错误日志

11-21 05:23:49.654 3793-3793/com.example.administrator.androiddemo E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                     Process: com.example.administrator.androiddemo, PID: 3793
                                                                                     android.database.sqlite.SQLiteException: Can't downgrade database from version 2 to 1
                                                                                         at android.database.sqlite.SQLiteOpenHelper.onDowngrade(SQLiteOpenHelper.java:360)
                                                                                         at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:254)
                                                                                         at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
                                                                                         at org.litepal.tablemanager.Connector.getWritableDatabase(Connector.java:58)
                                                                                         at org.litepal.tablemanager.Connector.getDatabase(Connector.java:81)
                                                                                         at org.litepal.LitePal.getDatabase(LitePal.java:62)
                                                                                         at com.example.administrator.androiddemo.MainActivity$1.onClick(MainActivity.java:21)
                                                                                         at android.view.View.performClick(View.java:5637)
                                                                                         at android.view.View$PerformClick.run(View.java:22429)
                                                                                         at android.os.Handler.handleCallback(Handler.java:751)
                                                                                         at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                         at android.os.Looper.loop(Looper.java:154)
                                                                                         at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                                         at java.lang.reflect.Method.invoke(Native Method)
                                                                                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

原因

由于后面对sqllite数据库修改了一次，使得数据库的版本号变成了2。

但是现在我又要创建相同名字的数据库，但是定义的数据库版本是1，所以产生错误了。

解决

修改sqlite数据库的版本。

<?xml version="1.0" encoding="utf-8" ?>
<litepal>
    <!--数据库名-->
    <dbname value="BookStore"/>

    <!--数据库版本号-->
    <version value="3"/>

    <!--映射模型-->
    <list>
        <mapping class="com.example.administrator.androiddemo.Book"/>
    </list>

</litepal>