android創建多個數據表，與數據庫操作

---恢復內容開始---

新做了一個小項目，多數地方用到數據庫操作，在此記錄。

android自帶sqlite，新建一個類繼承SQLiteOpenHelper,重寫oncreate，onupgrade代碼，如下。

public class SkbDbHelper extends SQLiteOpenHelper {
    // If you change the database schema, you must increment the database version.

    private static final String TEXT_TYPE = " TEXT";
    private static final String COMMA_SEP = ",";

    private static final String TIMESQL_CREATE_ENTRIES =
            "CREATE TABLE " + TimeEntry.TABLE_NAME + " (" +
                    TimeEntry._ID + " INTEGER PRIMARY KEY," +
                    TimeEntry.COLUMN_TITLE + TEXT_TYPE + COMMA_SEP +
                    TimeEntry.COLUMN_TIME + TEXT_TYPE + COMMA_SEP +
                    TimeEntry.COLUMN_BODY + TEXT_TYPE + COMMA_SEP +

                    TimeEntry.COLUMN_CLOSE + TEXT_TYPE + " )";

    private static final String STUSSQL_CREATE_ENTRIES =
            "CREATE TABLE " + StudentsEntry.TABLE_NAME + " (" +
                    StudentsEntry._ID + " INTEGER PRIMARY KEY," +
                    StudentsEntry.COLUMN_KID + TEXT_TYPE + COMMA_SEP +
                    StudentsEntry.COLUMN_NAME + TEXT_TYPE + COMMA_SEP +
                    StudentsEntry.COLUMN_CANJIA + TEXT_TYPE + COMMA_SEP +
                    StudentsEntry.COLUMN_WENTI + TEXT_TYPE + COMMA_SEP +
                    StudentsEntry.COLUMN_CLASS + TEXT_TYPE + " )";

    private static final String BODYSQL_CREATE_ENTRIES =
            "CREATE TABLE " + BodyEntry.TABLE_NAME + " (" +
                    BodyEntry._ID + " INTEGER PRIMARY KEY," +
                    BodyEntry.COLUMN_NAME + TEXT_TYPE + COMMA_SEP +
                    BodyEntry.COLUMN_CLASS + TEXT_TYPE + COMMA_SEP +
                    BodyEntry.COLUMN_PWD + TEXT_TYPE + COMMA_SEP +
                    BodyEntry.COLUMN_SHENFEN + TEXT_TYPE + COMMA_SEP +
                    BodyEntry.COLUMN_SHIYUE + TEXT_TYPE + " )";


    private static final String TIMESQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + TimeEntry.TABLE_NAME;
    private static final String STUSSQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + StudentsEntry.TABLE_NAME;
    private static final String BODYSQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + BodyEntry.TABLE_NAME;

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

    public SkbDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(TIMESQL_CREATE_ENTRIES);
        db.execSQL(STUSSQL_CREATE_ENTRIES);
        db.execSQL(BODYSQL_CREATE_ENTRIES);
    }
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // This database is only a cache for online data, so its upgrade policy is
        // to simply to discard the data and start over
        db.execSQL(TIMESQL_DELETE_ENTRIES);
        db.execSQL(STUSSQL_DELETE_ENTRIES);
        db.execSQL(BODYSQL_DELETE_ENTRIES);
        onCreate(db);
    }
    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        onUpgrade(db, oldVersion, newVersion);
    }
}

代碼中創建了三個表，個人認為如果用到多個表，這算是一種簡便的方法。

建好表以后創建數據表操作管理類，常用操作如下：

1、判斷表中是否有數據

public boolean isDataExist(){
        int count = 0;

        SQLiteDatabase db = null;
        Cursor cursor = null;

        try {
            db = SkbApplication.getInstance().getDbHelper().getReadableDatabase();
            // select count(Id) from Orders
            cursor = db.query(BodyEntry.TABLE_NAME, new String[]{"COUNT(" + BodyEntry._ID + ")"}, null, null, null, null, null);

            if (cursor.moveToFirst()) {
                count = cursor.getInt(0);
            }
            if (count > 0) return true;
        }
        catch (Exception e) {
            Log.e("db", "", e);
        }
        finally {
            if (cursor != null) {
                cursor.close();
            }
            if (db != null) {
                db.close();
            }
        }
        return false;
    }

注1：dbhelper寫到了application中，如下

public SkbDbHelper getDbHelper(){
        if (dbHelper == null){
            dbHelper = new SkbDbHelper(this);
        }
        return dbHelper;
    }

 注2:bodyEntry為實體類，繼承自BaseColumns，提供了_ID等。

public static class StudentsEntry implements BaseColumns {
        public static final String TABLE_NAME = "students";
        public static final String COLUMN_KID= "kid"; //課程id
        public static final String COLUMN_NAME = "name";
        public static final String COLUMN_CLASS = "class";
        public static final String COLUMN_CANJIA = "canjia"; // 0 不參加， 1參加
        public static final String COLUMN_WENTI = "wenti"; // 備注
    }

繼續表操作

2、查詢所有數據

public List<StudentsBean> getAllDate(){

        String[] projection = {
                StudentsEntry._ID,
                StudentsEntry.COLUMN_KID,
                StudentsEntry.COLUMN_NAME,
                StudentsEntry.COLUMN_CLASS,
                StudentsEntry.COLUMN_CANJIA,
                StudentsEntry.COLUMN_WENTI

        };

        SQLiteDatabase db = null;
        Cursor cursor = null;
        try {
            db = SkbApplication.getInstance().getDbHelper().getReadableDatabase();
            // select * from Orders
            cursor = db.query(StudentsEntry.TABLE_NAME, projection, null, null, null, null, null);

            if (cursor.getCount() > 0) {
                List<StudentsBean> orderList = new ArrayList<StudentsBean>(cursor.getCount());
                while (cursor.moveToNext()) {
                    orderList.add(parseOrder(cursor));
                }
                return orderList;
            }
        }
        catch (Exception e) {
            Log.e("db", "", e);
        }
        finally {
            if (cursor != null) {
                cursor.close();
            }
            if (db != null) {
                db.close();
            }
        }

        return null;
    }

3、插入數據

public boolean insertDate(String kid,String name,String sclass,String wenti){
        SQLiteDatabase db = null;
        try {
            db = SkbApplication.getInstance().getDbHelper().getWritableDatabase();
            db.beginTransaction();

            ContentValues contentValues = new ContentValues();
            contentValues.put(StudentsEntry.COLUMN_KID, kid);
            contentValues.put(StudentsEntry.COLUMN_NAME, name);
            contentValues.put(StudentsEntry.COLUMN_CLASS, sclass);
            contentValues.put(StudentsEntry.COLUMN_CANJIA, "0");
            contentValues.put(StudentsEntry.COLUMN_WENTI, wenti);

            db.insert(StudentsEntry.TABLE_NAME, null, contentValues);

            Toast.makeText(context,"報名成功",Toast.LENGTH_SHORT).show();
            db.setTransactionSuccessful();
            return true;
        }catch (SQLiteConstraintException e){
            Toast.makeText(context, "主鍵重復", Toast.LENGTH_SHORT).show();
        }catch (Exception e){
            Log.e("db", "", e);
        }finally {
            if (db != null) {
                db.endTransaction();
                db.close();
            }
        }
        return false;
    }

4、刪除數據

 public boolean deleteOrder(String id) {

        // Define 'where' part of query.
        String selection = StudentsEntry.COLUMN_KID + " LIKE ?";
        // Specify arguments in placeholder order.
        String[] selectionArgs = { id };

        SQLiteDatabase db = null;
        try {
            db = SkbApplication.getInstance().getDbHelper().getWritableDatabase();
            db.beginTransaction();

            db.delete(StudentsEntry.TABLE_NAME, selection, selectionArgs);
            db.setTransactionSuccessful();
            return true;
        } catch (Exception e) {
            Log.e("db", "", e);
        } finally {
            if (db != null) {
                db.endTransaction();
                db.close();
            }
        }
        return false;
    }

5、修改數據，此處查找_ID為“id”的數據，修改其COLUMN_CANJIA為“canjia”;

public boolean updateCanjia(String id,String canjia){
        SQLiteDatabase db = null;
        try {
            db = SkbApplication.getInstance().getDbHelper().getWritableDatabase();
            db.beginTransaction();

            // update Orders set OrderPrice = 800 where Id = 6
            ContentValues cv = new ContentValues();
            cv.put(StudentsEntry.COLUMN_CANJIA, canjia);

            // Which row to update, based on the title
            String selection = StudentsEntry._ID + " = ?";
            String[] selectionArgs = {id};

            db.update(StudentsEntry.TABLE_NAME,
                    cv,
                    selection,
                    selectionArgs);
            db.setTransactionSuccessful();
            return true;
        }
        catch (Exception e) {
            Log.e("db", "", e);
        }
        finally {
            if (db != null) {
                db.endTransaction();
                db.close();
            }
        }

        return false;
    }

6、按條件查詢，查詢_ID為“id”並且COLUMN_CANJIA為“canjia”的數據。

 public List<StudentsBean> gettitleBean(String id,String canjia){

        String[] projection = {
                StudentsEntry._ID,
                StudentsEntry.COLUMN_KID,
                StudentsEntry.COLUMN_NAME,
                StudentsEntry.COLUMN_CLASS,
                StudentsEntry.COLUMN_CANJIA,
                StudentsEntry.COLUMN_WENTI
        };

        // Filter results WHERE "title" = 'My Title'
        String selection = StudentsEntry.COLUMN_KID + " = ? and " + StudentsEntry.COLUMN_CANJIA + " = ?";
        String[] selectionArgs = { id , canjia };

        SQLiteDatabase db = null;
        Cursor cursor = null;

        try {
            db = SkbApplication.getInstance().getDbHelper().getReadableDatabase();
            // select * from Orders where CustomName = 'Bor'
            cursor = db.query(StudentsEntry.TABLE_NAME,
                    projection,
                    selection,
                    selectionArgs,
                    null, null, null);

            if (cursor.getCount() > 0) {
                List<StudentsBean> orderList = new ArrayList<StudentsBean>(cursor.getCount());
                while (cursor.moveToNext()) {
                    StudentsBean order = parseOrder(cursor);
                    orderList.add(order);
                }
                return orderList;
            }
        }
        catch (Exception e) {
            Log.e("db", "", e);
        }
        finally {
            if (cursor != null) {
                cursor.close();
            }
            if (db != null) {
                db.close();
            }
        }

        return null;
    }

 

最后附上 數據庫數據插入list的語句

 private StudentsBean parseOrder(Cursor cursor){
        StudentsBean bean = new StudentsBean();
        bean.setId(cursor.getInt(cursor.getColumnIndex(StudentsEntry._ID)));
        bean.setKid(cursor.getString(cursor.getColumnIndex(StudentsEntry.COLUMN_KID)));
        bean.setName(cursor.getString(cursor.getColumnIndex(StudentsEntry.COLUMN_NAME)));
        bean.setSclass(cursor.getString(cursor.getColumnIndex(StudentsEntry.COLUMN_CLASS)));
        bean.setCanjia(cursor.getString(cursor.getColumnIndex(StudentsEntry.COLUMN_CANJIA)));
        bean.setWenti(cursor.getString(cursor.getColumnIndex(StudentsEntry.COLUMN_WENTI)));
        return bean;
    }

目前用到這些。