如何在安卓中开发一个简单的数据库应用程序

Question

我不是安卓开发者，我更喜欢C#，但是，我想玩一下Android，因为我有一个安卓设备，我提前道歉。

我想在安卓上开发一个简单的应用程序，具有基本的CRUD功能（创建，读取，更新和删除）而基本选项是使用 SQLiteOpenHelper，我见过 DAO 生成器（如 greenDAO），它们使生活变得更加简单。

所以，第一个问题是使用什么DAO生成器（如果全部的话）？

接下来，如何正确显示它，虽然我知道我需要 listview，但我仍然不知道如何将数据库绑定到它和查询。每次从"搜索"屏幕到主"列表显示"屏幕进行新查询时，我都会正确显示。

Answer 1

你需要像这样创建第一个数据库处理程序文件。

public class DatabaseHandler extends SQLiteOpenHelper {
    private static final int DB_VERSION = 1;
    private static final String DB_NAME = "ContactManager";
    private static final String TABLE_NAME = "Contacts";
    private static final String KEY_ID = "id";
    private static final String KEY_NAME = "name";
    private static final String KEY_PH_NO = "phNo";

    public DatabaseHandler(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
        // TODO Auto-generated constructor stub
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        String createContact = "Create Table " + TABLE_NAME + " (" + KEY_ID
                + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT," + KEY_PH_NO
                + " TEXT)";
        db.execSQL(createContact);
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
        db.execSQL("Drop Table IF EXISTS" + TABLE_NAME);
        onCreate(db);
    }
    // Add New Contacts
    public void AddContact(Contact contact) {
        SQLiteDatabase DB = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_NAME, contact.getName());
        values.put(KEY_PH_NO, contact.getPhNo());
        DB.insert(TABLE_NAME, null, values);
        DB.close();
    }
    // Read Contact
    public Contact ReadContact(int id) {
        SQLiteDatabase DB = this.getReadableDatabase();
        Cursor cursor = DB.query(TABLE_NAME, new String[] { KEY_ID, KEY_NAME,
                KEY_PH_NO }, KEY_ID + "=?",
                new String[] { String.valueOf(id) }, null, null, null, null);
        if (cursor != null)
            cursor.moveToFirst();
        Contact contact = new Contact(Integer.parseInt(cursor.getString(0)),
                cursor.getString(1), cursor.getString(2));
        DB.close();
        return contact;
    }
    public List<Contact> ReadAllContact() {
        //AddContact(new Contact("Arpan", "1234567"));
        List<Contact> ContactList = new ArrayList<Contact>();
        String query = "Select * from " + TABLE_NAME;
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(query, null);
        if (cursor.moveToFirst()) {
            do {
                Contact contact = new Contact();
                contact.setID(Integer.parseInt(cursor.getString(0)));
                contact.setName(cursor.getString(1));
                contact.setPhNo(cursor.getString(2));
                ContactList.add(contact);
            } while (cursor.moveToNext());
        }
        cursor.close();
        db.close();
        return ContactList;
    }
    public int UpdateContact(Contact contact) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues value = new ContentValues();
        value.put(KEY_NAME, contact.getName());
        value.put(KEY_PH_NO, contact.getPhNo());
        int norow=db.update(TABLE_NAME, value, KEY_ID + "=?",
                new String[] { String.valueOf(contact.getID()) });
        db.close();
        return norow;
    }
    public void DeleteContact(Contact contact) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_NAME, KEY_ID + "=?",
                new String[] { String.valueOf(contact.getID()) });
        db.close();
    }
    public int getContactCount() {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery("Select * from " + TABLE_NAME, null);
        int norow=cursor.getCount();
        cursor.close();
        db.close();
        return norow;
    }
}