獲取錯誤 java.lang.NumberFormatException: 空字符串

Question

需要將 2 個文本框中的數字相乘（數字可以是整數或雙精度數）並在單擊 btn_warp 按鈕時在文本視圖框中顯示結果，但我收到 java.lang.NumberFormatException: empty String 錯誤

class SootCalc:AppCompatActivity() {

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

        btn_warp.setOnClickListener {

            val wpreed = txt_warpReed.text.toString().toDouble()
            val wppanna=txt_warpPanna.text.toString().toDouble()
            
            if(txt_warpReed.text.isEmpty()){
                txtViewWarp.text=""
                return@setOnClickListener
            }
            val result1=(wpreed*wppanna)
             txtViewWarp.text= result1.toString()
        }

    }
}

        

Answer 1

嘗試這個：

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

btn_warp.setOnClickListener {

    val wpreed = txt_warpReed.text.toString()
    val wppanna = txt_warpPanna.text.toString()
    
    if(wpreed == "" || wppanna == ""){
        txtViewWarp.text = ""
    } else {
        val result1=(wpreed.toDouble()*wppanna.toDouble())
        txtViewWarp.text= result1.toString()
    }
}}