Question

我按照教程创建了一个SQLite数据库，并在其中为应用程序创建了表。但所有这些都发生在运行时。现在我正在寻找一种创建数据库和表的方法，以便将来可以重用它们。因此，相同的表格将使用插入应用程序的数据进行更新。数据库和表格只会创建一次。

这是我用来在运行时创建数据库和表格的代码：

SQLiteHelperCourse courseDbHelper = new SQLiteHelperCourse(this);
    SQLiteDatabase dbw = courseDbHelper.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(CourseEntry.COLUMN_NAME_COURSE_ID, "1");
    values.put(CourseEntry.COLUMN_NAME_COURSE_NAME, "Android");
    values.put(CourseEntry.COLUMN_NAME_CREDITS, "3");
    values.put(CourseEntry.COLUMN_NAME_SEMESTER, "1st");
    values.put(CourseEntry.COLUMN_NAME_YEAR, "3rd");
    values.put(CourseEntry.COLUMN_NAME_COURSE_ID, "2");
    values.put(CourseEntry.COLUMN_NAME_COURSE_NAME, "SBP");
    values.put(CourseEntry.COLUMN_NAME_CREDITS, "3");
    values.put(CourseEntry.COLUMN_NAME_SEMESTER, "1st");
    values.put(CourseEntry.COLUMN_NAME_YEAR, "3rd");
    values.put(CourseEntry.COLUMN_NAME_COURSE_ID, "3");
    values.put(CourseEntry.COLUMN_NAME_COURSE_NAME, "IT Infrastructure");
    values.put(CourseEntry.COLUMN_NAME_CREDITS, "3");
    values.put(CourseEntry.COLUMN_NAME_SEMESTER, "1st");
    values.put(CourseEntry.COLUMN_NAME_YEAR, "3rd");
    dbw.insert(CourseEntry.TABLE_NAME, CourseEntry.COLUMN_NAME_NULLABLE, values);

    SQLiteDatabase dbr = courseDbHelper.getReadableDatabase();
    String[] projection = { CourseEntry.COLUMN_NAME_COURSE_NAME};
    final ArrayList<String> list = new ArrayList<String>();

    Cursor curs = dbr.query(CourseEntry.TABLE_NAME, 
            projection, 
            null, 
            null, 
            null, 
            null, 
            null);
    curs.moveToFirst();

    while(curs.moveToNext())
    {
        list.add(curs.getString(curs.getColumnIndexOrThrow(CourseEntry.COLUMN_NAME_COURSE_NAME)));
    }

修改我提供的代码是在活动的onCreate事件中调用的。

这是我的SQLiteHelper类代码：

public class SQLiteHelperCourse extends SQLiteOpenHelper {

public static final int DATABASE_VERSION = 1;
public static final String DATABASE_NAME = "AndroidApplication.db";

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

private static final String TEXT_TYPE = " TEXT";
private static final String COMMA_SEP = ", ";
private static final String SQL_CREATE_ENTRIES = 
        "CREATE TABLE " + CourseEntry.TABLE_NAME + " (" + CourseEntry._ID + " INTEGER PRIMARY KEY, "
                                                        + CourseEntry.COLUMN_NAME_COURSE_ID + TEXT_TYPE + COMMA_SEP
                                                        + CourseEntry.COLUMN_NAME_COURSE_NAME + TEXT_TYPE + COMMA_SEP
                                                        + CourseEntry.COLUMN_NAME_YEAR + TEXT_TYPE + COMMA_SEP
                                                        + CourseEntry.COLUMN_NAME_SEMESTER + TEXT_TYPE + COMMA_SEP
                                                        + CourseEntry.COLUMN_NAME_CREDITS + TEXT_TYPE + ")";

private static final String SQL_DELETE_ENTRIES = "DROP TABLE IF EXISTS " + CourseEntry.TABLE_NAME;

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL(SQL_CREATE_ENTRIES);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL(SQL_DELETE_ENTRIES);
    onCreate(db);
}

public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    onUpgrade(db, oldVersion, newVersion);
}

}

Answer 1

假设您只想在创建数据库时将三个课程插入数据库：

将插入代码移动到数据库帮助程序onCreate()。当数据库文件不存在时，它会被调用一次。使用提供的SQLiteDatabase作为参数，而不是递归调用getWritableDatabase()。
插入三次。 ContentValues put()使用相同的密钥覆盖任何值，因此基本上您只是插入第三个课程。

创建SQLite数据库+表并保存以供将来使用

1 个答案: