错误：java.lang.NullPointerException，需要任何帮助才能使其工作 [重复]

问：

每次按下 Medir 按钮时我都会收到此错误，其余的一切都适用

原因：java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo（）”

这是 MainActivity 代码：

    package com.example.kotlincalcinsu

    import android.content.Intent
    import androidx.appcompat.app.AppCompatActivity
    import android.os.Bundle
    import android.widget.Button
    import android.widget.TextView

    class MainActivity : AppCompatActivity() {
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)

            val admin = AdminSQLiteOpenHelper(this, "AppDB", null, 1)
            val bd = admin.readableDatabase

            val name = bd.rawQuery("SELECT nombre FROM usuario", null).toString()
            val weight = bd.rawQuery("SELECT peso FROM usuario", null).toString()
            bd.close()

            //declarando TextView
            val nombre = findViewById<TextView>(R.id.Nombre)
            val peso = findViewById<TextView>(R.id.Peso)
            //declarando botones
            val medir = findViewById<Button>(R.id.medir)
            val historial = findViewById<Button>(R.id.historial)
            val registro = findViewById<Button>(R.id.registro)

            if (name.isNotEmpty() && weight.isNotEmpty()){
                nombre.text = name
                peso.text = weight
            }

            medir.setOnClickListener {
                val intent = Intent(this, Medir::class.java)
                startActivity(intent)
            }
            historial.setOnClickListener {
                val intent = Intent(this, Historial::class.java)
                startActivity(intent)
            }
            registro.setOnClickListener {
                val intent = Intent(this, Registro::class.java)
                startActivity(intent)
            }
        }
     }

这就是我试图开始的活动

package com.example.kotlincalcinsu

import android.Manifest
import android.bluetooth.BluetoothAdapter
import android.bluetooth.BluetoothDevice
import android.content.Intent
import android.content.pm.PackageManager
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.AdapterView
import android.widget.ArrayAdapter
import android.widget.Button
import android.widget.ListView
import android.widget.Toast
import androidx.core.app.ActivityCompat

class Medir : AppCompatActivity() {

    private val REQUEST_CODE_ENABLE_BT:Int = 1
    private var bluetoothAdapter: BluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
    private lateinit var pairedDevices: Set<BluetoothDevice>

    val selectDeviceList = findViewById<ListView>(R.id.selectorLV)

    companion object{
        val EXTRA_ADDRESS: String = "Device_address"
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_medir)



        val refresh = findViewById<Button>(R.id.refresh)
        val conectar = findViewById<Button>(R.id.conectar)

        //inicializar BluetoothAdapter
        //bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
        //revisar si esta encendido el Bluetooth
        if (bluetoothAdapter == null){
            Toast.makeText(this, "This device doesn't support Bluetooth", Toast.LENGTH_LONG).show()
            return
        } else{
            Toast.makeText(this, "Bluetooth available", Toast.LENGTH_LONG).show()
        }

        if (!bluetoothAdapter!!.isEnabled){
            val enableBluetoothIntent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED) return
            startActivityForResult(enableBluetoothIntent, REQUEST_CODE_ENABLE_BT)
        }

        refresh.setOnClickListener { pairedDeviceList() }


    }
    private fun pairedDeviceList(){
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.BLUETOOTH_CONNECT) != PackageManager.PERMISSION_GRANTED) { }
        pairedDevices = bluetoothAdapter!!.bondedDevices
        val list : ArrayList<BluetoothDevice> = ArrayList()

        if (pairedDevices.isNotEmpty()){
            for (device: BluetoothDevice in pairedDevices){
                list.add(device)
                Log.i("device", ""+device)
            }
        } else{
            Toast.makeText(this, "No paired Bluetooth devices", Toast.LENGTH_LONG).show()
        }

        val adapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, list)
            selectDeviceList.adapter = adapter
            selectDeviceList.onItemClickListener = AdapterView.OnItemClickListener{ _, _, position, _ ->
            val device: BluetoothDevice = list[position]
            val address: String = device.address

            val intent = Intent(this, ControlActivity::class.java)
            intent.putExtra(EXTRA_ADDRESS, address)
            startActivity(intent)
    }
}

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    if (requestCode == REQUEST_CODE_ENABLE_BT){
        if (resultCode == RESULT_OK){
            if (bluetoothAdapter!!.isEnabled){
                Toast.makeText(this, "Bluetooth has been enabled", Toast.LENGTH_LONG).show()
            } else{
                Toast.makeText(this, "Bluetooth has been disabled", Toast.LENGTH_LONG).show()
            }
        } else if (resultCode == RESULT_CANCELED){
            Toast.makeText(this, "Bluetooth enableing has been canceled", Toast.LENGTH_LONG).show()
        }
    }
}

}

and the AndroidManifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADVERTISE" />
    <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
    <uses-permission android:name="android.permission.BLUETOOTH_SCAN" />
    <uses-feature
        android:name="android.hardware.bluetooth_le"
        android:required="true">
    </uses-feature>
    <uses-feature
        android:name="android.hardware.bluetooth"
        android:required="true">
    </uses-feature>

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.KotlinCalcInsu"
        tools:targetApi="31">
        <activity
            android:name=".Historial"
            android:exported="false">
            <meta-data
                android:name="android.app.lib_name"
                android:value="" />
        </activity>
        <activity
            android:name=".Medir"
            android:exported="false">
            <meta-data
                android:name="android.app.lib_name"
                android:value="" />
        </activity>
        <activity
            android:name=".Registro"
            android:exported="false">
            <meta-data
                android:name="android.app.lib_name"
                android:value="" />
        </activity>
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

            <meta-data
                android:name="android.app.lib_name"
                android:value="" />
        </activity>
    </application>

</manifest>

根据老师和其他看过它的人的说法，一切似乎都是正确的，但它只是不断抛出该错误并使应用程序崩溃。欢迎任何帮助，并事先表示感谢

我已经尝试了不同的计算机 Mac 和 Windows，尝试了不同版本的 Android 和 Android Studio。我重写了代码以检查是否存在一些输入错误或文件是否有问题，但没有任何效果。