I can't see the elements by their id in Android Studio

Question

I'm a new Kotlin Programmer. I tried to change the app icon by deleting the ic_launcher.png files and replacing my own images. As i see that is ridiculous what i'm trying to do, i copied the "Main Activity.kt" and "main_activity.xml" files and created a new project. As i tried to copy the files into the new project, the program throws a lot of errors:

It didn't imported the "kotlinx" packet and didn't perceive the elements in the xml file. As i tried to create an another new project to try whether the problem is only for this project, i realized that Android Studio doesn't perceive the xml elements anymore.

Here are some important infos about my project:

The Android Manifest XML File

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.ihdovanay.myapplication">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.MyApplication">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

The Build Gradle File of The Project

buildscript {
    ext.kotlin_version = "1.4.10"
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:4.1.0"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

The Build Gradle File of the Module

plugins {
    id 'com.android.application'
    id 'kotlin-android'
}

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.2"

    defaultConfig {
        applicationId "com.ihdovanay.myapplication"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {

    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.3.2'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.2'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}

I would be very happy if you could solve my problem.

Answer 1

弃用视图合成后修改了答案。

你kotlin-android-extensions的build.gradle. 它负责生成合成视图引用。

kotlin-android-extensions现已弃用，因此默认情况下不再包含它，也不应再将其添加到项目中。您应该使用findViewById或View Binding。

您可以通过执行以下操作来使其工作，但我不建议添加和依赖已弃用的库。将这一行添加到plugins顶部的块中：

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
}