Question

我不是Android开发者，我更喜欢C＃但是，因为我有一个Android设备，我想玩Android一点，我提前道歉。

我想在android中使用基本的CRUD函数（创建，读取，更新和删除）开发一个简单的应用程序虽然基本的选择是使用SQLiteOpenHelper我已经看到了DAO生成器（如greenDAO），它让生活变得更加简单。

那么，第一个问题是使用DAOgenerator（如果全部）？

接下来，如何正确显示它，虽然我知道我需要listview但我仍然没有弄清楚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，我都会进行正确的显示。

Answer 1

您需要创建第一个这样的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;
    }

}

如何在android中开发一个简单的数据库应用程序？

1 个答案: