如何在最新的Android中使用Kotlin启用数据绑定？

Question

请帮帮我，因为我是个学生。我刚开始通过观看Youtube视频来学习Android开发。但它已经两岁了。所以，请帮助我修复数据绑定功能！

我发现这个错误到处都是：

未解析引用:绑定

MainActivity.kt

package com.example.navigationapp

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import com.example.navigationapp.databinding.ActivityMainBinding

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

        @Suppress("UNUSED_VARIABLE")
        val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
    }
}

build.gradle (:app)

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

android {
    compileSdkVersion 33
    buildToolsVersion "31.0.0"

    defaultConfig {
        applicationId "com.example.android.navigation"
        minSdkVersion 19
        targetSdkVersion 33
        versionCode 1
        versionName "1.0"

        vectorDrawables.useSupportLibrary = true

        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 'androidx.core:core-ktx:1.6.0'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

build.gradle (导航应用程序) -> (这个是项目文件)

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:7.2.2"
        classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:1.7.10'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
    }
}

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

GameFragment.kt

package com.example.android.navigation

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import com.example.android.navigation.databinding.FragmentGameBinding
import com.example.navigationapp.R
import com.example.navigationapp.databinding.FragmentGameBinding

class GameFragment : Fragment() {
    data class Question(
        val text: String,
        val answers: List<String>)

    // The first answer is the correct one.  We randomize the answers before showing the text.
    // All questions must have four answers.  We'd want these to contain references to string
    // resources so we could internationalize. (or better yet, not define the questions in code...)
    private val questions: MutableList<Question> = mutableListOf(
        Question(text = "What is Android Jetpack?",
            answers = listOf("all of these", "tools", "documentation", "libraries")),
        Question(text = "Base class for Layout?",
            answers = listOf("ViewGroup", "ViewSet", "ViewCollection", "ViewRoot")),
        Question(text = "Layout for complex Screens?",
            answers = listOf("ConstraintLayout", "GridLayout", "LinearLayout", "FrameLayout")),
        Question(text = "Pushing structured data into a Layout?",
            answers = listOf("Data Binding", "Data Pushing", "Set Text", "OnClick")),
        Question(text = "Inflate layout in fragments?",
            answers = listOf("onCreateView", "onViewCreated", "onCreateLayout", "onInflateLayout")),
        Question(text = "Build system for Android?",
            answers = listOf("Gradle", "Graddle", "Grodle", "Groyle")),
        Question(text = "Android vector format?",
            answers = listOf("VectorDrawable", "AndroidVectorDrawable", "DrawableVector", "AndroidVector")),
        Question(text = "Android Navigation Component?",
            answers = listOf("NavController", "NavCentral", "NavMaster", "NavSwitcher")),
        Question(text = "Registers app with launcher?",
            answers = listOf("intent-filter", "app-registry", "launcher-registry", "app-launcher")),
        Question(text = "Mark a layout for Data Binding?",
            answers = listOf("<layout>", "<binding>", "<data-binding>", "<dbinding>"))
    )

    lateinit var currentQuestion: Question
    lateinit var answers: MutableList<String>
    private var questionIndex = 0
    private val numQuestions = Math.min((questions.size + 1) / 2, 3)

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {

        // Inflate the layout for this fragment
        val binding = DataBindingUtil.inflate<FragmentGameBinding>(
            inflater, R.layout.fragment_game, container, false)

        // Shuffles the questions and sets the question index to the first question.
        randomizeQuestions()

        // Bind this fragment class to the layout
        binding.game = this

        // Set the onClickListener for the submitButton
        binding.submitButton.setOnClickListener @Suppress("UNUSED_ANONYMOUS_PARAMETER")
        { view: View ->
            val checkedId = binding.questionRadioGroup.checkedRadioButtonId
            // Do nothing if nothing is checked (id == -1)
            if (-1 != checkedId) {
                var answerIndex = 0
                when (checkedId) {
                    R.id.secondAnswerRadioButton -> answerIndex = 1
                    R.id.thirdAnswerRadioButton -> answerIndex = 2
                    R.id.fourthAnswerRadioButton -> answerIndex = 3
                }
                // The first answer in the original question is always the correct one, so if our
                // answer matches, we have the correct answer.
                if (answers[answerIndex] == currentQuestion.answers[0]) {
                    questionIndex++
                    // Advance to the next question
                    if (questionIndex < numQuestions) {
                        currentQuestion = questions[questionIndex]
                        setQuestion()
                        binding.invalidateAll()
                    } else {
                        // We've won!  Navigate to the gameWonFragment.
                    }
                } else {
                    // Game over! A wrong answer sends us to the gameOverFragment.
                }
            }
        }
        return binding.root
    }

    // randomize the questions and set the first question
    private fun randomizeQuestions() {
        questions.shuffle()
        questionIndex = 0
        setQuestion()
    }

    // Sets the question and randomizes the answers.  This only changes the data, not the UI.
    // Calling invalidateAll on the FragmentGameBinding updates the data.
    private fun setQuestion() {
        currentQuestion = questions[questionIndex]
        // randomize the answers into a copy of the array
        answers = currentQuestion.answers.toMutableList()
        // and shuffle them
        answers.shuffle()
        (activity as AppCompatActivity).supportActionBar?.title = getString(R.string.title_android_trivia_question, questionIndex + 1, numQuestions)
    }
}

GameOverFragment.kt

package com.example.android.navigation

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import com.example.android.navigation.databinding.FragmentGameOverBinding
import com.example.navigationapp.R

class GameOverFragment : Fragment() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        val binding: FragmentGameOverBinding = DataBindingUtil.inflate(
            inflater, R.layout.fragment_game_over, container, false)
        return binding.root
    }
}

GameWonFragment.kt

package com.example.android.navigation

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import com.example.android.navigation.databinding.FragmentGameWonBinding
import com.example.navigationapp.R


class GameWonFragment : Fragment() {
    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        val binding: FragmentGameWonBinding = DataBindingUtil.inflate(
            inflater, R.layout.fragment_game_won, container, false)
        return binding.root
    }
}

Answer 1

要启用数据库，只需添加：

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

android {
    compileSdkVersion 33
    buildToolsVersion "31.0.0"

    defaultConfig {
        applicationId "com.example.android.navigation"
        minSdkVersion 19
        targetSdkVersion 33
        versionCode 1
        versionName "1.0"

        vectorDrawables.useSupportLibrary = true

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

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

dependencies {

    implementation 'androidx.core:core-ktx:1.6.0'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

或者你可以用

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

android {
    compileSdkVersion 33
    buildToolsVersion "31.0.0"

    defaultConfig {
        applicationId "com.example.android.navigation"
        minSdkVersion 19
        targetSdkVersion 33
        versionCode 1
        versionName "1.0"

        vectorDrawables.useSupportLibrary = true

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

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

dependencies {

    implementation 'androidx.core:core-ktx:1.6.0'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

两种方法都应该可以工作，在添加了清理和重建项目之后，这应该会自动生成所有必需的类(例如: ActivityMainBinding)。