Question

我正在将Kotlin与android一起使用，但出现此错误。

原因：java.lang.ClassCastException：java.lang.Float不能为在第60行中强制转换为java.lang.String

我不明白为什么它以为有一个Float。这是第60行：

val bal:String = sp.getString("Balance", "0.00")!!.toString()

其中sp是SharedPreferences的实例。

这是我的完整代码：

package com.applications.darshan.piggybank

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.content.SharedPreferences
import android.view.View
import android.widget.EditText
import android.widget.TextView

class MainActivity : AppCompatActivity() {
private var balance : TextView ?= null
private var amount : EditText ?= null


override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    balance = findViewById(R.id.balance)
    amount = findViewById(R.id.amount)
    var sp:SharedPreferences = this.getSharedPreferences("Balance", 0)
    addZero()
    balance!!.text = "Your balance is $" + sp.getString("Balance", "0.00")

}
fun onClick(v: View){
    var addAmount:Float ?
    try{
        addAmount = amount!!.text.toString().toFloat()
    }catch(e:Exception){
        addAmount = 0.00f
    }

    var sp:SharedPreferences = this.getSharedPreferences("Balance", 0)
    val editor = sp.edit()
    var amountNum = sp.getString("Balance", "0.00").toFloat()
    when(v.id.toString()){
        "2131165209" -> amountNum += addAmount!!
        "2131165314" -> amountNum -= addAmount!!
    }
    editor.putString("Balance", amountNum.toString())
    editor.apply()
    editor.commit()
    addZero()
    balance!!.text = "Your balance is $" + sp.getString("Balance", "0.00")

}
fun clearBalance(v:View){
    var sp:SharedPreferences = this.getSharedPreferences("Balance", 0)
    val editor = sp.edit()
    editor.putString("Balance",  "0.00")
    editor.apply()
    editor.commit()
    addZero()
    balance!!.text = "Your balance is $" + sp.getString("Balance", "0.00")
    addZero()

}
fun addZero(){
    val sp:SharedPreferences = this.getSharedPreferences("Balance", 0)
    val bal:String = sp.getString("Balance", "0.00")!!.toString()
    val editor = sp.edit()
    val balLen = bal.length
    val dot:Char = bal[balLen-2]
    if(dot.equals('.')){
        System.out.println(true)
        var x:String = bal + "0"
        editor.putString("Balance", x)
        System.out.println(x)
        editor.apply()
        editor.commit()
    }
}
}

Answer 1

尝试从sp中获取一个浮点数，然后将其转换为String

val bal:String = Float.toString(sp.getFloat("Balance", 0.0f));

Answer 2

您可以像下面这样使用，它将在Float中键入Cast

Float.valueOf(sp.getString("Balance", "0.00"));

为什么在这里出现“原因：java.lang.ClassCastException：java.lang.Float无法转换为java.lang.String”错误？

2 个答案: