者恢复出厂设置之后,一步一步引导用户完成各种设置的Setup Wizard程序,就是我们所说的开机向导,它的主要作用是:引导用户进行一些基本设置。在原生的Android系统中,Provision只有一个空白的Activity,我们可以根据需求自己定制开机向导。
来看看Provision应用的AndroidManifest配置文件:
<application> <activity android:name="DefaultActivity" android:theme="@android:style/Theme.NoDisplay" android:excludeFromRecents="true"> <intent-filter android:priority="3"> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.HOME" /> <category android:name="android.intent.category.DEFAULT" /> <category android:name="android.intent.category.SETUP_WIZARD" /> intent-filter> activity> application>
可以看到Provision也会响应android.intent.category.HOME属性,并且它的android:priority属性值为3,整数值越大,优先级越高,可见它的优先级要比一般的Launcher高,所以在AMS的startHomeActivityLocked()方法启动HomeLauncher的时候会先启动Provision应用,即开机向导,然后才启动Launcher。
看一下Provision中DefaultActivity.java源码:
public class DefaultActivity extends Activity { @Override protected void onCreate(Bundle icicle) { super.onCreate(icicle); // Add a persistent setting to allow other apps to know the device has been provisioned. Settings.Global.putInt(getContentResolver(), Settings.Global.DEVICE_PROVISIONED, 1); Settings.Secure.putInt(getContentResolver(), Settings.Secure.USER_SETUP_COMPLETE, 1); Settings.Secure.putInt(getContentResolver(), Settings.Secure.TV_USER_SETUP_COMPLETE, 1); // remove this activity from the package manager. PackageManager pm = getPackageManager(); ComponentName name = new ComponentName(this, DefaultActivity.class); pm.setComponentEnabledSetting(name, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP); // terminate the activity. finish(); }}
首先在Global表中将DEVICE_PROVISIONED属性设置为1(这个标志很重要,因为很多地方都会检查该标志是否被置为1来决定是否要走正常的流程,比如锁屏、各种Service等),在Secure表中将USER_SETUP_COMPETE属性和TV_USER_SETUP_COMPLETE属性设置为1。然后通过PackageManager对象的setComponentEnabledSetting()方法将自己设置成不可用状态,所以开机向导只会执行一次。最后关闭Activity。
如果开机向导没有执行,DEVICE_PROVISIONED属性没有被设置为1,则会导致很多功能不可用,比如无法锁屏、按home键没有反应等。
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