Android中提取JSON数组内TestID最大的学生最新考试成绩

我来帮你解决这个问题！要实现获取每个学生最新的考试成绩（通过TestID最大值判断），并在自定义ListView中展示，我们可以按照以下步骤来操作：

1. 先创建数据模型类（可选但推荐） #

为了更清晰地处理数据，避免直接操作JSONObject的繁琐和易出错，我们可以创建两个模型类：

Student.java #

public class Student {
    private int studentId;
    private StudentMark latestMark;

    public Student(int studentId, StudentMark latestMark) {
        this.studentId = studentId;
        this.latestMark = latestMark;
    }

    // Getter方法
    public int getStudentId() {
        return studentId;
    }

    public StudentMark getLatestMark() {
        return latestMark;
    }
}

StudentMark.java #

public class StudentMark {
    private int english;
    private int maths;
    private int science;
    private int history;
    private int testId;
    private String date;

    public StudentMark(int english, int maths, int science, int history, int testId, String date) {
        this.english = english;
        this.maths = maths;
        this.science = science;
        this.history = history;
        this.testId = testId;
        this.date = date;
    }

    // 各科成绩的Getter方法
    public int getEnglish() { return english; }
    public int getMaths() { return maths; }
    public int getScience() { return science; }
    public int getHistory() { return history; }
    public int getTestId() { return testId; }
    public String getDate() { return date; }
}

2. 修改JSON解析逻辑，提取每个学生的最新成绩 #

核心思路是：遍历每个学生对象，再遍历该学生的StudentMarks数组，找到TestID最大的那一条成绩记录。

try {
    JSONArray studentArray = new JSONArray(jsonStr);
    List<Student> studentList = new ArrayList<>();

    for (int i = 0; i < studentArray.length(); i++) {
        JSONObject studentObj = studentArray.getJSONObject(i);
        int studentId = studentObj.getInt("StudentID");
        
        // 获取当前学生的所有考试成绩数组
        JSONArray marksArray = studentObj.getJSONArray("StudentMarks");
        JSONObject latestMarkObj = null;
        int maxTestId = -1;

        // 遍历成绩数组，找到TestID最大的记录
        for (int j = 0; j < marksArray.length(); j++) {
            JSONObject markObj = marksArray.getJSONObject(j);
            int currentTestId = markObj.getInt("TestID");
            
            if (currentTestId > maxTestId) {
                maxTestId = currentTestId;
                latestMarkObj = markObj;
            }
        }

        // 将找到的最新成绩转为模型类，添加到列表中
        if (latestMarkObj != null) {
            int english = latestMarkObj.getInt("English");
            int maths = latestMarkObj.getInt("Maths");
            int science = latestMarkObj.getInt("Science");
            int history = latestMarkObj.getInt("History");
            String date = latestMarkObj.getString("Date");
            
            StudentMark latestMark = new StudentMark(english, maths, science, history, maxTestId, date);
            Student student = new Student(studentId, latestMark);
            studentList.add(student);
        }
    }

    // 现在studentList里就是每个学生ID和对应的最新成绩，接下来绑定到ListView
    StudentAdapter adapter = new StudentAdapter(this, studentList);
    listView.setAdapter(adapter);

} catch (JSONException e) {
    e.printStackTrace();
    // 处理JSON解析异常，比如提示用户数据加载失败
}

3. 实现自定义ListView Adapter #

接下来写一个简单的自定义Adapter，把数据展示到列表项中：

StudentAdapter.java #

public class StudentAdapter extends ArrayAdapter<Student> {
    private Context context;
    private List<Student> studentList;

    public StudentAdapter(Context context, List<Student> studentList) {
        super(context, 0, studentList);
        this.context = context;
        this.studentList = studentList;
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.list_item_student, parent, false);
        }

        Student student = studentList.get(position);
        StudentMark latestMark = student.getLatestMark();

        // 绑定数据到列表项的控件
        TextView tvStudentId = convertView.findViewById(R.id.tv_student_id);
        TextView tvEnglish = convertView.findViewById(R.id.tv_english);
        TextView tvMaths = convertView.findViewById(R.id.tv_maths);
        TextView tvScience = convertView.findViewById(R.id.tv_science);
        TextView tvHistory = convertView.findViewById(R.id.tv_history);
        TextView tvTestId = convertView.findViewById(R.id.tv_test_id);

        tvStudentId.setText("学生ID: " + student.getStudentId());
        tvEnglish.setText("英语: " + latestMark.getEnglish());
        tvMaths.setText("数学: " + latestMark.getMaths());
        tvScience.setText("科学: " + latestMark.getScience());
        tvHistory.setText("历史: " + latestMark.getHistory());
        tvTestId.setText("最新考试ID: " + latestMark.getTestId());

        return convertView;
    }
}

4. 列表项布局（list_item_student.xml） #

在res/layout下创建列表项的布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/tv_student_id"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="16sp"
        android:textStyle="bold"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginTop="8dp">

        <TextView
            android:id="@+id/tv_english"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>

        <TextView
            android:id="@+id/tv_maths"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>

        <TextView
            android:id="@+id/tv_science"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>

        <TextView
            android:id="@+id/tv_history"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"/>
    </LinearLayout>

    <TextView
        android:id="@+id/tv_test_id"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:textSize="12sp"
        android:textColor="@android:color/darker_gray"/>

</LinearLayout>

关键点说明： #

• 遍历StudentMarks数组时，一定要把TestID转为整数再比较，避免字符串比较的错误（比如"10"和"2"的字符串比较会认为"2"更大）。
• 记得处理JSONException，防止JSON格式错误导致崩溃。
• 使用模型类可以让代码更易读、易维护，后续如果需要扩展字段也更方便。

内容的提问来源于stack exchange，提问作者Roohi Zuwairiyah