android4.4组件分析--service组件-bindService源码分析

6.1.1.    bindService

    因为有前面分析startService的代码实现过程,则对于bindService的代码分析就不用那么详细介绍,在介绍流程的同时更关注一些细节上的部分。

 

首先,bindService也是通过 ContextWrapper.bindService,再到ContextImplbindService,然后是bindServiceCommon,需要注意的是,传入的ServiceConnection被转换成IServiceConnection类型,

    private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags,

            UserHandle user) {

        IServiceConnection sd;

            sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),

                    mMainThread.getHandler(), flags);

            int res = ActivityManagerNative.getDefault().bindService(

                mMainThread.getApplicationThread(), getActivityToken(),

                service, service.resolveTypeIfNeeded(getContentResolver()),

                sd, flags, user.getIdentifier());

}

 

接下去是进入AMS的bindService,再调用ActiveServices.java 的bindServiceLocked,它会把IServiceConnection实例存放到ConnectionRecord里面,并执行bringUpServiceLocked,

    int bindServiceLocked(IApplicationThread caller, IBinder token,

            Intent service, String resolvedType,

            IServiceConnection connection, int flags, int userId) {

            ConnectionRecord c = new ConnectionRecord(b, activity,

                    connection, flags, clientLabel, clientIntent);

 

            IBinder binder = connection.asBinder();

 

            if ((flags&Context.BIND_AUTO_CREATE) != 0) {

                s.lastActivity = SystemClock.uptimeMillis();

                if (bringUpServiceLocked(s, service.getFlags(), callerFg, false) != null){

                    return 0;

                }

            }

            if (s.app != null && b.intent.received) {

                // Service is already running, so we can immediately

                // publish the connection.

                try {

                    c.conn.connected(s.name, b.intent.binder);

                } catch (Exception e) {

                    Slog.w(TAG, "Failure sending service " + s.shortName

                            + " 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.

                if (b.intent.apps.size() == 1 && b.intent.doRebind) {

                    requestServiceBindingLocked(s, b.intent, callerFg, true);

                }

            } else if (!b.intent.requested) {

                requestServiceBindingLocked(s, b.intent, callerFg, false);

            }

}

 

 

根据之前的分析ServiceLocked会调用realStartServiceLocked,而realStartServiceLocked则先调用scheduleCreateService,完成service的创建和Oncreate()的执行,然后执行requestServiceBindingsLocked,这个是bind服务相关处理,最后是sendServiceArgsLocked,这个是Start服务的处理。

    private final void realStartServiceLocked(ServiceRecord r,

            ProcessRecord app, boolean execInFg) throws RemoteException {

            app.thread.scheduleCreateService(r, r.serviceInfo,                    mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),                 app.repProcState);

        requestServiceBindingsLocked(r, execInFg);

       sendServiceArgsLocked(r, execInFg, true);

}

 

 

requestServiceBindingsLocked再调用ActivityThread的方法scheduleBindService,在ActivityThread.java 中,它发出一个BIND_SERVICE事件,被handleBindService处理,

    private void handleBindService(BindServiceData data) {

                    if (!data.rebind) {

                        IBinder binder = s.onBind(data.intent);

                        ActivityManagerNative.getDefault().publishService(

                                data.token, data.intent, binder);

                    } else {

                        s.onRebind(data.intent);

                        ActivityManagerNative.getDefault().serviceDoneExecuting(

                                data.token, 0, 0, 0);

                    }

这里先调用服务的onBind方法,因为服务是重载的,所以会执行具体服务类的方法,并返回服务里的binder实例,这个binder随后会被使用到,

其中AMS的publishService方法被调用,在 ActivityManagerService.java中又会调用   ActiveServices.java 的publishServiceLocked,

    void publishServiceLocked(ServiceRecord r, Intent intent, IBinder service) {

                    for (int conni=r.connections.size()-1; conni>=0; conni--) {

                        ArrayList clist = r.connections.valueAt(conni);

                        for (int i=0; i

                            ConnectionRecord c = clist.get(i);

                            try {

                                c.conn.connected(r.name, service);

                             } …

 

                serviceDoneExecutingLocked(r, mDestroyingServices.contains(r), false);

这里主要调用到c.conn.connected,c就是ConnectionRecord,其成员conn是一个IServiceConnection类型实例,这在前面有提到,connected则是其实现类的方法。

 

对于IServiceConnection,它是一个接口,位置在(frameworks\base): core/java/android/app/IServiceConnection.aidlaidl定义如下,它只有一个接口方法connected

oneway interface IServiceConnection {

    void connected(in ComponentName name, IBinder service);

}

 

其服务端的实现在LoadedApk.java,如下,InnerConnection类是在ServiceDispatcher的内部类,并在ServiceDispatcher的构造函数里面实例化的,其方法connected也是调用的ServiceDispatcher的方法connected

        private static class InnerConnection extendsIServiceConnection.Stub {

            final WeakReference mDispatcher;

 

            InnerConnection(LoadedApk.ServiceDispatcher sd) {

                mDispatcher = new WeakReference(sd);

            }

 

            public void connected(ComponentName name, IBinder service) throws RemoteException {

                LoadedApk.ServiceDispatcher sd = mDispatcher.get();

                if (sd != null) {

                    sd.connected(name, service);

                }

            }

        }

 

        ServiceDispatcher(ServiceConnection conn,

                Context context, Handler activityThread, int flags) {

            mIServiceConnection = new InnerConnection(this);

            mConnection = conn;

            mContext = context;

            mActivityThread = activityThread;

            mLocation = new ServiceConnectionLeaked(null);

            mLocation.fillInStackTrace();

            mFlags = flags;

        }

 

这里就再回到我们前面的ContextImpl里面bindServiceCommon方法里面,这里进行ServiceConnection转化为IServiceConnection时,调用了mPackageInfo.getServiceDispatchermPackageInfo就是一个LoadedApk实例,

    /*package*/ LoadedApk mPackageInfo;

 

    private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags,

            UserHandle user) {

        IServiceConnection sd;

 

            sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),

                    mMainThread.getHandler(), flags);

}

 

所以,getServiceDispatcher会创建一个ServiceDispatcher实例,并将ServiceDispatcher实例和ServiceConnection实例形成KV对,并在ServiceDispatcher的构造函数里将ServiceConnection实例c赋值给ServiceConnection的成员变量mConnection

    public final IServiceConnection getServiceDispatcher(ServiceConnection c,

            Context context, Handler handler, int flags) {

        synchronized (mServices) {

            LoadedApk.ServiceDispatcher sd = null;

            ArrayMap map = mServices.get(context);

            if (map != null) {

                sd = map.get(c);

            }

            if (sd == null) {

                sd = new ServiceDispatcher(c, context, handler, flags);

                if (map == null) {

                    map = new ArrayMap();

                    mServices.put(context, map);

                }

                map.put(c, sd);

}

 

 

这样,在执行ServiceDispatcherconnected方法时,就会调用到ServiceConnection的

onServiceConnected,完成绑定ServiceConnection的触发。

        public void doConnected(ComponentName name, IBinder service) {

            if (old != null) {

                mConnection.onServiceDisconnected(name);

            }

            // If there is a new service, it is now connected.

            if (service != null) {

                mConnection.onServiceConnected(name, service);

            }

}

 

至此,就执行完了bindService的主要过程。

 

我们下面用一张图来总结这个流程,




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