尝试获取以编程方式生成的按钮的 ID 时崩溃

问题描述 投票：0回答：1

我有一个 Android 应用程序，它生成 5 个 5 个数字的列表。 enter image description here

其次，点击“选择号码”后，它将删除重复的号码，并将生成的所有号码打印为按钮。

enter image description here

我的程序在 MainActivity.kt

的这段代码上崩溃 
val generatedNumbersCollected: Button = findViewById(R.id.root)

generatedNumbersCollected.setOnClickListener {
            Toast.makeText(this, "Clicked 1", Toast.LENGTH_SHORT).show()
       }

我假设 

R.id.root
为空，因此它崩溃了。我正在寻找解决此问题的方法。可能的解决方案是什么？

MainActivity.kt

import android.content.Intent
import android.os.Bundle
import android.util.Log
import android.view.ViewGroup
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.constraintlayout.helper.widget.Flow
import androidx.constraintlayout.widget.ConstraintLayout
import kotlin.random.Random

class MainActivity : ComponentActivity() {

private var concat: Set<Int> = emptySet()


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

    val generateButton: Button = findViewById(R.id.buttonGenerate)
    val selNumbers: Button = findViewById(R.id.selectNumbers)

    val numberGenerated: TextView = findViewById(R.id.numberGenerated)
    val numberGenerated2: TextView = findViewById(R.id.numberGenerated2)
    val numberGenerated3: TextView = findViewById(R.id.numberGenerated3)
    val numberGenerated4: TextView = findViewById(R.id.numberGenerated4)
    val numberGenerated5: TextView = findViewById(R.id.numberGenerated5)
    val collectedNumbers: TextView = findViewById(R.id.collectedNumbers)


    //var addBtn: Button? = null
    //linearLayout = findViewById(R.id.linearLayout)

    generateButton.setOnClickListener {
        val randomNumbers = generateSequence {
            Random.nextInt(1..70)
        }.distinct().take(5).sorted().toSet()
        val randomNumbers2 = generateSequence {
            Random.nextInt(1..70)
        }.distinct().take(5).sorted().toSet()
        val randomNumbers3 = generateSequence {
            Random.nextInt(1..70)
        }.distinct().take(5).sorted().toSet()
        val randomNumbers4 = generateSequence {
            Random.nextInt(1..70)
        }.distinct().take(5).sorted().toSet()
        val randomNumbers5 = generateSequence {
            Random.nextInt(1..70)
        }.distinct().take(5).sorted().toSet()

        concat = concatenate(
            randomNumbers,
            randomNumbers2,
            randomNumbers3,
            randomNumbers4,
            randomNumbers5
        )


        numberGenerated.text = randomNumbers.toString()
        numberGenerated2.text = randomNumbers2.toString()
        numberGenerated3.text = randomNumbers3.toString()
        numberGenerated4.text = randomNumbers4.toString()
        numberGenerated5.text = randomNumbers5.toString()
    }

    selNumbers.setOnClickListener {
        numberGenerated.text = "none"
        numberGenerated2.text = "none"
        numberGenerated3.text = "none"
        numberGenerated4.text = "none"
        numberGenerated5.text = "none"
        collectedNumbers.text = concat.toString()
        createAndAddView()

        //val intent = Intent(this@MainActivity, SelectNumbers::class.java)
        //startActivity(intent)
    }

    /*val generatedNumbersCollected: Button = findViewById(R.id.root)
    generatedNumbersCollected.setOnClickListener {
        Toast.makeText(this, "Clicked 1", Toast.LENGTH_SHORT).show()
   }*/


}

    private fun createAndAddView()
{
    val root = findViewById<ConstraintLayout>(R.id.root)
    lateinit var button: Button

    val array: IntArray = concat.toIntArray()

    for ((index, i) in array.withIndex()) {
            button = Button(this).apply {
            layoutParams = ViewGroup.LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT)
            id = index + 1
            text = i.toString()
        }
        root.addView(button)

    }
    val flow = findViewById<Flow>(R.id.flow)
    flow.referencedIds = (1 .. array.size).toList().toIntArray()


}


}

private fun Random.nextInt(range: IntRange): Int {
return range.first + nextInt(range.last - range.first)
}

private fun concatenate(
randomNumbers: Set<Int>,
randomNumbers2: Set<Int>,
randomNumbers3: Set<Int>,
randomNumbers4: Set<Int>,
randomNumbers5: Set<Int>
): Set<Int> {
return randomNumbers + randomNumbers2 +     randomNumbers3 + randomNumbers4 + randomNumbers5
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/MainActivity"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical">

<TextView
    android:id="@+id/selectedRandom"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Selected Random" />

<TextView
    android:id="@+id/numberGenerated"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="List Number 1" />

<TextView
    android:id="@+id/numberGenerated2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="List Number 2" />

<TextView
    android:id="@+id/numberGenerated3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="List Number 3" />

<TextView
    android:id="@+id/numberGenerated4"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="List Number 4" />

<TextView
    android:id="@+id/numberGenerated5"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="List Number 5" />

<TextView
    android:id="@+id/collectedNumbers"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="none" />

<Button
    android:id="@+id/buttonGenerate"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Generate" />

<Button
    android:id="@+id/selectNumbers"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Select Numbers" />

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:fillViewport="true">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/root"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.constraintlayout.helper.widget.Flow
            android:id="@+id/flow"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:flow_horizontalGap="8dp"
            app:flow_maxElementsWrap="5"
            app:flow_verticalGap="8dp"
            app:flow_verticalStyle="packed"
            app:flow_wrapMode="aligned" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</ScrollView>

这是日志猫：

FATAL EXCEPTION: main
                                                                                                Process: com.example.randomgenerator, PID: 19302
                                                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.randomgenerator/com.example.randomgenerator.MainActivity}: java.lang.ClassCastException: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to android.widget.Button
                                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
                                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
                                                                                                    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
                                                                                                    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
                                                                                                    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
                                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
                                                                                                    at android.os.Handler.dispatchMessage(Handler.java:106)
                                                                                                    at android.os.Looper.loop(Looper.java:223)
                                                                                                    at android.app.ActivityThread.main(ActivityThread.java:7656)
                                                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                                                    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
                                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
                                                                                                Caused by: java.lang.ClassCastException: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to android.widget.Button
                                                                                                    at com.example.randomgenerator.MainActivity.onCreate(MainActivity.kt:84)
                                                                                                    at android.app.Activity.performCreate(Activity.java:7994)
                                                                                                    at android.app.Activity.performCreate(Activity.java:7978)
                                                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
                                                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
                                                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) 
                                                                                                    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
                                                                                                    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
                                                                                                    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
                                                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
                                                                                                    at android.os.Handler.dispatchMessage(Handler.java:106) 
                                                                                                    at android.os.Looper.loop(Looper.java:223) 
                                                                                                    at android.app.ActivityThread.main(ActivityThread.java:7656) 
                                                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                                                    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
                                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 
android kotlin
1个回答
0
投票

我尝试复制您的代码，并可以通过单击按钮来解决该问题，并通过对此功能进行更改来获取结果

private fun createAndAddView() {
        val root = findViewById<ConstraintLayout>(R.id.root)
        lateinit var button: Button

        val array: IntArray = concat.toIntArray()

        for ((index, i) in array.withIndex()) {
            button = Button(this).apply {
                layoutParams = ViewGroup.LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT)
                id = index + 1
                text = i.toString()
                // add this code
                setOnClickListener {
                    Toast.makeText(this@MainActivity, "Clicked ${i}", Toast.LENGTH_SHORT).show()
                }
            }
            root.addView(button)
        }
        val flow = findViewById<Flow>(R.id.flow)
        flow.referencedIds = (1..array.size).toList().toIntArray()
    }

但是，实际上我的建议是实现 recyclerview 将使您的代码更加干净和简单，而不是像这样生成流程。很高兴编码:)

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