如何通过一个方法更新整个 kotlin 类中的 var，然后用另一个方法调用更新它

Question

我编写了一个 kotlin 类，其中包含一个重写的乐趣和一个将 var 更新到类范围的乐趣（可悲的是，我是 Kotlin 的新手！）

class mySampleClass: sampleReference(){
    var varToBeUpdated:String = "my string" //var in class scope to be updated

    fun updateMyVar(gotString:String){

        //I tried this, it didn't work
        this.varToBeUpdated = gotString
        // also this didn't work
        varToBeUpdated = gotString

    }

    override fun sample(context: Context, intent: Intent){
        //here i need my varToBeUpdated with new string
        runSomeThing(varToBeUpdated)
        //some work to be done here
    }
}

在我调用方法的地方：

myObject.updateMyVar("new string")
myObject.sample()

我想知道如何更新我需要的 var，因为我无法在“有趣的示例”中添加新参数，因为它覆盖了类方法

提前致谢，向大家致以最诚挚的问候:)

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更新：添加我的实际代码，因为当我调用覆盖方法时，该类似乎无法保持正确的更新值：

这是我的 BroadcastReceiver，检查何时下载完成并执行一些操作

class DownloadBroadcastManager: BroadcastReceiver() {

    var myClassFilename:String = "default"
    var myClassExtension:String = ".default"

    override fun onReceive(context: Context, intent: Intent) {
        val action = intent.action

        if (DownloadManager.ACTION_DOWNLOAD_COMPLETE == action) {
            //Show a notification
            // here there's a log to check if var are updated
            println("myTag - variables $myClassFilename, $myClassExtension")

            Toast.makeText(context, "Download of $myClassFilename$myClassExtension completed", Toast.LENGTH_LONG).show()
            // richiama azioni come player o display image o altro?

            //player
            var uri = Uri.parse (Environment.getExternalStorageDirectory().getPath() + "/Download/$myClassFilename$myClassExtension") //myClassExtension is ".mp3", dot is included, however it seems class is re-intialized as i call the method
            println("myTag - uri: $uri")
            println("myTag - context: $context")

            var mPlayer = MediaPlayer() // I added this declaration (that's be re-done later) cause I had a problem in making the player running (of course giving it a valid path to a valid file). Now this is "junk code"
            mPlayer.stop()
            mPlayer.reset()
            mPlayer.release()
            mPlayer = MediaPlayer.create(context, uri) // here there's the proper declaration + initialization
            mPlayer.start()

        }
    }
}

这是我的 DownloaderClass 中的部分...

var brReceiver = DownloadBroadcastManager()
    // shows when download is completed
    println("myTag - ${brReceiver.myClassFilename}, ${brReceiver.myClassExtension}: originals") //here shows the default: it's right
    val intent = Intent(context, MainActivity::class.java)
    brReceiver.myClassFilename = myTitle // inject filename
    brReceiver.myClassExtension = ".mp3" // inject file extension
    println("myTag - ${brReceiver.myClassFilename}, ${brReceiver.myClassExtension}: modified") // here it shows my class property as correctly updated

    brReceiver.onReceive(context, intent) // here, as calling the override fun, it get back to default value of the property

Answer 1

您只需执行以下操作：

1. 摆脱updateMyVar函数：

   class MySampleClass: SampleReference(){
       var varToBeUpdated:String = "my string" //var in class scope to be updated
   
       override fun sample(context: Context, intent: Intent){
           //here i need my varToBeUpdated with new string
           runSomeThing(varToBeUpdated)
           //some work to be done here
       }
   }
   

2. 直接更新varToBeUpdated属性：

   val myObject = MySampleClass()
   myObject.varToBeUpdated = "new string"
   myObject.sample()
   

---

更新： 如果您调用brReceiver.onReceive(...)，DownloadBroadcastManager 中的值将被更新。但你不应该那样做。 Android 框架 为您调用它。并且当它发生时，会创建 DownloadBroadcastManager 类的新实例并设置默认值。我们使用 Intents 将数据传递给BroadcastReceiver，例如在创建BroadcastReceiver 时调用intent.putExtra("filename", "yourFileName")，并在onReceive() 函数中调用intent.getStringExtra("filename") 以获取值。 Here is how to pass/get data to/from BroadcastReceiver

Answer 2

根据 kotlin 的文档，您可以像这样为任何变量定义 getter 和 setter 方法：

var <propertyName>[: <PropertyType>] [= <property_initializer>]
[<getter>]
[<setter>]

你的情况可能是这样的：

var varToBeUpdated:String = "my string"
    get() = field
    set(value) { field = value }

Answer 3

好的，首先感谢 M.SamiAzar，尤其是 Sergey，感谢他们的回答和令人难以置信的耐心！ 不幸的是，当它被框架重新初始化时，BroadcastReceiver 似乎也丢失了我之前放入 Intent 变量的任何额外内容。 我终于解决了这个问题，让我检索我需要的字符串，只需将一行文本写入内部存储中的文件并在我的 BroadcastReceiver 类中检索它。 代码如下：

这是我在 BroadcastReceiver 类中的“onReceive”方法

 override fun onReceive(context: Context, intent: Intent) {
    val action = intent.action
    Log.i("Receiver", "myTag - Broadcast received: " + action)
    var myFilename = "deafult"

    if (DownloadManager.ACTION_DOWNLOAD_COMPLETE == action) {

        // read the previously created file from internal storage
        var fileInputStream: FileInputStream? = null
        fileInputStream = context.openFileInput("storeDownloadedData")
        var inputStreamReader: InputStreamReader = InputStreamReader(fileInputStream)
        val bufferedReader: BufferedReader = BufferedReader(inputStreamReader)

        // here setting string var and stringbuilder var to catch the text updated outside the while loop
        val stringBuilder: StringBuilder = StringBuilder()
        var text: String? = null
        var sumText:java.lang.StringBuilder? = null
        // while loop for reading the file line by line (in this case the file can contains just one line a time)
        while ({ text = bufferedReader.readLine(); text }() != null) {
            sumText = stringBuilder.append(text)
        }

        // convert stringBuilder to a list of string splitting the original string obtained by file reading
        var secondText:String = "default"
        println("myTag - text: $text, $sumText")
        if (sumText != null){
            secondText = sumText.toString()
            var listFromText = secondText.split(",")
            // set filename to the title contained in the string
            myFilename = listFromText[0]
        }

        //player - finally play the file retrieving the title from the file in internal storage
        var uri = Uri.parse (Environment.getExternalStorageDirectory().getPath() + "/Download/$myFilename.mp3")
        println("myTag - uri: $uri")
        println("myTag - context: $context")

        var mPlayer = MediaPlayer.create(context, uri)
        mPlayer.start()

    }

这是在我的 DownloadManager 类中添加的代码：

// strore into an internal storage file the data of title and extensione for the file's gonna be downloaded
    val myStoredFile:String = "storeDownloadedData"
    val data:String = "$myTitle,.mp3"
    val fileOutputStream: FileOutputStream
    // write file in internal storage
    try {
        fileOutputStream = context.openFileOutput(myStoredFile, Context.MODE_PRIVATE)
        fileOutputStream.write(data.toByteArray())
    }catch (e: Exception){
        e.printStackTrace()
    }

    // it notifies when download is completed
    val intent = Intent(context, MainActivity::class.java)
    var brReceiver = DownloadBroadcastManager()

我不知道这是否是“正统”，但它似乎在 atm 工作 :)