房间迁移未妥善处理

Question

获取以下异常：

预期：

TableInfo{name='chat_table',Columns={message=column{name='message',type='text',affinity='2',notnull=false,primarykeyposition=0},messageStatus=column{name='message status',type='text',affinity='2',notnull=false,primarykeyposition=0},id=column{name='id',type='integer',affinity='3',notnull=true,primarykeyposition=1}},ForeignKeys=[],indices=[]}

找到：

TableInfo{name='chat_table',Columns={messageStatus=Column{name='message status',type='text',affinity='2',notnull=false,PrimaryKeyPosition=0},id=Column{name='id',type='integer',affinity='3',notnull=false,PrimaryKeyPosition=1},message=Column{name='message',type='text',affinity='2',notnull=false,PrimaryKeyPosition=0},ForeignKeys=[],Indices=[]}

谁能说说这里的问题是什么吗？我只是将表列值复制到另一个表。然后删除第一个表,然后将新表重命名为旧名称。

 1. database.execSQL("CREATE TABLE chat_table_new (id INTEGER,
        messageStatus TEXT, message TEXT, PRIMARY KEY(id))")
 2. database.execSQL("INSERT INTO chat_table_new SELECT * FROM
        chat_table") 
 3. database.execSQL("DROP TABLE chat_table") 
 4. database.execSQL("ALTER TABLE chat_table_new RENAME TO chat_table")

Answer 1

试试看..

@Database(entities = {Student.class, BookIssue.class},version = 1)
public abstract class StudentDatabase extends RoomDatabase {
private static StudentDatabase studentDatabase;
public static StudentDatabase getStudentDatabase(Context context)
{
    if (studentDatabase==null)
    {
        studentDatabase= Room.databaseBuilder(context.getApplicationContext(),StudentDatabase.class,"student-database").addMigrations(StudentDatabase.MIGRATION_1_2).build();

    }

    return studentDatabase;
}

public abstract StudentDao studentDao();
public abstract BookDao bookDao();

public static final Migration MIGRATION_1_2 =new Migration(1,2) {
    @Override
    public void migrate(SupportSQLiteDatabase database) {
        database.execSQL("alter table Student "+"add column pf String");
    }
};
}

更多了解请参阅此链接https://medium.com/androiddeveloperers/derministration-migrations-with-room-F01E04B07929