基于 Android 7.1.1 源码分析，本文为原创，转载请注明出处，谢谢～～～爱你们的 Coolqi！
前言
我们先从基本的方法开始，也就是 schedule 方法，方法参数传递：
- JobInfo job：需要 schedule 的任务！
- int uId：调用方的 uid！
public int schedule(JobInfo job, int uId) {
return scheduleAsPackage(job, uId, null, -1, null);
}
public int scheduleAsPackage(JobInfo job, int uId, String packageName, int userId, String tag) {
// 创建新的 jobStatus
JobStatus jobStatus = JobStatus.createFromJobInfo(job, uId, packageName, userId, tag);
try {
if (ActivityManagerNative.getDefault().getAppStartMode(uId,
job.getService().getPackageName()) == ActivityManager.APP_START_MODE_DISABLED) {
Slog.w(TAG, "Not scheduling job " + uId + ":" + job.toString()
+ " -- package not allowed to start");
return JobScheduler.RESULT_FAILURE;
}
} catch (RemoteException e) {
}
if (DEBUG) Slog.d(TAG, "SCHEDULE: " + jobStatus.toShortString());
JobStatus toCancel;
synchronized (mLock) {
// Jobs on behalf of others don't apply to the per-app job cap
// 判断应用设置的任务数量是否超过上限：100
if (ENFORCE_MAX_JOBS && packageName == null) {
if (mJobs.countJobsForUid(uId) > MAX_JOBS_PER_APP) {
Slog.w(TAG, "Too many jobs for uid " + uId);
throw new IllegalStateException("Apps may not schedule more than "
+ MAX_JOBS_PER_APP + " distinct jobs");
}
}
// 如果同一个id，之前已经注册了一个任务，取消上一个任务
toCancel = mJobs.getJobByUidAndJobId(uId, job.getId());
if (toCancel != null) {
cancelJobImpl(toCancel, jobStatus);
}
// 开始追踪该任务
startTrackingJob(jobStatus, toCancel);
}
// 向 system_server 进程的主线程发送 message：MSG_CHECK_JOB
mHandler.obtainMessage(MSG_CHECK_JOB).sendToTarget();
return JobScheduler.RESULT_SUCCESS;
}
我们是使用 schedule 方法将我们需要的任务注册到系统中的，传入的参数主要是：
- JobInfo：封装任务的基本信息！
- uId：调用者的 uid！
我们接着来看，先调用 JobStatus 的 createFromJobInfo ，创建 JobStatus：
1 JobStatus.createFromJobInfo
参数传递：job, uId, null, -1, null，
/**
* Create a newly scheduled job.
* @param callingUid Uid of the package that scheduled this job.
* @param sourcePackageName Package name on whose behalf this job is scheduled. Null indicates
* the calling package is the source.
* @param sourceUserId User id for whom this job is scheduled. -1 indicates this is same as the
*/
public static JobStatus createFromJobInfo(JobInfo job, int callingUid, String sourcePackageName,
int sourceUserId, String tag) {
final long elapsedNow = SystemClock.elapsedRealtime(); // 从开机到现在的时间
final long earliestRunTimeElapsedMillis, latestRunTimeElapsedMillis;
// 判断这个任务是否是周期性的
if (job.isPeriodic()) {
latestRunTimeElapsedMillis = elapsedNow + job.getIntervalMillis();
earliestRunTimeElapsedMillis = latestRunTimeElapsedMillis - job.getFlexMillis();
} else {
earliestRunTimeElapsedMillis = job.hasEarlyConstraint() ?
elapsedNow + job.getMinLatencyMillis() : NO_EARLIEST_RUNTIME;
latestRunTimeElapsedMillis = job.hasLateConstraint() ?
elapsedNow + job.getMaxExecutionDelayMillis() : NO_LATEST_RUNTIME;
}
return new JobStatus(job, callingUid, sourcePackageName, sourceUserId, tag, 0,
earliestRunTimeElapsedMillis, latestRunTimeElapsedMillis);
}
这里通过 JobInfo 创建了对应的 JobStatus 对象，参数传递：
job, uId, null, -1, null，0，earliestRunTimeElapsedMillis，latestRunTimeElapsedMillis。
private JobStatus(JobInfo job, int callingUid, String sourcePackageName,
int sourceUserId, String tag, int numFailures, long earliestRunTimeElapsedMillis,
long latestRunTimeElapsedMillis) {
this.job = job;
this.callingUid = callingUid;
int tempSourceUid = -1;
if (sourceUserId != -1 && sourcePackageName != null) {
try {
tempSourceUid = AppGlobals.getPackageManager().getPackageUid(sourcePackageName, 0,
sourceUserId);
} catch (RemoteException ex) {
// Can't happen, PackageManager runs in the same process.
}
}
if (tempSourceUid == -1) {
this.sourceUid = callingUid;
this.sourceUserId = UserHandle.getUserId(callingUid);
this.sourcePackageName = job.getService().getPackageName();
this.sourceTag = null;
} else {
this.sourceUid = tempSourceUid;
this.sourceUserId = sourceUserId;
this.sourcePackageName = sourcePackageName;
this.sourceTag = tag;
}
this.batteryName = this.sourceTag != null
? this.sourceTag + ":" + job.getService().getPackageName()
: job.getService().flattenToShortString();
this.tag = "*job*/" + this.batteryName;
this.earliestRunTimeElapsedMillis = earliestRunTimeElapsedMillis;
this.latestRunTimeElapsedMillis = latestRunTimeElapsedMillis;
this.numFailures = numFailures;
int requiredConstraints = 0;
if (job.getNetworkType() == JobInfo.NETWORK_TYPE_ANY) {
requiredConstraints |= CONSTRAINT_CONNECTIVITY;
}
if (job.getNetworkType() == JobInfo.NETWORK_TYPE_UNMETERED) {
requiredConstraints |= CONSTRAINT_UNMETERED;
}
if (job.getNetworkType() == JobInfo.NETWORK_TYPE_NOT_ROAMING) {
requiredConstraints |= CONSTRAINT_NOT_ROAMING;
}
if (job.isRequireCharging()) {
requiredConstraints |= CONSTRAINT_CHARGING;
}
if (earliestRunTimeElapsedMillis != NO_EARLIEST_RUNTIME) {
requiredConstraints |= CONSTRAINT_TIMING_DELAY;
}
if (latestRunTimeElapsedMillis != NO_LATEST_RUNTIME) {
requiredConstraints |= CONSTRAINT_DEADLINE;
}
if (job.isRequireDeviceIdle()) {
requiredConstraints |= CONSTRAINT_IDLE;
}
if (job.getTriggerContentUris() != null) {
requiredConstraints |= CONSTRAINT_CONTENT_TRIGGER;
}
this.requiredConstraints = requiredConstraints;
}
这里很简单的，就是通过 JobInfo 来创建对应的 JobStatus，我们先看到这里！
2 JobStore.countJobsForUid
这里是统计 uid 对用的应用有多少个任务：
public int countJobsForUid(int uid) {
return mJobSet.countJobsForUid(uid);
}
JobStore 有一个集合，用来存放所有的 Job！
final JobSet mJobSet;
我们来看看这个 JobSet
static class JobSet {
// Key is the getUid() originator of the jobs in each sheaf
// mJobs 的 key 是应用的 uid！
private SparseArray<ArraySet<JobStatus>> mJobs;
public JobSet() {
mJobs = new SparseArray<ArraySet<JobStatus>>();
}
... ... ... ...
// We only want to count the jobs that this uid has scheduled on its own
// behalf, not those that the app has scheduled on someone else's behalf.
// 统计 uid 对应的应用注册的任务数！
public int countJobsForUid(int uid) {
int total = 0;
ArraySet<JobStatus> jobs = mJobs.get(uid);
if (jobs != null) {
for (int i = jobs.size() - 1; i >= 0; i--) {
JobStatus job = jobs.valueAt(i);
if (job.getUid() == job.getSourceUid()) {
total++;
}
}
}
return total;
}
... ... ... ...
}
JobSet 有很多的其他方法：getJobsByXXX，add，remove，getXXX，等等的方法，这里我们先不看！
3 JobStore.getJobByUidAndJobId
接着是根据 uid 和 jobId，来获得一个任务，这里的目的是判断是否之前已经注册过了一个相同的任务：
/**
* @param uid Uid of the requesting app.
* @param jobId Job id, specified at schedule-time.
* @return the JobStatus that matches the provided uId and jobId, or null if none found.
*/
public JobStatus getJobByUidAndJobId(int uid, int jobId) {
return mJobSet.get(uid, jobId);
}
还是调用的是 JobSet.get 方法：
public JobStatus get(int uid, int jobId) {
ArraySet<JobStatus> jobs = mJobs.get(uid);
if (jobs != null) {
for (int i = jobs.size() - 1; i >= 0; i--) {
JobStatus job = jobs.valueAt(i);
if (job.getJobId() == jobId) {
return job;
}
}
}
return null;
}
这个很简单，不详细说了！
4 JSS.cancelJobImpl
如果之前已经注册过一个任务了，需要先取消掉之前的任务！
private void cancelJobImpl(JobStatus cancelled, JobStatus incomingJob) {
if (DEBUG) Slog.d(TAG, "CANCEL: " + cancelled.toShortString());
// 停止追踪任务!
stopTrackingJob(cancelled, incomingJob, true /* writeBack */);
synchronized (mLock) {
// Remove from pending queue.
// 如果这个任务在等待队列中，移除它。
if (mPendingJobs.remove(cancelled)) {
mJobPackageTracker.noteNonpending(cancelled);
}
// Cancel if running.
// 如果正在运行，取消这个任务！
stopJobOnServiceContextLocked(cancelled, JobParameters.REASON_CANCELED);
reportActive();
}
}
这里主要做的是：停止对这个任务的监视，同时，将这个任务移除等待队列，如果这个任务正在运行，那么就要取消它，我们一个一个来看！
4.1 JSS.stopTrackingJob
我们先来看第一个方法，参数传递：
- JobStatus jobStatus：要被取消的任务；
- JobStatus incomingJob：本次要注册的任务；
- boolean writeBack：true；
/**
* Called when we want to remove a JobStatus object that we've finished executing. Returns the
* object removed.
*/
private boolean stopTrackingJob(JobStatus jobStatus, JobStatus incomingJob,
boolean writeBack) {
synchronized (mLock) {
// Remove from store as well as controllers.
final boolean removed = mJobs.remove(jobStatus, writeBack);
if (removed && mReadyToRock) {
for (int i=0; i<mControllers.size(); i++) {
StateController controller = mControllers.get(i);
controller.maybeStopTrackingJobLocked(jobStatus, incomingJob, false);
}
}
return removed;
}
}
这里的 mJobs 是 JobStore 对象！
4.1.1 JobStore.remove
我们来看看这个移除操作：
public boolean remove(JobStatus jobStatus, boolean writeBack) {
// 先从 mJobSet 中移除要删除的 JobStatus！
boolean removed = mJobSet.remove(jobStatus);
if (!removed) {
if (DEBUG) {
Slog.d(TAG, "Couldn't remove job: didn't exist: " + jobStatus);
}
return false;
}
// 如果 writeBack 是 true，并且 jobStatus 是 isPersisted 的，那就要更新 Jobs.xml 文件！
if (writeBack && jobStatus.isPersisted()) {
maybeWriteStatusToDiskAsync();
}
return removed;
}
从 JobSet 集合中移除 Job，并且，如果需要写入操作，并且这个 Job 是设备重启后仍然需要保留的，那就要调用 remove 方法，将更新后的 JobSet 写入到 system/job/jobs.xml，因为所有 Persisted 为 true 的 Job ，都是会被写入到这个文件中去的，用于重启恢复！！
我们来看 maybeWriteStatusToDiskAsync 方法：
/**
* Every time the state changes we write all the jobs in one swath, instead of trying to
* track incremental changes.
* @return Whether the operation was successful. This will only fail for e.g. if the system is
* low on storage. If this happens, we continue as normal
*/
private void maybeWriteStatusToDiskAsync() {
mDirtyOperations++;
if (mDirtyOperations >= MAX_OPS_BEFORE_WRITE) {
if (DEBUG) {
Slog.v(TAG, "Writing jobs to disk.");
}
mIoHandler.post(new WriteJobsMapToDiskRunnable());
}
}
... ... ... ... ... ...
/**
* Runnable that writes {@link #mJobSet} out to xml.
* NOTE: This Runnable locks on mLock
*/
private class WriteJobsMapToDiskRunnable implements Runnable {
@Override
public void run() {
final long startElapsed = SystemClock.elapsedRealtime();
final List<JobStatus> storeCopy = new ArrayList<JobStatus>();
synchronized (mLock) {
// Clone the jobs so we can release the lock before writing.
// 这里是将 mJobSet 拷贝一份到 storeCopy 中。
mJobSet.forEachJob(new JobStatusFunctor() {
@Override
public void process(JobStatus job) {
if (job.isPersisted()) {
storeCopy.add(new JobStatus(job));
}
}
});
}
// 将更新后的拷贝写入 jobs.xml。
writeJobsMapImpl(storeCopy);
if (JobSchedulerService.DEBUG) {
Slog.v(TAG, "Finished writing, took " + (SystemClock.elapsedRealtime()
- startElapsed) + "ms");
}
}
... ... ... ...
}
我们接着看！
4.1.2 SC.maybeStopTrackingJobLocked
接着，就是遍历控制器集合，让控制器停止对该任务的监视，参数传递：
- JobStatus jobStatus：要被删除的 Job！
- JobStatus incomingJob：同一个 uid，同一个 jobId 的要被注册执行的 Job！
- boolean forUpdate：false
/**
* Remove task - this will happen if the task is cancelled, completed, etc.
*/
public abstract void maybeStopTrackingJobLocked(JobStatus jobStatus, JobStatus incomingJob,
boolean forUpdate);
StateController 是一个抽象类，具体的实现，我们在 JobSchedulerService 的构造器中有看到：
mControllers.add(ConnectivityController.get(this));
mControllers.add(TimeController.get(this));
mControllers.add(IdleController.get(this));
mControllers.add(BatteryController.get(this));
mControllers.add(AppIdleController.get(this));
mControllers.add(ContentObserverController.get(this));
mControllers.add(DeviceIdleJobsController.get(this));
这里有很多的控制器：
4.1.2.1 ConnectivityController
我们先来看看 ConnectivityController 类的方法：
@Override
public void maybeStopTrackingJobLocked(JobStatus jobStatus, JobStatus incomingJob,
boolean forUpdate) {
if (jobStatus.hasConnectivityConstraint() || jobStatus.hasUnmeteredConstraint()
|| jobStatus.hasNotRoamingConstraint()) {
mTrackedJobs.remove(jobStatus);
}
}
其他控制器的方法很类似的哦！
4.2 JobPackageTracker.noteNonpending
这个就是这样的
public void noteNonpending(JobStatus job) {
final long now = SystemClock.uptimeMillis();
mCurDataSet.decPending(job.getSourceUid(), job.getSourcePackageName(), now);
rebatchIfNeeded(now);
}
这里我们先不看！
4.3 JSS.stopJobOnServiceContextLocked
如果 Job 有在运行，那就停止它，参数传递：cancelled, JobParameters.REASON_CANCELED
private boolean stopJobOnServiceContextLocked(JobStatus job, int reason) {
for (int i=0; i<mActiveServices.size(); i++) {
JobServiceContext jsc = mActiveServices.get(i);
final JobStatus executing = jsc.getRunningJob();
if (executing != null && executing.matches(job.getUid(), job.getJobId())) {
jsc.cancelExecutingJob(reason);
return true;
}
}
return false;
}
这里调用了 JobServiceContext 的 cancelExecutingJob 这个方法：
4.3.1 JobServiceContext.cancelExecutingJob
我们进入 JobServiceContext 文件中来看看：
/** Called externally when a job that was scheduled for execution should be cancelled. */
void cancelExecutingJob(int reason) {
mCallbackHandler.obtainMessage(MSG_CANCEL, reason, 0 /* unused */).sendToTarget();
}
其中：mCallbackHandler = new JobServiceHandler(looper)，这里的 looper 是 system_server 的主线程的 looper，这个在第二篇初始化和启动就可以看到！
这里我们向 JobServiceHandler 发送了一个 MSG_CANCEL 的消息，我们去看看：
private class JobServiceHandler extends Handler {
@Override
public void handleMessage(Message message) {
switch (message.what) {
... ... ... ...
case MSG_CANCEL: // 收到 MSG_CANCEL 的消息！
// 处理出入的参数：reason
if (mVerb == VERB_FINISHED) {
if (DEBUG) {
Slog.d(TAG, "Trying to process cancel for torn-down context, ignoring.");
}
return;
}
mParams.setStopReason(message.arg1); // 保存停止的原因！
if (message.arg1 == JobParameters.REASON_PREEMPT) {
mPreferredUid = mRunningJob != null ? mRunningJob.getUid() :
NO_PREFERRED_UID;
}
handleCancelH();
break;
case MSG_TIMEOUT:
handleOpTimeoutH();
break;
case MSG_SHUTDOWN_EXECUTION:
closeAndCleanupJobH(true /* needsReschedule */);
break;
default:
Slog.e(TAG, "Unrecognised message: " + message);
}
}
... ... ... ...
}
我们进入到 handleCancelH 方法中来看看：
/**
* A job can be in various states when a cancel request comes in:
* VERB_BINDING -> Cancelled before bind completed. Mark as cancelled and wait for
* {@link #onServiceConnected(android.content.ComponentName, android.os.IBinder)}
* _STARTING -> Mark as cancelled and wait for
* {@link JobServiceContext#acknowledgeStartMessage(int, boolean)}
* _EXECUTING -> call {@link #sendStopMessageH}}, but only if there are no callbacks
* in the message queue.
* _ENDING -> No point in doing anything here, so we ignore.
*/
private void handleCancelH() {
if (JobSchedulerService.DEBUG) {
Slog.d(TAG, "Handling cancel for: " + mRunningJob.getJobId() + " "
+ VERB_STRINGS[mVerb]);
}
switch (mVerb) {
case VERB_BINDING:
case VERB_STARTING:
mCancelled.set(true);
break;
case VERB_EXECUTING:
if (hasMessages(MSG_CALLBACK)) {
// If the client has called jobFinished, ignore this cancel.
return;
}
sendStopMessageH();
break;
case VERB_STOPPING:
// Nada.
break;
default:
Slog.e(TAG, "Cancelling a job without a valid verb: " + mVerb);
break;
}
}
mVerb 使用来保存 Job 的状态的，一个 Job 在 JobServiceContext 中会有如下的几种状态：
- VERB_BINDING
- _STARTING
- _EXECUTING
- _ENDING
这里我先不看，下面的调用流程会涉及到的！
5 JSS.startTrackingJob
接下来，就是开始 track 任务，参数传递：
- JobStatus jobStatus：本次注册的 job！
- JobStatus lastJob：同一个 uid，同一个 jobId，上次注册的已经被取消的任务，可以为 null！
/**
* Called when we have a job status object that we need to insert in our
* {@link com.android.server.job.JobStore}, and make sure all the relevant controllers know
* about.
*/
private void startTrackingJob(JobStatus jobStatus, JobStatus lastJob) {
synchronized (mLock) {
// 添加到 JobStore 中!
final boolean update = mJobs.add(jobStatus);
if (mReadyToRock) {
for (int i = 0; i < mControllers.size(); i++) {
StateController controller = mControllers.get(i);
if (update) {
controller.maybeStopTrackingJobLocked(jobStatus, null, true);
}
controller.maybeStartTrackingJobLocked(jobStatus, lastJob);
}
}
}
}
第一步，可以看到，先将这一次要注册执行的任务，加入到 JobStore 中：
5.1 JobStore.add
这里是将要好注册执行的 Job 添加到 JobStore 中，这里和上面有些类似：
* Add a job to the master list, persisting it if necessary. If the JobStatus already exists,
* it will be replaced.
* @param jobStatus Job to add.
* @return Whether or not an equivalent JobStatus was replaced by this operation.
*/
public boolean add(JobStatus jobStatus) {
boolean replaced = mJobSet.remove(jobStatus);
mJobSet.add(jobStatus); // 添加到 JobSets 集合中！
if (jobStatus.isPersisted()) {
maybeWriteStatusToDiskAsync();
}
if (DEBUG) {
Slog.d(TAG, "Added job status to store: " + jobStatus);
}
return replaced;
}
如果这个 Job 是 isPersisted 的，那就需要更新 Jobs.xml 文件！
5.2 SC.maybeStopTrackingJobLocked
这里先要停止 track 这个任务，参数传递：
- JobStatus jobStatus：要被注册执行的新的 Job！
- JobStatus incomingJob：null
- boolean forUpdate：true
/**
* Remove task - this will happen if the task is cancelled, completed, etc.
*/
public abstract void maybeStopTrackingJobLocked(JobStatus jobStatus, JobStatus incomingJob,
boolean forUpdate);
接着看！
5.3 SC.maybeStartTrackingJobLocked
接着，调用这个方法，来开始 track 任务，方法参数：
- JobStatus jobStatus：这次要注册的任务
- JobStatus lastJob：同一个 uid，同一个 jobId 已经被取消掉的上一个任务，可以为 null！
/**
* Implement the logic here to decide whether a job should be tracked by this controller.
* This logic is put here so the JobManager can be completely agnostic of Controller logic.
* Also called when updating a task, so implementing controllers have to be aware of
* preexisting tasks.
*/
public abstract void maybeStartTrackingJobLocked(JobStatus jobStatus, JobStatus lastJob);
这里同样是一个抽象接口，具体的实现是子类：
5.3.1 ConnectivityController
让我们来看看 ConnectivityController 对象的这个方法：
@Override
public void maybeStartTrackingJobLocked(JobStatus jobStatus, JobStatus lastJob) {
if (jobStatus.hasConnectivityConstraint() || jobStatus.hasUnmeteredConstraint()
|| jobStatus.hasNotRoamingConstraint()) {
updateConstraintsSatisfied(jobStatus);
// 将这个 Job 添加到 ConnectivityController 的跟踪列表中！
mTrackedJobs.add(jobStatus);
}
}
首先，判断 Job 是否有设置和 Connectivity 网络相关的属性：
- jobStatus.hasConnectivityConstraint()
- jobStatus.hasUnmeteredConstraint()
- jobStatus.hasNotRoamingConstraint()
这里我们先不看！
6 JSS.JobHandler
接着，就是向 JobHandler 发送了 MSG_CHECK_JOB 的消息，我们来看看：
private class JobHandler extends Handler {
public JobHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message message) {
synchronized (mLock) {
if (!mReadyToRock) {
return;
}
}
switch (message.what) {
case MSG_JOB_EXPIRED:
... ... ... ...
break;
case MSG_CHECK_JOB: // 接收到 MSG_CHECK_JOB 的消息！
synchronized (mLock) {
if (mReportedActive) { // 为 true，表示 JSS 通知了设备管理器，自己处于活跃状态！
// if jobs are currently being run, queue all ready jobs for execution.
queueReadyJobsForExecutionLockedH();
} else {
// Check the list of jobs and run some of them if we feel inclined.
maybeQueueReadyJobsForExecutionLockedH();
}
}
break;
case MSG_CHECK_JOB_GREEDY:
synchronized (mLock) {
queueReadyJobsForExecutionLockedH();
}
break;
case MSG_STOP_JOB:
cancelJobImpl((JobStatus)message.obj, null);
break;
}
// 处理 mPendingJobs 中的任务！
maybeRunPendingJobsH();
// Don't remove JOB_EXPIRED in case one came along while processing the queue.
removeMessages(MSG_CHECK_JOB);
}
... ... ... ... ...
}
接着，收到了 MSG_CHECK_JOB 的消息，开始遍历队列，执行准备好的任务！
6.1 queueReadyJobsForExecutionLockedH
下面是这个方法的代码：
/**
* Run through list of jobs and execute all possible - at least one is expired so we do
* as many as we can.
*/
private void queueReadyJobsForExecutionLockedH() {
if (DEBUG) {
Slog.d(TAG, "queuing all ready jobs for execution:");
}
noteJobsNonpending(mPendingJobs);
mPendingJobs.clear();
mJobs.forEachJob(mReadyQueueFunctor);
mReadyQueueFunctor.postProcess();
if (DEBUG) {
final int queuedJobs = mPendingJobs.size();
if (queuedJobs == 0) {
Slog.d(TAG, "No jobs pending.");
} else {
Slog.d(TAG, queuedJobs + " jobs queued.");
}
}
}
啦啦啦啦啦啦，天啦撸啊撸！
6.2 maybeQueueReadyJobsForExecutionLockedH
这个方法的代码：
private void maybeQueueReadyJobsForExecutionLockedH() {
if (DEBUG) Slog.d(TAG, "Maybe queuing ready jobs...");
noteJobsNonpending(mPendingJobs);
// 清除 mPendingJobs 集合!
mPendingJobs.clear();
// 将准备好的 Job 加入到 JobHandler 内部的 runnableJobs 集合中。
mJobs.forEachJob(mMaybeQueueFunctor);
// 将 runnableJobs 加入到 mPendingJobs 集合中!
mMaybeQueueFunctor.postProcess();
}
首先清除了：mPendingJobs 集合！
接着，这里传入了 mMaybeQueueFunctor 对象！
public void forEachJob(JobStatusFunctor functor) {
mJobSet.forEachJob(functor);
}
进入了 JobSet：
public void forEachJob(JobStatusFunctor functor) {
for (int uidIndex = mJobs.size() - 1; uidIndex >= 0; uidIndex--) {
ArraySet<JobStatus> jobs = mJobs.valueAt(uidIndex);
for (int i = jobs.size() - 1; i >= 0; i--) {
// 对每个 uid 的应用程序的 Job，执行下面操作：
functor.process(jobs.valueAt(i));
}
}
}
可以看出，这对所有的 Job，都调用了 MaybeReadyJobQueueFunctor 的 process 方法：
class MaybeReadyJobQueueFunctor implements JobStatusFunctor {
int chargingCount;
int idleCount;
int backoffCount;
int connectivityCount;
int contentCount;
List<JobStatus> runnableJobs; // 符合条件的即将运行的 Job
public MaybeReadyJobQueueFunctor() {
reset();
}
// Functor method invoked for each job via JobStore.forEachJob()
@Override
public void process(JobStatus job) {
// 判断这个 Job 是否是准备了！
if (isReadyToBeExecutedLocked(job)) {
try {
if (ActivityManagerNative.getDefault().getAppStartMode(job.getUid(),
job.getJob().getService().getPackageName())
== ActivityManager.APP_START_MODE_DISABLED) {
Slog.w(TAG, "Aborting job " + job.getUid() + ":"
+ job.getJob().toString() + " -- package not allowed to start");
mHandler.obtainMessage(MSG_STOP_JOB, job).sendToTarget();
return;
}
} catch (RemoteException e) {
}
if (job.getNumFailures() > 0) {
backoffCount++;
}
if (job.hasIdleConstraint()) {
idleCount++;
}
if (job.hasConnectivityConstraint() || job.hasUnmeteredConstraint()
|| job.hasNotRoamingConstraint()) {
connectivityCount++;
}
if (job.hasChargingConstraint()) {
chargingCount++;
}
if (job.hasContentTriggerConstraint()) {
contentCount++;
}
if (runnableJobs == null) {
runnableJobs = new ArrayList<>();
}
// 将满足条件的 Job，先加入到 runnableJobs 集合！
runnableJobs.add(job);
} else if (areJobConstraintsNotSatisfiedLocked(job)) {
stopJobOnServiceContextLocked(job,
JobParameters.REASON_CONSTRAINTS_NOT_SATISFIED);
}
}
这里调用了 isReadyToBeExecutedLocked 方法来判断，这个 job 是否已经准备好了：
/**
* Criteria for moving a job into the pending queue:
* - It's ready.
* - It's not pending.
* - It's not already running on a JSC.
* - The user that requested the job is running.
* - The component is enabled and runnable.
*/
private boolean isReadyToBeExecutedLocked(JobStatus job) {
final boolean jobReady = job.isReady();
final boolean jobPending = mPendingJobs.contains(job);
final boolean jobActive = isCurrentlyActiveLocked(job);
final int userId = job.getUserId();
final boolean userStarted = ArrayUtils.contains(mStartedUsers, userId);
final boolean componentPresent;
try {
componentPresent = (AppGlobals.getPackageManager().getServiceInfo(
job.getServiceComponent(), PackageManager.MATCH_DEBUG_TRIAGED_MISSING,
userId) != null);
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
if (DEBUG) {
Slog.v(TAG, "isReadyToBeExecutedLocked: " + job.toShortString()
+ " ready=" + jobReady + " pending=" + jobPending
+ " active=" + jobActive + " userStarted=" + userStarted
+ " componentPresent=" + componentPresent);
}
return userStarted && componentPresent && jobReady && !jobPending && !jobActive;
}
可以看出，一个准备好的 Job 要满足这些条件：
*- It's ready.
*- It's not pending.
*- It's not already running on a JSC.
*- The user that requested the job is running.
*- The component is enabled and runnable.
(英文很简单，我就不翻译了，哈哈哈哈，逼近记不住键盘！)
最后，调用 MaybeQueueFunctor.postProcess 方法：
public void postProcess() {
if (backoffCount > 0 ||
idleCount >= mConstants.MIN_IDLE_COUNT ||
connectivityCount >= mConstants.MIN_CONNECTIVITY_COUNT ||
chargingCount >= mConstants.MIN_CHARGING_COUNT ||
contentCount >= mConstants.MIN_CONTENT_COUNT ||
(runnableJobs != null
&& runnableJobs.size() >= mConstants.MIN_READY_JOBS_COUNT)) {
if (DEBUG) {
Slog.d(TAG, "maybeQueueReadyJobsForExecutionLockedH: Running jobs.");
}
noteJobsPending(runnableJobs);
// 将 runnableJobs 加入到 mPendingJobs 集合中!
mPendingJobs.addAll(runnableJobs);
} else {
if (DEBUG) {
Slog.d(TAG, "maybeQueueReadyJobsForExecutionLockedH: Not running anything.");
}
}
// Be ready for next time
reset();
}
该功能:
先将 JobStore 的 JobSet 中满足条件的 job 对应的 JobStatus 加入 runnableJobs 队列；
再将 runnableJobs 中满足触发条件的 JobStatus 加入到 mPendingJobs 队列；
6.3 maybeRunPendingJobsH
接着，就是处理 mPendingJobs 中的 Job：
/**
* Reconcile jobs in the pending queue against available execution contexts.
* A controller can force a job into the pending queue even if it's already running, but
* here is where we decide whether to actually execute it.
*/
private void maybeRunPendingJobsH() {
synchronized (mLock) {
if (DEBUG) {
Slog.d(TAG, "pending queue: " + mPendingJobs.size() + " jobs.");
}
assignJobsToContextsLocked();
reportActive();
}
}
结合就是调用 JSS 的 assignJobsToContextLocked 方法：
6.3.1 JSS.assignJobsToContextsLocked
这个方法其实从名字上就可以看出，就是把 Job 分配给 JobServiceContext 方法，我们去那个方法里面看一下：
/**
* Takes jobs from pending queue and runs them on available contexts.
* If no contexts are available, preempts lower priority jobs to
* run higher priority ones.
* Lock on mJobs before calling this function.
*/
private void assignJobsToContextsLocked() {
if (DEBUG) {
Slog.d(TAG, printPendingQueue());
}
// 根据当前系统的内存级别，设定最大的活跃 Job 数，保存到 mMaxActiveJobs！
int memLevel;
try {
memLevel = ActivityManagerNative.getDefault().getMemoryTrimLevel();
} catch (RemoteException e) {
memLevel = ProcessStats.ADJ_MEM_FACTOR_NORMAL;
}
switch (memLevel) {
case ProcessStats.ADJ_MEM_FACTOR_MODERATE:
mMaxActiveJobs = mConstants.BG_MODERATE_JOB_COUNT;
break;
case ProcessStats.ADJ_MEM_FACTOR_LOW:
mMaxActiveJobs = mConstants.BG_LOW_JOB_COUNT;
break;
case ProcessStats.ADJ_MEM_FACTOR_CRITICAL:
mMaxActiveJobs = mConstants.BG_CRITICAL_JOB_COUNT;
break;
default:
mMaxActiveJobs = mConstants.BG_NORMAL_JOB_COUNT;
break;
}
JobStatus[] contextIdToJobMap = mTmpAssignContextIdToJobMap; // 大小为 16，和 mActiveServices 相对应！
boolean[] act = mTmpAssignAct;
int[] preferredUidForContext = mTmpAssignPreferredUidForContext; // 大小为 16，和 mActiveServices 相对应！
int numActive = 0;
int numForeground = 0;
for (int i=0; i<MAX_JOB_CONTEXTS_COUNT; i++) {
final JobServiceContext js = mActiveServices.get(i);
final JobStatus status = js.getRunningJob();
// 初始化 contextIdToJobMap，里面保存当前运行着的 Job，和空闲的用于增加的 Job 位置!
// 然后，分别计算活跃 job 和前台 job 的个数！
if ((contextIdToJobMap[i] = status) != null) {
numActive++;
if (status.lastEvaluatedPriority >= JobInfo.PRIORITY_TOP_APP) {
numForeground++;
}
}
act[i] = false;
preferredUidForContext[i] = js.getPreferredUid();
}
if (DEBUG) {
Slog.d(TAG, printContextIdToJobMap(contextIdToJobMap, "running jobs initial"));
}
// 遍历 mPendingJos 任务集合，开始做准备工作!
for (int i=0; i<mPendingJobs.size(); i++) {
JobStatus nextPending = mPendingJobs.get(i);
// If job is already running, go to next job.
// 判断当前的 Job 是不是在 contextIdToJobMap 中了，即他是不是已经在运行了!
int jobRunningContext = findJobContextIdFromMap(nextPending, contextIdToJobMap);
if (jobRunningContext != -1) {
continue;
}
// 计算 Job 的优先级!
final int priority = evaluateJobPriorityLocked(nextPending);
nextPending.lastEvaluatedPriority = priority;
// Find a context for nextPending. The context should be available OR
// it should have lowest priority among all running jobs
// (sharing the same Uid as nextPending)
// 遍历 contextIdToJobMap
// 给这个即将被执行的 Job 找一个合适的 context，至少要满足两个中的一个要求：1、可利用；2、优先级最低！
int minPriority = Integer.MAX_VALUE;
int minPriorityContextId = -1;
for (int j=0; j<MAX_JOB_CONTEXTS_COUNT; j++) {
JobStatus job = contextIdToJobMap[j];
int preferredUid = preferredUidForContext[j];
if (job == null) {
if ((numActive < mMaxActiveJobs ||
(priority >= JobInfo.PRIORITY_TOP_APP &&
numForeground < mConstants.FG_JOB_COUNT)) &&
(preferredUid == nextPending.getUid() ||
preferredUid == JobServiceContext.NO_PREFERRED_UID)) {
// This slot is free, and we haven't yet hit the limit on
// concurrent jobs... we can just throw the job in to here.
// 如果 context 原有的 job 为空，并且满足以下条件：
// 活跃 job 数小于最大活跃数，或者即将执行的 job 的优先级不低于 PRIORITY_TOP_APP，并且前台 job 数小于 4，那么这个 context 是合适的!
minPriorityContextId = j;
break;
}
// No job on this context, but nextPending can't run here because
// the context has a preferred Uid or we have reached the limit on
// concurrent jobs.
continue;
}
if (job.getUid() != nextPending.getUid()) { // 如果 context 原有的 job 不为空，且 uid 和即将执行的 job 不一样，那么这个 context 不合适!
continue;
}
if (evaluateJobPriorityLocked(job) >= nextPending.lastEvaluatedPriority) { // 如果 context 原有的 job 不为空，且 uid 相同，但优先级不低于即将执行的 job，那么这个 context 不合适!
continue;
}
if (minPriority > nextPending.lastEvaluatedPriority) { // 如果 context 原有的 job 不为空，且 uid 相同，且优先级低于即将执行的 job，那么这个 context 合适!
minPriority = nextPending.lastEvaluatedPriority;
minPriorityContextId = j;
}
}
if (minPriorityContextId != -1) { // 找到了合适的 context 的下标!
// 将这个要被执行的 Job 放入合适的 Context 中！
contextIdToJobMap[minPriorityContextId] = nextPending;
// 对应的 act 位置为 true，表示可以运行!
act[minPriorityContextId] = true;
numActive++; //
if (priority >= JobInfo.PRIORITY_TOP_APP) {
numForeground++;
}
}
}
if (DEBUG) {
Slog.d(TAG, printContextIdToJobMap(contextIdToJobMap, "running jobs final"));
}
mJobPackageTracker.noteConcurrency(numActive, numForeground);
// 执行任务!
for (int i=0; i<MAX_JOB_CONTEXTS_COUNT; i++) {
boolean preservePreferredUid = false;
if (act[i]) { // art 为 true 的位置，对应的就是上面添加的即将执行的 Job
JobStatus js = mActiveServices.get(i).getRunningJob();
if (js != null) {
if (DEBUG) {
Slog.d(TAG, "preempting job: " + mActiveServices.get(i).getRunningJob());
}
// preferredUid will be set to uid of currently running job.
// 如果这个 context 已经在运行了一个优先级低的 job，那就要取消它！
mActiveServices.get(i).preemptExecutingJob();
preservePreferredUid = true;
} else {
// 从 contextIdToJobMap 中获得即将执行的 Job!
final JobStatus pendingJob = contextIdToJobMap[i];
if (DEBUG) {
Slog.d(TAG, "About to run job on context "
+ String.valueOf(i) + ", job: " + pendingJob);
}
// 通知控制器!
for (int ic=0; ic<mControllers.size(); ic++) {
mControllers.get(ic).prepareForExecutionLocked(pendingJob);
}
// 使用对应的 JobServiceContext 来执行 Job
if (!mActiveServices.get(i).executeRunnableJob(pendingJob)) {
Slog.d(TAG, "Error executing " + pendingJob);
}
// Job 已经开始执行了，从 mPendingJobs 中移除这个 Job!
if (mPendingJobs.remove(pendingJob)) {
mJobPackageTracker.noteNonpending(pendingJob);
}
}
}
if (!preservePreferredUid) {
mActiveServices.get(i).clearPreferredUid();
}
}
}
接着我们继续来看：
6.3.1.1 JSS.findJobContextIdFromMap
这个方法的作用很简单，就是判断 job 是否已经在 map 集合中了！
int findJobContextIdFromMap(JobStatus jobStatus, JobStatus[] map) {
for (int i=0; i<map.length; i++) {
if (map[i] != null && map[i].matches(jobStatus.getUid(), jobStatus.getJobId())) {
return i;
}
}
return -1;
}
6.3.1.2 JSS.evaluateJobPriorityLocked
这个方法是为 job 计算优先级：
private int evaluateJobPriorityLocked(JobStatus job) {
int priority = job.getPriority();
if (priority >= JobInfo.PRIORITY_FOREGROUND_APP) {
return adjustJobPriority(priority, job);
}
int override = mUidPriorityOverride.get(job.getSourceUid(), 0);
if (override != 0) {
return adjustJobPriority(override, job);
}
return adjustJobPriority(priority, job);
}
接着：
6.3.1.3 JSC.preemptExecutingJob
这里调用了 JobServiceContext 的 preemptExecutingJob 方法来取消优先级低的任务，之前有说过，如果 Context 已经在执行一个 job，并且这个 job 和即将被执行的 job 属于同一个 apk，那么要取消优先级低的！
void preemptExecutingJob() {
Message m = mCallbackHandler.obtainMessage(MSG_CANCEL);
// 参数为 JobParameters.REASON_PREEMPT，表示要取代！
m.arg1 = JobParameters.REASON_PREEMPT;
m.sendToTarget();
}
这个消息会发给 JSC 内部的 JobServiceHandler 来处理：
JobServiceHandler.MSG_CANCEL
我们接着来看：
private class JobServiceHandler extends Handler {
JobServiceHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message message) {
switch (message.what) {
... ... ... ...
case MSG_CANCEL:
if (mVerb == VERB_FINISHED) { // 这个 mVerb 表示的是，这个 Context 的 job 的当前状态!
if (DEBUG) {
Slog.d(TAG,
"Trying to process cancel for torn-down context, ignoring.");
}
return;
}
mParams.setStopReason(message.arg1);
if (message.arg1 == JobParameters.REASON_PREEMPT) {
mPreferredUid = mRunningJob != null ? mRunningJob.getUid() :
NO_PREFERRED_UID;
}
// 执行取消操作!
handleCancelH();
break;
case MSG_TIMEOUT:
handleOpTimeoutH();
break;
case MSG_SHUTDOWN_EXECUTION:
closeAndCleanupJobH(true /* needsReschedule */);
break;
default:
Slog.e(TAG, "Unrecognised message: " + message);
}
}
... ... ... ... ... ...
private void handleCancelH() {
if (JobSchedulerService.DEBUG) {
Slog.d(TAG, "Handling cancel for: " + mRunningJob.getJobId() + " "
+ VERB_STRINGS[mVerb]);
}
switch (mVerb) { // 这里因为是取消的是这个 context 里面正在执行的 job，所以 mVerb 的值为 VERB_EXECUTING!
case VERB_BINDING:
case VERB_STARTING:
mCancelled.set(true);
break;
case VERB_EXECUTING:
if (hasMessages(MSG_CALLBACK)) { // 如果 client 已经调用了 jobFinished 方法结束了 job，那就 return!
// If the client has called jobFinished, ignore this cancel.
return;
}
sendStopMessageH(); // 否则，就再次发送停止的消息!
break;
case VERB_STOPPING:
// Nada.
break;
default:
Slog.e(TAG, "Cancelling a job without a valid verb: " + mVerb);
break;
}
}
... ... ... ...
}
如果有优先级低的 job 正在运行，那就 stop job，这时 mVerb 会从：VERB_EXECUTING -> VERB_STOPPING.
/**
* Already running, need to stop. Will switch {@link #mVerb} from VERB_EXECUTING ->
* VERB_STOPPING.
*/
private void sendStopMessageH() {
removeOpTimeOut();
if (mVerb != VERB_EXECUTING) {
Slog.e(TAG, "Sending onStopJob for a job that isn't started. " + mRunningJob);
closeAndCleanupJobH(false /* reschedule */);
return;
}
try {
mVerb = VERB_STOPPING; // mVerb 状态变为 VERB_STOPPING！
scheduleOpTimeOut();
service.stopJob(mParams); // 这里就调用了 client 的 JobService 的
} catch (RemoteException e) {
Slog.e(TAG, "Error sending onStopJob to client.", e);
closeAndCleanupJobH(false /* reschedule */);
}
}
这里的 service 是一个 IJobService 对象，对应的是一个 .aidl 文件，表示的是 Binder 服务端，代码定义位于：JobService 中。
JobService
注意：这里对于 Binder 机制来说：应用程序 client 的 JobService 所在进程是 Binder 服务端，JobServiceContext 所在的进程 system_server 是 Binder 客户端！也就是说，应用程序定义的 JobService 是被 JobSerivceContext 来 bind 的，所以，你会发现，你无法 override JobService 的 onbind 方法！
static final class JobInterface extends IJobService.Stub {
final WeakReference<JobService> mService;
JobInterface(JobService service) {
mService = new WeakReference<>(service);
}
@Override
public void startJob(JobParameters jobParams) throws RemoteException {
JobService service = mService.get();
if (service != null) {
service.ensureHandler();
Message m = Message.obtain(service.mHandler, MSG_EXECUTE_JOB, jobParams);
m.sendToTarget();
}
}
@Override
public void stopJob(JobParameters jobParams) throws RemoteException { // 通过 binder 机制来来调用指定应用的 JobService 的 stopJob 方法！
JobService service = mService.get();
if (service != null) {
service.ensureHandler();
// 发送到 JobService 内部的 JobHandler 对象中！
Message m = Message.obtain(service.mHandler, MSG_STOP_JOB, jobParams);
m.sendToTarget();
}
}
}
这里发送了 MSG_STOP_JOB 消息给 JobService.JobHandler，我们去 JobHandler 内部去看看：
JobHandler
JobHandler 位于应用程序的主线程：
/**
* Runs on application's main thread - callbacks are meant to offboard work to some other
* (app-specified) mechanism.
* @hide
*/
class JobHandler extends Handler {
JobHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message msg) {
// 这里获得传递过来的 JobParameters
final JobParameters params = (JobParameters) msg.obj;
switch (msg.what) {
... ... ...
case MSG_STOP_JOB:
try {
// 调用 JobService onStopJob 方法，把参数传递过去，这里是不是很熟悉，就不多说!
// onStopJob 会返回 true / false， true 表示还会 reschedule 这个 job!
boolean ret = JobService.this.onStopJob(params);
ackStopMessage(params, ret);
} catch (Exception e) {
Log.e(TAG, "Application unable to handle onStopJob.", e);
throw new RuntimeException(e);
}
break;
... ... ... ...
default:
Log.e(TAG, "Unrecognised message received.");
break;
}
}
... ... ... ... ...
private void ackStopMessage(JobParameters params, boolean reschedule) {
// 这里获得了 IJobCallback 对象，这里显示是 Binder 机制，服务端是 JobServiceContext
final IJobCallback callback = params.getCallback();
final int jobId = params.getJobId();
if (callback != null) {
try {
// 发送消息给 JobServiceContext
callback.acknowledgeStopMessage(jobId, reschedule);
} catch(RemoteException e) {
Log.e(TAG, "System unreachable for stopping job.");
}
} else {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "Attempting to ack a job that has already been processed.");
}
}
}
}
这里的 IJobCallback 又是使用了 Binder 机制，Binder 客户端是应用程序的 JobService 所在进程，Binder 服务端是 JobServiceContext 所在的进程，最后调用的是 JobServiceContext.acknowledgeStopMessage 方法：
JobServiceContext
通过 Binder 机制，将回调信息发回给 JobServiceContext
@Override
public void acknowledgeStopMessage(int jobId, boolean reschedule) {
if (!verifyCallingUid()) {
return;
}
// 发送 MSG_CALLBACK 给 JobServiceHandler
mCallbackHandler.obtainMessage(MSG_CALLBACK, jobId, reschedule ? 1 : 0)
.sendToTarget();
}
然后又会发送 MSG_CALLBACK 给 JobServiceContext.JobServiceHandler，这里我们只看关键代码：
JobServiceHandler
JobServiceHandler 同样的也是位于主线程：
case MSG_CALLBACK:
if (DEBUG) {
Slog.d(TAG, "MSG_CALLBACK of : " + mRunningJob
+ " v:" + VERB_STRINGS[mVerb]);
}
removeOpTimeOut();
if (mVerb == VERB_STARTING) {
final boolean workOngoing = message.arg2 == 1;
handleStartedH(workOngoing);
} else if (mVerb == VERB_EXECUTING ||
mVerb == VERB_STOPPING) { // 从前面跟代码，可以看出 mVerb 的值为 VERB_STOPPING.
final boolean reschedule = message.arg2 == 1;
handleFinishedH(reschedule);
} else {
if (DEBUG) {
Slog.d(TAG, "Unrecognised callback: " + mRunningJob);
}
}
break;
接着，调用 JobServiceContext 的 handleFinishedH 方法：
private void handleFinishedH(boolean reschedule) {
switch (mVerb) {
case VERB_EXECUTING:
case VERB_STOPPING:
closeAndCleanupJobH(reschedule); // 调用了 closeAndCleanupJobH，reschedul
break;
default:
Slog.e(TAG, "Got an execution complete message for a job that wasn't being" +
"executed. Was " + VERB_STRINGS[mVerb] + ".");
}
}
接着进入 closeAndCleanupJobH 方法：
/**
* The provided job has finished, either by calling
* {@link android.app.job.JobService#jobFinished(android.app.job.JobParameters, boolean)}
* or from acknowledging the stop message we sent. Either way, we're done tracking it and
* we want to clean up internally.
*/
private void closeAndCleanupJobH(boolean reschedule) {
final JobStatus completedJob;
synchronized (mLock) {
if (mVerb == VERB_FINISHED) {
return;
}
completedJob = mRunningJob;
mJobPackageTracker.noteInactive(completedJob);
try {
mBatteryStats.noteJobFinish(mRunningJob.getBatteryName(),
mRunningJob.getSourceUid());
} catch (RemoteException e) {
// Whatever.
}
if (mWakeLock != null) {
mWakeLock.release();
}
mContext.unbindService(JobServiceContext.this); // 取消绑定 JobService
mWakeLock = null;
mRunningJob = null;
mParams = null;
mVerb = VERB_FINISHED;
mCancelled.set(false);
service = null;
mAvailable = true;
}
removeOpTimeOut(); // 移除已经处理的消息
removeMessages(MSG_CALLBACK);
removeMessages(MSG_SERVICE_BOUND);
removeMessages(MSG_CANCEL);
removeMessages(MSG_SHUTDOWN_EXECUTION);
// 调用了 mCompletedListener 的 onJobCompleted 方法!
mCompletedListener.onJobCompleted(completedJob, reschedule);
}
}
这里 mCompletedListener 大家去看 JobServiceContext 的初始化，也就是第一篇，其实就是 JobSchedulerService.this：
JobSchedulerService.onJobCompleted
@Override
public void onJobCompleted(JobStatus jobStatus, boolean needsReschedule) {
if (DEBUG) {
Slog.d(TAG, "Completed " + jobStatus + ", reschedule=" + needsReschedule);
}
// Do not write back immediately if this is a periodic job. The job may get lost if system
// shuts down before it is added back.
// 停止 track 这个 job!
if (!stopTrackingJob(jobStatus, null, !jobStatus.getJob().isPeriodic())) {
if (DEBUG) {
Slog.d(TAG, "Could not find job to remove. Was job removed while executing?");
}
// We still want to check for jobs to execute, because this job may have
// scheduled a new job under the same job id, and now we can run it.
mHandler.obtainMessage(MSG_CHECK_JOB_GREEDY).sendToTarget();
return;
}
// Note: there is a small window of time in here where, when rescheduling a job,
// we will stop monitoring its content providers. This should be fixed by stopping
// the old job after scheduling the new one, but since we have no lock held here
// that may cause ordering problems if the app removes jobStatus while in here.
// 重新 schedule 这个 job
if (needsReschedule) {
JobStatus rescheduled = getRescheduleJobForFailure(jobStatus);
startTrackingJob(rescheduled, jobStatus);
} else if (jobStatus.getJob().isPeriodic()) {
JobStatus rescheduledPeriodic = getRescheduleJobForPeriodic(jobStatus);
startTrackingJob(rescheduledPeriodic, jobStatus);
}
reportActive();
// 发送 MSG_CHECK_JOB_GREEDY 给 JobSchedulerService.JobHandler
mHandler.obtainMessage(MSG_CHECK_JOB_GREEDY).sendToTarget();
}
这里首先调用了 stopTrackingJob 将这个 job 从 JobStore 和 controller 中移除：
/**
* Called when we want to remove a JobStatus object that we've finished executing. Returns the
* object removed.
*/
private boolean stopTrackingJob(JobStatus jobStatus, JobStatus incomingJob,
boolean writeBack) {
synchronized (mLock) {
// Remove from store as well as controllers.
// 从 JobStore 中移除这个 job，如果 writeback 为 true，还要更新本地的 job.xml 文件!
final boolean removed = mJobs.remove(jobStatus, writeBack);
if (removed && mReadyToRock) {
for (int i=0; i<mControllers.size(); i++) {
StateController controller = mControllers.get(i);
// 从 Controller 的跟踪队列中移除！
controller.maybeStopTrackingJobLocked(jobStatus, incomingJob, false);
}
}
return removed;
}
}
最后是发 MSG_CHECK_JOB_GREEDY 给 JobHandler：
JobHandler
private class JobHandler extends Handler {
@Override
public void handleMessage(Message message) {
synchronized (mLock) {
if (!mReadyToRock) {
return;
}
}
switch (message.what) {
... ... ... ...
case MSG_CHECK_JOB_GREEDY:
synchronized (mLock) {
// 作用和 maybeQueueReadyJobsForExecutionLockedH 一样的都是更新 mPendingJobs 集合！
queueReadyJobsForExecutionLockedH();
}
break;
... ... ... ...
}
// 再次执行 mPendingJobs 中的 job
maybeRunPendingJobsH();
// Don't remove JOB_EXPIRED in case one came along while processing the queue.
removeMessages(MSG_CHECK_JOB);
}
... ... ... ...
}
最后继续 maybeRunPendingJobsH，这里又回到了第 6 节了，就不多说了！
6.3.1.4 SC.prepareForExecutionLocked
这个方法其实很简单，就是一个抽象类的方法：
/**
* Optionally implement logic here to prepare the job to be executed.
*/
public void prepareForExecutionLocked(JobStatus jobStatus) {
}
表示通知 StateController，做好准备，具体实现是在 Controller 中，我们先看看 ConnectivityController，其他类似：
6.3.1.5 JSC.executeRunnableJob
这里就是调用 JobSchedulerContext 方法来执行 Job：
/**
* Give a job to this context for execution. Callers must first check {@link #getRunningJob()}
* and ensure it is null to make sure this is a valid context.
* @param job The status of the job that we are going to run.
* @return True if the job is valid and is running. False if the job cannot be executed.
*/
boolean executeRunnableJob(JobStatus job) {
synchronized (mLock) {
if (!mAvailable) {
Slog.e(TAG, "Starting new runnable but context is unavailable > Error.");
return false;
}
mPreferredUid = NO_PREFERRED_UID;
// 保存到 mRunningJob 中，
mRunningJob = job;
final boolean isDeadlineExpired =
job.hasDeadlineConstraint() &&
(job.getLatestRunTimeElapsed() < SystemClock.elapsedRealtime());
Uri[] triggeredUris = null;
if (job.changedUris != null) {
triggeredUris = new Uri[job.changedUris.size()];
job.changedUris.toArray(triggeredUris);
}
String[] triggeredAuthorities = null;
if (job.changedAuthorities != null) {
triggeredAuthorities = new String[job.changedAuthorities.size()];
job.changedAuthorities.toArray(triggeredAuthorities);
}
// 创建 job 需要的 JobParamters
mParams = new JobParameters(this, job.getJobId(), job.getExtras(), isDeadlineExpired,
triggeredUris, triggeredAuthorities);
mExecutionStartTimeElapsed = SystemClock.elapsedRealtime();
// mVerb 的值变为 VERB_BINDING!
mVerb = VERB_BINDING;
scheduleOpTimeOut();
// 这里很关键，bind 应用程序中注册的 JobService！
final Intent intent = new Intent().setComponent(job.getServiceComponent());
boolean binding = mContext.bindServiceAsUser(intent, this,
Context.BIND_AUTO_CREATE | Context.BIND_NOT_FOREGROUND,
new UserHandle(job.getUserId()));
if (!binding) {
if (DEBUG) {
Slog.d(TAG, job.getServiceComponent().getShortClassName() + " unavailable.");
}
mRunningJob = null;
mParams = null;
mExecutionStartTimeElapsed = 0L;
mVerb = VERB_FINISHED;
removeOpTimeOut();
return false;
}
// 记录信息!
try {
mBatteryStats.noteJobStart(job.getBatteryName(), job.getSourceUid());
} catch (RemoteException e) {
// Whatever.
}
mJobPackageTracker.noteActive(job);
mAvailable = false;
return true;
}
}
这便是由 system_server 进程的主线程来执行 bind Service 的方式来拉起的进程，当服务启动后回调到发起端的 onServiceConnected。
关于 bindService 这里不讨论，另开一贴！
6.3.1.5.1 JSC.onServiceConnected
bind 成功后，作为 Binder 机制的客户端，JobServiceContext 的
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
JobStatus runningJob;
synchronized (mLock) {
// This isn't strictly necessary b/c the JobServiceHandler is running on the main
// looper and at this point we can't get any binder callbacks from the client. Better
// safe than sorry.
runningJob = mRunningJob;
}
// 异常检测
if (runningJob == null || !name.equals(runningJob.getServiceComponent())) {
mCallbackHandler.obtainMessage(MSG_SHUTDOWN_EXECUTION).sendToTarget();
return;
}
// 获得了应用程序的 JobService 的代理对象！
this.service = IJobService.Stub.asInterface(service);
final PowerManager pm =
(PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
runningJob.getTag());
wl.setWorkSource(new WorkSource(runningJob.getSourceUid()));
wl.setReferenceCounted(false);
wl.acquire();
synchronized (mLock) {
// We use a new wakelock instance per job. In rare cases there is a race between
// teardown following job completion/cancellation and new job service spin-up
// such that if we simply assign mWakeLock to be the new instance, we orphan
// the currently-live lock instead of cleanly replacing it. Watch for this and
// explicitly fast-forward the release if we're in that situation.
if (mWakeLock != null) {
Slog.w(TAG, "Bound new job " + runningJob + " but live wakelock " + mWakeLock
+ " tag=" + mWakeLock.getTag());
mWakeLock.release();
}
mWakeLock = wl;
}
// 发送 MSG_SERVICE_BOUND 给 JobServiceHandler 中！
mCallbackHandler.obtainMessage(MSG_SERVICE_BOUND).sendToTarget();
}
可以看到，这里会发送消息到 JobServiceHandler 中：
6.3.1.5.2 JSC.JobServiceHandler
JobServiceHandler 方法也是在主线程中！
private class JobServiceHandler extends Handler {
JobServiceHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message message) {
switch (message.what) {
case MSG_SERVICE_BOUND: // 绑定成功的消息！
removeOpTimeOut();
handleServiceBoundH();
break;
... ... ... ...
case MSG_SHUTDOWN_EXECUTION: // 绑定是出现异常的消息！
closeAndCleanupJobH(true /* needsReschedule */);
break;
default:
Slog.e(TAG, "Unrecognised message: " + message);
}
}
... ... ... ...
}
接着我们来分别看一下：
6.3.1.5.2.1 JSH.MSG_SERVICE_BOUND
收到这个消息后，调用 handleServiceBoundH 方法：
/** Start the job on the service. */
private void handleServiceBoundH() {
if (DEBUG) {
Slog.d(TAG, "MSG_SERVICE_BOUND for " + mRunningJob.toShortString());
}
if (mVerb != VERB_BINDING) { // 状态异常
Slog.e(TAG, "Sending onStartJob for a job that isn't pending. "
+ VERB_STRINGS[mVerb]);
closeAndCleanupJobH(false /* reschedule */);
return;
}
if (mCancelled.get()) { // 如果发现 JobService 对应的 job 被取消了，那就 return！
if (DEBUG) {
Slog.d(TAG, "Job cancelled while waiting for bind to complete. "
+ mRunningJob);
}
closeAndCleanupJobH(true /* reschedule */);
return;
}
try {
// mVerb 的值设置为 VERB_STARTING！
mVerb = VERB_STARTING;
scheduleOpTimeOut();
// 这里调用了 JobService 的 startJob 方法
service.startJob(mParams);
} catch (RemoteException e) {
Slog.e(TAG, "Error sending onStart message to '" +
mRunningJob.getServiceComponent().getShortClassName() + "' ", e);
}
}
这里就不细看了！
7 总结
通过分析，我们可以看到 JobSchedulerService 相关类的关系：
不好意思，图我还没画完，后面会补上的，请相信我，请打赏我，让我感受到你们的爱。。。
网友评论