我是C＃和Android开发的新手（使用Xamarin）。我正在尝试创建一个简单的登录屏幕来检查用户输入，如果用户输入与文本文件中的数据匹配，它将显示登录成功，否则它将显示登录失败。
我不得不提到我将近一天的努力。我以为我在编码中搞砸了一些东西，所以我创建了简单的控制台应用程序，在那里复制代码并且它工作得很好，所以我认为我的问题与将字符串与来自EditText的用户输入进行比较有关。
应用程序构建成功，但每次按下与下面显示的方法相关的按钮时，我的应用程序崩溃并抛弃我。
我创建了两个名为user.txt和pass.txt的文本文件。 pass.txt中的第一行是user.txt第一行上用户的密码。
再一次，我必须提到代码在控制台应用程序中完美运行（我使用简单的Console.Readline替换了EditText中的user_input，使用Console.Writeline替换了Toast.MakeText）。拜托，我做错了什么？
public void read_list(object sender, EventArgs e)
{
k = FindViewById<EditText>(Resource.Id.user);
z = FindViewById<EditText>(Resource.Id.pass);
string user_input = k.Text.ToString();
string pass_input = z.Text.ToString();
int count = 0;
bool valid = false;
const string person = "user.txt";
List<string> users = new List<string>();
using (StreamReader username = new StreamReader(person))
{
string line;
while ((line = username.ReadLine()) != null)
{
users.Add(line);
}
foreach (string s in users)
{
if (Equals(s, user_input))
{
valid = true;
break;
}
count++;
}
}
const string key = "pass.txt";
List<string> passwords = new List<string>();
bool pass_valid = false;
using (StreamReader password = new StreamReader(key))
{
string pass_line;
while ((pass_line = password.ReadLine()) != null)
{
passwords.Add(pass_line);
}
if (Equals(passwords[count], pass_input))
{
pass_valid = true;
}
else
{
pass_valid = false;
}
}
if ((pass_valid) && (valid))
{
Toast.MakeText(this, "Login successful", ToastLength.Short).Show();
}
else
{
Toast.MakeText(this, "Login failed", ToastLength.Short).Show();
}
}
答案 0 :(得分：0)
正如我所说，你的主要观念是错误的。让我们看看我的例子，看看这个：
MainActivity 看起来像
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using System.IO;
namespace TestStuff
{
[Activity(Label = "Main",MainLauncher=true,Icon = "@drawable/icon")]
public class MainActivity : Activity
{
//path of folder,where we want to save our .txt File(Downloads)
Java.IO.File FolderToSave = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDownloads);
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.Second);
EditText login = FindViewById<EditText>(Resource.Id.editText1);
EditText password = FindViewById<EditText>(Resource.Id.editText2);
Button btn = FindViewById<Button>(Resource.Id.btn);
//here is final Path of our Credentials.txt
string filePath = System.IO.Path.Combine(FolderToSave.Path, "Credentials.txt");
//method,that will write correct login/password to .txt file
this.WriteFile("Vasya", "12345",filePath);
//eventhandler,when we pressing the button,method "check credentials will do some stuff
btn.Click += (sender, e) =>
{
//put parametrs: location of Credentials.txt and current login and password
CheckForCredentials(filePath,login.Text,password.Text);
};
}
//create and write credentials.txt with login and pass
void WriteFile(string Login,string Password,string Path)
{
using (StreamWriter Credentials = new StreamWriter (Path))
{
//first row will be our login
Credentials.WriteLine(Login);
//second is password
Credentials.WriteLine(Password);
}
}
//check for correct data
void CheckForCredentials(string Path,string CurrentLogin,string CurrentPassword)
{
string Login, Password;
if (File.Exists(Path))
{
//reading from Credentials.txt first rows(that is our login)
Login = File.ReadLines(Path).First();
//same for password
Password = File.ReadLines(Path).Last();
//check if introduced values are correct!
if (Login == CurrentLogin && Password == CurrentPassword)
{
Toast.MakeText(this, "Credentials are correct", ToastLength.Short).Show();
}
else
{
Toast.MakeText(this, "Something going wrong", ToastLength.Short).Show();
}
}
else
{
//credentials for some reason doest exist in your app.
Toast.MakeText(this, "Not exist file", ToastLength.Short).Show();
}
}
}
}
MainLayout.axml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/editText1"
android:layout_centerInParent="true"
android:layout_marginLeft="60dp"
android:hint="UserName" />
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/editText1"
android:id="@+id/editText2"
android:layout_centerInParent="true"
android:layout_marginLeft="60dp"
android:hint="Password" />
<Button
android:text="Check Credentials"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/editText2"
android:id="@+id/btn"
android:layout_centerInParent="true"
android:layout_marginTop="20dp" />
</RelativeLayout>
</LinearLayout>
此外，您需要在 AndroidManifest.xml （位于文件夹 Propreties ）中添加权限：
这就是全部:)。