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：
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。
- 有序广播：串行分发，效率低，可以通过abortBroadcast截断
- 无序广播：默认无序，并行分发。
- 处理类型：
AMS中前台广播和后台广播分别有一个广播队列，互不干扰。
- 前台广播：超时时间60s，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10s
常见命令
- dumpsys activity broadcasts
- Registered Receivers: 注册的receivers
- Receiver Resolver Table:
- 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
- dumpsys activity broadcast-stats :广播的统计
android.intent.action.DROPBOX_ENTRY_ADDED:
Number received: 0, skipped: 302
Total dispatch time: +24s731ms, max: +13s538ms
Package android: 151 times
Bg Check Violation com.google.android.gms: 302 times
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
@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
20 <!-- Broadcast actions that are currently exempted from O+ background
21 delivery restrictions. -->
22 <allow-implicit-broadcast action="android.intent.action.ACTION_DEFAULT_DATA_SUBSCRIPTION_CHANGED" />
23 <allow-implicit-broadcast action="android.intent.action.ACTION_DEFAULT_VOICE_SUBSCRIPTION_CHANGED" />
24 <allow-implicit-broadcast action="android.intent.action.DATA_SMS_RECEIVED" />
25 <allow-implicit-broadcast action="android.intent.action.MEDIA_SCANNER_SCAN_FILE" />
26 <allow-implicit-broadcast action="android.intent.action.PACKAGE_CHANGED" />
27 <allow-implicit-broadcast action="android.intent.action.SIM_STATE_CHANGED" />
28 <allow-implicit-broadcast action="android.media.action.CLOSE_AUDIO_EFFECT_CONTROL_SESSION" />
29 <allow-implicit-broadcast action="android.media.action.OPEN_AUDIO_EFFECT_CONTROL_SESSION" />
30 <allow-implicit-broadcast action="android.provider.Telephony.SECRET_CODE" />
31 <allow-implicit-broadcast action="android.provider.Telephony.SMS_CB_RECEIVED" />
32 <allow-implicit-broadcast action="android.provider.Telephony.SMS_DELIVER" />
33 <allow-implicit-broadcast action="android.provider.Telephony.SMS_RECEIVED" />
34 <allow-implicit-broadcast action="android.provider.Telephony.SMS_REJECTED" />
35 <allow-implicit-broadcast action="android.provider.Telephony.WAP_PUSH_DELIVER" />
36 <allow-implicit-broadcast action="android.provider.Telephony.WAP_PUSH_RECEIVED" />
37 <allow-implicit-broadcast action="android.telephony.action.CARRIER_CONFIG_CHANGED" />
38 <allow-implicit-broadcast action="android.telephony.action.DEFAULT_SMS_SUBSCRIPTION_CHANGED" />
39 <allow-implicit-broadcast action="android.telephony.action.DEFAULT_SUBSCRIPTION_CHANGED" />
40 <allow-implicit-broadcast action="android.telephony.action.MULTI_SIM_CONFIG_CHANGED" />
41 <allow-implicit-broadcast action="android.telephony.action.SECRET_CODE" />
42 <allow-implicit-broadcast action="android.telephony.action.SIM_APPLICATION_STATE_CHANGED" />
43 <allow-implicit-broadcast action="android.telephony.action.SIM_CARD_STATE_CHANGED" />
44 <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;
}
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