android开发 greendao学习及使用笔记

最新推荐文章于 2024-07-15 21:52:53 发布

原创最新推荐文章于 2024-07-15 21:52:53 发布 · 555 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#greendao

本文介绍了如何使用GreenDaoGenerator构建Java的实体模型和DAO工具类，包括表的增删改查操作。重点涵盖了查询、插入、修改和删除等数据库操作方法，并详细说明了数据库升级的实现方式。此外，还提供了MigrationHelper类用于数据库迁移，确保数据在升级过程中不丢失。

一、用GreenDaoGenerator构建Java的实体模型和DAO工具类；

private static void addBirdStoreEx(Schema schema){

Entity birdStoreEx = schema.addEntity("BirdStoreEx");

birdStoreEx.addIdProperty().primaryKey().autoincrement();

birdStoreEx.addStringProperty("netCode");

birdStoreEx.addStringProperty("netName");

birdStoreEx.addStringProperty("expressNumber");

birdStoreEx.addStringProperty("receiverMobile");

birdStoreEx.addDateProperty("arriveTime");

birdStoreEx.addDateProperty("storeTime");

birdStoreEx.addDateProperty("retrievalTime");

birdStoreEx.addDateProperty("overdueTime");

birdStoreEx.addDateProperty("recallTime");

birdStoreEx.addIntProperty("expressState");

birdStoreEx.addBooleanProperty("syncData");//是否已上传数据

birdStoreEx.addStringProperty("remark");//备注

}

二、表的增删改查

1.查询

范例1：查询某个表是否包含某个id:

public boolean isSaved(int ID)
{
QueryBuilder<SaveList>
 qb = saveListDao.queryBuilder();
qb.where(Properties.Id.eq(ID));
qb.buildCount().count();
return qb.buildCount().count()
 > 0 ? true : false;
}
范例2：获取整个表的数据集合,一句代码就搞定！
1
2
3
4
public List<PhotoGalleryDB>
 getPhotoGallery()
{
return photoGalleryDao.loadAll();//
 获取图片相册
}
范例3：通过一个字段值查找对应的另一个字段值(为简便直接使用下面方法，也许有更简单的方法，尚未尝试)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
/** 通过图片id查找其目录id */
public int getTypeId(int picId)
{
QueryBuilder<PhotoGalleryDB>
 qb = photoGalleryDao.queryBuilder();
qb.where(Properties.Id.eq(picId));
if (qb.list().size()
 > 0)
{
return qb.list().get(0).getTypeId();
}
else
{
return -1;
}
}
范例4：查找所有第一姓名是“Joe”并且以lastname排序。
1
2
3
4
List joes = userDao.queryBuilder()
.where(Properties.FirstName.eq("Joe"))
.orderAsc(Properties.LastName)
.list();
范例5：多重条件查询

(1)获取id为cityId并且infotype为HBContant.CITYINFO_SL的数据集合：

1
2
3
4
5
6
7
public List<CityInfoDB>
 getSupportingList(int cityId)
{
QueryBuilder<CityInfoDB>
 qb = cityInfoDao.queryBuilder();
qb.where(qb.and(Properties.CityId.eq(cityId),Properties.InfoType.eq(HBContant.CITYINFO_SL)));
qb.orderAsc(Properties.Id);//
 排序依据
return qb.list();
}

(2)获取firstname为“Joe”并且出生于1970年10月以后的所有user集合:

1
2
3
4
5
QueryBuilder qb = userDao.queryBuilder();
qb.where(Properties.FirstName.eq("Joe"),
qb.or(Properties.YearOfBirth.gt(1970),
qb.and(Properties.YearOfBirth.eq(1970),
 Properties.MonthOfBirth.ge(10))));
List youngJoes = qb.list();

源码》》》》》》》》》》》》》》》》》》》》》》》》》》》

    /** Creates an "greater than ('>')" condition for this property. */

    public WhereCondition gt(Object value) {

        return new PropertyCondition(this, ">?", value);

    }

    /** Creates an "less than ('<')" condition for this property. */

    public WhereCondition lt(Object value) {

        return new PropertyCondition(this, "<?", value);

    }

    /** Creates an "greater or equal ('>=')" condition for this property. */

    public WhereCondition ge(Object value) {

        return new PropertyCondition(this, ">=?", value);

    }

    /** Creates an "less or equal ('<=')" condition for this property. */

    public WhereCondition le(Object value) {

        return new PropertyCondition(this, "<=?", value);

    }
范例6：获取某列对象
1
picJsonDao.loadByRowId(picId);
2.增添/插入、修改

插入数据更加简单，也是只要一句代码便能搞定!

1
2
3
4
public void addToPhotoTable(Photo
 p)
{
photoDao.insert(p);
}
修改更新：
1
2
photoDao.insertOrReplace(photo);
photoDao.insertInTx(photo);
3.删除:
(1)清空表格数据

1
2
3
4
5
/** 清空相册图片列表的数据 */
public void clearPhoto()
{
photoDao.deleteAll();
}

(2)删除某个对象

1
2
3
4
5
6
public void deleteCityInfo(int cityId)
{
QueryBuilder<DBCityInfo>
 qb = cityInfoDao.queryBuilder();
DeleteQuery<DBCityInfo>
 bd = qb.where(Properties.CityId.eq(cityId)).buildDelete();
bd.executeDeleteWithoutDetachingEntities();
}

三、数据库升级

经测试，只要改变表结构，原先的数据内容就会丢失，原因：DevOpenHelper中先dropAllTables再新建数据库。因此，为了保留原先表中的数据内容，原理：先把原表复制一份，再往新表上拷贝数据。

具体步骤如下：

1.先升级表，run as Java application

2.在DaoMaster类里有个内部类DevOpenHelper里的方法onUpgrade里写上数据库结构变化的代码，比如某个表新增字段，并要把里面dropAllTables和onCreate方法删掉

3.MigrationHelper.getInstance().migrate(db,
UserDao.class,ItemDao.class);

四、keep代码

五、最后附上MigrationHelper.java

/**

 * Created by pokawa on 18/05/15.

 */

public class MigrationHelper {

    privatestatic
final String
CONVERSION_CLASS_NOT_FOUND_EXCEPTION ="MIGRATION HELPER - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS";

    private static MigrationHelperinstance;

    public static MigrationHelper getInstance() {

        if(instance ==null) {

            instance = 
new MigrationHelper();

        }

        return instance;

    }

    public void migrate(SQLiteDatabase db, Class<?extends AbstractDao<?, ?>>... daoClasses) {

        generateTempTables(db, daoClasses);

        DaoMaster.dropAllTables(db, true);

        DaoMaster.createAllTables(db, false);

        restoreData(db, daoClasses);

    }

    private void generateTempTables(SQLiteDatabase db, Class<?extends AbstractDao<?, ?>>... daoClasses) {

        for(int i = 0; i < daoClasses.length; i++) {

            DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);

            String divider = "";

            String tableName = daoConfig.tablename;

            String tempTableName = daoConfig.tablename.concat("_TEMP");

            ArrayList<String> properties = new ArrayList<String>();

            StringBuilder createTableStringBuilder = 
new StringBuilder();

            createTableStringBuilder.append("CREATE TABLE ").append(tempTableName).append(" (");

            for(int j = 0; j < daoConfig.properties.length; j++) {

                String columnName = daoConfig.properties[j].columnName;

                if(getColumns(db, tableName).contains(columnName)) {

                    properties.add(columnName);

                    String type = null;

                    try {

                        type = getTypeByClass(daoConfig.properties[j].type);

                    } catch (Exception exception) {

                    }

                    createTableStringBuilder.append(divider).append(columnName).append(" ").append(type);

                    if(daoConfig.properties[j].primaryKey) {

                        createTableStringBuilder.append(" PRIMARY KEY");

                    }

                    divider = ",";

                }

            }

            createTableStringBuilder.append(");");

            db.execSQL(createTableStringBuilder.toString());

            StringBuilder insertTableStringBuilder = 
new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tempTableName).append(" (");

            insertTableStringBuilder.append(TextUtils.join(",", properties));

            insertTableStringBuilder.append(") SELECT ");

            insertTableStringBuilder.append(TextUtils.join(",", properties));

            insertTableStringBuilder.append(" FROM ").append(tableName).append(";");

            db.execSQL(insertTableStringBuilder.toString());

        }

    }

    private void restoreData(SQLiteDatabase db, Class<?extends AbstractDao<?, ?>>... daoClasses) {

        for(int i = 0; i < daoClasses.length; i++) {

            DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);

            String tableName = daoConfig.tablename;

            String tempTableName = daoConfig.tablename.concat("_TEMP");

            ArrayList<String> properties = new ArrayList<String>();

            for (int j = 0; j < daoConfig.properties.length; j++) {

                String columnName = daoConfig.properties[j].columnName;

                if(getColumns(db, tempTableName).contains(columnName)) {

                    properties.add(columnName);

                }

            }

            StringBuilder insertTableStringBuilder = 
new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");

            insertTableStringBuilder.append(TextUtils.join(",", properties));

            insertTableStringBuilder.append(") SELECT ");

            insertTableStringBuilder.append(TextUtils.join(",", properties));

            insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");

            StringBuilder dropTableStringBuilder = new StringBuilder();

            dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);

            db.execSQL(insertTableStringBuilder.toString());

            db.execSQL(dropTableStringBuilder.toString());

        }

    }

    private String getTypeByClass(Class<?> type)throws Exception {

        if(type.equals(String.class)) {

            return 
"TEXT";

        }

        if(type.equals(Long.class) || type.equals(Integer.class) || type.equals(long.class))
 {

            return 
"INTEGER";

        }

        if(type.equals(Boolean.class)) {

            return 
"BOOLEAN";

        }

        Exception exception = new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));

        throw exception;

    }

    private static List<String> getColumns(SQLiteDatabase db, String tableName) {

        List<String> columns = new ArrayList<String>();

        Cursor cursor = null;

        try {

            cursor = db.rawQuery("SELECT * FROM " + tableName +" limit 1",
null);

            if (cursor != 
null) {

                columns = new ArrayList<String>(Arrays.asList(cursor.getColumnNames()));

            }

        } catch (Exception e) {

            Log.v(tableName, e.getMessage(), e);

            e.printStackTrace();

        } finally {

            if (cursor != 
null)

                cursor.close();

        }

        return columns;

    }

}