Launcher 启动流程

1 启动Launcher
在之前分析了一下SystemServer源码，最后启动boot/core/other … Service,在startOtherService 中，有调用到 mActivityManagerService.systemReady();

mActivityManagerService.systemReady(new Runnable() {
            @Override
            public void run() {
                Slog.i(TAG, "Making services ready");
                mSystemServiceManager.startBootPhase(
            SystemService.PHASE_ACTIVITY_MANAGER_READY);
                try { mActivityManagerService.startObservingNativeCrashes();
                } catch (Throwable e) {
                    reportWtf("observing native crashes", e);
                }
                try {
                    startSystemUi(context);
                } catch (Throwable e) {
                    reportWtf("starting System UI", e);
                }
                try {
                    if (networkScoreF != null) networkScoreF.systemReady();
                } catch (Throwable e) {
                    reportWtf("making Network Score Service ready", e);
                }
                try {
                    if (networkManagementF != null) networkManagementF.systemReady();
                } catch (Throwable e) {
                    reportWtf("making Network Managment Service ready", e);
                }
                try {
                    if (networkStatsF != null) networkStatsF.systemReady();
                } catch (Throwable e) {
                    reportWtf("making Network Stats Service ready", e);
                }
                try {
                    if (networkPolicyF != null) networkPolicyF.systemReady();
                } catch (Throwable e) {
                    reportWtf("making Network Policy Service ready", e);
                }
                try {
                    if (connectivityF != null) connectivityF.systemReady();
                } catch (Throwable e) {
                    reportWtf("making Connectivity Service ready", e);
                }
                try {
                    if (audioServiceF != null) audioServiceF.systemReady();
                } catch (Throwable e) {
                    reportWtf("Notifying AudioService running", e);
                }
                Watchdog.getInstance().start();
            }
        });
    }

通过源码可以看到其中大多是系统服务systemReady()操作，重点关注一下Launcher所进行的操作流程，ActivityManagerService.systemReady();

public void systemReady(final Runnable goingCallback) {
        ......  各种校验 System ready 情况 ......
        Slog.i(TAG, "System now ready");
            
        // Make sure we have no pre-ready processes sitting around.
        retrieveSettings();
        loadResourcesOnSystemReady();
        // Start up initial activity.
        mBooting = true;
        startHomeActivityLocked(mCurrentUserId, "systemReady");
        
        ......
    }

这里主要是校验各种System ready 情况,最后调用startHomeActivityLocked();

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.instrumentationClass == null) {
                intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
                mStackSupervisor.startHomeActivity(intent, aInfo, reason);
            }
        }
        return true;
    }
    
    
   Intent getHomeIntent() {
        Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);
        intent.setComponent(mTopComponent);
        if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
            intent.addCategory(Intent.CATEGORY_HOME);
        }
        return intent;
    }

这里很清晰，先通过getHomeIntent获取 Intent之后，startHomeActivity进行start。而了Intent.CATEGORY_HOME常量是Android的androidmanifest.xml清单文件中的常量。

void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason) {
        moveHomeStackTaskToTop(HOME_ACTIVITY_TYPE, reason);
        startActivityLocked(...);
        
       if (inResumeTopActivity) {
            scheduleResumeTopActivities();
        }
    }

最后调用到的是startActivityLocked(),这里其实启动的是清单文件中声明的Launcher的Activity类
2.LauncherActivity
LauncherActivity 继承自 ListActivity,layout 文件十分简单，一个ListView,一个TextView,从生命周期OnCreate()来看

protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        
        mPackageManager = getPackageManager();
        if (!mPackageManager.hasSystemFeature(PackageManager.FEATURE_WATCH)) {
            requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
            setProgressBarIndeterminateVisibility(true);
        }
        onSetContentView();
        mIconResizer = new IconResizer();
        
        mIntent = new Intent(getTargetIntent());
        mIntent.setComponent(null);
        mAdapter = new ActivityAdapter(mIconResizer);
        setListAdapter(mAdapter);
        getListView().setTextFilterEnabled(true);
        updateAlertTitle();
        updateButtonText();
        if (!mPackageManager.hasSystemFeature(PackageManager.FEATURE_WATCH)) {
            setProgressBarIndeterminateVisibility(false);
        }
    }
* 其中 getPackageManager() 是获取应用列表，以及应用信息，并将数据注入Adapter，显示到桌面。
protected void onListItemClick(ListView l, View v, int position, long id) {
        Intent intent = intentForPosition(position);
        startActivity(intent);
    }

在点击图标的点击事件回调中，将Intent取出来后，并启动Activity.至此启动应用。Launcher 启动结束。

Launcher 启动流程

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