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Service 的绑定原理
---
1. 知道 bindService 的用法
2. 了解 bindService 的大致流程
3. bindService 涉及哪些参与者,通信过程是怎样的?
```java
IRemoteCaller mCaller;
ServiceConnection mServiceConnection = new ServiceConnection(){
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
mCaller = IRemoteCaller.Stub.asInterface(service);
mCaller.call();
}
}
Intent service = new Intent(this, MyService.class);
bindService(service, mServiceConnection, BIND_AUTO_CREATE);
```
Bind Service 总体流程:
![](https://i.loli.net/2020/03/24/F4HYsiel7phDGBw.png)
```java
@Override
boolean bindService(Intent service, ServiceConnection conn, int flags) {
return bindServiceCommon(service, conn, flags, ...);
}
boolean bindServiceCommon(Intent service, ServiceConnection conn, ...) {
IServiceConnection sd;
// 为 ServiceConnection 接口生成一个 binder 对象,可用于跨进程传递给 AMS
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(), mMainThread.getHandler(), flags);
ActivityManagerNative.getDefult().bindService(mMainThread.getApplicationThread(), service, sd, ...);
}
IServiceConnection getServiceDispatcher(ServiceConnection c, ...) {
ServiceDispatcher sd = null;
Map<ServiceConnection, ServiceDispatcher> 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<ServiceConnection, ServiceDispatcher>();
mService.put(context, map);
}
map.put(c, sd);
}
return sd.getIServiceConnection();
}
ServiceDispatcher(ServiceConnection conn, ...){
mIServiceConnection = new InnerConnection(this);
mConnection = conn;
}
static class InnerConnection extends IServiceConnection.Stub {
final WeakReference<ServiceDispatcher> mDispatcher;
public void connected(ComponentName name, IBinder service) {
LoadedApk.ServiceDispatcher sd = mDispatcher.get();
if(sd != null){
sd.connected(name, service);
}
}
}
void connected(){
mActivityThread.post(new RunConnection(name, service, 0));
}
public void doConnected(ComponentName name, IBinder service) {
old = mActiveConnections.get(name);
if(old!=null && old.binder == service){
return;
}
if(service != null){
info = new ConnectionInfo(service);
mActiveConnections.put(name, info);
}else{
mActiveConnections.remove(name);
}
if(old != null){
mConnection.onServiceDisconnected(name);
}
if(service != null){
mConnection.onServiceConnected(name, service);
}
}
```
```java
// AMS#bindServiceLocked
bindServiceLocked(IApplicationThread caller, ...){
//...
if((flag&Context.BIND_AUTO_CREATE)!=0){
bringUpServiceLocked(s, );
}
if(s.app != null && b.intent.received){
c.conn.connected(s.name, b.intent.binder);
}else if(!b.intent.requested){
requestServiceBindingLocked(s, b.intent, false);
}
}
```