Service可能大家都能说上两句，比如四大组件之一，同Activity的区别是没前台交互界面，可以启动后台任务等等。不过Service到底什么意思，
03-23 04:18:41.744 2444 2782 I ActivityManager: Killing 14008:com.snail.labaffinity/u0a61 (adj 16): remove task
03-23 04:18:41.776 2444 2633 W ActivityManager: Scheduling restart of crashed service com.snail.labaffinity/.service.BackGroundService in 1000ms
03-23 04:18:41.776 2444 2633 D GraphicsStats: Buffer count: 2
03-23 04:18:42.781 14528 14528 I art : Late-enabling -Xcheck:jni
03-23 04:18:42.790 2444 2468 I ActivityManager: Start proc 14528:com.snail.labaffinity/u0a61 for service com.snail.labaffinity/.service.BackGroundService
03-23 04:18:42.814 14528 14528 W System : ClassLoader referenced unknown path: /data/app/com.snail.labaffinity-1/lib/x86
03-23 04:18:42.824 14528 14528 V lishang : service onCreate
双binder服务保活，无法从最近层任务列表杀死的原因
启动方式
startService
bindService
重启时机
onStartCommand的返回值：
private void cleanUpRemovedTaskLocked(TaskRecord tr, boolean killProcess) { mRecentTasks.remove(tr); tr.removedFromRecents(); ComponentName component = tr.getBaseIntent().getComponent(); if (component == null) { Slog.w(TAG, “No component for base intent of task: “ + tr); return; }
// Find any running services associated with this app and stop if needed.
mServices.cleanUpRemovedTaskLocked(tr, component, new Intent(tr.getBaseIntent()));
if (!killProcess) {
return;
}
// Determine if the process(es) for this task should be killed.
final String pkg = component.getPackageName();
// 包名 相同的包名 可以有不同的任务名字，以及不同的pid
ArrayList<ProcessRecord> procsToKill = new ArrayList<>();
ArrayMap<String, SparseArray<ProcessRecord>> pmap = mProcessNames.getMap();
for (int i = 0; i < pmap.size(); i++) {
SparseArray<ProcessRecord> uids = pmap.valueAt(i);
for (int j = 0; j < uids.size(); j++) {
ProcessRecord proc = uids.valueAt(j);
if (proc.userId != tr.userId) {
// Don't kill process for a different user.
continue;
}
// 不杀home进程
if (proc == mHomeProcess) {
// Don't kill the home process along with tasks from the same package.
continue;
}
if (!proc.pkgList.containsKey(pkg)) {
// Don't kill process that is not associated with this task.
continue;
}
for (int k = 0; k < proc.activities.size(); k++) {
TaskRecord otherTask = proc.activities.get(k).task;
if (tr.taskId != otherTask.taskId && otherTask.inRecents) {
// Don't kill process(es) that has an activity in a different task that is
// also in recents.
return;
}
}
//不杀前台服务进程 就算是从最近任务列表删除
if (proc.foregroundServices) {
// Don't kill process(es) with foreground service.
return;
}
// Add process to kill list.
procsToKill.add(proc);
}
}
// Kill the running processes.
for (int i = 0; i < procsToKill.size(); i++) {
ProcessRecord pr = procsToKill.get(i);
if (pr.setSchedGroup == Process.THREAD_GROUP_BG_NONINTERACTIVE
&& pr.curReceiver == null) {
pr.kill("remove task", true);
} else {
// We delay killing processes that are not in the background or running a receiver.
pr.waitingToKill = "remove task";
}
}
}
常用的返回值有3种，START_STICKY、START_NOT_STICKY和START_REDELIVER_INTENT。其中START_STICKY和START_REDELIVER_INTENT在service没有执行完就被系统杀掉后的一段时间内会被系统重启，被系统杀掉的情形可能是在系统内存不足或者某些ROM定制了管理后台任务的策略，比如锁屏一段时间后，不在白名单中的应用会被杀掉以释放内存。如果是service本身的错误导致在没有执行完就crash退出，是不会被系统重启的。
void serviceDoneExecutingLocked(ServiceRecord r, int type, int startId, int res) {
boolean inStopping = mStoppingServices.contains(r);
if (r != null) {
if (type == 1) {
// This is a call from a service start... take care of
// book-keeping.
r.callStart = true;
switch (res) {
case Service.START_STICKY_COMPATIBILITY:
case Service.START_STICKY: {
// We are done with the associated start arguments.
r.findDeliveredStart(startId, true);
// Don't stop if killed.
r.stopIfKilled = false;
break;
}
case Service.START_NOT_STICKY: {
// We are done with the associated start arguments.
r.findDeliveredStart(startId, true);
if (r.getLastStartId() == startId) {
// There is no more work, and this service
// doesn't want to hang around if killed.
r.stopIfKilled = true;
}
break;
}
case Service.START_REDELIVER_INTENT: {
// We'll keep this item until they explicitly
// call stop for it, but keep track of the fact
// that it was delivered.
ServiceRecord.StartItem si = r.findDeliveredStart(startId, false);
if (si != null) {
si.deliveryCount = 0;
si.doneExecutingCount++;
// Don't stop if killed.
r.stopIfKilled = true;
}
break;
}
case Service.START_TASK_REMOVED_COMPLETE: {
// Special processing for onTaskRemoved(). Don't
// impact normal onStartCommand() processing.
r.findDeliveredStart(startId, true);
break;
}
default:
throw new IllegalArgumentException(
"Unknown service start result: " + res);
}
if (res == Service.START_STICKY_COMPATIBILITY) {
r.callStart = false;
}
}
final long origId = Binder.clearCallingIdentity();
serviceDoneExecutingLocked(r, inStopping);
Binder.restoreCallingIdentity(origId);
} else {
}
}