Android Studio：无效缓存/重启后未解决的对activity main的引用

Question

所以我是编程新手，想参与其中。我开始学习Kotlin并创建了一个简单的骰子滚动应用程序，其中添加了我所学到的新功能。然而，当我按照教程学习时，那个人按下了File>InvalidadeCaches/Restart键，然后我就按下了，在那之后，一切都不起作用了，我完全被难住了。我的Mainactivity中的所有引用都未解析，我无法使其工作。

My build.gradle包含应用插件:'kotlin-android-extensions'

我的build.gradle项目包含

依赖关系{

类路径'com.android.tools.build:gradle:3.5.3'

类路径“org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version”}

这就是我的研究让我得到的，但现在我被困住了。：（

这是我的代码：

package com.example.diceroller

import android.R
import android.media.MediaPlayer
import android.os.Bundle
import android.text.method.ScrollingMovementMethod
import android.widget.Button
import android.widget.ImageView
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.util.*


class MainActivity : AppCompatActivity() {

    lateinit var mp: MediaPlayer
    lateinit var diceImage: ImageView
    var setDiceInt = 6
    private var mediaPlayer: MediaPlayer? = null

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

        val rollButton: Button = findViewById(R.id.roll_button)
        val rollList: TextView = findViewById(R.id.roll_list)

        val fourButton: Button = findViewById(R.id.d4)
        val sixButton: Button = findViewById(R.id.d6)
        val eightButton: Button = findViewById(R.id.d8)
        val tenButton: Button = findViewById(R.id.d10)
        val twelveButton: Button = findViewById(R.id.d12)
        val twentyButton: Button = findViewById(R.id.d20)


        rollList.movementMethod = ScrollingMovementMethod()
       // mp = MediaPlayer.create(this, R.raw.) to be added later


        fourButton.setOnClickListener {
            setDiceInt = 4
            Toast.makeText(this, "$setDiceInt sided picked", Toast.LENGTH_SHORT).show()

        }

        sixButton.setOnClickListener {
            setDiceInt = 6
            Toast.makeText(this,"$setDiceInt sided picked", Toast.LENGTH_SHORT).show()

        }

        eightButton.setOnClickListener {
            setDiceInt = 8
            Toast.makeText(this,"$setDiceInt sided picked", Toast.LENGTH_SHORT).show()

        }

        tenButton.setOnClickListener {
            setDiceInt = 10
            Toast.makeText(this,"$setDiceInt sided picked", Toast.LENGTH_SHORT).show()

        }

        twelveButton.setOnClickListener {
            setDiceInt = 12
            Toast.makeText(this,"$setDiceInt sided picked", Toast.LENGTH_SHORT).show()

        }

        twentyButton.setOnClickListener {
            setDiceInt = 20
            Toast.makeText(this,"$setDiceInt sided picked", Toast.LENGTH_SHORT).show()

        }

        rollList.text = ""
        rollButton.text = "Lets roll!"

        rollButton.setOnClickListener {
            rollDice()
        }

        diceImage = findViewById(R.id.result_image)
    }


    fun rollDice() {
        val resultText: TextView = findViewById(R.id.result_text)
        val rollList: TextView = findViewById(R.id.roll_list)

        val randomInt = Random().nextInt(setDiceInt) +1



        val drawableResource = when (randomInt) {
            1 -> R.drawable.dice_1
            2 -> R.drawable.dice_2
            3 -> R.drawable.dice_3
            4 -> R.drawable.dice_4
            5 -> R.drawable.dice_5
            else -> R.drawable.dice_6
        }
        val scream = if (randomInt != 1) {
        } else {
            mp.start()


        }

        diceImage.setImageResource(drawableResource)
        resultText.text = randomInt.toString()
        rollList.append(setDiceInt.toString() + " sided dice hit: " + randomInt.toString() + "\n")


    }

}

Answer 1

请尝试清理以下缓存文件夹以重新下载库-

c:\Users\<user>\.gradle\caches\
c:\Users\<user>\.AndroidStudio3.x\system\caches\