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Android AB升级（三） - update engine架构概述

news 2025/11/14 7:26:31

update engine是通过AIDL对上层client端和server端分离，实现跨进程。上层提供服务绑定接口，以及升级触发和回调接口，底层实现升级的具体逻辑。本篇只是简单梳理下流程流转的过程。

1. 应用升级接口相关文件

1.framework层应用接口（systemApi）

frameworks/base/core/java/android/os/UpdateEngineCallback.java
frameworks/base/core/java/android/os/UpdateEngine.java

2.AIDL接口文件：

system/update_engine/binder_bindings/android/os/IUpdateEngine.aidl
system/update_engine/binder_bindings/android/os/IUpdateEngineCallback.aidl

3.服务端接口文件：

继承BnUpdateEngine： system/update_engine/binder_service_android.h
继承BnUpdateEngineCallback： system/update_engine/update_engine_client_android.cc

1.1. UpdateEngine类接口

UpdateEngine类（@SystemApi）主要提供bind和applyPayload接口给应用

1.1.1. 代码流程（bind和applyPayload）

1.UpdateEngine.java

bind(final UpdateEngineCallback callback, final Handler handler) 主要接受UpdateEngineCallback对象，同步代码块中会实现callback的两个接口，获取升级服务的状态码和结果错误码
applyPayload传递升级包路径大小等信息，并会传递到服务端进行实际逻辑的操作

//frameworks/base/core/java/android/os/UpdateEngine.java//传递升级包信息public void applyPayload(String url, long offset, long size, String[] headerKeyValuePairs) {try {mUpdateEngine.applyPayload(url, offset, size, headerKeyValuePairs);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}}public boolean bind(final UpdateEngineCallback callback, final Handler handler) {synchronized (mUpdateEngineCallbackLock) {//IUpdateEngineCallback对象mUpdateEngineCallback = new IUpdateEngineCallback.Stub() {//重写回调类的接口，其中会调用到服务端的对应实现接口@Overridepublic void onStatusUpdate(final int status, final float percent) {if (handler != null) {handler.post(new Runnable() {@Overridepublic void run() {callback.onStatusUpdate(status, percent);}});} else {callback.onStatusUpdate(status, percent);}}@Overridepublic void onPayloadApplicationComplete(final int errorCode) {if (handler != null) {handler.post(new Runnable() {@Overridepublic void run() {callback.onPayloadApplicationComplete(errorCode);}});} else {callback.onPayloadApplicationComplete(errorCode);}}};try {return mUpdateEngine.bind(mUpdateEngineCallback);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}}}

2.AIDL接口

interface IUpdateEngine {/** @hide */void applyPayload(String url,in long payload_offset,in long payload_size,in String[] headerKeyValuePairs);/** @hide */boolean bind(IUpdateEngineCallback callback);....

3.服务端接口

//system/update_engine/binder_service_android.h
class BinderUpdateEngineAndroidService : public android::os::BnUpdateEngine,public ServiceObserverInterface {...//system/update_engine/binder_service_android.cc
Status BinderUpdateEngineAndroidService::applyPayload(const android::String16& url,int64_t payload_offset,int64_t payload_size,const std::vector<android::String16>& header_kv_pairs) {const std::string payload_url{android::String8{url}.string()};std::vector<std::string> str_headers;str_headers.reserve(header_kv_pairs.size());for (const auto& header : header_kv_pairs) {str_headers.emplace_back(android::String8{header}.string());}brillo::ErrorPtr error;//调用system/update_engine/update_attempter_android.cc的接口if (!service_delegate_->ApplyPayload(payload_url, payload_offset, payload_size, str_headers, &error)) {return ErrorPtrToStatus(error);}return Status::ok();
}Status BinderUpdateEngineAndroidService::bind(const android::sp<IUpdateEngineCallback>& callback, bool* return_value) {callbacks_.emplace_back(callback);const android::sp<IBinder>& callback_binder =IUpdateEngineCallback::asBinder(callback);auto binder_wrapper = android::BinderWrapper::Get();binder_wrapper->RegisterForDeathNotifications(callback_binder,base::Bind(base::IgnoreResult(&BinderUpdateEngineAndroidService::UnbindCallback),base::Unretained(this),base::Unretained(callback_binder.get())));// Send an status update on connection (except when no update sent so far),// since the status update is oneway and we don't need to wait for the// response.if (last_status_ != -1)callback->onStatusUpdate(last_status_, last_progress_);*return_value = true;return Status::ok();
}

1.2. UpdateEngineCallback类接口

主要是onStatusUpdate和onPayloadApplicationComplete接口

1.2.1. 代码流程（onStatusUpdate和onPayloadApplicationComplete）

1.抽象类，实现在UpdateEngine的bind方法中：

//frameworks/base/core/java/android/os/UpdateEngineCallback.java
@SystemApi
public abstract class UpdateEngineCallback {public abstract void onStatusUpdate(int status, float percent);public abstract void onPayloadApplicationComplete(int errorCode);
}

2.AIDL接口：

//system/update_engine/binder_bindings/android/os/IUpdateEngineCallback.aidl
oneway interface IUpdateEngineCallback {/** @hide */void onStatusUpdate(int status_code, float percentage);/** @hide */void onPayloadApplicationComplete(int error_code);
}

3.服务端接口：

//system/update_engine/update_engine_client_android.cc
private:class UECallback : public android::os::BnUpdateEngineCallback {public:explicit UECallback(UpdateEngineClientAndroid* client) : client_(client) {}// android::os::BnUpdateEngineCallback overrides.Status onStatusUpdate(int status_code, float progress) override;Status onPayloadApplicationComplete(int error_code) override;private:UpdateEngineClientAndroid* client_;};
...android::sp<android::os::IUpdateEngine> service_;android::sp<android::os::BnUpdateEngineCallback> callback_;
};
//升级过程中会打印这两个接口的日志
Status UpdateEngineClientAndroid::UECallback::onStatusUpdate(int status_code,float progress) {update_engine::UpdateStatus status =static_cast<update_engine::UpdateStatus>(status_code);LOG(INFO) << "onStatusUpdate(" << UpdateStatusToString(status) << " ("<< status_code << "), " << progress << ")";return Status::ok();
}Status UpdateEngineClientAndroid::UECallback::onPayloadApplicationComplete(int error_code) {ErrorCode code = static_cast<ErrorCode>(error_code);LOG(INFO) << "onPayloadApplicationComplete(" << utils::ErrorCodeToString(code)<< " (" << error_code << "))";client_->ExitWhenIdle((code == ErrorCode::kSuccess || code == ErrorCode::kUpdatedButNotActive)? EX_OK: 1);return Status::ok();
}