Android 仅在ViewModel中切换线程

安卓工作室4

RxJava2，MVVM

方法#1

在我的活动中：

 val dispose = filmsRxJavaViewModel.filmsListSingle
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .doOnSubscribe( {// call before .doOnTerminate()
                Debug.d(TAG, "initLogic: doOnSubscribe:")
                binding.progressBarLayout.containerProgressBarLayout.setVisibility(View.VISIBLE)
            })
            .doOnTerminate({// call before .subscribe()
                Debug.d(TAG, "initLogic: doOnTerminate:")
                binding.filmsSwipeRefreshLayout.isRefreshing = false
                binding.progressBarLayout.containerProgressBarLayout.setVisibility(View.GONE)
            })
            // Only after call subscribe() then execute network request
            .subscribe({ filmsList -> // success
                Debug.d(TAG, "initLogic: subscribe: success")
                // Hide swipe to refresh icon animation
                if (filmsList.size > 0) { // list<Film>
filmItemListDataBindingAdapter!!.updateData(filmsList)
                } else {
                    binding.filmsRecyclerView.visibility = View.GONE
                    binding.emptyLayoutContainer.root.visibility = View.VISIBLE
                }
            }, {// error
                    throwable ->
                Debug.e(TAG, "initLogic: subscribe: error = $throwable")
                Toast.makeText(this, throwable.message, Toast.LENGTH_LONG).show()
            })

正如您所看到的，我将在线程之间切换到viewModel

我认为这是一个正确的方法。只有viewModel必须需要在线程之间切换。因此，我的活动仅适用于视图小部件（如ShowToast）

---

这是正确的方法吗？

将沉重的Rx逻辑放在ViewModel中才是正确的方法

这是为了可测试性：片段和活动很重，很难测试。相比之下，ViewModel易于测试

因此，我们按照模式使片段和活动“愚蠢”

片段和活动应该只观察ViewModel的模型（这是一包原语）的更改。这是由公开LiveData的ViewModel完成的。对于视图的瞬时更改（如Toast），片段或活动可以观察处理时过期的事件流的LiveData

请查看Android架构蓝图和

SingleLiveEvent

而且，它们不是RxJava中的“线程”——它们是调度器

class FilmsRxJavaViewModel(application: Application) : AndroidViewModel(application) {
    companion object {
        private val TAG = FilmsRxJavaViewModel::class.java.name
    }

    lateinit var filmsListSingle: Single<List<Film>>

    init {
        Debug.d(TAG, "init:")
        loadData()
    }

    fun loadData() {
        Debug.d(TAG, "loadData:")
        filmsListSingle = TransportServiceRxJava.getFilms()
    }

}

fun getFilms() : Single<List<Film>> {
            return testRxJavaRestClient.getFilms()
        }

import io.reactivex.Single
import retrofit2.http.GET

interface TestRxJavaRestClient {

    @GET("films")
    fun getFilms(): Single<List<Film>>

}

val dispose = filmsRxJavaViewModel.filmsListSingle
            .doOnSubscribe( {// call before .doOnTerminate()
                Debug.d(TAG, "initLogic: doOnSubscribe:")
                binding.progressBarLayout.containerProgressBarLayout.setVisibility(View.VISIBLE)
            })
            .doOnTerminate({// call before .subscribe()
                Debug.d(TAG, "initLogic: doOnTerminate:")
                binding.filmsSwipeRefreshLayout.isRefreshing = false
                binding.progressBarLayout.containerProgressBarLayout.setVisibility(View.GONE)
            })
            // Only after call subscribe() then execute network request
            .subscribe({ filmsList -> // success
                Debug.d(TAG, "initLogic: subscribe: success")
                // Hide swipe to refresh icon animation
                if (filmsList.size > 0) { // list<Film>
filmItemListDataBindingAdapter!!.updateData(filmsList)
                } else {
                    binding.filmsRecyclerView.visibility = View.GONE
                    binding.emptyLayoutContainer.root.visibility = View.VISIBLE
                }
            }, {// error
                    throwable ->
                Debug.e(TAG, "initLogic: subscribe: error = $throwable")
                Toast.makeText(this, throwable.message, Toast.LENGTH_LONG).show()
            })

fun loadData() {
        Debug.d(TAG, "loadData:")
        filmsListSingle = TransportServiceRxJava.getFilms()
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
    }