如何使用意图将变量从 MainActivity 传递到 ListAdapter

Question

我想在 MainActivity 和 ListAdapter 之间共享数据。问题是意图显示为“未解决的参考”。主要问题是我无法将“主”变量从 MainActivity 传输到 ListAdapter，我真的需要这个变量，因为我需要在我的应用程序中加密我的密码。

列表适配器

package com.example.roomapp.fragments.list
import android.app.PendingIntent.getActivity
import android.content.ContentValues.TAG
import android.content.Context
import android.content.Intent
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.example.roomapp.AESKnowledgeFcatory.encrypt
import com.example.roomapp.R
import com.example.roomapp.data.User
import kotlinx.android.synthetic.main.custom_row.view.*
import android.content.SharedPreferences
import com.example.roomapp.HashUtils.sha256
import com.example.roomapp.MainActivity
import android.content.Intent.getIntent

import android.os.Bundle
import android.util.Log
import android.widget.Toast


class ListAdapter(): RecyclerView.Adapter<ListAdapter.MyViewHolder>() {


    private var userList = emptyList<User>()


    class MyViewHolder(itemView: View): RecyclerView.ViewHolder(itemView) {}

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {

        return MyViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.custom_row, parent, false))

    }

    override fun getItemCount(): Int {
       return userList.size
    }


    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {


        val extras = getIntent().extras
        if(extras!=null)
        {
            val value = extras.getString("key")
        }

        val currentItem = userList[position]
        holder.itemView.id_txt.text = currentItem.id.toString()
        holder.itemView.firstName_txt.text = currentItem.firstName
        holder.itemView.lastName_txt.text = encrypt(currentItem.lastName,sha256(i+currentItem.salt.toString()))
        holder.itemView.salt_txt.text = currentItem.salt
    }

    fun setData(user: List<User>){
        this.userList = user
        notifyDataSetChanged()
    }
}

主活动

package com.example.roomapp

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.fragment.app.Fragment
import androidx.navigation.findNavController
import androidx.navigation.ui.setupActionBarWithNavController
import com.example.roomapp.AESKnowledgeFcatory.decrypt
import com.example.roomapp.HashUtils.sha256
import com.example.roomapp.fragments.add.AddFragment
import com.example.roomapp.fragments.list.ListAdapter
import com.example.roomapp.fragments.list.ListFragment
import kotlinx.android.synthetic.main.activitycreate.*
import kotlinx.android.synthetic.main.activitylogin.*
import kotlinx.android.synthetic.main.custom_row.*
import kotlin.properties.ReadOnlyProperty
import kotlin.reflect.KProperty

class MainActivity : AppCompatActivity() {
    var master: String = "0"
    var checkLogin2: String = ""
    var lf_ch = false


    fun createMaster(v:View){
        this.master = this.editmasterpass.text.toString()

        val sharedPref = this.getPreferences(MODE_PRIVATE) ?:return
        with (sharedPref.edit()){
            putString("cheie",sha256(master))
            commit()
        }

        val sharedPref2 = this.getPreferences(MODE_PRIVATE) ?: return
        val defaultValue = sharedPref2.getString("cheie", "ABA")
        System.out.println(" Key value = " + defaultValue)
        setContentView(R.layout.activity_main)
    }

    fun checklogin(v: View)
    {
        this.checkLogin2 = this.editTextTextPassword.text.toString()
        val castoras = this.getPreferences(MODE_PRIVATE)
        val defaultValue2 = castoras.getString("cheie", "ABA")
        if(sha256(this.checkLogin2)==defaultValue2.toString())
        {

            val value: String = this.master // or just your string
            val intent = Intent(this, ListAdapter::class.java)
            intent.putExtra("value", value)
            startActivity(intent)


            setContentView(R.layout.activity_main)
        }
        else {
            textView3.text="Incorrect Password"
        }

    }


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val castoras = this.getPreferences(MODE_PRIVATE)
        val defaultValue2 = castoras.getString("cheie", "key not found")

        System.out.println("Abracanabra= "+defaultValue2.toString())

        if ((defaultValue2.toString())=="key not found") {
            setContentView(R.layout.activitycreate)
        }
        else {
            setContentView((R.layout.activitylogin))
        }




    }


    override fun onSupportNavigateUp(): Boolean {
        val navController = findNavController(R.id.fragment)
        return navController.navigateUp() || super.onSupportNavigateUp()
    }



}

Answer 1

那是因为您试图以 ListAdapter 作为类而不是另一个活动或片段来调用 startActivity。

见docu