Android 开发的 Kotlin：文本字段到 TextView？

Question

我两周前开始学习使用 Kotlin 开发 Android 应用程序。我目前正在尝试对我的小费计算器应用程序进行一些更改，并尝试将输入的文本字段显示到 totalCost TextView 中（您会在其中看到“小费金额：20.00 美元”下方的“服务成本”文本），但我我不知道该怎么做。

Click here to see the app layout

这是代码：

文件activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/icon_cost_of_service"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:importantForAccessibility="no"
        app:srcCompat="@drawable/ic_store"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@id/cost_of_service"
        app:layout_constraintBottom_toBottomOf="@id/cost_of_service"/>

    <com.google.android.material.textfield.TextInputLayout
        android:id="@+id/cost_of_service"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        android:hint="@string/cost_of_service"
        android:layout_marginStart="16dp"
        app:layout_constraintStart_toEndOf="@id/icon_cost_of_service"
        app:layout_constraintTop_toTopOf="parent" >

        <com.google.android.material.textfield.TextInputEditText
            android:id="@+id/cost_of_service_edit_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:inputType="numberDecimal"/>
    </com.google.android.material.textfield.TextInputLayout>

    <ImageView
        android:id="@+id/icon_service_question"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:importantForAccessibility="no"
        app:srcCompat="@drawable/ic_service"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@id/service_question"
        app:layout_constraintBottom_toBottomOf="@id/service_question"/>

    <TextView
        android:id="@+id/service_question"
        style="@style/Widget.TipTime.TextView"
        android:layout_marginTop="16dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/how_was_the_service"
        app:layout_constraintStart_toStartOf="@id/cost_of_service"
        app:layout_constraintTop_toBottomOf="@id/cost_of_service" />

    <RadioGroup
        android:id="@+id/tip_options"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:checkedButton="@id/option_twenty_percent"
        android:orientation="vertical"
        app:layout_constraintStart_toStartOf="@id/service_question"
        app:layout_constraintTop_toBottomOf="@id/service_question">

        <RadioButton
            android:id="@+id/option_twenty_percent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/amazing_service" />

        <RadioButton
            android:id="@+id/option_eighteen_percent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/good_service" />

        <RadioButton
            android:id="@+id/option_fifteen_percent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/ok_service" />
    </RadioGroup>

    <ImageView
        android:id="@+id/icon_round_up"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:importantForAccessibility="no"
        app:srcCompat="@drawable/ic_round_up"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@id/round_up_switch"
        app:layout_constraintBottom_toBottomOf="@id/round_up_switch"/>


    <com.google.android.material.switchmaterial.SwitchMaterial
        android:id="@+id/round_up_switch"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:checked="true"
        android:text="@string/round_up_tip"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginStart="16dp"
        app:layout_constraintStart_toEndOf="@id/icon_round_up"
        app:layout_constraintTop_toBottomOf="@id/tip_options" />

    <Button
        android:id="@+id/calculate_button"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/calculate"
        android:layout_marginTop="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@id/round_up_switch"
        app:layout_constraintTop_toBottomOf="@id/round_up_switch" />

    <TextView
        android:id="@+id/tip_result"
        style="@style/Widget.TipTime.TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@id/calculate_button"
        tools:text="Tip Amount: " />

</androidx.constraintlayout.widget.ConstraintLayout>

文件MainActivity.kt

package com.example.tiptime

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.example.tiptime.databinding.ActivityMainBinding
import java.text.NumberFormat

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.calculateButton.setOnClickListener { calculateTip() }
    }

    fun calculateTip() {
        val stringInTextField = binding.costOfServiceEditText.text.toString()
        val cost = stringInTextField.toDoubleOrNull()
        if (cost == null) {
            binding.tipResult.text = ""
            return
        }

        val tipPercentage = when (binding.tipOptions.checkedRadioButtonId) {
            R.id.option_twenty_percent -> 0.20
            R.id.option_eighteen_percent -> 0.18
            else -> 0.15
        }

        var tip = tipPercentage * cost
        if (binding.roundUpSwitch.isChecked) {
            tip = kotlin.math.ceil(tip)
        }

        val formattedTip = NumberFormat.getCurrencyInstance().format(tip)
        binding.tipResult.text = getString(R.string.tip_amount, formattedTip)
    }

}

Answer 1

要从编辑文本框中获取文本，您可以执行以下操作：

    val editText = findViewById<EditText>(R.id.cost_of_service_edit_text)
    val textValue = text.text.toString()

要将文本设置为 textView，您可以这样做：

    val textView = findViewById<EditText>(R.id.textViewId)
    textView.text = textValue

Android 开发的 Kotlin：文本字段到 TextView？

Kotlin for Android development: Text field to TextView?

xml

android

textview

kotlin

android-studio

文件activity_main.xml

文件MainActivity.kt