如何在 Android 版 Kotlin 中正确处理观察数据

Question

我有一个从数据库检索数据的应用程序。下载数据时，屏幕上会出现进度条和文本，通知数据正在下载。下载数据后，文本和旋转图标消失。然而，在某些情况下，应用程序的行为并不完全正确。有时应用程序会冻结，有时进度条和文本会消失，但数据无法正确下载。我正确执行了代码吗？ 微调器仅用于在活动开始时显示某些默认值。

这是存储库：

 fun getAllZebra(): LiveData<List<Int>>{
        return sybaseDao.getAllZebra()
    }

这是视图模型：

@HiltViewModel
class ZebraViewModel @Inject constructor(
    private val repository: SybaseRepository
):ViewModel(){
    val skladnici = repository.getSkladnik().asLiveData()

    fun getAllZebra(): LiveData<List<Int>>{
        return repository.getAllZebra()
    }
}

这就是活动

@AndroidEntryPoint
class ZebraActivity : AppCompatActivity()  {
    //private val viewModel : ZebraViewModel by viewModels()
    var idZebra : Int = 0
    var idExp: Int = 0
    private val zebraViewModel: ZebraViewModel by viewModels()
    private val spinner3 by lazy {findViewById<Spinner>(R.id.zebra_spinner)}
    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)        
        SybaseApi.initilaizeBaseUrl(this)
        val binding = ActivityZebraBinding.inflate(layoutInflater)
        val view = binding.root
        setContentView(view)     

        binding.apply {
            zebraViewModel.skladnici.observe(this@ZebraActivity) { result ->
                val skladnici: List<Skladnik>? = result.data
                if (skladnici != null) {
                    Log.e("Skladnici", skladnici.size.toString())
                }
                else{
                    Log.e("Skladnici", "NULL")
                }
                progressBarLogin.isVisible =
                    result is Resource.Loading && result.data.isNullOrEmpty()
                textViewProgressBar.isVisible =
                    result is Resource.Loading && result.data.isNullOrEmpty()
                textViewProgressBar.text = "Loading data from database"
                textViewErrorLogin.isVisible =
                    result is Resource.Error && result.data.isNullOrEmpty()
                textViewErrorLogin.text = result.error?.localizedMessage
                textViewErrorLogin.isVisible = result is Resource.Success
                textViewErrorLogin.text = "Data uploaded:"
            }
        }

        
        

    override fun onResume() {
        super.onResume()
        SybaseApi.initilaizeBaseUrl(this)
        initSpinnerData()
    }

    private fun initSpinnerData(){
        val allDevices = this?.let {
            ArrayAdapter<Any>(it, R.layout.simple_item_spinner, R.id.tv_simple_item)
        }        
        allDevices?.clear()
        zebraViewModel.getAllZebra()
            .observe(this, { devices ->
                devices?.forEach{
                    allDevices?.getPosition(it)?.let { it1 -> if (it1 < 0) allDevices?.add(it) }
                }
            } )
        spinner3.adapter = allDevices
        spinner3.onItemSelectedListener = object : AdapterView.OnItemSelectedListener{
            override fun onItemSelected(parent: AdapterView<*>?, p1: View?, position: Int, p3: Long) {
                if (parent != null) {
                    val idZebraString = parent.getItemAtPosition(position).toString()
                    idZebra = idZebraString.toInt()

                }
            }

            override fun onNothingSelected(p0: AdapterView<*>?) {
                Toast.makeText(this@ZebraActivity, "You need to choose some item", Toast.LENGTH_LONG).show()            }

        }
    }

}

Answer 1

我认为问题不在于数据库，而在于视图，我看到您正在将 Spinner 与 ArrayAdapter 一起使用，您是否使用该数据通过 ArrayAdapter 为 Spinner 提供数据？如果是，您可以检查是否可以使用 RecyclerView.Adapter。