我尝试引用java中的fragment类中的Kotlin类，结果出现错误，提示无法找到kotlin类的符号。

碎片类
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//Instructions audio
        instruct = (ImageButton) rootview.findViewById(R.id.soundBtn);
        MediaPlayer.create(getActivity(), R.raw.instructions);

        //Click go button to explore flashcards
        go.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(getActivity(), Flashcards1.class)); 
            }
        });
        return rootview;
    }
}

这就是错误所在

startActivity(new Intent(getActivity(), Flashcards1.class));

构建.gradle应用程序

plugins {
    id 'com.android.application'
    id 'com.google.gms.google-services'
}

android {
    compileSdk 33

    defaultConfig {
        applicationId "com.example.salitongue_updated"
        minSdk 27
        targetSdk 33
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

    buildFeatures {
        viewBinding true
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.5.0'
    implementation 'com.google.android.material:material:1.6.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    implementation 'com.google.firebase:firebase-database:20.0.5'
    implementation 'com.google.firebase:firebase-firestore:24.2.2'
    implementation 'com.google.firebase:firebase-auth:21.0.7'
    implementation 'androidx.navigation:navigation-fragment:2.5.1'
    implementation 'androidx.navigation:navigation-ui:2.5.1'
    implementation "androidx.fragment:fragment-ktx:1.6.0-alpha02"
    //testImplementation 'junit:junit:4.13.2'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

build.gradle

buildscript {
    dependencies {
        classpath 'com.google.gms:google-services:4.3.13'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.7.10"
    }
}// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
    id 'com.android.application' version '7.2.2' apply false
    id 'com.android.library' version '7.2.2' apply false
}

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