7

我在项目中有 2 个数据库，其中一个是在我打开应用程序时创建的，另一个是由资产提供的。

生成 DaoSession 时，将为所有模型创建 DaoSession。

gradle 文件中的 Schema 也用于两个数据库

如何区分这 2 个数据库及其模式？

4

2 回答 2

6

您需要创建两个不同的扩展类org.greenrobot.greendao.database.DatabaseOpenHelper。这两个不同的类DevOpenHelperForDatabase1将DevOpenHelperForDatabase2 处理 db realted I/o。从下面的代码中很容易理解创建两个具有相同和不同架构或表或实体的不同数据库：

public class App extends Application {
private DaoSessionForDatabase1 mDaoSessionForDatabase1;
private DaoSessionForDatabase2 mDaoSessionForDatabase2;

@Override
public void onCreate() {
    super.onCreate();

    //Create Doa session for database1
    DevOpenHelperForDatabase1 devOpenHelperForDatabase1 = new DevOpenHelperForDatabase1(this,
        "database1-db");
    Database databse1 =  devOpenHelperForDatabase1.getWritableDb();
    mDaoSessionForDatabase1 = new DaoMasterForDatabase1(databse1).newSession();

    //Create Doa session for database2
    DevOpenHelperForDatabase2 devOpenHelperForDatabase2 = new DevOpenHelperForDatabase2(this,
        "database2-db");
    Database databse2 =  devOpenHelperForDatabase2.getWritableDb();
    mDaoSessionForDatabase2 = new DaoMasterForDatabase2(databse2).newSession();
}

public DaoSessionForDatabase1 getDaoSessioForDatabase1() {
    return mDaoSessionForDatabase1;
}

public DaoSessionForDatabase2 getDaoSessioForDatabase2() {
    return mDaoSessionForDatabase2;
}
}

例如，您可以从 Activity 访问相同和不同的架构或表或实体，如下所示：

// get the Schema1 DAO for Database1
DaoSessionForDatabase1 daoSessionForDatabase1 = ((App)    getApplication()).getDaoSessioForDatabase1();
Schema1Dao schema1Dao = daoSessionForDatabase1.getSchema1Dao();

// get the Schema2 DAO for Database2
DaoSessionForDatabase2 daoSessionForDatabase2 = ((App)  getApplication()).getDaoSessioForDatabase2();
Schema2Dao schema2Dao = daoSessionForDatabase2.getSchema2Dao();

更新 2:: 可以丢弃上述内容，但方法相同。根据以下评论中的讨论完成更新：

我在示例greenDAO -> 示例中进行了更改

package org.greenrobot.greendao.example;

import android.app.Application;

import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.example.DaoMaster.DevOpenHelper;

public class App extends Application {
/** A flag to show how easily you can switch from standard SQLite to  the encrypted SQLCipher. */
public static final boolean ENCRYPTED = true;

private DaoSession daoSession;

private DaoSession daoSession1;

@Override
public void onCreate() {
    super.onCreate();

    DevOpenHelper helper = new DevOpenHelper(this, ENCRYPTED ? "notes-db-encrypted" : "notes-db");
    Database db = ENCRYPTED ? helper.getEncryptedWritableDb("super-secret") : helper.getWritableDb();
    daoSession = new DaoMaster(db).newSession();


    DevOpenHelper helper1 = new DevOpenHelper(this, "notes1-db");
    Database db1 = helper1.getWritableDb();
    daoSession1 = new DaoMaster(db1).newSession();
}

public DaoSession getDaoSession() {
    return daoSession;
}

public DaoSession getDaoSession1() {
    return daoSession1;
}
}

现在进行以下更改NoteActivity.java

//Add below class members
private static boolean switchDbBetweenOneAndTwo = false;
private NoteDao noteDao2;
private Query<Note> notesQuery2;

//In on craete add the following as the last statement after   notesQuery = noteDao.queryBuilder().orderAsc(NoteDao.Properties.Text).build();
@Override
public void onCreate(Bundle savedInstanceState) {
......
Log.d("Database 1", "notesQuery.list()="+notesQuery.list().toString());

    // get the note DAO for Database2
    DaoSession daoSessionForDb2 = ((App) getApplication()).getDaoSession1();
    noteDao2 = daoSessionForDb2.getNoteDao();

    // query all notes, sorted a-z by their text
    notesQuery2 = noteDao2.queryBuilder().orderAsc(NoteDao.Properties.Text).build();
    Log.d("Database 2", "notesQuery2.list()="+notesQuery2.list().toString());
    updateNotes();
}

//Replace updateNotes as
private void updateNotes() {
    List<Note> notes = notesQuery.list();
    List<Note> notes2 = notesQuery2.list();
    notes.addAll(notes2);
    notesAdapter.setNotes(notes);
}

//Replace addNote as
private void addNote() {
    String noteText = editText.getText().toString();
    editText.setText("");

    final DateFormat df = DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.MEDIUM);
    String comment = "Added on " + df.format(new Date());

    Note note = new Note();
    note.setText(noteText);
    note.setComment(comment);
    note.setDate(new Date());
    note.setType(NoteType.TEXT);
    if(!switchDbBetweenOneAndTwo){
        note.setText(noteText + " In database 1");
        noteDao.insert(note);
    }
    else {
        note.setText(noteText + " In database 2");
        noteDao2.insert(note);
    }
    Log.d("DaoExample", "Inserted new note, ID: " + note.getId());
    switchDbBetweenOneAndTwo = true;
    updateNotes();
}

我没有对 gradle 文件进行任何更改或添加任何内容，因为它对我没有任何意义。

于 2017-03-06T11:03:38.017 回答
1

对于 Greendao 版本 3，模式不能超过 1 个。

github.com/greenrobot/greenDAO/issues/356

正如他们在他们的网站上所写的那样：

请注意，使用 Gradle 插件时当前不支持多个模式。暂时，继续使用你的生成器项目。

他们已经将此功能添加到新的 GreenDao 中。

于 2017-03-09T06:55:37.193 回答