Need help in Using Java or Kotlin source files as plug-ins

Hi All!
I am working with project which need use source java file as plugin for android, I followed like this document:
https://docs.unity3d.com/Manual/AndroidJavaSourcePlugins.html

When I tested with empty project: copy empty activity from android project to unity, I got this error when build android:

D:\Programing\All about Unity\PROJECT\TaggleCo\PROJECT\taggle-ihealth-project\Ref\unity-project-test-androidLib\unity-test-javaLib\Temp\gradleOut\unityLibrary\src\main\java\com\taggle\testlib2\MainActivity.java:3: error: package androidx.appcompat.app does not exist
import androidx.appcompat.app.AppCompatActivity;
^
D:\Programing\All about Unity\PROJECT\TaggleCo\PROJECT\taggle-ihealth-project\Ref\unity-project-test-androidLib\unity-test-javaLib\Temp\gradleOut\unityLibrary\src\main\java\com\taggle\testlib2\MainActivity.java:7: error: cannot find symbol
public class MainActivity extends AppCompatActivity {
^
symbol: class AppCompatActivity
D:\Programing\All about Unity\PROJECT\TaggleCo\PROJECT\taggle-ihealth-project\Ref\unity-project-test-androidLib\unity-test-javaLib\Temp\gradleOut\unityLibrary\src\main\java\com\taggle\testlib2\MainActivity.java:9: error: method does not override or implement a method from a supertype
@override
^
D:\Programing\All about Unity\PROJECT\TaggleCo\PROJECT\taggle-ihealth-project\Ref\unity-project-test-androidLib\unity-test-javaLib\Temp\gradleOut\unityLibrary\src\main\java\com\taggle\testlib2\MainActivity.java:11: error: cannot find symbol
super.onCreate(savedInstanceState);
^
symbol: variable super
location: class MainActivity
D:\Programing\All about Unity\PROJECT\TaggleCo\PROJECT\taggle-ihealth-project\Ref\unity-project-test-androidLib\unity-test-javaLib\Temp\gradleOut\unityLibrary\src\main\java\com\taggle\testlib2\MainActivity.java:12: error: package R does not exist
setContentView(R.layout.activity_main);
^
Note: D:\Programing\All about Unity\PROJECT\TaggleCo\PROJECT\taggle-ihealth-project\Ref\unity-project-test-androidLib\unity-test-javaLib\Temp\gradleOut\unityLibrary\src\main\java\com\unity3d\player\UnityPlayerActivity.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
5 errors
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':unityLibrary:compileReleaseJavaWithJavac'.
> Compilation failed; see the compiler error output for details.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 1s
Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF-8
UnityEngine.GUIUtilityrocessEvent (int,intptr)



So I don't know exactly which library need integrating to unity? Anyone can help me solve this issue?

 

Many thanks for your reply!
Do I have to copy gradle file from android project to unity project? I also tried to do that, but it's still error same as above.

I just use empty android project to test, gradle file I copied to unity :

plugins {
id 'com.android.application'
}

android {
compileSdkVersion 29
buildToolsVersion "30.0.3"

defaultConfig {
applicationId "com.taggle.testlib2"
minSdkVersion 21
targetSdkVersion 29
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
}
}

dependencies {

implementation 'androidx.appcompat:appcompat:1.3.0'
implementation 'com.google.android.material:material:1.3.0'
implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
testImplementation 'junit:junit:4.+'
androidTestImplementation 'androidx.test.ext:junit:1.1.2'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}