android - 使用ViewModel处理屏幕旋转而不会丢失数据-Android

Question

我有一个 Activity 的方向不确定，并且有一个与该 Activity 相关的片段具有纵向和横向模式的不同布局，并且在该片段上有条件地调用了多个API，我的问题是当屏幕旋转时所有数据都丢失了而且该片段上有很多数据，因此我不想将每个数据保存在saveInstance方法上。我尝试了android:configChanges="keyboardHidden|orientation|screenSize"，但这没有解决我的问题。我想使用viewModel处理此问题。请帮助，在此先感谢。
这是我的代码
资料库

class GetDataRepository {
val TAG = GetDataRepository::class.java.canonicalName
var job: CompletableJob = Job()

fun getData(
    token: String?,
    sslContext: SSLContext,
    matchId: Int
): LiveData<ResponseModel> {
    job = Job()
    return object : LiveData<ResponseModel>() {
        override fun onActive() {
            super.onActive()
            job.let { thejob ->
                CoroutineScope(thejob).launch {
                    try {
                        val apiResponse = ApiService(sslContext).getData(
                            token
                         
                        )
                        LogUtil.debugLog(TAG, "apiResponse ${apiResponse}")
                        withContext(Dispatchers.Main) {
                            value = apiResponse
                        }
                    } catch (e: Throwable) {
                        LogUtil.errorLog(TAG, "error: ${e.message}")
                        withContext(Dispatchers.Main) {
                            when (e) {
                                is HttpException -> {
                                    value =
                                        Gson().fromJson<ResponseModel>(
                                            (e as HttpException).response()?.errorBody()
                                                ?.string(),
                                            ResponseModel::class.java
                                        )
                                }
                                else -> value = ResponseModel(error = e)
                            }
                        }

                    } finally {
                        thejob.complete()
                    }
                }

            }
        }
    }
}

fun cancelJob() {
    job.cancel()
}

}
ViewMode:

class DataViewModel : ViewModel() {
val TAG = DataViewModel::class.java.canonicalName
var mListener: DataListener? = null

private val mGetDataRepository: GetDataRepository = GetDataRepository()


fun getData() {
    LogUtil.debugLog(TAG, "getData")
    if (mListener?.isInternetAvailable()!!) {
        mListener?.onStartAPI()

        val context = mListener?.getContext()

        val token: String? = String.format(
            context?.resources!!.getString(R.string.user_token),
            PreferenceUtil.getUserData(context).token
        )

        val sslContext = mListener?.getSSlContext()

        if (sslContext != null) {
            val getData =
                mGetDataRepository.getData(
                    token
                )
            LogUtil.debugLog(TAG, "getData ${getData}")
            mListener?.onApiCall(getData)
        } else {
            LogUtil.debugLog(TAG, "getData Invalid certificate")
            mListener?.onError("Invalid certificate")
        }
    } else {
        LogUtil.debugLog(TAG, "getData No internet")
        mListener?.onError("Please check your internet connectivity!!!")
    }
    LogUtil.debugLog(TAG, "Exit getData()")
}

}
Activity :

class DataActivity : AppCompatActivity() {
val TAG = DataActivity::class.java.canonicalName
lateinit var fragment: DataFragment

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    LogUtil.debugLog(TAG, "onCreate: Enter")

    var binding: ActivityDataBinding =
        DataBindingUtil.setContentView(this, R.layout.activity_data)
    if (savedInstanceState == null) {
         fragment = DataFragment.newInstance()
        supportFragmentManager.beginTransaction().add(R.id.container, fragment, DataFragment.TAG)
    } else {
        fragment = supportFragmentManager.findFragmentByTag(DataFragment.TAG) as DataFragment
    }

    LogUtil.debugLog(TAG, "onCreate: Exit")
}

}
分段:

class DataFragment : Fragment(), DataListener {
private var mBinding: FragmentDataBinding? = null
private lateinit var mViewModel: DataViewModel

companion object {
    val TAG = DataFragment::class.java.canonicalName
    fun newInstance(): DataFragment {
        return DataFragment()
    }
}

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    mBinding =
        DataBindingUtil.inflate(inflater, R.layout.fragment_data, container, false)
    mViewModel = ViewModelProvider(this).get(DataViewModel::class.java)
    mViewModel.mListener = this
    getData()
    return mBinding?.root
}

private fun getData() {
    LogUtil.debugLog(TAG, "Enter getMatchScore()")
    mViewModel.getData()
    LogUtil.debugLog(TAG, "Exit getMatchScore()")
}

override fun <T> onApiCall(response: LiveData<T>) {
    response.observe(this, Observer {
        it as DataResponseModel
        //
    })

}

}

Answer 1

默认情况下，viewModel的生命周期长于您的 Activity (在您的情况下为屏幕旋转)。
Activity 因配置更改而销毁后，ViewModel不会销毁，您可以看到此link。
您似乎在 Activity /片段中的其他地方犯了一个错误，请在此处输入 Activity /片段代码。
在片段中，您可以在onCreateView中调用mViewModel.getData()，并且每次旋转 Activity 时，都会调用此方法调用并重置所有存储数据并再次获取!!您只需检查片段中ViewModel的数据，是否为空即可getData()，似乎您对View(Fragment)的ViewModel引用(您将片段中的监听器传递给ViewModel)，并且它也是一种反模式(建议使用此article)