android - 我的协程出现 "Cannot access database on the main thread since it may potentially lock the UI for a long period of time."错误

Question

我的协程在主线程上运行，我在协程上下文中指定了它:

class ClickPreference(context: Context, attrs: AttributeSet) : Preference(context, attrs), CoroutineScope, View.OnClickListener {

    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main

override fun onClick(v: View?) {
    when (key){
        "logout" -> {
            CoroutineScope(coroutineContext).launch {
                CustomApplication.database?.clearAllTables()
                Log.d("MapFragment", "Cleared Tables")
            }
            if (Profile.getCurrentProfile() != null) LoginManager.getInstance().logOut()
            FirebaseAuth.getInstance().signOut()
            val intent = Intent(context, MainActivity::class.java)
            context.startActivity(intent)
        }
    }
}

但我仍然收到此错误:

java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.

在我上面的协程调用 CustomApplication.database?.clearAllTables() 到我的 Room 数据库。

这是我的CustomApplication:

class CustomApplication : Application() {

    companion object {
        var database: AppDatabase? = null
    }

    override fun onCreate() {
        super.onCreate()
        CustomApplication.database = Room.databaseBuilder(this, AppDatabase::class.java, "AppDatabase").build()
    }

如果我的协程上下文在主线程上运行，为什么我仍然会收到错误？

Answer 1

错误表明它不应该在主线程上运行。数据库操作(以及所有其他形式的 IO)可能需要很长时间，应该在后台运行。

您应该使用专为运行 IO 操作而设计的 Dispatchers.IO。