bindService的过程

    @Override
    public boolean bindService(Intent service, ServiceConnection conn,
            int flags) {
        return mBase.bindService(service, conn, flags);
    }

public abstract class Context

    @Override
    public boolean bindService(Intent service, ServiceConnection conn, int flags) {
        warnIfCallingFromSystemProcess();
        return bindServiceCommon(service, conn, flags, null, mMainThread.getHandler(), null,
                getUser());
    }

    private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags,
            String instanceName, Handler handler, Executor executor, UserHandle user) {
        // Keep this in sync with DevicePolicyManager.bindDeviceAdminServiceAsUser.
        IServiceConnection sd;
        if (conn == null) {
            throw new IllegalArgumentException("connection is null");
        }
        if (handler != null && executor != null) {
            throw new IllegalArgumentException("Handler and Executor both supplied");
        }
        if (mPackageInfo != null) {
            if (executor != null) {
                将ServiceConnection封装为IServiceConnection类型的对象sd，实现跨进程调用
                sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), executor, flags);
            } else {
                sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), handler, flags);
            }
        } else {
            throw new RuntimeException("Not supported in system context");
        }
        validateServiceIntent(service);
        try {
            IBinder token = getActivityToken();
            if (token == null && (flags&BIND_AUTO_CREATE) == 0 && mPackageInfo != null
                    && mPackageInfo.getApplicationInfo().targetSdkVersion
                    < android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
                flags |= BIND_WAIVE_PRIORITY;
            }
            service.prepareToLeaveProcess(this);
            调用AMS的bindIsolatedService方法
            int res = ActivityManager.getService().bindIsolatedService(
                mMainThread.getApplicationThread(), getActivityToken(), service,
                service.resolveTypeIfNeeded(getContentResolver()),
                sd, flags, instanceName, getOpPackageName(), user.getIdentifier());
            if (res < 0) {
                throw new SecurityException(
                        "Not allowed to bind to service " + service);
            }
            return res != 0;
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

 
    public int bindIsolatedService(IApplicationThread caller, IBinder token, Intent service,
            String resolvedType, IServiceConnection connection, int flags, String instanceName,
            String callingPackage, int userId) throws TransactionTooLargeException {
        enforceNotIsolatedCaller("bindService");
 
        // Refuse possible leaked file descriptors
        if (service != null && service.hasFileDescriptors() == true) {
            throw new IllegalArgumentException("File descriptors passed in Intent");
        }
 
        if (callingPackage == null) {
            throw new IllegalArgumentException("callingPackage cannot be null");
        }
 
        // Ensure that instanceName, which is caller provided, does not contain
        // unusual characters.
        if (instanceName != null) {
            for (int i = 0; i < instanceName.length(); ++i) {
                char c = instanceName.charAt(i);
                if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
                            || (c >= '0' && c <= '9') || c == '_' || c == '.')) {
                    throw new IllegalArgumentException("Illegal instanceName");
                }
            }
        }
 
        synchronized(this) {
            return mServices.bindServiceLocked(caller, token, service,
                    resolvedType, connection, flags, instanceName, callingPackage, userId);
        }
    }

int bindServiceLocked(IApplicationThread caller, IBinder token, Intent service,
            String resolvedType, final IServiceConnection connection, int flags,
            String instanceName, String callingPackage, final int userId)
            throws TransactionTooLargeException {
 
            boolean needOomAdj = false;
            if ((flags&Context.BIND_AUTO_CREATE) != 0) {
                s.lastActivity = SystemClock.uptimeMillis();
                needOomAdj = true;
                if (bringUpServiceLocked(s, service.getFlags(), callerFg, false,
                        permissionsReviewRequired, packageFrozen, true) != null) {
                    mAm.updateOomAdjPendingTargetsLocked(OomAdjuster.OOM_ADJ_REASON_BIND_SERVICE);
                    return 0;
                }
            }
            setFgsRestrictionLocked(callingPackage, callingPid, callingUid, service, s, userId,
                    false);
s.app != null 表示Service已经运行，其中s是ServiceRecord类型对象，app是ProcessRecord类型对象
            if (s.app != null) {
                ProcessServiceRecord servicePsr = s.app.mServices;
                if ((flags&Context.BIND_TREAT_LIKE_ACTIVITY) != 0) {
                    servicePsr.setTreatLikeActivity(true);
                }
                if (s.allowlistManager) {
                    servicePsr.mAllowlistManager = true;
                }
                // This could have made the service more important.
                mAm.updateLruProcessLocked(s.app, (callerApp.hasActivitiesOrRecentTasks()
                            && servicePsr.hasClientActivities())
                        || (callerApp.mState.getCurProcState() <= PROCESS_STATE_TOP
                            && (flags & Context.BIND_TREAT_LIKE_ACTIVITY) != 0),
                        b.client);
                needOomAdj = true;
                mAm.enqueueOomAdjTargetLocked(s.app);
            }
b.intent.received表示当前应用程序进程的Client端已经接收到绑定Service时返回的Binder，这样应用程序进程的Client端就可以通过Binder来获取要绑定的Service的访问接口
 
            if (s.app != null && b.intent.received) {
                // Service is already running, so we can immediately
                // publish the connection.
                try {
c.conn指的是IServiceConnection，它的具体实现为ServiceDispatcher.InnerConnection，其中ServiceDispatcher是LoadedApk的内部类，InnerConnection的connected方法内部会调用H的post方法向主线程发送消息，从而解决当前应用程序进程和Service跨进程通信的问题
                    c.conn.connected(s.name, b.intent.binder, false);
                } catch (Exception e) {
                    Slog.w(TAG, "Failure sending service " + s.shortInstanceName
                            + " to connection " + c.conn.asBinder()
                            + " (in " + c.binding.client.processName + ")", e);
                }
 
                // If this is the first app connected back to this binding,
                // and the service had previously asked to be told when
                // rebound, then do so.
如果当前应用程序进程的Client端第一次与Service进行绑定的，并且Service已经调用过onUnBind方法
                if (b.intent.apps.size() == 1 && b.intent.doRebind) {
                    requestServiceBindingLocked(s, b.intent, callerFg, true);
                }
            } else if (!b.intent.requested) {如果应用程序进程的Client端没有发送过绑定Service的请求
                requestServiceBindingLocked(s, b.intent, callerFg, false);
            }
}

    private final boolean requestServiceBindingLocked(ServiceRecord r, IntentBindRecord i,
            boolean execInFg, boolean rebind) throws TransactionTooLargeException {
        if (r.app == null || r.app.getThread() == null) {
            // If service is not currently running, can't yet bind.
            return false;
        }
        if (DEBUG_SERVICE) Slog.d(TAG_SERVICE, "requestBind " + i + ": requested=" + i.requested
                + " rebind=" + rebind);
i.requested表示是否发送过绑定Service的请求
        if ((!i.requested || rebind) && i.apps.size() > 0) {
            try {
                bumpServiceExecutingLocked(r, execInFg, "bind",
                        OomAdjuster.OOM_ADJ_REASON_BIND_SERVICE);
r.app.thread的类型为IApplicationThread，是ActivityThread的内部类ApplicationThread
                r.app.getThread().scheduleBindService(r, i.intent.getIntent(), rebind,
                        r.app.mState.getReportedProcState());
                if (!rebind) {
                    i.requested = true;
                }
                i.hasBound = true;
                i.doRebind = false;
            } catch (TransactionTooLargeException e) {
                // Keep the executeNesting count accurate.
                if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "Crashed while binding " + r, e);
                final boolean inDestroying = mDestroyingServices.contains(r);
                serviceDoneExecutingLocked(r, inDestroying, inDestroying, false);
                throw e;
            } catch (RemoteException e) {
                if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "Crashed while binding " + r);
                // Keep the executeNesting count accurate.
                final boolean inDestroying = mDestroyingServices.contains(r);
                serviceDoneExecutingLocked(r, inDestroying, inDestroying, false);
                return false;
            }
        }
        return true;
    }

ProcessRecord app;      // where this service is running or null.

    @GuardedBy(anyOf = {"mService", "mProcLock"})
    IApplicationThread getThread() {
        return mThread;
    }

private class ApplicationThread extends IApplicationThread.Stub {

        public final void scheduleBindService(IBinder token, Intent intent,
                boolean rebind, int processState) {
            updateProcessState(processState, false);
            BindServiceData s = new BindServiceData();
            s.token = token;
            s.intent = intent;
            s.rebind = rebind;
 
            if (DEBUG_SERVICE)
                Slog.v(TAG, "scheduleBindService token=" + token + " intent=" + intent + " uid="
                        + Binder.getCallingUid() + " pid=" + Binder.getCallingPid());
            sendMessage(H.BIND_SERVICE, s);
        }

    private void sendMessage(int what, Object obj, int arg1, int arg2, boolean async) {
        if (DEBUG_MESSAGES) {
            Slog.v(TAG,
                    "SCHEDULE " + what + " " + mH.codeToString(what) + ": " + arg1 + " / " + obj);
        }
        Message msg = Message.obtain();
        msg.what = what;
        msg.obj = obj;
        msg.arg1 = arg1;
        msg.arg2 = arg2;
        if (async) {
            msg.setAsynchronous(true);
        }
        mH.sendMessage(msg);
    }

                case BIND_SERVICE:
                    Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceBind");
                    handleBindService((BindServiceData)msg.obj);
                    Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
                    break;

    private void handleBindService(BindServiceData data) {
        CreateServiceData createData = mServicesData.get(data.token);
        Service s = mServices.get(data.token);获取要绑定的Service
        if (DEBUG_SERVICE)
            Slog.v(TAG, "handleBindService s=" + s + " rebind=" + data.rebind);
        if (s != null) {
            try {
                data.intent.setExtrasClassLoader(s.getClassLoader());
                data.intent.prepareToEnterProcess(isProtectedComponent(createData.info),
                        s.getAttributionSource());
                try {
                    if (!data.rebind) {如果没有绑定 调用Service的onBind方法，这样Service处于绑定状态了
                        IBinder binder = s.onBind(data.intent);
                        ActivityManager.getService().publishService(
                                data.token, data.intent, binder);
                    } else {绑定过就调用Service的onRebind方法
                        s.onRebind(data.intent);
                        ActivityManager.getService().serviceDoneExecuting(
                                data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
                    }
                } catch (RemoteException ex) {
                    throw ex.rethrowFromSystemServer();
                }
            } catch (Exception e) {
                if (!mInstrumentation.onException(s, e)) {
                    throw new RuntimeException(
                            "Unable to bind to service " + s
                            + " with " + data.intent + ": " + e.toString(), e);
                }
            }
        }
    }

    public void publishService(IBinder token, Intent intent, IBinder service) {
        // Refuse possible leaked file descriptors
        if (intent != null && intent.hasFileDescriptors() == true) {
            throw new IllegalArgumentException("File descriptors passed in Intent");
        }
 
        synchronized(this) {
            if (!(token instanceof ServiceRecord)) {
                throw new IllegalArgumentException("Invalid service token");
            }
            mServices.publishServiceLocked((ServiceRecord)token, intent, service);
        }
    }

    void publishServiceLocked(ServiceRecord r, Intent intent, IBinder service) {
        final long origId = Binder.clearCallingIdentity();
        try {
            if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "PUBLISHING " + r
                    + " " + intent + ": " + service);
            if (r != null) {
                Intent.FilterComparison filter
                        = new Intent.FilterComparison(intent);
                IntentBindRecord b = r.bindings.get(filter);
                if (b != null && !b.received) {
                    b.binder = service;
                    b.requested = true;
                    b.received = true;
                    ArrayMap<IBinder, ArrayList<ConnectionRecord>> connections = r.getConnections();
                    for (int conni = connections.size() - 1; conni >= 0; conni--) {
                        ArrayList<ConnectionRecord> clist = connections.valueAt(conni);
                        for (int i=0; i<clist.size(); i++) {
                            ConnectionRecord c = clist.get(i);
                            if (!filter.equals(c.binding.intent.intent)) {
                                if (DEBUG_SERVICE) Slog.v(
                                        TAG_SERVICE, "Not publishing to: " + c);
                                if (DEBUG_SERVICE) Slog.v(
                                        TAG_SERVICE, "Bound intent: " + c.binding.intent.intent);
                                if (DEBUG_SERVICE) Slog.v(
                                        TAG_SERVICE, "Published intent: " + intent);
                                continue;
                            }
                            if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "Publishing to: " + c);
                            try {
                                c.conn.connected(r.name, service, false);
                            } catch (Exception e) {
                                Slog.w(TAG, "Failure sending service " + r.shortInstanceName
                                      + " to connection " + c.conn.asBinder()
                                      + " (in " + c.binding.client.processName + ")", e);
                            }
                        }
                    }
                }
 
                serviceDoneExecutingLocked(r, mDestroyingServices.contains(r), false, false);
            }
        } finally {
            Binder.restoreCallingIdentity(origId);
        }
    }

ConnectionRecord c = clist.get(i);
 
final class ConnectionRecord {
final AppBindRecord binding;    // The application/service binding.
final ActivityServiceConnectionsHolder<ConnectionRecord> activity;  // If non-null, the owning activity.
final IServiceConnection conn; 

static final class ServiceDispatcher {
        private final ServiceDispatcher.InnerConnection mIServiceConnection;
        @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
        private final ServiceConnection mConnection;
        @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023)
        private final Context mContext;
        private final Handler mActivityThread;
        private final Executor mActivityExecutor;
        private final ServiceConnectionLeaked mLocation;
        private final int mFlags;
 
        private RuntimeException mUnbindLocation;
 
        private boolean mForgotten;
 
        private static class ConnectionInfo {
            IBinder binder;
            IBinder.DeathRecipient deathMonitor;
        }
 
        private static class InnerConnection extends IServiceConnection.Stub {
 @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
            final WeakReference<LoadedApk.ServiceDispatcher> mDispatcher;
 
            InnerConnection(LoadedApk.ServiceDispatcher sd) {
                mDispatcher = new WeakReference<LoadedApk.ServiceDispatcher>(sd);
            }
 
            public void connected(ComponentName name, IBinder service, boolean dead)
                    throws RemoteException {
                LoadedApk.ServiceDispatcher sd = mDispatcher.get();
                if (sd != null) {
                    sd.connected(name, service, dead);
                }
            }

        public void connected(ComponentName name, IBinder service, boolean dead) {
            if (mActivityExecutor != null) {
                mActivityExecutor.execute(new RunConnection(name, service, 0, dead));
            } else if (mActivityThread != null) {
                mActivityThread.post(new RunConnection(name, service, 0, dead));
            } else {
                doConnected(name, service, dead);
            }
        }

        private final class RunConnection implements Runnable {
            RunConnection(ComponentName name, IBinder service, int command, boolean dead) {
                mName = name;
                mService = service;
                mCommand = command;
                mDead = dead;
            }
 
            public void run() {
                if (mCommand == 0) {
                    doConnected(mName, mService, mDead);
                } else if (mCommand == 1) {
                    doDeath(mName, mService);
                }
            }
 
            final ComponentName mName;
            final IBinder mService;
            final int mCommand;
            final boolean mDead;
        }

 public void doConnected(ComponentName name, IBinder service, boolean dead) {
 
 if (service != null) {
         mConnection.onServiceConnected(name, service);
     } else {
         // The binding machinery worked, but the remote returned null from onBind().
         mConnection.onNullBinding(name);
      }
}