Android 调用ContentObserver时更新设备联系人的页面列表

我正在使用ContentResolver和体系结构组件库LiveData、ViewModel和Paging检索具有分页功能的android设备联系人

我还注册了一个ContentObserver，以便在联系人发生更改时得到通知，以便能够更新我的联系人页面列表，但问题是我不知道怎么做

class ContactsViewModel : ViewModel() {
    private val config by lazy { PagedList.Config.Builder()
        .setPageSize(20)
        .setEnablePlaceholders(false)
        .build()
    }

    val contacts by lazy {
        LivePagedListBuilder<Int, Contact>(ContactsDataSourceFactory(), config).build()
    }
}

class ContactsDataSourceFactory : DataSource.Factory<Int, Contact>() {

    override fun create(): DataSource<Int, Contact> {
        return ContactsDataSource()
    }
}

class ContactsDataSource : PositionalDataSource<Contact>() {

    companion object {
        private val PROJECTION = arrayOf(
            ContactsContract.Contacts._ID,
            ContactsContract.Contacts.DISPLAY_NAME_PRIMARY,
            ContactsContract.Contacts.PHOTO_URI,
            ContactsContract.Contacts.LOOKUP_KEY
        )
    }

    override fun loadInitial(params: LoadInitialParams, callback: LoadInitialCallback<Contact>) {
        callback.onResult(getContacts(params.requestedLoadSize, params.requestedStartPosition), 0)
    }

    override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<Contact>) {
        callback.onResult(getContacts(params.loadSize, params.startPosition))
    }

    private fun getContacts(limit: Int, offset: Int): MutableList<Contact> {
        val cursor = App.appContext.contentResolver.query(
            ContactsContract.Contacts.CONTENT_URI,
            PROJECTION,
            null,
            null,
            "${ContactsContract.Contacts.DISPLAY_NAME_PRIMARY} ASC LIMIT $limit OFFSET $offset"
        )

        val contacts: MutableList<Contact> = mutableListOf()

        cursor?.run {
            while (moveToNext()) {
                val id = getLong(getColumnIndex(PROJECTION[0]))
                val name = getString(getColumnIndex(PROJECTION[1]))
                val photoUri = getString(getColumnIndex(PROJECTION[2]))
                val lookupKey = getString(getColumnIndex(PROJECTION[3]))
                val lookupUri = ContactsContract.Contacts.getLookupUri(id, lookupKey)
                contacts.add(Contact(id, name, photoUri, lookupUri))
            }
            close()
        }

        return contacts
    }
}

我知道我不明白发生了什么变化

我只需要获取新列表并将其传递给DiffUtil，它将为我完成其余的工作。换句话说，我需要以某种方式刷新我当前的页面列表

如果有人给我一个正确的方法我会很感激的谢谢

private val contactsViewModel by lazy { ViewModelProviders.of(this).get(ContactsViewModel::class.java) }

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    activity?.contentResolver.registerContentObserver(
        ContactsContract.Contacts.CONTENT_URI,
        true,
        OnContactsChangedListener(Handler())
    ) 
    contactsViewModel.contacts.observe(this, Observer { adapter.submitList(it) })
}


inner class OnContactsChangedListener(handler: Handler) : ContentObserver(handler) {
    override fun onChange(selfChange: Boolean) {
        //A change has occurred. What to do next?!!
    }
}