sqlite之DbHelper&ObjectService

1. DbHelper类，继承系统的SQLiteOpenHelper类，创建，更新，获取游标

package tool;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DbHelper extends SQLiteOpenHelper {

    public final static String DATABASE_NAME = "photo_db";
    public final static String TABLE_NAME = "photo_table";
    public final static String FIELD_ID = "id";
    public final static String FIELD_NAME = "name";
    public final static String FIELD_SCORE = "score";

    public DbHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stubsss
        String sql = "create table " + TABLE_NAME + "(" + FIELD_ID
                + " integer primary key autoincrement," + FIELD_NAME + " text,"
                + FIELD_SCORE + " float);";
        db.execSQL(sql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
        String sql = "drop table if exists " + TABLE_NAME;
        db.execSQL(sql);
        onCreate(db);
    }

    public Cursor select() {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.query(TABLE_NAME, null, null, null, null, null,
                " id asc");
        return cursor;
    }

}

2. ObjectService类，封装操作数据库的常用方法。Object这里用的是具体的Photo类来保存对象

package tool;

import java.util.ArrayList;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

public class PhotoService {
    public static final String TAG = "dbtest";
    DbHelper testdb;

    public PhotoService(Context context) {
        testdb = new DbHelper(context);

    }

    public void save(Photo photo) {// test ok

        SQLiteDatabase db = testdb.getWritableDatabase();
        // ContentValues cv = new ContentValues();
        // cv.put(FIELD_NAME, photo.getName());
        // cv.put(FIELD_SCORE, photo.getScore());
 25         // long row = db.insert(TABLE_NAME, null, cv);
        db.execSQL("insert into photo_table(name,score) values(?,?)",
                new Object[] { photo.getName(), photo.getScore() });
    }

    public void saveAll(ArrayList<Photo> photos) {// test ok
        for (Photo photo : photos) {
            save(photo);
        }
    }

    public void delete(Photo photo) {// test ok
        SQLiteDatabase db = testdb.getWritableDatabase();
        // String where = FIELD_ID + "=?";
        // String[] whereValue = { Integer.toString(photo.getId()) };
        // db.delete(TABLE_NAME, where, whereValue);
        db.execSQL("delete from photo_table where id=?",
                new Object[] { photo.getId() });
    }

    public void update(Photo photo) {// test ok
        SQLiteDatabase db = testdb.getWritableDatabase();
        // String where = FIELD_ID + "=?";
        // String[] whereValue = { Integer.toString(photo.getId()) };
        // ContentValues cv = new ContentValues();
 50         // cv.put(FIELD_SCORE, score);
 51         // db.update(TABLE_NAME, cv, where, whereValue);
        db.execSQL(
                "update photo_table set name=?,score=? where id=?",
                new Object[] { photo.getName(), photo.getScore(), photo.getId() });
    }

    public void updateAll(ArrayList<Photo> photos) {// test ok
        for (Photo photo : photos) {
            update(photo);
        }
    }

    public ArrayList<Photo> initiallize(ArrayList<Photo> filephotos,// test ok
            ArrayList<Photo> dbphotos) {
        if (dbphotos.isEmpty()) {
            saveAll(filephotos);
        } else {
            for (Photo filephoto : filephotos) {// 从文件目录中逐一向数据库中查找，没有则向数据库中进行添加
                for (int i = 0; i < dbphotos.size(); i++) {
                    if (filephoto.equals(dbphotos.get(i))) {
                        break;
                    } else {
                        if (i == dbphotos.size() - 1) {
                            save(filephoto);
                        }
                    }
                }
            }
            for (Photo dbphoto : dbphotos) {// 数据库中逐一向文件目录中查找，没有则向数据库中进行删除
                for (int i = 0; i < filephotos.size(); i++) {
                    if (dbphoto.equals(filephotos.get(i))) {
                        break;
                    } else {
                        if (i == filephotos.size() - 1) {
                            delete(dbphoto);
                        }
                    }
                }
            }
        }
        return findAll();
    }

    public Photo find(String name) {// test ok
        Photo photo = new Photo();
        SQLiteDatabase db = testdb.getReadableDatabase();
        Cursor cursor = db.rawQuery(
                "select id,name,score from photo_table where name=?",
                new String[] { name });
        if (cursor.moveToNext()) {
            photo.setId(cursor.getInt(0));
            photo.setName(cursor.getString(1));
            photo.setScore(cursor.getFloat(2));
            Log.v(TAG, photo.toString());
            cursor.close();
            return photo;
        }
        cursor.close();
        return null;
    }

    public ArrayList<Photo> findAll() {// test ok
        ArrayList<Photo> photos = new ArrayList<Photo>();
        Cursor cursor = testdb.select();
        while (cursor.moveToNext()) {
            Photo photo = new Photo(cursor.getInt(0), cursor.getString(1),
                    cursor.getFloat(2));
            photos.add(photo);
            Log.v(TAG, photo.toString());

        }
        cursor.close();
        return photos;
    }

    public long getCount() {// test ok
        SQLiteDatabase db = testdb.getWritableDatabase();
        Cursor cursor = db.rawQuery("select count(*) from photo_table", null);
        cursor.moveToFirst();
        long count = cursor.getLong(0);
        Log.v(TAG, String.valueOf(count));
        cursor.close();
        return count;
    }

    public void clear() {// test ok
        SQLiteDatabase db = testdb.getWritableDatabase();
        db.execSQL("delete from photo_table");
    }
}