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danilshik
Asked:2020-04-02 19:59:38 +0000 UTC2020-04-02 19:59:38 +0000 UTC

单例 Android Kotlin

  • 772

需要帮助创建单例。

有一个类 - 文件资源管理器。

在片段中，我创建了一个类的实例，如果文件是文件夹，那么在文件资源管理器中，我移动到文件夹级别，片段被简单地重新打开，当前文件夹中的数据应该已经加载

class FileManager(context: Context) {

    private lateinit var currentDirectory: File
    private var rootDirecory: File
    private var instance : FileManager? = null

    init {
        Log.d("Класс создался", "тут")
        val directory: File
        if (Environment.MEDIA_MOUNTED == Environment.getExternalStorageState())
            directory = Environment.getExternalStorageDirectory()
        else
            directory = ContextCompat.getDataDir(context)!!
        rootDirecory = directory
        navigateTo(directory)
    }

    fun navigateTo(directory: File): Boolean {
        /**
         * Проверяем является ли файл директорией
         */
        if (!directory.isDirectory) {
            Log.d("FileManager", "${directory.absolutePath} is not a directory!")
            return false
        }

        /**
         * Проверим, не поднялись ли мы выше rootDirectory
         */

        if ((directory != rootDirecory) && rootDirecory.absolutePath.contains(directory.absolutePath)) {
            Log.w(
                "FileManager",
                "Trying to navigate upper than root directory to " + directory.absolutePath
            );
            return false
        }

        currentDirectory = directory
        return true
    }

    fun navigateUp(): Boolean {
        return navigateTo(currentDirectory.parentFile!!)
    }

    fun getFiles(): ArrayList<File> {
        val items = ArrayList<File>()
        val files = currentDirectory.listFiles()
        files?.let {
            items.addAll(currentDirectory.listFiles())
        }
        return items
    }

    fun getInstance(context: Context): FileManager{
        if(instance == null)
            instance = FileManager(context)
        return instance as FileManager
    }
}

我不知道如何将代码从 init 移动到主构造函数，并且由于 Init 始终有效，结果证明这不是单例

而且我还是不喜欢我的调用方式，你需要去掉不必要的参数

fileManager = FileManager(context!!).getInstance(context!!)

分段

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        fileManager = FileManager(context!!).getInstance(context!!)
        val bundle = this.arguments

        fileProviderAdapter = FileProviderAdapter{

            if(it.isDirectory){
                fileManager.navigateTo(it.absoluteFile)
                Log.d("нафигация", it.absoluteFile.toString())
                Snackbar.make(getView()!!, "Навигация ${it.name}", Snackbar.LENGTH_LONG)
                    .show()
                loadFragment(FileProviderFragment())
            }
            else{
                Snackbar.make(getView()!!, "Клик по ${it.name}", Snackbar.LENGTH_LONG)
                    .show()
            }
android

1 个回答

  1. Best Answer

    您需要像这样重写代码：

    class FileManager {

    private constructor(context: Context) {
        Log.d("Класс создался", "тут")
        val directory: File = if (Environment.MEDIA_MOUNTED == Environment.getExternalStorageState())
            Environment.getExternalStorageDirectory()
        else ContextCompat.getDataDir(context) ?: throw Exception("File does not exist!")
        rootDirectory = directory
        navigateTo(directory)
    }

    private lateinit var currentDirectory: File
    private var rootDirectory: File

    fun navigateTo(directory: File): Boolean {
        /**
         * Проверяем является ли файл директорией
         */
        if (!directory.isDirectory) {
            Log.d("FileManager", "${directory.absolutePath} is not a directory!")
            return false
        }

        /**
         * Проверим, не поднялись ли мы выше rootDirectory
         */

        if ((directory != rootDirectory) && rootDirectory.absolutePath.contains(directory.absolutePath)) {
            Log.w(
                    "FileManager",
                    "Trying to navigate upper than root directory to " + directory.absolutePath
            );
            return false
        }

        currentDirectory = directory
        return true
    }

    fun navigateUp(): Boolean {
        return navigateTo(currentDirectory.parentFile!!)
    }

    fun getFiles(): ArrayList<File> {
        val items = ArrayList<File>()
        val files = currentDirectory.listFiles()
        files?.let {
            items.addAll(currentDirectory.listFiles())
        }
        return items
    }

    companion object {
        private lateinit var instance: FileManager
        fun getInstance(context: Context): FileManager {
            if (!::instance.isInitialized)
                instance = FileManager(context)
            return instance
        }
    }
}

    呼叫现在将如下所示：

    FileMAnager.getInstance(context)
    • 2

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