要实现将常量对象存储在Android SQLite数据库中,并以JSON格式存储在List中,可以按照以下步骤进行:
public class Constant {
private int id;
private String name;
private String value;
// 构造函数和getter/setter方法省略
}
public class ConstantDatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "constants.db";
private static final int DATABASE_VERSION = 1;
private static final String TABLE_NAME = "constants";
private static final String COLUMN_ID = "id";
private static final String COLUMN_NAME = "name";
private static final String COLUMN_VALUE = "value";
public ConstantDatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String createTableQuery = "CREATE TABLE " + TABLE_NAME + " (" +
COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
COLUMN_NAME + " TEXT, " +
COLUMN_VALUE + " TEXT)";
db.execSQL(createTableQuery);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
}
public class ConstantDAO {
private SQLiteDatabase database;
private ConstantDatabaseHelper dbHelper;
public ConstantDAO(Context context) {
dbHelper = new ConstantDatabaseHelper(context);
}
public void open() throws SQLException {
database = dbHelper.getWritableDatabase();
}
public void close() {
dbHelper.close();
}
public void insert(Constant constant) {
ContentValues values = new ContentValues();
values.put(ConstantDatabaseHelper.COLUMN_NAME, constant.getName());
values.put(ConstantDatabaseHelper.COLUMN_VALUE, constant.getValue());
database.insert(ConstantDatabaseHelper.TABLE_NAME, null, values);
}
public List getAllConstants() {
List constants = new ArrayList<>();
Cursor cursor = database.query(ConstantDatabaseHelper.TABLE_NAME, null, null, null, null, null, null);
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
Constant constant = new Constant();
constant.setId(cursor.getInt(cursor.getColumnIndex(ConstantDatabaseHelper.COLUMN_ID)));
constant.setName(cursor.getString(cursor.getColumnIndex(ConstantDatabaseHelper.COLUMN_NAME)));
constant.setValue(cursor.getString(cursor.getColumnIndex(ConstantDatabaseHelper.COLUMN_VALUE)));
constants.add(constant);
cursor.moveToNext();
}
cursor.close();
return constants;
}
}
// 创建ConstantDAO对象
ConstantDAO constantDAO = new ConstantDAO(context);
// 打开数据库连接
constantDAO.open();
// 创建常量对象
Constant constant1 = new Constant();
constant1.setName("Constant1");
constant1.setValue("Value1");
// 插入常量对象到数据库
constantDAO.insert(constant1);
// 获取所有常量对象
List constants = constantDAO.getAllConstants();
// 关闭数据库连接
constantDAO.close();
通过以上步骤,我们可以将常量对象存储在Android SQLite数据库中,并以JSON格式存储在List中。