如何使用新的 android 应用更新来更新现有的 SQLite db 表数据？

Question

我最近在 android 应用商店推出了一个包含 SQLite 数据库的应用。

我现在正在尝试发布应用程序的更新，并希望将更多数据添加到现有数据库中，但是有点卡住了。我已经阅读了关于 SO 的答案，其中概述了对数据库本身进行更改，但是我希望我的表和列保持不变，只添加新数据。

我要添加到数据库的数据是从Raw 文件中的 CSV 文件中提取的，最初是在用户注册应用程序时加载到数据库中的。

我觉得我需要实现onUpgrade 方法，但是我是否也应该在此时添加来自 CSV 文件的新数据？更新数据库版本并使用onUpgrade加载新数据是不是很简单？

我对 SQLite DB 还很陌生，因此非常感谢任何帮助。

CourseDBHelper 代码

public class CourseDBHelper extends SQLiteOpenHelper {

// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "CourseDB";

// Create two table names
private static final String TABLE_COURSES = "courses";

// Universities Table Columns names
private static final String COURSE_NAME = "Course_name";
private static final String UNI_NAME = "Uni_name";
private static final String COURSE_DURATION = "Duration";
private static final String COURSE_STUDY_MODE = "Study_mode";
private static final String COURSE_QUALIFICATION = "Qualification";
private static final String COURSE_ENTRY_STANDARDS = "Entry_standards";
private static final String COURSE_GRADUATE_PROSPECTS = "Graduate_prospects";
private static final String COURSE_STUDENT_SATISFACTION = "Student_satisfaction";


private String CREATE_COURSES_TABLE = "CREATE TABLE courses" +
        "(" +
        "_id INTEGER PRIMARY KEY AUTOINCREMENT," +
        "Course_name TEXT NOT NULL," +
        "Uni_name TEXT NOT NULL," +
        "Duration TEXT NOT NULL," +
        "Study_mode TEXT NOT NULL," +
        "Qualification TEXT NOT NULL," +
        "Entry_standards TEXT NOT NULL," +
        "Graduate_prospects TEXT NOT NULL," +
        "Student_satisfaction TEXT NOT NULL" +
        ");";

private static final String[] COLUMNS = {
        COURSE_NAME,
        UNI_NAME,
        COURSE_DURATION,
        COURSE_STUDY_MODE,
        COURSE_QUALIFICATION,
        COURSE_ENTRY_STANDARDS,
        COURSE_GRADUATE_PROSPECTS,
        COURSE_STUDENT_SATISFACTION
};

public CourseDBHelper(Context context)
{
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

// TODO: REMOVED NOT NULL FROM EVERY COLUMN FOR TEST PURPOSES, WILL NEED TO BE READDED
@Override
public void onCreate(SQLiteDatabase db)
{
    db.execSQL(CREATE_COURSES_TABLE);
}

public void deleteAll()
{
    SQLiteDatabase db = this.getWritableDatabase();
    db.delete("courses", null, null);
    db.execSQL("delete from " + "courses");
    db.close();
}

// Getting one course by course name and uni name
public Course getCourse(String courseName, String uniName) {
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(TABLE_COURSES, COLUMNS, " Course_name = ? AND Uni_name = ?",
            new String[]{courseName, uniName},
            null,
            null,
            null,
            null);

    if (cursor != null)
        cursor.moveToFirst();


    Course course = new Course();

    /*

    System.out.println(cursor.getString(0));
    System.out.println(cursor.getString(1));
    System.out.println(cursor.getString(2));
    System.out.println(cursor.getString(3));
    System.out.println(cursor.getString(4));
    System.out.println(cursor.getString(5));
    System.out.println(cursor.getString(6));
    */

    course.setCourseName(cursor.getString(0));
    course.setUniversity(cursor.getString(1));
    course.setCourseDuration(cursor.getString(2));
    course.setStudyMode(cursor.getString(3));
    course.setQualification(cursor.getString(4));
    course.setEntryStandards(cursor.getString(5));
    course.setGradProspects(cursor.getString(6));
    course.setStudentSatisfaction(cursor.getString(7));


    return course;

}

public void addCourse(Course course)
{
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();

    values.put(COURSE_NAME, course.getCourseName());
    values.put(UNI_NAME, course.getUniversity());
    values.put(COURSE_DURATION, course.getCourseDuration());
    values.put(COURSE_STUDY_MODE, course.getStudyMode());
    values.put(COURSE_QUALIFICATION, course.getQualification());
    values.put(COURSE_ENTRY_STANDARDS, course.getEntryStandards());
    values.put(COURSE_GRADUATE_PROSPECTS, course.getGradProspects());
    values.put(COURSE_STUDENT_SATISFACTION, course.getStudentSatisfaction());

    db.insert(TABLE_COURSES,
            null, //nullColumnHack
            values);

    db.close();
}


public ArrayList<Course> getAllCourses()
{
    ArrayList<Course> courses = new ArrayList<>();
    // 1. build the query
    String query = "SELECT  * FROM " + TABLE_COURSES;
    // 2. get reference to writable DB
    SQLiteDatabase db = this.getWritableDatabase();

    Cursor cursor = db.rawQuery(query, null);

    // 3. go over each row, build course and add it to list
    Course course;
    if(cursor.moveToFirst()){
        cursor.moveToNext();
        do{
            course = new Course();
            course.setCourseName(cursor.getString(1));
            course.setUniversity(cursor.getString(2));
            course.setCourseDuration(cursor.getString(3));
            course.setStudyMode(cursor.getString(4));
            course.setQualification(cursor.getString(5));
            course.setEntryStandards(cursor.getString(6));
            course.setGradProspects(cursor.getString(7));
            course.setStudentSatisfaction(cursor.getString(8));

            // Add course to courses list
            courses.add(course);
        } while(cursor.moveToNext());
    }

    // return courses
    return courses;
}

public int getDBCount()
{
    SQLiteDatabase db = this.getWritableDatabase();
    String count = "SELECT count(*) FROM courses";
    Cursor mcursor = db.rawQuery(count, null);
    mcursor.moveToFirst();
    int icount = mcursor.getInt(0);
    return icount;
}

public void deleteCourse(Course course) {

    // 1. get reference to writable DB
    SQLiteDatabase db = this.getWritableDatabase();

    // 2. delete
    db.delete("courses", //table name
            "Course_name = ? AND Uni_name = ?",  // selections
            new String[] { course.getCourseName(), course.getUniversity() }); //selections args

    // 3. close
    db.close();
}



@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {


}
}

将数据从 CSV 文件加载到 SQlite DB 的方法

public void populateCourseDatabase(int id) {

        // NOW POPULATE THE COURSE DATABASE FILE
inputStream = getResources().openRawResource(R.raw.coursesone);


        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
        String word;
        String cvsSplitBy = ",";

        try{
            while((word = reader.readLine()) != null){

                Log.d(TAG, "constructing Course object from: " + word);

                String[] segment = word.split(cvsSplitBy);

                Course course = new Course();
                course.setCourseName(segment[0]);
                course.setUniversity(segment[1]);
                course.setCourseDuration(segment[2]);
                course.setStudyMode(segment[3]);
                course.setQualification(segment[4]);
                course.setEntryStandards(segment[5]);
                course.setGradProspects(segment[6]);
                course.setStudentSatisfaction(segment[7]);


                myCourseDBHelper.addCourse(course);

                progressBar.setProgress(count);

                count = count + 1;

                System.out.println("Sucessfully added: " + course.toString());
            }
        }
        catch(IOException e1){
            e1.printStackTrace();
            System.out.println("SOMETHING WENT WRONG");
        }

    }

Answer 1

SQLiteOpenHelper onCreate() 和 onUpgrade() 回调在数据库实际打开时调用，例如通过调用 getWritableDatabase().onCreate() 仅在数据库文件不存在且刚刚创建时运行。 onUpgrade() 仅在数据库文件存在但存储的版本号低于构造函数中请求时调用。增加数据库版本以便调用 onUpgrade()。 下面的示例伪代码

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    switch(oldVersion) {

    case 1:
        //upgrade logic from version 1 to 2
    case 2:
        //upgrade logic from version 2 to 3
    case 3:
        //upgrade logic from version 3 to 4
        break;
    default:
        throw new IllegalStateException(
        "onUpgrade() with unknown oldVersion " + oldVersion);
    }
}