如何从协程 kotlin 中获取价值？

Question

我有一个用户登录的功能。 但它被暂停了。 我试图得到它的返回值，但我做不到。 这是我尝试做的事情

代码

class LoginViewModel @ViewModelInject constructor(private val remoteDataSource: OrderRemoteDataSource) :
    ViewModel() {

    private fun areValidCredentials(username: String?, password: String?): Boolean {
        return username != null && password != null && username.length > 4 && password.length > 4
    }

    suspend fun login(username: String?, password: String?): Boolean {
        return suspendCoroutine { it ->
            val valid = areValidCredentials(username, password)
            if (valid) {
                // call finish so login activity won't show up after back button clicked in home fragment
                try {
                    viewModelScope.launch {
                        //TODO CHECK if error code
                        val loginResponse =
                            remoteDataSource.login(LoginRequest(username!!, password!!))
                        if (loginResponse.status == Resource.Status.SUCCESS) {
                            val jwtToken = loginResponse.data?.jwtToken
                            if (!jwtToken.isNullOrEmpty()) {
                                sessionManager.saveAuthToken(jwtToken!!)
                                //ERROR!
                                it.resume(true)
                            }

                        }
                    }
                } catch (e: Exception) {
                    Log.i("[LoginActivity]", e.localizedMessage!!)
                    it.resume(false)
                    e.printStackTrace()
                }
            } else {
                Toast.makeText(
                    LOGIN_ACTIVITY,
                    "Username and password must be at least 5 letters long",
                    Toast.LENGTH_SHORT
                ).show()
            }
            it.resume(false)
        }
    }
}

我称之为

@AndroidEntryPoint
class LoginFragment : Fragment() {
    private val mViewModel: LoginViewModel by viewModels()
    private lateinit var navController: NavController

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        return inflater.inflate(R.layout.frg_login, container, false)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Log.d("[LoginFragment]", "onCreate fun started!")

    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        navController = findNavController()
        loginButton.setOnClickListener {
            //TODO navigate to new fragmnet
            lifecycleScope.launch {
                mViewModel.login(
                    loginUsernameText.text.toString(),
                    loginPasswordText.text.toString()
                )
            }
        }
    }

我有错误

E/AndroidRuntime: 致命异常: main 进程：ru.gkomega.navigation，PID：11863 java.lang.IllegalStateException：已经恢复 在 kotlin.coroutines.SafeContinuation.resumeWith(SafeContinuationJvm.kt:45) 在 ru.gkomega.maumarket.ui.login.LoginViewModel$login$$inlined$suspendCoroutine$lambda$1.invokeSuspend(LoginViewModel.kt:40) 在 kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) 在 kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241) 在 android.os.Handler.handleCallback(Handler.java:938) 在 android.os.Handler.dispatchMessage(Handler.java:99) 在 android.os.Looper.loop(Looper.java:223) 在 android.app.ActivityThread.main(ActivityThread.java:7656) 在 java.lang.reflect.Method.invoke（本机方法） 在 com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 我/chatty： uid=10163(ru.gkomega.navigation) 相同的 16 行 W/mega.navigatio： 收到关于不可去优化方法的去优化请求 java.lang.Class java.lang.Class.classForName(java.lang.String, boolean, java.lang.ClassLoader) I/Process: 发送信号。 PID：11863 SIG: 9 与目标 VM 断开连接，地址：'localhost:58264'， 传输：“套接字”

我对协程了解不多，所以它们可能是问题所在

Answer 1

无论请求是否发生，无论是否失败，您都在恢复协程。

suspend fun login(username: String?, password: String?): Boolean = suspendCoroutine { cont ->
    if (areValidCredentials(username, password)) {
        try {
            viewModelScope.launch {
                val loginResponse = remoteDataSource.login(LoginRequest(username!!, password!!))
                val jwtToken = loginResponse.data?.jwtToken
                if (loginResponse.status == Resource.Status.SUCCESS && !jwtToken.isNullOrEmpty()) {
                    sessionManager.saveAuthToken(jwtToken!!)
                    cont.resume(true)
                } else cont.resume(false)  // <-- Don't forget
            }
        } catch (e: Exception) {
            Log.i("[LoginActivity]", e.localizedMessage!!)
            cont.resume(false)
            e.printStackTrace()
        }
    } else {
        Toast.makeText(
            LOGIN_ACTIVITY,
            "Username and password must be at least 5 letters long",
            Toast.LENGTH_SHORT
        ).show()
        cont.resume(false)  // <-- Put it right here.
    }
    // cont.resume(false)  // <-- Not here
}

Answer 2

试试这个代码！

覆盖 fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState)

navController = findNavController()
loginButton.setOnClickListener {
    //TODO navigate to new fragment
        val isAuth = mViewModel.login(
            loginUsernameText.text.toString(),
            loginPasswordText.text.toString()
        )
        if (isAuth) {
            val startMainAction =
                LoginFragmentDirections.actionStartMain(loginUsernameText.text.toString())
            navController.navigate(startMainAction)
        }       
     }

}

以及 viewModel 上的这个片段

fun login(username: String?, password: String?): Boolean {
        var isAuth = false
        val valid = areValidCredentials(username, password)
        if (valid) {
            // call finish so login activity won't show up after back button clicked in home fragment
            try {
                //TODO CHECK if error code
                runBlocking {
                    val loginResponse = remoteDataSource.login(LoginRequest(username!!, password!!))
                    if (loginResponse.status == Resource.Status.SUCCESS) {
                        val jwtToken = loginResponse.data?.jwtToken.toString()
                        if (!jwtToken.isNullOrEmpty()) {
                            sessionManager.saveAuthToken(jwtToken)
                            isAuth = true
                        }
                    }
                }
            } catch (e: Exception) {
                Log.i("[LoginActivity]", e.localizedMessage!!)
                e.printStackTrace()
            }

我不确定这段代码是否正确，但它可以工作！