房間遷移未正確處理

Question

得到以下異常：

預期：

TableInfo {name ='chat_table'，列= {message = Column {name ='message'，type ='TEXT'，affinity ='2'，notNull = false，primaryKeyPosition = 0}，messageStatus = Column {name ='messageStatus '，type ='TEXT'，affinity ='2'，notNull = false，primaryKeyPosition = 0}，id = Column {name ='id'，type ='INTEGER'，affinity ='3'，notNull = true，primaryKeyPosition = 1}}，foreignKeys = []，索引= []}

實測：

TableInfo {name ='chat_table'，column = {messageStatus = Column {name ='messageStatus'，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 = []，索引= []}

任何人都可以提出這里的問題嗎？ 我只是將表列值復制到另一個表。 然后刪除第一個表，然后將新表重命名為舊名稱。

 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

嘗試這種方式..

@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");
    }
};
}

更多理解請參閱此鏈接https://medium.com/androiddevelopers/understanding-migrations-with-room-f01e04b07929