Android Studio 将 Java 转换为 Kotlin 2 错误

Question

将 Java 文件转换为 Kotlin 文件后，在同一行中出现两个错误:在下面的代码中显示有错误的变量和函数

     lateinit var ncArr: Array<ImageButton>
     lateinit var xBitmap: Bitmap
     lateinit var oBitmap: Bitmap
     lateinit var intArr: IntArray
     lateinit var btnStartGame: Button
     lateinit var btnMenu: Button
     var stop: Boolean = false
     var gameMode: Int = 0
     var umove: Int = 0

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

    ncArr = arrayOfNulls(9)

    ncArr[0] = findViewById(R.id.nc0) as ImageButton
    ncArr[1] = findViewById(R.id.nc1) as ImageButton
    ncArr[2] = findViewById(R.id.nc2) as ImageButton
    ncArr[3] = findViewById(R.id.nc3) as ImageButton
    ncArr[4] = findViewById(R.id.nc4) as ImageButton
    ncArr[5] = findViewById(R.id.nc5) as ImageButton
    ncArr[6] = findViewById(R.id.nc6) as ImageButton
    ncArr[7] = findViewById(R.id.nc7) as ImageButton
    ncArr[8] = findViewById(R.id.nc8) as ImageButton

    ncArr[0].setOnClickListener(this)
    ncArr[1].setOnClickListener(this)
    ncArr[2].setOnClickListener(this)
    ncArr[3].setOnClickListener(this)
    ncArr[4].setOnClickListener(this)
    ncArr[5].setOnClickListener(this)
    ncArr[6].setOnClickListener(this)
    ncArr[7].setOnClickListener(this)
    ncArr[8].setOnClickListener(this)

    xBitmap = BitmapFactory.decodeResource(resources, R.drawable.x)
    oBitmap = BitmapFactory.decodeResource(resources, R.drawable.o)

    intArr = IntArray(9)

    for (i in 0..8) {
        intArr[i] = 0
    }

    btnMenu = findViewById(R.id.btnMenu) as Button
    btnStartGame = findViewById(R.id.btnStartGame) as Button
    btnMenu.setOnClickListener(this)
    btnStartGame.setOnClickListener(this)

    stop = false

    gameMode = intent.getIntExtra("game_mode", 1)
    umove = 1
}

行内ncArr = arrayOfNulls(9) 有错误:

我试图解决这个问题，但我没有更多的想法......

有什么解决办法吗？

提前致谢

Answer 1

ncArr = arrayOfNulls(9)

ncArr的类型将是Array<ImageButton?>

ncArr[0] = findViewById(R.id.nc0) as ImageButton

您正在使用不安全的强制转换运算符as ，因为如果无法进行强制转换，则强制转换运算符会引发异常。因此，我们称其为不安全。如果会发生什么

findViewById(R.id.nc0) as ImageButton

返回null ，然后null无法分配给 ImageButton ，它会抛出异常并使您的应用程序崩溃。

为了避免上述错误，您可以使用

ncArr[0] = findViewById(R.id.nc0) as ImageButton?

或使用安全转换运算符 as?

ncArr[0] = findViewById(R.id.nc0) as? ImageButton

记得申请ncArr[0]至ncArr[8] .

更新:根据您的请求，您可以使用以下解决方案:

lateinit var ncArr: Array<ImageButton>
    lateinit var xBitmap: Bitmap
    lateinit var oBitmap: Bitmap
    lateinit var intArr: IntArray
    lateinit var btnStartGame: Button
    lateinit var btnMenu: Button
    var stop: Boolean = false
    var gameMode: Int = 0
    var umove: Int = 0

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

        ncArr = arrayOf(
                findViewById<ImageButton>(R.id.nc0).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc1).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc2).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc3).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc4).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc5).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc6).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc7).apply{setOnClickListener(this@GameActivity)},
                findViewById<ImageButton>(R.id.nc8).apply{setOnClickListener(this@GameActivity)}

        )

        xBitmap = BitmapFactory.decodeResource(resources, R.drawable.x)
        oBitmap = BitmapFactory.decodeResource(resources, R.drawable.o)

        // Your code here
        ...
}