Android Studio 致命异常：主计数器应用答案

【问题标题】：Android Studio Fatal Exception: main counter appAndroid Studio 致命异常：主计数器应用
【发布时间】：2021-10-13 04:00:02
【问题描述】：

大家好，我想构建一个计数器应用程序。但是当我想测试它时会弹出这个错误：

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.change, PID: 7804
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.change/com.example.change.MainActivity}: kotlin.UninitializedPropertyAccessException: lateinit property fighter1 has not been initialized
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
 Caused by: kotlin.UninitializedPropertyAccessException: lateinit property fighter1 has not been initialized
    at com.example.change.MainActivity.onCreate(MainActivity.kt:21)
    at android.app.Activity.performCreate(Activity.java:7802)
    at android.app.Activity.performCreate(Activity.java:7791)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016) 
    at android.os.Handler.dispatchMessage(Handler.java:107) 
    at android.os.Looper.loop(Looper.java:214) 
    at android.app.ActivityThread.main(ActivityThread.java:7356) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

我不知道我的代码是否正确，因为我刚开始学习 Android Studio，所以我对它还不是很了解。这是我的代码（我是 Kotlin 的新手）：

package com.example.change

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView


class MainActivity : AppCompatActivity() {

    private var counter1 = 0;
    private lateinit var counterRed1: TextView
    private lateinit var fighter1: Button

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

        counterRed1  = findViewById(R.id.counterRed1);

        fighter1.setOnClickListener {
            counter1 ++
            counterRed1.text = (Integer.toString(counter1))
        }
    }
}

【问题讨论】：

标签： android android-studio error-handling counter

【解决方案1】：

您错过了初始化fighter1 按钮字段。您需要像初始化 counterRed1 文本字段一样对其进行初始化。

counterRed1  = findViewById(R.id.counterRed1);
fighter1 = findViewById(R.id.fighter1);

还要确保您的activity_main 布局文件有一个Button 和id fighter1。

【讨论】：