Question

我开始做一个简单的Android应用程序，用Kotlin编程语言练习计算年龄，当我单击该应用程序按钮时，有人可以帮我解决这个问题，并知道我的错误在哪里，因为我只是一个初学者

package com.calcult.age.agecalcult

    import android.support.v7.app.AppCompatActivity
    import android.os.Bundle
    import android.widget.Toast
    import kotlinx.android.synthetic.main.activity_main.*
    import java.util.*

    class MainActivity : AppCompatActivity() {


        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            var ageInput = ageText.text.toString()

            doIT.setOnClickListener{

                var currentYear = Calendar.getInstance().get(Calendar.YEAR)
                var getAge = currentYear-ageInput.toInt()
                Toast.makeText(this, getAge, Toast.LENGTH_LONG)
            }
        }

    }

XML文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">


    <Button android:layout_width="wrap_content" android:layout_height="wrap_content"
            android:layout_marginEnd="148dp"
            app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent"
            android:layout_marginStart="148dp"
            android:id="@+id/doIT"
            android:text="@string/button_text1"
            android:textSize="18sp"
            app:layout_constraintHorizontal_bias="0.0" android:layout_marginTop="8dp"
            app:layout_constraintTop_toTopOf="parent" android:layout_marginBottom="8dp"
            app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintVertical_bias="0.771"/>
    <EditText
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:inputType="textPersonName"
            android:ems="10"
            android:id="@+id/ageText" app:layout_constraintTop_toTopOf="parent"
            android:layout_marginTop="215dp" app:layout_constraintEnd_toEndOf="parent" android:layout_marginEnd="85dp"
            app:layout_constraintStart_toStartOf="parent" android:layout_marginStart="84dp"
            android:layout_marginBottom="250dp" app:layout_constraintBottom_toTopOf="@+id/doIT"/>

</android.support.constraint.ConstraintLayout>

Answer 1

正如Vladyslav Matviienko所说，您正在尝试在onCreate上获取文本，您需要做的是这样的事情：

//Here the view is already created, so you'll be able to setup everything you need.

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    setupListener()
}

//If you are learning, you should consider reading a bit about clean code, 
//it's always nice that a function does just one job, that's why I broke the code 
//below in two little functions. Have in mind, this code is not the best, but at the 
//moment i don't have much time to write this.

private fun setupListener() {
    doIT.setOnClickListener{

//Always be aware of the type of the variables, when i wrote the first answer i was 
//trying to do a math operatiton using a string, so it would not work. =P

        var currentYear = Calendar.getInstance().get(Calendar.YEAR)
        var getAge = (currentYear-getAge().toInt()).toString()
        Toast.makeText(this, getAge, Toast.LENGTH_LONG).show()
    }
}

private fun getAge(): String {
    return ageText.text.toString
}

Android Kotlin-当我单击按钮时，应用程序保持停止

1 个答案: