Question

我想从txt文件中读取行，并将每行显示为列表视图中的项目我尝试了几种方法，但对我没有用这是我的代码：

private var fileDir:File?=null
private var items: ArrayList<String>? = null
private var itemsAdapter: ArrayAdapter<String>? = null
private var listVIL: ListView? = null
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_todo1)
//create file txt if not exist
    fileDir = File(Environment.getExternalStorageDirectory(), "todo.txt")
    if (!fileDir!!.exists()) {
        fileDir?.createNewFile()
    }
//read items from the file
    readFromFile()
listVIL = findViewById(R.id.listVI)
    items = ArrayList()
    itemsAdapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, items)
    listVIL?.adapter=itemsAdapter
}

我尝试了此功能，但有一些遗漏，尽管未引发异常，但列表视图中未显示任何内容

fun readFromFile() {
    try {
        var br = BufferedReader(InputStreamReader(FileInputStream(fileDir)))
    items?.addAll(br.readLines())
    br.close()
        }
    catch (e:Exception){
        Toast.makeText(applicationContext,e.toString(),Toast.LENGTH_LONG).show()
    }
    }

在这里，我尝试了另一种方法，但没有起作用

fun readFromFile() {
    try {
        var br = BufferedReader(InputStreamReader(FileInputStream(fileDir)))
        var hasNextLine = true
        while (hasNextLine) {
            var line = br.readLine()
            items?.add(line)
            hasNextLine = line != null
        }
        listVIL?.adapter = itemsAdapter
        br.close()
        itemsAdapter?.notifyDataSetChanged()
        }
    catch (e:Exception){
        Toast.makeText(applicationContext,e.toString(),Toast.LENGTH_LONG).show()
    }
}

Answer 1

在readFromFile()之后移动items = ArrayList()

Answer 2

科特琳（Kotlin）有一种tpass方法，您可以不用自己写一个方法

File.readLines

从txt文件读取行到listview

2 个答案: