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简要介绍

本demo按照MVVM方式实现最简单的数据展示(支持自动分页加载)和删除的demo,用于展示一个完整的MVVM架构.

1. 包含:ViewModel+LiveData+Room+Paging
2. 语言:Kotlin
4. 包含databinding

代码实现(只贴出重点代码,完整代码见源代码)

1. UserActivity

class UserActivity : AppCompatActivity() {    private lateinit var viewModel: UserViewModel    override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        val binding: ActivityUserBinding = DataBindingUtil.setContentView(this, R.layout.activity_user)        val factory = InjectorUtils.provideUserViewModelFactory(this)        viewModel = ViewModelProviders.of(this, factory).get(UserViewModel::class.java)        val adapter = UserAdapter()        adapter.listener = View.OnClickListener { view ->            view?.let {                val user = view.tag as User                viewModel.delUser(user.id)            }        }        binding.userRv.adapter = adapter        viewModel.userList.observe(this, Observer { adapter.submitList(it) })    }}

2. UserAdapter

class UserAdapter : PagedListAdapter
   
    (UserDiffCallback()) {    lateinit var listener: View.OnClickListener    override fun onBindViewHolder(holder: ViewHolder, position: Int) {        val data = getItem(position) ?: return        holder.apply {            bind(listener, data)            itemView.tag = data        }    }    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {        return ViewHolder(ItemUserBinding.inflate(                LayoutInflater.from(parent.context), parent, false))    }    class ViewHolder(            private val binding: ItemUserBinding    ) : RecyclerView.ViewHolder(binding.root) {        fun bind(listener: View.OnClickListener, item: User) {            binding.apply {                clickListener = listener                user = item                executePendingBindings()            }        }    }}private class UserDiffCallback : DiffUtil.ItemCallback
    
     () {    override fun areContentsTheSame(oldItem: User, newItem: User): Boolean {        return oldItem.id == newItem.id    }    override fun areItemsTheSame(oldItem: User, newItem: User): Boolean {        return oldItem == newItem    }}
    
   

3. UserViewModel

class UserViewModel internal constructor(private val userRepository: UserRepository) : ViewModel() {    val userList = userRepository.getUserList()    fun delUser(id: Int) {        GlobalScope.launch {            userRepository.delUser(id)        }    }}

4. UserRepository

class UserRepository private constructor(private val userDao: UserDao) {    fun getUserList() = userDao.getUserList().toLiveData(Config(            pageSize = 30,            enablePlaceholders = true))    suspend fun addUser(name: String) {        withContext(Dispatchers.IO) {            val user = User(0, name)            userDao.add(user)        }    }    suspend fun delUser(id: Int) {        withContext(Dispatchers.IO) {            val user = User(id, "")            userDao.del(user)        }    }    companion object {        @Volatile        private var instance: UserRepository? = null        fun getInstance(userDao: UserDao) =                instance ?: synchronized(this) {                    instance                            ?: UserRepository(userDao).also { instance = it }                }    }}

5. UserDao

@Daointerface UserDao {    @Query("SELECT * FROM User")    fun getUserList(): DataSource.Factory
   
        @Insert    fun add(user: User)    @Insert    fun add(users: List
    
     )    @Delete    fun del(user:User)}
    
   

Demo源代码

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