android6.0默认Home(Launcher3)的启动分析
Launcher是默认的桌面应用，在系统启动后开始启动Launcher，进而才加载桌面数据。那么如何实现开机进入默认Launcher,比如把自己写的应用设置成开机默认启动的桌面呢？带着这个问题来分析Launcher是如何被选中并成为默认桌面应用而启动的。
SystemServer启动ActivityManagerService并调用了它的systemReady()函数。
ActivityManagerService
public void systemReady(final Runnable goingCallback){
//Start up initial actiivty
mBooting = true;
startHomeActivityLocked(mCurrentUserId, "systemReady");
}接着调用startHomeActivityLocked()启动Launcher
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;
}
//给Intent设置Category
Intent intent = getHomeIntent();
//获取ActivityInfo
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);
//启动launcher
mStackSupervisor.startHomeActivity(intent, aInfo, reason);
}
}
return true;
}这个函数主要完成的工作：函数首先创建一个CATEGORY_HOME类型的Intent，然后通过 Intent.resolveActivityInfo函数向 PackageManagerService查询Category类型为HOME的Activity。
1、getHomeIntent()给Intent设置Category:CATEGORY_HOME
mTopAction = Intent.MAIN
Intent getHomeIntent(){
Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);
intent.setComponent(mTopComponent);
if(mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL){
//设置category
intent.addCategory(Intent.CATEGORY_HOME);
}
return intent;
}2、resolveActivityInfo()获取ActivityInfo信息
private ActivityInfo resolveActivityInfo(Intent intent, int flags, int userId){
ActivityInfo ai = null;
ComponentName comp = intent.getComponent();
try{
if(comp != null){
//Factory test
ai = AppGlobals.getPackageManager().getActivityInfo(comp, flags, userId);
}else{
ResolveInfo info = AppGlobals.getPackageManager().resolveIntent(
intent,
intent.resolveTypeIfNeed(mContext.getContentResolver()
flags,userId);
if(info != null){
ai = info.activityInfo;
}
}
}catch(RemoteException e){
}
return ai;
}2.1、AppGlobal.getPacakgeManager()返回的是IPackageManager对象，PackageManagerService extends IPacakgeManager,因此调用的是PackageManagerService的resolveIntent()函数。
public ResolveInfo resolveIntent(Intent intent, String resolvedType,
int flags, int userId) {
if (!sUserManager.exists(userId)) return null;
//检查权限
enforceCrossUserPermission(Binder.getCallingUid(), userId, false, false, "resolve intent");
List query = queryIntentActivities(intent, resolvedType, flags, userId);
return chooseBestActivity(intent, resolvedType, flags, query, userId);
} 这里主要完成的工作是：
(1)检查权限
(2)查找符合要求的Activities，ActivityInfo是ResolveInfo的一个变量，这里返回的是符合条件的装有ResolveInfo的集合。
public List queryIntentActivities(Intent intent,
String resolvedType, int flags, int userId) {
if (!sUserManager.exists(userId)) return Collections.emptyList();
enforceCrossUserPermission(Binder.getCallingUid(), userId, false, false, "query intent activities");
ComponentName comp = intent.getComponent();
if (comp == null) {
if (intent.getSelector() != null) {
intent = intent.getSelector();
comp = intent.getComponent();
}
}
//判断Intent指定的模块不为空，则返回list，满足条件的只有一个
if (comp != null) {
final List list = new ArrayList(1);
final ActivityInfo ai = getActivityInfo(comp, flags, userId);
if (ai != null) {
final ResolveInfo ri = new ResolveInfo();
ri.activityInfo = ai;
list.add(ri);
}
return list;
}
// reader
synchronized (mPackages) {
final String pkgName = intent.getPackage();
//如果Intent没有指定包名，在系统所有包中查找
if (pkgName == null) {
List matchingFilters =
getMatchingCrossProfileIntentFilters(intent, resolvedType, userId);
// Check for results that need to skip the current profile.
ResolveInfo xpResolveInfo = querySkipCurrentProfileIntents(matchingFilters, intent,
resolvedType, flags, userId);
if (xpResolveInfo != null && isUserEnabled(xpResolveInfo.targetUserId)) {
List result = new ArrayList(1);
result.add(xpResolveInfo);
return filterIfNotPrimaryUser(result, userId);
}
// Check for results in the current profile.
List result = mActivities.queryIntent(
intent, resolvedType, flags, userId);
// Check for cross profile results.
xpResolveInfo = queryCrossProfileIntents(
matchingFilters, intent, resolvedType, flags, userId);
if (xpResolveInfo != null && isUserEnabled(xpResolveInfo.targetUserId)) {
result.add(xpResolveInfo);
Collections.sort(result, mResolvePrioritySorter);
}
result = filterIfNotPrimaryUser(result, userId);
if (hasWebURI(intent)) {
CrossProfileDomainInfo xpDomainInfo = null;
final UserInfo parent = getProfileParent(userId);
if (parent != null) {
xpDomainInfo = getCrossProfileDomainPreferredLpr(intent, resolvedType,
flags, userId, parent.id);
}
if (xpDomainInfo != null) {
if (xpResolveInfo != null) {
// If we didn't remove it, the cross-profile ResolveInfo would be twice
// in the result.
result.remove(xpResolveInfo);
}
if (result.size() == 0) {
result.add(xpDomainInfo.resolveInfo);
return result;
}
} else if (result.size() <= 1) {
return result;
}
result = filterCandidatesWithDomainPreferredActivitiesLPr(intent, flags, result,
xpDomainInfo, userId);
Collections.sort(result, mResolvePrioritySorter);
}
return result;
}
final PackageParser.Package pkg = mPackages.get(pkgName);
//如果Intent指定的包名不为空，则查找安装包中指定的包
if (pkg != null) {
return filterIfNotPrimaryUser(
mActivities.queryIntentForPackage(
intent, resolvedType, flags, pkg.activities, userId),
userId);
}
return new ArrayList();
}
} 这里根据Intent中指定的信息来处理。如果Intent有指定ComponentName则调用getActivityInfo()函数并返回ActivityInfo。如果Intent只指定包名，则调用queryIntentForPackage()函数在指定的安装包中查找符合条件的Activity。如果Intent没有指定包名也没有指定组件名，则调用queryIntent()函数来查找所有安装包。
(3)选择并返回返回最合适的ResolveInfo
private ResolveInfo chooseBestActivity(Intent intent, String resolvedType,
int flags, List query, int userId) {
if (query != null) {
final int N = query.size();
if (N == 1) {
return query.get(0);
} else if (N > 1) {
final boolean debug = ((intent.getFlags() & Intent.FLAG_DEBUG_LOG_RESOLUTION) != 0);
// If there is more than one activity with the same priority,
// then let the user decide between them.
ResolveInfo r0 = query.get(0);
ResolveInfo r1 = query.get(1);
if (DEBUG_INTENT_MATCHING || debug) {
Slog.v(TAG, r0.activityInfo.name + "=" + r0.priority + " vs "
+ r1.activityInfo.name + "=" + r1.priority);
}
// If the first activity has a higher priority, or a different
// default, then it is always desireable to pick it.
if (r0.priority != r1.priority
|| r0.preferredOrder != r1.preferredOrder
|| r0.isDefault != r1.isDefault) {
return query.get(0);
}
// If we have saved a preference for a preferred activity for
// this Intent, use that.
ResolveInfo ri = findPreferredActivity(intent, resolvedType,
flags, query, r0.priority, true, false, debug, userId);
if (ri != null) {
return ri;
}
ri = new ResolveInfo(mResolveInfo);
ri.activityInfo = new ActivityInfo(ri.activityInfo);
ri.activityInfo.applicationInfo = new ApplicationInfo(
ri.activityInfo.applicationInfo);
if (userId != 0) {
ri.activityInfo.applicationInfo.uid = UserHandle.getUid(userId,
UserHandle.getAppId(ri.activityInfo.applicationInfo.uid));
}
// Make sure that the resolver is displayable in car mode
if (ri.activityInfo.metaData == null) ri.activityInfo.metaData = new Bundle();
ri.activityInfo.metaData.putBoolean(Intent.METADATA_DOCK_HOME, true);
return ri;
}
}
return null;
}
从查询到的符合条件的集合中选择最符合的Activity。如果符合条件的只有一个应用，则返回该应用信息(源码中确实只有Launcher3符合)，否则，选出前两个，比较优先级priority、preferredOrder、isDefault三个参数，选出优先级最高的Activity。如何那三个参数都一样则查找看用户是否选择了永久使用的Activity,如果有则返回该Activity对应的ResolveInfo。
在Launcher的清单文件中设置了
<activity
android:name="com.android.launcher3.Launcher"
android:launchMode="singleTask"
android:clearTaskOnLaunch="true"
android:stateNotNeeded="true"
android:theme="@style/Theme"
android:windowSoftInputMode="adjustPan"
android:screenOrientation="nosensor"
android:resumeWhilePausing="false"
android:taskAffinity=""
android:enabled="true">
<intent-filter>
<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.MONKEY"/>
intent-filter>
activity>显然Launcher是最符合条件的应用。
3、startHomeActivity()//启动launcher
ActivityStackSupervisor.java
void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason) {
moveHomeStackTaskToTop(HOME_ACTIVITY_TYPE, reason);
startActivityLocked(null /* caller */, intent, null /* resolvedType */, aInfo,
null /* voiceSession */, null /* voiceInteractor */, null /* resultTo */,
null /* resultWho */, 0 /* requestCode */, 0 /* callingPid */, 0 /* callingUid */,
null /* callingPackage */, 0 /* realCallingPid */, 0 /* realCallingUid */,
0 /* startFlags */, null /* options */, false /* ignoreTargetSecurity */,
false /* componentSpecified */,
null /* outActivity */, null /* container */, null /* inTask */);
if (inResumeTopActivity) {
// If we are in resume section already, home activity will be initialized, but not
// resumed (to avoid recursive resume) and will stay that way until something pokes it
// again. We need to schedule another resume.
scheduleResumeTopActivities();
}
}分析到这里对默认的Launcher选定的过程就有了大概的了解。设置默认启动的Launcher方法很多，我的思路是从chooseBestActivity()这个函数入手，三种方法：
(1)在Manifest.xml设置优先级属性priority默认值为0，设置的值越大优先级越高。
(2)给默认的Launcher的清单文件配置属性： android.intent.category.DEFAULT
(3)当N > 1时做出相应处理：返回要启动的桌面应用。
else if (N > 1) {
//添加代码返回需要启动的应用信息
for(int i = 0; i < N; i++){
ResolveInfo ri = query.get(i);
if (ri.activityInfo.packageName.equals("包名")) {
return ri;
}
}
}