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android - 如何在 Activity 中的 API 调用上从 ViewModel 获取错误？

问题描述

当我在 Android 中使用 ViewModel 时，我在 ViewModel 类中使用了两个 MutableLiveData 对象。

var imageList: MutableLiveData<List<HitsItem>> = MutableLiveData()
var errorMessage: MutableLiveData<String> = MutableLiveData()

我想要的是每当设置 API 调用 errorMessage 中发生错误时，同样，当 API 调用成功时，会设置 imageList。

如何在 Activity 中检查 API 是否成功，当 API 调用不成功时，我想在 Activity 中显示 Toast 错误消息..？

ImageViewModel.kt

fun getImages(): LiveData<List<HitsItem>> {
    imageList = MutableLiveData()
    loadImages()
    return imageList
}

fun loadImages() {
    val api = PexelClient.getClient().create(ApiInterface::class.java)
    val imageObservable = api.images
    imageObservable.subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .map({ result -> result })
        .subscribe(
            Consumer<ImageModel> { this.handleResults(it) },
            Consumer<Throwable> { this.handleError(it) }
        )
}

private fun handleResults(list: ImageModel) {
    imageList.value = list.hits
    errorMessage.value = null
}

private fun handleError(t: Throwable) {
    imageList.value = null
    errorMessage.value = t.message
}

活动

lateinit var imagesViewModel:ImagesViewModel
lateinit var adapter:ImageAdapter

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_mvvm_rx_retrofit)


    rv_images.setHasFixedSize(true)
    rv_images.layoutManager = LinearLayoutManager(this)

    imagesViewModel = ViewModelProviders.of(this).get(ImagesViewModel::class.java)
    imagesViewModel.getImages().observe(this, object : Observer<List<HitsItem>> {
        override fun onChanged(imageList: List<HitsItem>?) {
            if(imageList != null){
                adapter = ImageAdapter(this@MvvmRxRetrofit,imageList)
                rv_images.adapter = adapter
            }
        }
    })


}

标签： androidmvvmrx-java2rx-androidandroid-viewmodel

解决方案

  1. 创建一个网络响应类：

公共类 AsyncResponse {

public ResponseStatus responseStatus ;
public Throwable error ;
public JsonElement data ;


AsyncResponse(ResponseStatus responseStatus, JsonElement data ,Throwable error){
    this.responseStatus = responseStatus ;
    this.data = data ;
    this.error = error ;
}

public static AsyncResponse loading(){
    return new AsyncResponse(ResponseStatus.LOADING,null,null);
}

public static AsyncResponse success(JsonElement data){
    return new AsyncResponse(ResponseStatus.SUCCESS,data,null);
}

public static AsyncResponse error(Throwable error){
    return new AsyncResponse(ResponseStatus.ERROR,null,error);
}

}

  1. 创建一个枚举类：

    公共枚举响应状态{加载，成功，错误}

  2. 在您的视图模型类中，无论您在哪里收到响应，只需发布​​值：

    私有 MutableLiveData asyncResponseMutableLiveData = new MutableLiveData<>();

    响应成功：

    asyncResponseMutableLiveData.postValue(AsyncResponse.success());

    响应错误：

    asyncResponseMutableLiveData.postValue(AsyncResponse.error(new Throwable(e)));

4.在Activity Class中，观察响应

 mChatDialogViewModel.getResponse().observe(this, new Observer<AsyncResponse>() {
            @Override
            public void onChanged(@Nullable AsyncResponse asyncResponse) {
                if (asyncResponse != null)
                    consumeResponse(asyncResponse);
            }
        });

private void consumeResponse(AsyncResponse asyncResponse) {

        switch (asyncResponse.responseStatus) {

            case LOADING: {
                break;
            }
            case SUCCESS: {

                break;
            }
            case ERROR: {

                break;
            }
            default:
                break;

        }

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