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---
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Service 的绑定原理
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---
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1. 知道 bindService 的用法
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2. 了解 bindService 的大致流程
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3. bindService 涉及哪些参与者，通信过程是怎样的？
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```java
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IRemoteCaller mCaller;
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ServiceConnection mServiceConnection = new ServiceConnection(){
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@Override
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public void onServiceConnected(ComponentName name, IBinder service) {
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mCaller = IRemoteCaller.Stub.asInterface(service);
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mCaller.call();
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}
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}
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Intent service = new Intent(this, MyService.class);
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bindService(service, mServiceConnection, BIND_AUTO_CREATE);
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```
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Bind Service 总体流程：
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```java
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@Override
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boolean bindService(Intent service, ServiceConnection conn, int flags) {
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return bindServiceCommon(service, conn, flags, ...);
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}
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boolean bindServiceCommon(Intent service, ServiceConnection conn, ...) {
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IServiceConnection sd;
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// 为 ServiceConnection 接口生成一个 binder 对象，可用于跨进程传递给 AMS
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sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), mMainThread.getHandler(), flags);
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ActivityManagerNative.getDefult().bindService(mMainThread.getApplicationThread(), service, sd, ...);
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}
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IServiceConnection getServiceDispatcher(ServiceConnection c, ...) {
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ServiceDispatcher sd = null;
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Map<ServiceConnection, ServiceDispatcher> map = mServices.get(context);
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if(map != null){
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sd = map.get(c);
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}
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if(sd == null){
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sd = new ServiceDispatcher(c, context, handler,flags);
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if(map == null){
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map = new ArrayMap<ServiceConnection, ServiceDispatcher>();
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mService.put(context, map);
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}
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map.put(c, sd);
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}
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return sd.getIServiceConnection();
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}
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ServiceDispatcher(ServiceConnection conn, ...){
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mIServiceConnection = new InnerConnection(this);
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mConnection = conn;
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}
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static class InnerConnection extends IServiceConnection.Stub {
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final WeakReference<ServiceDispatcher> mDispatcher;
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public void connected(ComponentName name, IBinder service) {
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LoadedApk.ServiceDispatcher sd = mDispatcher.get();
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if(sd != null){
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sd.connected(name, service);
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}
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}
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}
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void connected(){
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mActivityThread.post(new RunConnection(name, service, 0));
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}
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public void doConnected(ComponentName name, IBinder service) {
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old = mActiveConnections.get(name);
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if(old!=null && old.binder == service){
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return;
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}
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if(service != null){
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info = new ConnectionInfo(service);
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mActiveConnections.put(name, info);
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}else{
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mActiveConnections.remove(name);
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}
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if(old != null){
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mConnection.onServiceDisconnected(name);
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}
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if(service != null){
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mConnection.onServiceConnected(name, service);
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}
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}
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```
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```java
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// AMS#bindServiceLocked
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bindServiceLocked(IApplicationThread caller, ...){
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//...
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if((flag&Context.BIND_AUTO_CREATE)!=0){
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bringUpServiceLocked(s, );
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}
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if(s.app != null && b.intent.received){
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c.conn.connected(s.name, b.intent.binder);
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}else if(!b.intent.requested){
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requestServiceBindingLocked(s, b.intent, false);
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}
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}
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```
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```java
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final String bringUpServiceLocked(ServiceRecord r, ...) {
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if(r.app != null && r.app.thread != null){
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// 如果 Service 已经启动，就执行 Service#onStartCommand
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// 在 bind service 中没啥用
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sendServiceArgsLocked(r, ...);
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return null;
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}
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ProcessRecord app = mAm.getProcessRecordLocked(procName, ...);
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if(app != null && app.thread != null) {
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realStartServiceLocked(r, app, execlnFg);
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return null;
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}
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if(app == null){
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app = mAm.startProcessLocked(procName, ...);
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}
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if(!mPendingService.contains(r)){
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mPendingService.add(r);
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}
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return null;
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}
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```
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```java
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void realStartServiceLocked(ServiceRecord r, ProcessRecord app, ...) {
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r.app = app;
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// scheduleCreateService: 向应用端发起 IPC 调用
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// 应用端收到之后就会去创建 Service，并执行 onCreate 回调
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// r: class ServiceRecord extends Binder{}
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app.thread.scheduleCreateService(r, r.serviceInfo, ...);
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// 请求 Service 发布它的 binder 句柄给 AMS
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requestServiceBindingLocked(r, ...);
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// 触发 Service 的 onStartCommand 回调
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sendServiceArgsLocked(r, ...);
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}
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boolean requestServiceBindingLocked(ServiceRecord r, ...) {
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if(r.app == null || r.app.thread == null){
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return false;
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}
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if((!i.requested||rebind)&&i.apps.size()>0){
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r.app.thread.scheduleBindService(r, rebind, ...);
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if(!rebind){
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i.requested = true;
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}
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i.doRebind = false;
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}
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return true;
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}
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// scheduleBindService 的处理过程
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private void handleBindService(BindServiceData data) {
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Service s = mService.get(data.token);
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if(!data.rebind){
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IBinder binder = s.onBind(data.intent);
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ActivityManagerNative.getDefault().publishService(data.token, data.intent, binder);
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}else {
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s.onRebind(data.intent);
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}
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}
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```
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```java
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// AMS#publishServiceLocked
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void publishServiceLocked(ServiceRecord r, Intent intent, IBinder service) {
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Intent.FilterComparison filter = new Intent.FilterComparison(intent);
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IntentBindRecord b = r.bindings.get(filter);
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if(b!=null && !b.received){
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b.binder = service;
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b.requested = true;
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b.received = true;
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for(int conni=r.connections.size()-1;conni>=0;conni--) {
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ArrayList<ConnectionRecord> clist = r.connections.valueAt(conni);
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for(int i=0;i<clist.size();i++){
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ConnectionRecord c = clist.get(i);
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if(!filter.equals(c.binding.intent.intent)){
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continue;
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}
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c.conn.connected(r.name, service);
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}
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}
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}
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}
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```
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onRebind 什么时候调用？
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```java
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int bindServiceLocked(IApplicationThread caller, IBinder token, ) {
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if(s.app!=null&&b.intent.received){
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if(b.intent.apps.size()==1&&b.intent.doRebind){
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requestServiceBindingLocked(s, b.intent, callerFg, true);
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}
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}
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}
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boolean unbindServiceLocked(IServiceConnection connection) {
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IBinder binder = connection.asBinder();
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ArrayList<ConnectionRecord> clist = mServiceConnections.get(binder);
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while(clist.size()>0){
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ConnectionRecord r = clist.get(0);
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removeConnectionLocked(r, null, null);
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if(clist.size()>0&&clist.get(0)==r){
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clist.remove(0);
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}
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}
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return true;
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}
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void removeConnectionLocked(ConnectionRecord c, ...){
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if(s.app!=null&&s.app.thread!=null&&b.intent.apps.size()==0&&b.intent.hasBound){
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b.intent.hasBound = false;
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b.intent.doRebind = false;
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s.app.thread.scheduleUnbindService(s, b.intent.intent.getIntent());
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}
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}
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private void handleUnbindService(BindServiceData data) {
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Service s = mService.get(data.token);
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boolean doRebind = s.onUnbind(data.intent);
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if(doRebind){
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ActivityManagerNative.getDefault().unbindFinished(doRebind);
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}
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}
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// AMS#unbindFinishedLocked
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void unbindFinishedLocked(ServiceRecord r, Intent intent, boolean doRebind) {
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Intent.FilterComparison filter = new Intent.FilterComparison(intent);
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IntentBindRecord b = r.bindings.get(filter);
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if(b.apps.size()>0&&!inDestorying) {
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}else {
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b.doRebind = true;
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}
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}
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```
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