您好,我正在尝试在我的应用程序中使用 listadapter 和 diffcallback 。不知何故,当我做某事时,视图根本不更新。
当我将一些日志放入回调内的“areItemsTheSame”和“areContentsTheSame”中时,根本不会调用它。
这是我的主要活动
class MainActivity : AppCompatActivity() {
private lateinit var recyclerView: RecyclerView
private lateinit var viewAdapter: TodoAdapter
private lateinit var viewManager: RecyclerView.LayoutManager
private lateinit var viewModel : TodoViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
//viewModel
viewModel = ViewModelProviders.of(this).get(TodoViewModel::class.java)
viewManager = LinearLayoutManager(this)
viewAdapter = TodoAdapter(viewModel.todos)
binding.btnNew.setOnClickListener {
viewModel.todos.value!!.add(Todo(3, binding.newText.text.toString()))
}
recyclerView = binding.myRecyclerView
recyclerView.apply {
layoutManager = viewManager
adapter = viewAdapter
}
viewModel.todos.observe(this, Observer{ list ->
viewAdapter.submitList(list)
Log.i("debug", "im @observe " + list.toString())
})
}
}
这是我的适配器
class TodoAdapter(var items: MutableLiveData<ArrayList<Todo>>):
ListAdapter<Todo, TodoAdapter.MyViewHolder>(TodoDiffCallback()) {
// Create new views (invoked by the layout manager)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
// create a new view
val inflater = LayoutInflater.from(parent.context)
val binding = ListItemBinding.inflate(inflater)
return MyViewHolder(binding)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
holder.todoText.text = getItem(position).task
//delete
holder.delBtn.setOnClickListener {
items.value!!.removeAt(position)
submitList(items.value)
Log.i("debug", "@adapter what is items " + items.value.toString())
}
//override fun getItemCount() = items.value!!.size
class MyViewHolder(val binding: ListItemBinding) : RecyclerView.ViewHolder(binding.root) {
val todoText = binding.todoItem
val delBtn = binding.btnDelete
val ediBtn = binding.btnEdit
}
}
class TodoDiffCallback : DiffUtil.ItemCallback<Todo>(){
override fun areItemsTheSame(p0: Todo, p1: Todo): Boolean {
Log.i("debug", " here " +p0 + " inItems " + p1 )
return p0 == p1
}
override fun areContentsTheSame(p0: Todo, p1: Todo): Boolean {
Log.i("debug", "here " + p0 + " inContents" + p1 )
return p0.equals(p1)
}
}
我的视图模型
class TodoViewModel: ViewModel() {
val todos = MutableLiveData<ArrayList<Todo>>()
init{
todos.value = arrayListOf(
Todo(1, "cooking"),
Todo(2, "washing")
)
}
}
不幸的是,android 文档没有给出更多的例子。
同样,我的 DiffUtil 类中的两个“日志”根本没有被调用。当我单击“删除”按钮时,用户界面未更新,但日志显示正确的结果。
thanks