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c# - 为什么重新加载页面时通过 StreamWriter 写入文件的文本不会保存？(Xamarin)

问题描述

我正在尝试将多个字符串写入 txt 文件，以便在用户切换页面时保存该信息。但是，字符串似乎永远不会被保存。

入口。（写入文件的字符串源）

<Entry 
x:Name="Entry"
Placeholder="Username"
WidthRequest = "200"
VerticalOptions = "Start"
HorizontalOptions = "Center"
/>

将信息写入文件的代码。

        private void Write()
        {

            StreamWriter sw = new StreamWriter(path);
            sw.WriteLine(txtStorage.Length);

            //Writes length so that txtStorage can be correct length later

            sw.WriteLine(Entry.Text);

            //Writes username entered in this instance of the page

            for (int i = 0; i < txtStorage.Length; i++)
            {
                sw.WriteLine(txtStorage[i]);

                //Writes usernames stored from previous instances
            };
            sw.Close();
        }

读取文件的代码。

        {
            StreamReader sr = new StreamReader(path);
            txtStorage = new string[Convert.ToInt32(sr.ReadLine())];

            //updates txtstorage to new length written in text file

            for (int i = 0; i < txtStorage.Length; i++)
            {
                txtStorage[i] = sr.ReadLine();
                //puts all usernames back into txtstorage
            };

            sr.Close();
        }

以前实例中的所有用户名都不会保存。我究竟做错了什么？

标签： c#xamarin.formsstreamreaderstreamwriter

解决方案

当你写文件时，你正在这样做

// 1. write the length of the array
sw.WriteLine(txtStorage.Length);

// 2. write the user name
sw.WriteLine(Entry.Text);

// 3. write the array
for (int i = 0; i < txtStorage.Length; i++)

这将生成一个类似这样的文件

3
myusername
user1
user2
user3

那么当你阅读文件时，你正在这样做

// 1. read the length as a string
txtStorage = new string[Convert.ToInt32(sr.ReadLine())];

// 2. you aren't doing anything to handle line #2

// 3. you are using the LENGTH of txtstorage, which is 1, so your loop is only executing once
// and since you skipped #2, you are also starting on the wrong line
for (int i = 0; i < txtStorage.Length; i++)

相反，这样做

// 1. read the length as an int
var ndx = int.Parse(sr.ReadLine());

// 2. read the user name
var user = sr.ReadLine();

// 3. use ndx as the loop counter, starting on the correct line
for (int i = 0; i < ndx; i++)

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