如何构建Android MVVM应用程序

Posted 2023-04-25

参考技术A 可以使用框架,参考内容如下:
1、概述
Databinding
是一种框架，MVVM是一种模式，两者的概念是不一样的。咱的理解DataBinding是一个实现数据和UI绑定的框架，只是一个实现MVVM模式的工具。ViewModel和View可以通过DataBinding来实现单向绑定和双向绑定，这套UI和数据之间的动态监听和动态更新的框架Google已经帮咱们做好了。在MVVM模式中ViewModel和View是用绑定关系来实现的，所以有了DataBinding
使咱们构建android
MVVM
应用程序成为可能。
之前看了很多关于DataBinding的博客和相关的一些Demo，大多数就是往xml布局文件传入一些数据，然后把这些数据绑定到控件上(
如TextView
binding:text=“@user.name
)，接着在这些控件上（如Button
binding:setOnClickListener=”@user.listener”)
设置一些事件到控件上，基本讲述都是DataBinding的基本用法。但是并没有人告诉把一个onClickListener
写到一个类并把这个listener绑定到xml里面上是不是不太好，也没有人告诉这个和xml布局绑定的ViewModel类应该放哪些数据，应该做什么事？应该如何设计？更是很少有博文来告诉在Android
中如何通过Data
Binding
去构建MVVM
的应用框架。这也就是是本篇文章的重点。接下来，咱们先来看看什么是MVVM，然后在一步一步来设计整个应用程序框架。

如何使用 MVVM 架构实现 Firebase Google SignIn？

【中文标题】如何使用 MVVM 架构实现 Firebase Google SignIn？

【英文标题】：How to implement Firebase Google SignIn with MVVM architecture?

【发布时间】：2019-10-20 18:46:13

【问题描述】：

我正在构建一个应用程序，但我目前面临一个问题：我按照google guide 在 LoginActivity 中编写了我的 Google/Facebook 登录按钮的所有事件。但是，我不想将业务代码保留在活动中以遵循 MVVM 架构。因此，如何放置 Firebase 方法（需要活动引用和生命周期回调）？

我尝试了一个正在运行的 LoginViewModel，但它引用了 LoginActivity

class LoginViewModel(application: Application) : BaseViewModelContext(application) 

    lateinit var auth: FirebaseAuth
    val Tag: String = LoginViewModel::class.java.simpleName;
    val gso: GoogleSignInOptions
    val googleSignInClient: GoogleSignInClient

    init 
        auth = FirebaseAuth.getInstance()
        gso = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestIdToken(application.getString(R.string.default_client_id))
            .build()

        googleSignInClient = GoogleSignIn.getClient(application, gso)
    



    fun activityForResultLogin(requestCode:Int, resultCode: Int, data: Intent?, activity: Activity)
        if(requestCode == Constants.RC_SIGN_IN)
            val task = GoogleSignIn.getSignedInAccountFromIntent(data)
            try 
                // Google Sign In was successful, authenticate with Firebase
                val account = task.getResult(ApiException::class.java)
                firebaseAuthWithGoogle(account!!, activity)
             catch (e: ApiException) 
                // Google Sign In failed, update UI appropriately
                Log.w(Tag, "Google sign in failed", e)
                // ...
            
        
    

    private fun firebaseAuthWithGoogle(acct: GoogleSignInAccount, activity: Activity) 
        Log.d(Tag, "firebaseAuthWithGoogle:" + acct.id!!)

        val credential = GoogleAuthProvider.getCredential(acct.idToken, null)
        auth.signInWithCredential(credential)
            .addOnCompleteListener(activity)  task ->
                if (task.isSuccessful) 
                    // Sign in success, update UI with the signed-in user's information
                    Log.d(Tag, "signInWithCredential:success")
                    val user = auth.currentUser
                    activity.shortToast("SignInSuccess")
                 else 
                    // If sign in fails, display a message to the user.
                    Log.w(Tag, "signInWithCredential:failure", task.exception)
                    activity.shortToast("SignInFailed")
                

            
    

    fun signInGoogle(activity: Activity)
        val signInIntent = googleSignInClient.signInIntent
        activity.startActivityForResult(signInIntent, Constants.RC_SIGN_IN)
    

    fun signOutGoogle(activity: Activity)
        googleSignInClient.signOut().addOnCompleteListener(activity)
            //Update ui
        
    

【问题讨论】：

看看 Paha 实现 GoogleSignIn 的实现：github.com/jojink/Android-Kotlin-FirebaseAuth/blob/feature/…希望这会有所帮助。

那个 git 看起来更像 MVP no MVVM

如果您对干净的 Firebase 身份验证感兴趣，可以查看此article。

在 codelab github.com/googlecodelabs/android-kotlin-logingoogle 上查看这个例子

你好@ELTEGANIMOHAMED！谢谢 ！这正是我想要的:)

【参考方案1】：

这是我所做的。

创建用户模型：

data class User(
    val uid: String,
    val name: String?,
    val email: String?,
    var isAuthenticated: Boolean = false,
    var isNew: Boolean? = false,
    var isCreated: Boolean = false

) : Serializable

    constructor() : this("","","") 

    

创建 AuthRepository 类：

class AuthRepository 

    private val firebaseAuth: FirebaseAuth = FirebaseAuth.getInstance()
    private val rootRef: FirebaseFirestore = FirebaseFirestore.getInstance()
    private val usersRef: CollectionReference = rootRef.collection(USERS)

    // Sign in using google
    fun firebaseSignInWithGoogle(googleAuthCredential: AuthCredential): MutableLiveData<ResponseState<User>> 
        val authenticatedUserMutableLiveData: MutableLiveData<ResponseState<User>> =
            MutableLiveData()
       
         firebaseAuth.signInWithCredential(googleAuthCredential).addOnCompleteListener  authTask ->
            if (authTask.isSuccessful) 
                var isNewUser = authTask.result?.additionalUserInfo?.isNewUser
                val firebaseUser: FirebaseUser? = firebaseAuth.currentUser
                if (firebaseUser != null) 
                    val uid = firebaseUser.uid
                    val name = firebaseUser.displayName
                    val email = firebaseUser.email
                    val user = User(uid = uid, name = name, email = email)
                    user.isNew = isNewUser
                    authenticatedUserMutableLiveData.value = ResponseState.Success(user)

                


             else 

                authenticatedUserMutableLiveData.value = authTask.exception?.message?.let 
                    ResponseState.Error(it)
                

            


        
        return authenticatedUserMutableLiveData
    

创建 LoginViewModel 类：

class LoginViewModel constructor(private val authRepository: AuthRepository) :
    ViewModel() 

    private var _authenticateUserLiveData: MutableLiveData<ResponseState<User>> = MutableLiveData()
  val authenticateUserLiveData: LiveData<ResponseState<User>> get() = _authenticateUserLiveData

    fun signInWithGoogle(googleAuthCredential: AuthCredential) 
        _authenticateUserLiveData = authRepository.firebaseSignInWithGoogle(googleAuthCredential)
    

这里的ResponseState类如下：

sealed class ResponseState<T>(
    val data: T? = null,
    val message: String? = null
) 


    class Success<T>(data: T) : ResponseState<T>(data)
    class Error<T>(message: String) : ResponseState<T>(message = message)
    class Loading<T> : ResponseState<T>()

在您的活动或片段中，您可以将其用作：

lateinit var googleSignInClient: GoogleSignInClient
private fun initGoogleSignInClient() 
    val gso = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
        .requestIdToken(getString(R.string.default_web_client_id))
        .requestEmail()
        .build()

    googleSignInClient = GoogleSignIn.getClient(this, gso)


private fun signInUsingGoolge() 
    val signInGoogleIntent = (activity as MainActivity).googleSignInClient.signInIntent
    startActivityForResult(signInGoogleIntent, RC_SIGN_IN)

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent ? ) 
    super.onActivityResult(requestCode, resultCode, data)

    if (requestCode == RC_SIGN_IN) 
        val task = GoogleSignIn.getSignedInAccountFromIntent(data)
        try 
            // Google Sign In was successful, authenticate with Firebase
            val account = task.getResult(ApiException::class.java) !!
                if (account != null) 
                    getGoogleAuthCredential(account)
                

         catch (e: ApiException) 
            // Google Sign In failed, update UI appropriately
        
    


private fun getGoogleAuthCredential(account: GoogleSignInAccount) 
    binding.progressBar.visible()
    val googleTokeId = account.idToken
    val googleAuthCredential = GoogleAuthProvider.getCredential(googleTokeId, null)
    signInWithGoogleAuthCredential(googleAuthCredential)


private fun signInWithGoogleAuthCredential(googleAuthCredential: AuthCredential) 

    loginViewModel.signInWithGoogle(googleAuthCredential)
    loginViewModel.authenticateUserLiveData.observe(viewLifecycleOwner, 
        authenticatedUser - >
        when(authenticatedUser) 
            is ResponseState.Error - > 
                authenticatedUser.message ? .let 
                    context ? .toast(it)
                
            
            is ResponseState.Success - > 
                if (authenticatedUser.data != null)
                //update ui
            
            is ResponseState.Loading - > 
                //show progress
            
        
    )