状态机及策略模式的使用

状态机：

// 定义状态枚举
enum State {
    FLYING, LANDING, RETURNING, PAUSED
}

// 定义事件枚举
enum Event {
    BATTERY_LOW, GPS_LOST
}

// 状态机类
class DroneStateMachine {
    private State currentState;

    public DroneStateMachine() {
        // 初始状态
        currentState = State.FLYING;
    }

    // 发送事件，处理状态转移
    public void sendEvent(Event event) {
        switch (currentState) {
            case FLYING:
                if (event == Event.BATTERY_LOW) {
                    System.out.println("Battery low, initiating return...");
                    currentState = State.RETURNING;  // 电池低，返航
                } else if (event == Event.GPS_LOST) {
                    System.out.println("GPS lost, pausing...");
                    currentState = State.PAUSED;  // GPS丢失，暂停
                }
                break;
            case PAUSED:
                if (event == Event.BATTERY_LOW) {
                    System.out.println("Battery low, initiating return...");
                    currentState = State.RETURNING;
                }
                break;
            case RETURNING:
                if (event == Event.GPS_LOST) {
                    System.out.println("GPS lost, pausing...");
                    currentState = State.PAUSED;
                }
                break;
            default:
                break;
        }
    }

    // 获取当前状态
    public State getCurrentState() {
        return currentState;
    }
}

public class Main {
    public static void main(String[] args) {
        DroneStateMachine droneStateMachine = new DroneStateMachine();
        
        // 模拟触发事件
        droneStateMachine.sendEvent(Event.BATTERY_LOW);  // 电池低，触发返航
        System.out.println("Current state: " + droneStateMachine.getCurrentState());

        droneStateMachine.sendEvent(Event.GPS_LOST);  // GPS丢失，触发暂停
        System.out.println("Current state: " + droneStateMachine.getCurrentState());
    }
}

最后调用时，只需要关心无人机本身当前的状态即可，根据当前的状态做出对应事件触发。

策略模式：

1.定义飞行策略接口

public interface FlightStrategy {
    void execute();
}

2.实现具体策略类

// 电量低策略
public class LowBatteryStrategy implements FlightStrategy {
    @Override
    public void execute() {
        System.out.println("电量过低，执行紧急降落！");
        // 控制硬件：sendCommand("LAND_IMMEDIATELY");
    }
}

// GPS 丢失策略
public class GpsLostStrategy implements FlightStrategy {
    @Override
    public void execute() {
        System.out.println("GPS 丢失，悬停等待...");
        // 控制硬件：sendCommand("HOVER");
    }
}

// 信号丢失策略
public class SignalLostStrategy implements FlightStrategy {
    @Override
    public void execute() {
        System.out.println("信号丢失，执行自动返航！");
        // 控制硬件：sendCommand("RETURN_HOME");
    }
}

3.定义策略上下文类（封装切换逻辑）

public class FlightContext {
    private FlightStrategy strategy;

    public void setStrategy(FlightStrategy strategy) {
        this.strategy = strategy;
    }

    public void handleFlightEvent() {
        if (strategy != null) {
            strategy.execute();
        }
    }
}

4.在主业务中使用策略

public void handleEvent(DroneEvent event) {
    switch (event) {
        case BATTERY_LOW:
            context.setStrategy(new LowBatteryStrategy());
            break;
        case GPS_LOST:
            context.setStrategy(new GpsLostStrategy());
            break;
        case SIGNAL_LOST:
            context.setStrategy(new SignalLostStrategy());
            break;
    }

    context.handleFlightEvent();
}