基础知识
framework层广播相关的逻辑主要在AMS.java和BroadcastQueue.java中,代表一个广播的是BroadcastRecord。
分类
- 注册方式：
- 静态注册: android manifest文件注册，常驻广播，分发慢。
- 动态注册：代码中注册，非常驻，分发快。
- 接收者：
- 显示广播：指定接收方的class类型
- 隐式广播：只指定action，uri等, android 8.0开始限制了隐式广播的接收
- 发送方式：
- 有序广播：串行分发，效率低，可以通过abortBroadcast截断,在入队时会根据优先级对receiver进行排序。
- 无序广播：默认无序；并行分发；不可以被拦截、终止、修改；无优先级问题；传递数据用intent.putExtra
静态注册的广播，一律按照串行广播处理，因为可能会设计到拉起多个进程等，串行广播才有超时处理。
- 处理类型：
-
前台广播：发送时添加Intent.FLAG_RECEIVER_FOREGROUND，超时时间10s
-
后台广播：默认后台，超时时间60s
AMS中前台广播和后台广播分别有一个广播队列，互不干扰。
常见命令
- dumpsys activity broadcasts
- Registered Receivers: 列出所有已注册的receivers列表
- Receiver Resolver Table: receiver的解析表
- Historical broadcasts [foreground]: 前台广播历史记录
- Historical broadcasts summary [foreground]: 前台广播历史记录简要
- Historical broadcasts [background]：后台广播历史记录
- Historical broadcasts summary [background]: 后台广播历史记录简要
// 已注册的receiver
* ReceiverList{7657857 3271 com.android.systemui/1000/u0 remote:5d6fdd6}
app=3271:com.android.systemui/1000 pid=3271 uid=1000 user=0 // 进程相关信息，pid，uid，user等
Filter #0: BroadcastFilter{b28ef44} // 列出当前receiver的所有BroadcastFilter
Action: "android.intent.action.CLOSE_SYSTEM_DIALOGS"
// receiver的查询表
android.intent.action.CLOSE_SYSTEM_DIALOGS:
BroadcastFilter{cd0b64d 1000/u0 ReceiverList{5cd41e4 2477 system/1000/u0 local:7b2f177}}
BroadcastFilter{766ac91 1000/u0 ReceiverList{b2bd6b8 2477 system/1000/u0 local:dd6451b}}
BroadcastFilter{707a39e 1000/u-1 ReceiverList{6db3dd9 2477 system/1000/u-1 local:28e4020}}
BroadcastFilter{921cf0a 1000/u0 ReceiverList{a168375 3271 com.android.systemui/1000/u0 remote:792eaac}}
BroadcastFilter{eb0f625 1000/u-1 ReceiverList{f9ba1c 3271 com.android.systemui/1000/u-1 remote:311c78f}}
BroadcastFilter{b28ef44 1000/u0 ReceiverList{**7657857** 3271 com.android.systemui/1000/u0 remote:5d6fdd6}}
BroadcastFilter{3dc5af6 1000/u0 ReceiverList{9ad5b91 2477 system/1000/u0 local:ab3e1b8}}
BroadcastFilter{84a1c2 1000/u0 ReceiverList{27a8e0d 5062 com.miui.securitycenter.remote/1000/u0 remote:49ca0a4}}
BroadcastFilter{6151148 1000/u0 ReceiverList{6ac8feb 5062 com.miui.securitycenter.remote/1000/u0 remote:17c273a}}
BroadcastFilter{1525a45 1000/u0 ReceiverList{caf9abc 5062 com.miui.securitycenter.remote/1000/u0 remote:aa646af}}
Historical Broadcast foreground #1: // 前台广播队列第一条广播
BroadcastRecord{8888912 u0 com.xiaomi.mi_connect_service.mi_mover_endpoint_found} to user 0 // user 0
Intent { act=com.xiaomi.mi_connect_service.mi_mover_endpoint_found flg=0x11000030 (has extras) } // flag有：FLAG_RECEIVER_FOREGROUND | FLAG_RECEIVER_INCLUDE_BACKGROUND | |FLAG_INCLUDE_STOPPED_PACKAGES | FLAG_EXCLUDE_STOPPED_PACKAGES
extras: Bundle[{STRIPPED=1}]
caller=com.xiaomi.mi_connect_service 9219:com.xiaomi.mi_connect_service/1000 pid=9219 uid=1000 // 发送广播app的信息
requiredPermissions=[com.xiaomi.mi_connect_service.permission.RECEIVE_ENDPOINT] appOp=-1 // 广播要求receiver的权限
enqueueClockTime=2021-09-11 16:04:57.623 dispatchClockTime=2021-09-11 16:04:57.623 // 入队时间和分发时间
dispatchTime=-1m2s207ms (0 since enq) finishTime=-1m2s164ms (+43ms since disp) // 结束时间 & 分发用时
resultTo=null resultCode=0 resultData=null // 一般resultCode为0且resultTo为null且无” ordered= “表示静态注册的无序广播
nextReceiver=1 receiver=null
Deliver +42ms #0: (manifest) //派发给静态注册的receiver
priority=0 preferredOrder=0 match=0x108000 specificIndex=-1 isDefault=false //优先级默认为0，
ActivityInfo: // receiver的信息
name=com.miui.huanji.ble.MiConnectBleReceiver
packageName=com.miui.huanji
enabled=true exported=true directBootAware=false
resizeMode=RESIZE_MODE_RESIZEABLE
Historical Broadcast background #29: // 后台广播队列第29条
BroadcastRecord{e0ebea0 u-1 android.intent.action.PHONE_STATE{color}} to user -1 // -1代表user_all
Intent { act=android.intent.action.PHONE_STATE flg=0x1000010 (has extras) } // intent信息
extras: Bundle[\{incoming_number=18381098208, state=IDLE}]
caller=android 1309:system/1000 pid=1309 uid=1000 // 发送广播app的信息
requiredPermissions=[android.permission.READ_PHONE_STATE, android.permission.READ_CALL_LOG] appOp=-1 // 广播要求receiver的权限
enqueueClockTime=2021-06-23 11:41:05.687 dispatchClockTime=2021-06-23 11:41:05.687 // 入队时间和分发时间
dispatchTime=-1m39s763ms (0 since enq) finishTime=-1m39s755ms (+8ms since disp) // 结束时间 & 分发用时
// 分发每一个receiver的分发信息以及状态
// Deliver代表当前receiver已分发到
Deliver 0 #0: BroadcastFilter{12c9c23 1000/u-1 ReceiverList{5b06152 1309 system/1000/u-1 local:4a651dd}}
Deliver 0 #1: BroadcastFilter{672acd7 1000/u0 ReceiverList{5be3456 1780 com.android.systemui/1000/u0 remote:b33e71}}
Deliver 0 #2: BroadcastFilter{f932daf 1000/u-1 ReceiverList{1ef518e 1780 com.android.systemui/1000/u-1 remote:35e2d89}}
Deliver 0 #3: BroadcastFilter{d0d467b 1001/u0 ReceiverList{b4a5e0a 1996 com.android.phone/1001/u0 remote:65bee75}}
Deliver 0 #4: BroadcastFilter{4081988 1002/u0 ReceiverList{661912b 2315 com.xiaomi.bluetooth/1002/u0 remote:34b657a}}
Deliver 0 #5: BroadcastFilter{b6bda66 1000/u0 ReceiverList{73672c1 5261 com.miui.powerkeeper/1000/u0 remote:bc317a8}}
// skip表示由于权限等原因，跳过分发到该app
Skipped 0 #6: BroadcastFilter{ebabe72 10243/u0 ReceiverList{5596f7d 21465 com.smile.gifmaker/10243/u0 remote:96d61d4}}
Skipped 0 #7: BroadcastFilter{f7d90ab 10243/u0 ReceiverList{261b2fa 21465 com.smile.gifmaker/10243/u0 remote:ef8c125}}
Skipped 0 #8: BroadcastFilter{1f05292 10250/u0 ReceiverList{396401d 12339 com.tencent.mobileqq/10250/u0 remote:e8e90f4}}
Skipped 0 #9: BroadcastFilter{d98737f 10250/u0 ReceiverList{469cc9e 12339 com.tencent.mobileqq/10250/u0 remote:b386ad9}}
Skipped 0 #10: BroadcastFilter{4e1588 10250/u0 ReceiverList{851fd2b 29070 com.tencent.mobileqq:tool/10250/u0 remote:64a017a}}
- dumpsys activity broadcast-stats :广播的统计
android.intent.action.DROPBOX_ENTRY_ADDED:
Number received: 0, skipped: 302 // 分发0次，跳过302次
Total dispatch time: +24s731ms, max: +13s538ms // 总分发用时，和最大分发用时
Package android: 151 times
Bg Check Violation com.google.android.gms: 302 times
常见的一些Intent中的flag
- FLAG_RECEIVER_REGISTERED_ONLY
表示当前广播只允许动态注册的receiver接收，避免避免一些系统广播（如TIME_TICK等）拉起静态注册的app进程。
-
FLAG_RECEIVER_REPLACE_PENDING
如果广播队列中存在没有被处理的相同广播，则直接替换掉之前的广播，无序再入队分发 -
FLAG_RECEIVER_FOREGROUND
发送广播时添加这个flag，广播将会被添加到前台广播队列中。
AMS中的一些属性
// 已注册的动态广播的receiver，receiver IBinder为key, ReceiverList为value；ReceiverList继承自ArrayList<BroadcastFilter>
final HashMap<IBinder, ReceiverList> mRegisteredReceivers = new HashMap<>();
// 记录着已注册广播的receiver的resolver，广播发送时可根据intent和type等查询得到对应的动态广播接收者
final IntentResolver<BroadcastFilter, BroadcastFilter> mReceiverResolver
= new IntentResolver<BroadcastFilter, BroadcastFilter>();
BroadcastRecord的一些属性
int state; //当前广播状态，初始是idle
final int[] delivery; // 每一个receiver的处理状态
final List receivers; // 广播的接收者列表，包括静态注册的ResolveInfo和动态注册的BroadcastFilter
int nextReceiver; // 下一个要处理的广播接收者的索引，对应于receivers的索引
IIntentReceiver resultTo; // 有序广播指定的最后一个接收者
long enqueueClockTime; // 广播的入队时间
long dispatchTime; // 分发时间
long receiverTime; //开始派发广播到app端的时间，用于计算anr超时时间
long finishTime; //结束广播时间
IBinder receiver; // 当前正在处理的receiver（ReceiverDispatcher.InnerReceiver），有序广播和静态注册的才会赋值
ResolveInfo的一些属性
public int priority; // 优先级
public int preferredOrder; //偏好优先级
public int match; // 系统评估活动与IntentFilter的匹配情况。
public int specificIndex = -1; //仅当由 queryIntentActivityOptions(ComponentName, Intent[], Intent, int)返回时设置，这告诉你这个结果来自哪个给定的特定意图。
public boolean isDefault; //此过滤器指定了Intent.CATEGORY_DEFAULT，这意味着它将被视为用户可以对此数据执行的默认操作。
广播的状态
static final int IDLE = 0; // 广播的初始状态，派发时只处理这种状态的广播
static final int APP_RECEIVE = 1; // 表示广播正在派发到app进程，静态receiver
static final int CALL_IN_RECEIVE = 2; // 表示广播正在派发到app进程，有序广播，动态receiver
static final int CALL_DONE_RECEIVE = 3; // 广播已经派发到app进程，有序广播，动态receiver
static final int WAITING_SERVICES = 4; // 等待后台service启动
广播接收者的处理状态
static final int DELIVERY_PENDING = 0; // 默认状态
static final int DELIVERY_DELIVERED = 1; // 表示已经派发到app进程
static final int DELIVERY_SKIPPED = 2; // 表示由于某种原因，未派发到app进程
static final int DELIVERY_TIMEOUT = 3; // 表示派发到app端，超时未结束派发
广播不被处理的情况
实际上广播不被处理的情况有很多种，这里只是列出常遇到的一些情况。
接收端未声明广播指定权限
W/BroadcastQueue: Permission Denial: receiving Intent { act=android.intent.action.ORDER_BROADCAST flg=0x10 } to com.example.myapplication/com.example.receive.MyReceiver requires com.android.permission.ORDER_PERMISSION due to sender com.example.testapplication (uid 10255)
在BroadcastQueue的deliverToRegisteredReceiverLocked（动态注册）或processNextBroadcastLocked（静态注册）方法中，会去校验接收端是否都具备广播要求的权限，如果不具备，会跳过此次广播的分发到app端。
if (!skip && r.requiredPermissions != null && r.requiredPermissions.length > 0) {
for (int i = 0; i < r.requiredPermissions.length; i++) {
String requiredPermission = r.requiredPermissions[i];
int perm = mService.checkComponentPermission(requiredPermission,
filter.receiverList.pid, filter.receiverList.uid, -1, true);
if (perm != PackageManager.PERMISSION_GRANTED) {
Slog.w(TAG, "Permission Denial: receiving " + r.intent.toString() + " to " + filter.receiverList.app + " (pid=" + filter.receiverList.pid
+ ", uid=" + filter.receiverList.uid + ")" + " requires " + requiredPermission + " due to sender " + r.callerPackage + " (uid " + r.callingUid + ")");
skip = true;
break;
}
android 8.0对隐式广播的限制
W BroadcastQueue: Background execution not allowed: receiving Intent { act=android.intent.action.PACKAGE_RESTARTED dat=package:com.android.soundrecorder flg=0x10 (has extras) } to com.xiaomi.misubscreenui/.receiver.LightDeviceStatusReceiver
限制如下两种情况下的广播分发
- Intent中添加了FLAG_RECEIVER_EXCLUDE_BACKGROUND
- Intent中无FLAG_RECEIVER_INCLUDE_BACKGROUND flag的隐式广播
FLAG_RECEIVER_INCLUDE_BACKGROUND 添加的场景
也就是如下这些隐式广播处于后台清单文件注册的也能接收到
- ACTION_BOOT_COMPLETED
@BroadcastBehavior(includeBackground = true)
public static final String ACTION_BOOT_COMPLETED = "android.intent.action.BOOT_COMPLETED";
allow-implicit-broadcast 列表内的intent会在broadcastIntentLocked中添加
if (action != null) {
if (getBackgroundLaunchBroadcasts().contains(action)) {
intent.addFlags(Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND);
}
<!-- Broadcast actions that are currently exempted from O+ background
delivery restrictions. -->
<allow-implicit-broadcast action="android.intent.action.ACTION_DEFAULT_DATA_SUBSCRIPTION_CHANGED" />
<allow-implicit-broadcast action="android.intent.action.ACTION_DEFAULT_VOICE_SUBSCRIPTION_CHANGED" />
<allow-implicit-broadcast action="android.intent.action.DATA_SMS_RECEIVED" />
<allow-implicit-broadcast action="android.intent.action.MEDIA_SCANNER_SCAN_FILE" />
<allow-implicit-broadcast action="android.intent.action.PACKAGE_CHANGED" />
<allow-implicit-broadcast action="android.intent.action.SIM_STATE_CHANGED" />
<allow-implicit-broadcast action="android.media.action.CLOSE_AUDIO_EFFECT_CONTROL_SESSION" />
<allow-implicit-broadcast action="android.media.action.OPEN_AUDIO_EFFECT_CONTROL_SESSION" />
<allow-implicit-broadcast action="android.provider.Telephony.SECRET_CODE" />
<allow-implicit-broadcast action="android.provider.Telephony.SMS_CB_RECEIVED" />
<allow-implicit-broadcast action="android.provider.Telephony.SMS_DELIVER" />
<allow-implicit-broadcast action="android.provider.Telephony.SMS_RECEIVED" />
<allow-implicit-broadcast action="android.provider.Telephony.SMS_REJECTED" />
<allow-implicit-broadcast action="android.provider.Telephony.WAP_PUSH_DELIVER" />
<allow-implicit-broadcast action="android.provider.Telephony.WAP_PUSH_RECEIVED" />
<allow-implicit-broadcast action="android.telephony.action.CARRIER_CONFIG_CHANGED" />
<allow-implicit-broadcast action="android.telephony.action.DEFAULT_SMS_SUBSCRIPTION_CHANGED" />
<allow-implicit-broadcast action="android.telephony.action.DEFAULT_SUBSCRIPTION_CHANGED" />
<allow-implicit-broadcast action="android.telephony.action.MULTI_SIM_CONFIG_CHANGED" />
<allow-implicit-broadcast action="android.telephony.action.SECRET_CODE" />
<allow-implicit-broadcast action="android.telephony.action.SIM_APPLICATION_STATE_CHANGED" />
<allow-implicit-broadcast action="android.telephony.action.SIM_CARD_STATE_CHANGED" />
<allow-implicit-broadcast action="android.telephony.action.SIM_SLOT_STATUS_CHANGED" />
final void processNextBroadcastLocked(boolean fromMsg, boolean skipOomAdj, boolean parallelOnce) {
.....
boolean skip = false;
if (!skip) {
// 检查当前app的启动权限
final int allowed = mService.getAppStartModeLocked(
info.activityInfo.applicationInfo.uid, info.activityInfo.packageName,
info.activityInfo.applicationInfo.targetSdkVersion, -1, true, false, false, r.callerPackage);
if (allowed != ActivityManager.APP_START_MODE_NORMAL) {
if (allowed == ActivityManager.APP_START_MODE_DISABLED) {
skip = true;
// 1. FLAG_RECEIVER_EXCLUDE_BACKGROUND , 2. 隐式广播的限制
} else if (((r.intent.getFlags()&Intent.FLAG_RECEIVER_EXCLUDE_BACKGROUND) != 0)
|| (r.intent.getComponent() == null
&& r.intent.getPackage() == null
&& ((r.intent.getFlags()
& Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND) == 0)
&& !isSignaturePerm(r.requiredPermissions))) {
mService.addBackgroundCheckViolationLocked(r.intent.getAction(),
component.getPackageName());
Slog.w(TAG, "Background execution not allowed: receiving " + r.intent + " to "
+ component.flattenToShortString());
skip = true;
}
}
}
}
进程频繁crash
W BroadcastQueue: Unable to launch app com.bsp.catchlog/1000 for broadcast Intent { act=android.provider.Telephony.SECRET_CODE dat=android_secret_code://284 flg=0x1400010 }: process is bad
在AppErrors中处理当前crash时会去判断是否标记当前进程为bad进程。
boolean handleAppCrashLocked(ProcessRecord app, String reason,
String shortMsg, String longMsg, String stackTrace, AppErrorDialog.Data data) {
.......
if (crashTime != null && now < crashTime + ProcessList.MIN_CRASH_INTERVAL) {
Slog.w(TAG, "Process " + app.info.processName
+ " has crashed too many times: killing!");
EventLog.writeEvent(EventLogTags.AM_PROCESS_CRASHED_TOO_MUCH,
app.userId, app.info.processName, app.uid);
mService.mAtmInternal.onHandleAppCrash(app.getWindowProcessController());
if (!app.isPersistent()) {
EventLog.writeEvent(EventLogTags.AM_PROC_BAD, app.userId, app.uid,
app.info.processName);
if (!app.isolated) {
mBadProcesses.put(app.info.processName, app.uid,
new BadProcessInfo(now, shortMsg, longMsg, stackTrace));
mProcessCrashTimes.remove(app.info.processName, app.uid);
}
app.bad = true;
app.removed = true;
.......
}
而在启动进程时,ProcessList的startProcessLocked中会去判断如果时后台启动且进程为bad，则返回null，终止启动进程
ProcessRecord app;
if (!isolated) {
app = getProcessRecordLocked(processName, info.uid, keepIfLarge);
if ((intentFlags & Intent.FLAG_FROM_BACKGROUND) != 0) {
if (mService.mAppErrors.isBadProcessLocked(info)) {
return null;
}
}
BroadcastQueue中processNextBroadcastLocked中进程不存在去创建进程时如果失败，就会打印上面那行log
if ((r.curApp=mService.startProcessLocked(targetProcess,
info.activityInfo.applicationInfo, true,
r.intent.getFlags() | Intent.FLAG_FROM_BACKGROUND,
new HostingRecord("broadcast", r.curComponent),
isActivityCapable ? ZYGOTE_POLICY_FLAG_LATENCY_SENSITIVE : ZYGOTE_POLICY_FLAG_EMPTY,
// MIUI MOD
// (r.intent.getFlags()&Intent.FLAG_RECEIVER_BOOT_UPGRADE) != 0, false, false))
(r.intent.getFlags()&Intent.FLAG_RECEIVER_BOOT_UPGRADE) != 0, false, false, r.callerPackage))
== null) {
// Ah, this recipient is unavailable. Finish it if necessary,
// and mark the broadcast record as ready for the next.
Slog.w(TAG, "Unable to launch app "
+ info.activityInfo.applicationInfo.packageName + "/"
+ receiverUid + " for broadcast "
+ r.intent + ": process is bad");
logBroadcastReceiverDiscardLocked(r);
finishReceiverLocked(r, r.resultCode, r.resultData,
r.resultExtras, r.resultAbort, false);
scheduleBroadcastsLocked();
r.state = BroadcastRecord.IDLE;
return;
}
广播的三千问
- 有序广播的receiver在什么时候进行排序？
- 广播的入队和分发流程是同步还是异步？
- 静态注册的receiver（有序&无序）对应的广播入有序广播队列还是无序（并行）广播队列？
- 广播有哪些状态？分别代表什么？
- receiver有哪些状态，分别代表什么？
- 广播过程中涉及到哪些超时逻辑？
- 系统有几个广播队列？
- 如何发送有序广播？粘性广播？前台广播？
- android O 加入了后台启动限制，主要限制逻辑是？
- 什么情况下发送的广播不会入队？
- 通过广播Receiver拉起进程的进程优先级有什么特点？
- 如何通过log查看广播的是否分发超时？以及广播是否派給对应的receiver？分发状态？
- 如果通过log查看广播是否是有序广播？静态注册？
- 哪个广播享受总分发超时豁免？
- 哪些隐式广播可以派发给后台进程？
- 有序广播可以通过什么传递数据？无序广播呢？
- 有序广播的resultTo（最终接收者）的派发时机？
- 发送受保护的广播有什么限制？
- 发送sticky广播有什么限制？
- 如何做到广播只派发给动态注册的receiver？
- 派发静态广播时，进程不存在，如何处理？
- 广播入队前如何获取静态receivers？如何获取动态receivers？
为方便学习了解到更多的Handler知识点，特此我将一些 Android 开发相关的学习文档、面试题、Android 核心笔记等文档进行了整理，并上传之我GitHub项目中，如有需要参考的可以直接去我 GitHub ，希望能帮助到大家学习提升。
