如何在我的代码中插入 CALLBACK 代码

Posted 2023-02-19

【中文标题】如何在我的代码中插入 CALLBACK 代码

【英文标题】：how can i insert CALLBACK code in my code

【发布时间】：2019-11-29 15:05:23

【问题描述】：

当我在 android 应用上创建 JOIN Action 和 LOGIN Action 时， 发生了问题。 在 LOGIN Action 中使用 MVP 模式。 但是登录的结果并不是我想要的。 我给你看代码。

class LoginModel 

    var TAG = "LoginModel"
    private var ID: String
    private var PW: String
    var resultTxt: String = ""
    var auth: FirebaseAuth = FirebaseAuth.getInstance()

    constructor(ID: String, PW: String) 
        this.ID = ID
        this.PW = PW
    

    fun login(ID: String, PW: String) : String
        this.ID = ID
        this.PW = PW
        auth.signInWithEmailAndPassword(ID, PW)
            .addOnCompleteListener  task ->
            // 
                if (task.isSuccessful) 
                    val user = auth.currentUser
                    resultTxt = "Login Success"
                 else 
                    resultTxt = "Login Failed"
                
            
       return resultTxt
       // I'd like to process the results based on the return.
       // But it doesn't return the way I want it.
       // I know it's related to asynchronous processing.
       // So where should I put the callback function, and how should I write 
       // it?
    

【问题讨论】：

查看我的回答，希望对您有所帮助

请考虑给这个问题并回答一个upvote，这是未来如何为人们进行回调的基本示例：D ***.com/questions/57330766/…

【参考方案1】：

fun login(ID: String, PW: String, callback:(String) -> Unit) 
        this.ID = ID
        this.PW = PW
        auth.signInWithEmailAndPassword(ID, PW)
            .addOnCompleteListener  task ->

                if (task.isSuccessful) 
                    val user = auth.currentUser
                    resultTxt = "Login Success"
                 else 
                    resultTxt = "Login Failed"
                
                callback.invoke(resultTxt)
              
    

尝试将此作为回调，它会在执行后返回resultTxt 的值。

然后，当你调用登录方法时：

login(ID,PW) result ->
//here, result is the value of the callback 

交替

您可以在回调中返回调用的结果和用户，如下所示：

 fun login(ID: String, PW: String, callback:(Boolean, User?) -> Unit) 
        this.ID = ID
        this.PW = PW
        auth.signInWithEmailAndPassword(ID, PW)
            .addOnCompleteListener  task ->

                if (task.isSuccessful) 
                   callback.invoke(true, auth.currentUser)
                 else 
                  callback.invoke(false, null)
                
              
    

然后你可以这样使用它：

Login(id, password) result: Boolean, user: User? ->
    if(result)
     //the result is successful 
     user?.let authUser ->
       //here, authUser is your user
     
     else
    //the result was not successful
 

【参考方案2】：

为您的登录函数添加一个回调，在设置resultTxt 后调用该函数。以下几行应该可以工作，

class LoginModel 

    var TAG = "LoginModel"
    private var ID: String
    private var PW: String
    var resultTxt: String = ""
    var auth: FirebaseAuth = FirebaseAuth.getInstance()

    constructor(ID: String, PW: String) 
        this.ID = ID
        this.PW = PW
    

    fun login(ID: String, PW: String, callback: (String)->Unit) 
        this.ID = ID
        this.PW = PW
        auth.signInWithEmailAndPassword(ID, PW)
            .addOnCompleteListener  task ->
            // 
                if (task.isSuccessful) 
                    val user = auth.currentUser
                    resultTxt = "Login Success"
                 else 
                    resultTxt = "Login Failed"
                
                //The callback get's invoked with your expected result value.
                callback.invoke(resultTxt)
            
       //Don't return here
       //return resultTxt
       // I'd like to process the results based on the return.
       // But it doesn't return the way I want it.
       // I know it's related to asynchronous processing.
       // So where should I put the callback function, and how should I write 
       // it?
    

然后您可以使用以下方法调用该方法，

login(id,password)  result ->
    //Do what you want with the result here

【讨论】：

我专门针对与回调相关的问题发表了这篇文章，如果您认为它可能有用，请考虑给它投票：D ***.com/questions/57330766/…