这里以浏览器为例进行说明。 如果之前设置了默认浏览器，再安装另外一个浏览器后，再次打开链接，会重新弹框要求用户选择打开方式，这样设计的目的是让新安装的应用有机会得到用户的选择使用。
在之前的文章中，已经知道了存储偏好设置的文件是package-restrictions.xml 现在来查看下package-restrictions.xml，把UC设置为默认浏览器 package-restrictions.xml <item name="com.UCMobile/.main.UCMobile" match="200000" always="true" set="2"> <set name="com.UCMobile/.main.UCMobile" /> <set name="com.android.browser/.BrowserActivity" /> <filter> <action name="android.intent.action.VIEW" /> <cat name="android.intent.category.DEFAULT" /> <scheme name="http" /> </filter> </item>
安装另外一个浏览器后，调用到findPreferredActivity if (always && !pa.mPref.sameSet(query)) {
Slog.d(TAG, "===== pa.mPref.Set =" + pa.mPref.mSetPackages); for (String astr : pa.mPref.mSetPackages) { Slog.d(TAG, "set[]=" + astr); }
Slog.i(TAG, "Result set changed, dropping preferred activity for " + intent + " type " + resolvedType); if (DEBUG_PREFERRED) { Slog.v(TAG, "Removing preferred activity since set changed " + pa.mPref.mComponent); }
pa.mPref.mSetPackages 为package-restrictions.xml里set的内容，如 <set name="com.UCMobile/.main.UCMobile" /> <set name="com.android.browser/.BrowserActivity" />
query为实时从pms里查询得到的满足条件的activity相关信息
当发现两个数据不一致的时候，就认为系统里的ap发生了变化，走到 Slog.i(TAG, "Result set changed, dropping preferred activity for " + intent + " type " + resolvedType);删除掉之前的默认设置。然后由ResolverActivity去处理，显示选择界面
基本处理流程是 点击url网络连接 -> findPreferredActivity, 查看是否有默认打开方式 如果有，直接打开 如果没有，ResolverActivity去处理，显示选择界面，这个时候，选择“总是”（always），ResolverActivity调用 pm.addPreferredActivity(filter, bestMatch, set, intent.getComponent());
去重新设置偏好。
可参考下图
值得注意的是，ResolverActivity里对activity的priority进行了处理，如果一个ap注册的时候，把intent-filter里的priority写为了负数，如下所示<intent-filter android:priority="-1" > <category android:name="android.intent.category.DEFAULT" /> <action android:name="android.intent.action.VIEW" /> <data android:scheme="http" />
那么，在选择默认浏览器的时候，就不会显示出这个应用。因为在private void rebuildList() 里有这样的处理 for (int i=1; i<N; i++) { ResolveInfo ri = currentResolveList.get(i); if (DEBUG) Log.v( TAG, r0.activityInfo.name + "=" + r0.priority + "/" + r0.isDefault + " vs " + ri.activityInfo.name + "=" + ri.priority + "/" + ri.isDefault); if (r0.priority != ri.priority || r0.isDefault != ri.isDefault) { while (i < N) { if (mOrigResolveList == currentResolveList) { mOrigResolveList = new ArrayList<ResolveInfo>(mOrigResolveList); } currentResolveList.remove(i);
导致priority为负数的不会显示出来。
了解了这些，就可以去分析这个问题http://www.zhihu.com/question/27313953/answer/36308142
在6.0的版本上，对priority的处理有些变化，比如对于自定义的ap Test，priority设置为大于0的数<intent-filter android:priority="3" > <category android:name="android.intent.category.DEFAULT" /> <action android:name="android.intent.action.VIEW" /> <data android:scheme="http" />
之前手机上安装了3个浏览器（priority都为0的），其中UC设置为了默认浏览器，再安装Test，接着打开网络链接，会弹出选择界面，在L版本上会列出所有的浏览器，M上呢？
答案是只显示出UC和Test因为M里的做了些修改，查看PackageManagerService.java的queryIntentActivities可以很容易的找到
附package-restrictions.xml <item name="com.UCMobile/.main.UCMobile" match="200000" always="true" set="2"> <set name="com.UCMobile/.main.UCMobile" /> <set name="com.android.browser/.BrowserActivity" /> <filter> <action name="android.intent.action.VIEW" /> <cat name="android.intent.category.DEFAULT" /> <scheme name="http" /> </filter> </item>里match的来源这个查看过程非常复杂，这里直接说下结果，是IntentFilter.java里的matchData方法
附相关log，注意，pms里的DEBUG_PREFERRED开关需要打开
05-01 08:53:56.290: D/PackageManager(918): ===== findPreferredActivity called05-01 08:53:56.290: D/PackageManager(918): ===== begin =====05-01 08:53:56.290: D/PackageManager(918): com.android.server.pm.PackageManagerService.findPreferredActivity(PackageManagerService.java:3575)05-01 08:53:56.290: D/PackageManager(918): com.android.server.pm.PackageManagerService.chooseBestActivity(PackageManagerService.java:3494)05-01 08:53:56.290: D/PackageManager(918): com.android.server.pm.PackageManagerService.resolveIntent(PackageManagerService.java:3432)05-01 08:53:56.290: D/PackageManager(918): android.content.pm.IPackageManager$Stub.onTransact(IPackageManager.java:507)05-01 08:53:56.290: D/PackageManager(918): com.android.server.pm.PackageManagerService.onTransact(PackageManagerService.java:2264)05-01 08:53:56.290: D/PackageManager(918): android.os.Binder.execTransact(Binder.java:451)05-01 08:53:56.290: V/PackageManager(918): Looking for presistent preferred activities...05-01 08:53:56.290: V/PackageManager(918): Looking for preferred activities...05-01 08:53:56.290: D/IntentResolver(918): ===== queryIntent called05-01 08:53:56.290: V/IntentResolver(918): Resolving type=null scheme=http defaultOnly=true userId=0 of Intent { act=android.intent.action.VIEW dat=http://wap.uc.cn flg=0x8 }05-01 08:53:56.290: V/IntentResolver(918): Scheme list: [PreferredActivity{0x43bb27d com.UCMobile/.main.UCMobile}, null]05-01 08:53:56.290: D/IntentResolver(918): ===== buildResolveList called05-01 08:53:56.291: D/IntentResolver(918): ===== begin =====05-01 08:53:56.291: D/IntentResolver(918): com.android.server.IntentResolver.buildResolveList(IntentResolver.java:677)05-01 08:53:56.291: D/IntentResolver(918): com.android.server.IntentResolver.queryIntent(IntentResolver.java:458)05-01 08:53:56.291: D/IntentResolver(918): com.android.server.pm.PackageManagerService.findPreferredActivity(PackageManagerService.java:3597)05-01 08:53:56.291: D/IntentResolver(918): com.android.server.pm.PackageManagerService.chooseBestActivity(PackageManagerService.java:3494)05-01 08:53:56.291: D/IntentResolver(918): com.android.server.pm.PackageManagerService.resolveIntent(PackageManagerService.java:3432)05-01 08:53:56.291: D/IntentResolver(918): android.content.pm.IPackageManager$Stub.onTransact(IPackageManager.java:507)05-01 08:53:56.291: D/IntentResolver(918): com.android.server.pm.PackageManagerService.onTransact(PackageManagerService.java:2264)05-01 08:53:56.291: D/IntentResolver(918): android.os.Binder.execTransact(Binder.java:451)05-01 08:53:56.291: V/IntentResolver(918): Matching against filter PreferredActivity{0x43bb27d com.UCMobile/.main.UCMobile}05-01 08:53:56.291: D/IntentFilter(918): ===== matchData called05-01 08:53:56.291: D/IntentFilter(918): ===== match=20000005-01 08:53:56.291: V/IntentResolver(918): Filter matched! match=0x208000 hasDefault=true05-01 08:53:56.291: V/IntentResolver(918): 43bb27d com.UCMobile/.main.UCMobile05-01 08:53:56.292: V/IntentResolver(918): mMatch=0x200000 mAlways=true05-01 08:53:56.292: V/IntentResolver(918): Selected from:05-01 08:53:56.292: V/IntentResolver(918): com.UCMobile/.main.UCMobile05-01 08:53:56.292: V/IntentResolver(918): com.android.browser/.BrowserActivity05-01 08:53:56.292: V/IntentResolver(918): Action: "android.intent.action.VIEW"05-01 08:53:56.292: V/IntentResolver(918): Category: "android.intent.category.DEFAULT"05-01 08:53:56.292: V/IntentResolver(918): Scheme: "http"05-01 08:53:56.292: V/IntentResolver(918): Final result list:05-01 08:53:56.292: V/IntentResolver(918): PreferredActivity{0x43bb27d com.UCMobile/.main.UCMobile}05-01 08:53:56.292: V/PackageManager(918): Figuring out best match...05-01 08:53:56.292: V/PackageManager(918): Match for ActivityInfo{21f95286 com.android.browser.BrowserActivity}: 0x005-01 08:53:56.292: V/PackageManager(918): Match for ActivityInfo{7f12747 com.UCMobile.main.UCMobile}: 0x20800005-01 08:53:56.292: V/PackageManager(918): Match for ActivityInfo{38f8b74 com.taobao.browser.BrowserActivity}: 0x20800005-01 08:53:56.292: D/PackageManager(918): ===== query list is:05-01 08:53:56.292: D/PackageManager(918): ===== ResolveInfo{2e13ff6b com.android.browser/.BrowserActivity m=0x208000}05-01 08:53:56.292: D/PackageManager(918): ===== ResolveInfo{2e188ac8 com.UCMobile/.main.UCMobile m=0x208000}05-01 08:53:56.292: D/ResolveInfo(918): tos ===== priority=-105-01 08:53:56.292: D/PackageManager(918): ===== ResolveInfo{396c3761 com.taobao.taobao/com.taobao.browser.BrowserActivity p=-1 m=0x208000}05-01 08:53:56.292: V/PackageManager(918): Best match: 0x20800005-01 08:53:56.292: V/PackageManager(918): Checking PreferredActivity ds=http05-01 08:53:56.292: V/PackageManager(918): component=ComponentInfo{com.UCMobile/com.UCMobile.main.UCMobile}05-01 08:53:56.292: V/PackageManager(918): Action: "android.intent.action.VIEW"05-01 08:53:56.292: V/PackageManager(918): Category: "android.intent.category.DEFAULT"05-01 08:53:56.292: V/PackageManager(918): Scheme: "http"05-01 08:53:56.292: V/PackageManager(918): Found preferred activity:05-01 08:53:56.292: V/PackageManager(918): name=com.UCMobile.main.UCMobile05-01 08:53:56.292: V/PackageManager(918): packageName=com.UCMobile05-01 08:53:56.292: V/PackageManager(918): labelRes=0x7f070004 nonLocalizedLabel=null icon=0x0 banner=0x005-01 08:53:56.292: V/PackageManager(918): enabled=true exported=true processName=com.UCMobile05-01 08:53:56.292: V/PackageManager(918): taskAffinity=com.UCMobile targetActivity=null persistableMode=PERSIST_ROOT_ONLY05-01 08:53:56.292: V/PackageManager(918): launchMode=2 flags=0x8a theme=0x103000f05-01 08:53:56.292: V/PackageManager(918): screenOrientation=-1 configChanges=0x400004a3 softInputMode=0x2005-01 08:53:56.292: V/PackageManager(918): ApplicationInfo:05-01 08:53:56.292: V/PackageManager(918): packageName=com.UCMobile05-01 08:53:56.292: V/PackageManager(918): labelRes=0x7f070004 nonLocalizedLabel=null icon=0x7f020089 banner=0x005-01 08:53:56.292: V/PackageManager(918): className=com.uc.browser.UCMobileApp05-01 08:53:56.292: V/PackageManager(918): processName=com.UCMobile05-01 08:53:56.292: V/PackageManager(918): taskAffinity=com.UCMobile05-01 08:53:56.292: V/PackageManager(918): uid=10073 flags=0x883e44 theme=0x0 flagsEx=0x005-01 08:53:56.292: V/PackageManager(918): requiresSmallestWidthDp=0 compatibleWidthLimitDp=0 largestWidthLimitDp=005-01 08:53:56.292: V/PackageManager(918): sourceDir=/data/app/com.UCMobile-1/base.apk05-01 08:53:56.292: V/PackageManager(918): seinfo=default05-01 08:53:56.292: V/PackageManager(918): dataDir=/data/data/com.UCMobile05-01 08:53:56.292: V/PackageManager(918): enabled=true targetSdkVersion=23 versionCode=64805-01 08:53:56.292: V/PackageManager(918): manageSpaceActivityName=com.uc.application.cleaner.SystemManageData.ManageDataActivity05-01 08:53:56.292: V/PackageManager(918): supportsRtl=false05-01 08:53:56.292: D/PackageManager(918): ===== pa.mPref.Set =[Ljava.lang.String;@1053e89d, always=true05-01 08:53:56.292: D/PackageManager(918): set[]=com.UCMobile05-01 08:53:56.292: D/PackageManager(918): set[]=com.android.browser05-01 08:53:56.292: D/PackageManager(918): ===== pa.mPref.Set =[Ljava.lang.String;@1053e89d05-01 08:53:56.292: D/PackageManager(918): set[]=com.UCMobile05-01 08:53:56.293: D/PackageManager(918): set[]=com.android.browser05-01 08:53:56.293: I/PackageManager(918): Result set changed, dropping preferred activity for Intent { act=android.intent.action.VIEW dat=http://wap.uc.cn flg=0x8 } type null05-01 08:53:56.293: V/PackageManager(918): Removing preferred activity since set changed ComponentInfo{com.UCMobile/com.UCMobile.main.UCMobile}05-01 08:53:56.293: V/IntentResolver(918): Removing filter: PreferredActivity{0x43bb27d com.UCMobile/.main.UCMobile}05-01 08:53:56.293: V/IntentResolver(918): Action: "android.intent.action.VIEW"05-01 08:53:56.293: V/IntentResolver(918): Category: "android.intent.category.DEFAULT"05-01 08:53:56.293: V/IntentResolver(918): Scheme: "http"05-01 08:53:56.293: V/IntentResolver(918): Cleaning Lookup Maps:05-01 08:53:56.293: V/IntentResolver(918): Scheme: http05-01 08:53:56.293: V/IntentResolver(918): Adding filter: PreferredActivity{0xb081112 com.UCMobile/.main.UCMobile}05-01 08:53:56.293: V/IntentResolver(918): Action: "android.intent.action.VIEW"05-01 08:53:56.293: V/IntentResolver(918): Category: "android.intent.category.DEFAULT"05-01 08:53:56.293: V/IntentResolver(918): Scheme: "http"05-01 08:53:56.293: V/IntentResolver(918): Building Lookup Maps:05-01 08:53:56.293: V/IntentResolver(918): Scheme: http05-01 08:53:56.293: V/PackageManager(918): Preferred activity bookkeeping changed; writing restrictions