使用Room Persistence遇到问题

当你在进行数据库插入或查询时会报如下错误信息：

java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.
    at android.arch.persistence.room.RoomDatabase.assertNotMainThread(RoomDatabase.java:143)
    at android.arch.persistence.room.RoomDatabase.beginTransaction(RoomDatabase.java:190)
    at cn.labelnet.android.roomdb.base.data.dao.UserDao_Impl.insertUser(UserDao_Impl.java:63)
    at cn.labelnet.android.roomdb.main.MainActivity.onItemClick(MainActivity.kt:53)
    at cn.labelnet.android.roomdb.main.adapter.MainAdapter$onBindViewHolder$1.onClick(MainAdapter.kt:53)
    at android.view.View.performClick(View.java:5637)
    at android.view.View$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)

这是因为你写的下面代码是默认操作必须放在io线程，不能放在ui线程中做

AppDatabase db = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, "database-name").build();

解决方式：

• 1、把操作放在io线程中(官方建议)
• 2、如果真要把操作放在ui线程中，就必须加个allowMainThreadQueries()方法，这样数据库的操作就可以在ui线程中使用了！

AppDatabase db = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, "database-name").allowMainThreadQueries().build();