软工随笔（软件工程日报）

今天完成了一个地铁售票计算票价的android app；
代码如下：
package com.example.subwayapp;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;

public class MainActivity extends AppCompatActivity {

private Spinner startStationSpinner, endStationSpinner;
private EditText ticketCountEditText;
private Button buyTicketButton;
private TextView resultTextView;

// 石家庄地铁线路信息
private static final List<String> LINE_1 = List.of("西王", "时光街", "长城桥", "和平医院", "烈士陵园", "新百广场", "解放广场", "平安大街", "北国商城", "博物院", "体育场", "北宋", "谈固", "朝晖桥", "白佛", "留村", "火炬广场", "石家庄东站", "南村", "洨河大道", "西庄", "东庄", "会展中心", "商务中心", "园博园", "福泽");
private static final List<String> LINE_2 = List.of("嘉华", "南位", "塔坛", "塔谈南", "石家庄站", "元村", "欧韵公园", "槐中路", "裕华路", "北国商城", "长安公园", "建和桥", "义堂", "庄窠·铁道大学", "柳辛庄");
private static final List<String> LINE_3 = List.of("西三庄", "高柱", "柏林庄", "市庄", "市二中", "新百广场", "东里", "槐安桥", "西三教", "石家庄站", "汇通路", "孙村", "塔冢", "东王", "南王", "位同", "东二环南路", "西仰陵", "中仰陵", "南豆", "太行南大街", "东乡");

private static final Map<String, List<String>> STATION_LINES = new HashMap<>();
private static final Map<String, List<String>> GRAPH = new HashMap<>();

static {
    // 初始化站点和线路的映射
    for (String station : LINE_1) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            STATION_LINES.computeIfAbsent(station, k -> new ArrayList<>()).add("1号线");
        }
    }
    for (String station : LINE_2) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            STATION_LINES.computeIfAbsent(station, k -> new ArrayList<>()).add("2号线");
        }
    }
    for (String station : LINE_3) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            STATION_LINES.computeIfAbsent(station, k -> new ArrayList<>()).add("3号线");
        }
    }

    // 构建图
    buildGraph(LINE_1);
    buildGraph(LINE_2);
    buildGraph(LINE_3);
}

private static void buildGraph(List<String> line) {
    for (int i = 0; i < line.size(); i++) {
        String station = line.get(i);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            GRAPH.computeIfAbsent(station, k -> new ArrayList<>());
        }
        if (i > 0) {
            GRAPH.get(station).add(line.get(i - 1));
        }
        if (i < line.size() - 1) {
            GRAPH.get(station).add(line.get(i + 1));
        }
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    startStationSpinner = findViewById(R.id.startStationSpinner);
    endStationSpinner = findViewById(R.id.endStationSpinner);
    ticketCountEditText = findViewById(R.id.ticketCountEditText);
    buyTicketButton = findViewById(R.id.buyTicketButton);
    resultTextView = findViewById(R.id.resultTextView);

    // 获取所有站点
    List<String> allStations = new ArrayList<>();
    allStations.addAll(LINE_1);
    allStations.addAll(LINE_2);
    allStations.addAll(LINE_3);

    // 去除重复站点
    Set<String> uniqueStations = new HashSet<>(allStations);
    List<String> stationList = new ArrayList<>(uniqueStations);

    // 创建适配器
    ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, stationList);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    // 设置适配器
    startStationSpinner.setAdapter(adapter);
    endStationSpinner.setAdapter(adapter);

    buyTicketButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String startStation = startStationSpinner.getSelectedItem().toString();
            String endStation = endStationSpinner.getSelectedItem().toString();
            String ticketCountStr = ticketCountEditText.getText().toString();

            if (ticketCountStr.isEmpty()) {
                Toast.makeText(MainActivity.this, "请输入购票数量", Toast.LENGTH_SHORT).show();
                return;
            }

            int ticketCount = Integer.parseInt(ticketCountStr);
            int stationCount = calculateStationCount(startStation, endStation);
            int price = calculatePrice(stationCount);
            int totalPrice = price * ticketCount;

            resultTextView.setText("购票成功，总金额：" + totalPrice + " 元");
        }
    });
}

private int calculateStationCount(String startStation, String endStation) {
    // 使用广度优先搜索（BFS）计算最短路径
    Queue<String> queue = new LinkedList<>();
    Set<String> visited = new HashSet<>();
    Map<String, Integer> distance = new HashMap<>();

    queue.add(startStation);
    visited.add(startStation);
    distance.put(startStation, 0);

    while (!queue.isEmpty()) {
        String current = queue.poll();
        if (current.equals(endStation)) {
            return distance.get(current);
        }

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            for (String neighbor : GRAPH.getOrDefault(current, new ArrayList<>())) {
                if (!visited.contains(neighbor)) {
                    queue.add(neighbor);
                    visited.add(neighbor);
                    distance.put(neighbor, distance.get(current) + 1);
                }
            }
        }
    }

    return 0;
}

private int calculatePrice(int stationCount) {
    return (int) Math.ceil((double) stationCount / 3);
}

}
下面是layout部分：

<Spinner
    android:id="@+id/startStationSpinner"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textSize="18dp"/>


<Spinner
    android:id="@+id/endStationSpinner"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textSize="18dp"/>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="购票数量:"
    android:textSize="18sp" />

<EditText
    android:id="@+id/ticketCountEditText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="number" />

<Button
    android:id="@+id/buyTicketButton"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="购票" />

<TextView
    android:id="@+id/resultTextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="18sp" />