车辆

管理 Qt gRPC™客户端和 C++gRPC 服务器之间的两个线程连接。

该示例模拟了一个车辆仪表盘，显示gRPC 服务器发送的数据。

车辆示例仪表板截图

示例代码包含以下组件：

vehicle_client Qt 客户端应用程序，使用gRPC qt_add_protobuf()和qt_add_grpc()CMake 函数生成消息和服务 Qt 代码。
vehicle_server 调用 C++ 插件生成服务器代码并执行简单服务器逻辑的应用程序。gRPC

注意： 您需要安装 C++gRPC 插件。详情请点击此处：模块先决条件

两个组件都使用从文件vehicleservice.proto 和navigationservice.proto 中描述的 protobuf 模式生成的信息。

车辆服务：

message SpeedMsg {
    int32 speed = 1;
}

message RpmMsg {
    int32 rpm = 1;
}

message AutonomyMsg {
    int32 autonomy = 1;
}

service VehicleService {
    rpc getSpeedStream(google.protobuf.Empty) returns (stream SpeedMsg) {}
    rpc getRpmStream(google.protobuf.Empty) returns (stream RpmMsg) {}
    rpc getAutonomy(google.protobuf.Empty) returns (AutonomyMsg) {}
}

导航服务

enum DirectionEnum {
    RIGHT = 0;
    LEFT = 1;
    STRAIGHT = 2;
    BACKWARD = 3;
}

message NavigationMsg {
    int32 totalDistance = 1;
    int32 traveledDistance = 2;
    DirectionEnum direction = 3;
    string street = 4;
}

service NavigationService {
    rpc getNavigationStream(google.protobuf.Empty) returns (stream NavigationMsg) {}
}

VehicleManager C++ 单例使用两个QThread 实例与服务器并行通信。这些线程具有不同的gRPC 连接类型。本例中有两种类型：

服务器流 RPC 例如，车辆线程的速度流。它使用两个回调函数：QGrpcServerStream::messageReceived 和QGrpcOperation::finished

Empty speedRequest; m_streamSpeed=  m_client->getSpeedStream(speedRequest); connect(m_streamSpeed.get(), &QGrpcServerStream::messageReceived, this, [this]() {if(const autospeedResponse=  m_streamSpeed->read<SpeedMsg>()) {emitspeedChanged(speedResponse->speed()); } }); connect( m_streamSpeed.get(), &QGrpcServerStream::finished, this,[this](constQGrpcStatus&status) {if(!status.isOk()) {autoerror=QString("Stream error fetching speed %1 (%2)").arg(status.message()).arg(QVariant::fromValue(status.code()).toString());emitconnectionError(error)；            qWarning() << error;
           return; }}、    Qt::SingleShotConnection);

一元 RPC RPCgetAutonomy 操作是一元 RPC。它只返回一个响应。它只与QGrpcOperation::finished 信号相连。

空 autonomyRequest; std::unique_ptr<QGrpcCallReply>autonomyReply=  m_client->getAutonomy(autonomyRequest);const auto *autonomyReplyPtr =autonomyReply.get(); connect( autonomyReplyPtr, &QGrpcCallReply::finished, this,[this,autonomyReply=std::move(autonomyReply)](constQGrpcStatus&status) {if(!status.isOk()) {autoerror=QString("Call error fetching autonomy %1 (%2)").arg(status.message()).arg(QVariant::fromValue(status.code()).toString());emitconnectionError(error)；            qWarning() << error;
           return; }if(const autoautonomyMsg=  autonomyReply->read<AutonomyMsg>()) {emitautonomyChanged(autonomyMsg->autonomy()); }}、    Qt::SingleShotConnection);

客户端主窗口界面在 Main.qml 文件中定义。它使用 QMLConnections 类型，以便将VehicleManager C++ 单例的信号连接到自定义插槽：

    Connections {
        target: VehicleManager

        // This slot will be executed when the VehicleManager::totalDistanceChanged
        // signal is emitted
        function onTotalDistanceChanged(distance: int): void {
            root.totalDistance = distance;
        }

        function onSpeedChanged(speed: int): void {
            root.speed = speed;
        }

        function onRpmChanged(rpm: int): void {
            root.rpm = rpm;
        }

        function onTraveledDistanceChanged(distance: int): void {
            root.traveledDistance = distance;
        }

        function onDirectionChanged(direction: int): void {
            if (direction == VehicleManager.RIGHT) {
                root.directionImageSource = "qrc:/direction_right.svg";
            } else if (direction == VehicleManager.LEFT) {
                root.directionImageSource =  "qrc:/direction_left.svg";
            } else if (direction == VehicleManager.STRAIGHT) {
                root.directionImageSource =  "qrc:/direction_straight.svg";
            } else {
                root.directionImageSource =  "";
            }
        }

收到响应后，客户端窗口会用收到的数据更新用户界面。这样，信息就能在不同线程中接收，并通过信号以线程安全的方式发送到客户端用户界面。

示例项目 @ code.qt.io

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