Error after add simple_permission or permission_handler on flutter - dart

Question

I want to create a folder to try downloading files. so I added simple_permission but I got an error migrating to androidX even though I migrated to androidX. how can I resolve this error?
Launching lib\main.dart on Coolpad E502 in debug mode...
D:\Flutter\flutter.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:9: error: cannot find symbol
import android.support.v4.app.ActivityCompat;
^
symbol: class ActivityCompat
location: package android.support.v4.app
D:\Flutter\flutter.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:10: error: package android.support.v4.content does not exist
import android.support.v4.content.ContextCompat;
^
D:\Flutter\flutter.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:156: error: cannot find symbol
ActivityCompat.requestPermissions(activity, perm, 0);
^
symbol: variable ActivityCompat
location: class SimplePermissionsPlugin
D:\Flutter\flutter.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:163: error: cannot find symbol
return PackageManager.PERMISSION_GRANTED == ContextCompat.checkSelfPermission(activity, permission);
^
symbol: variable ContextCompat
location: class SimplePermissionsPlugin
D:\Flutter\flutter.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:171: error: cannot find symbol
if (ActivityCompat.shouldShowRequestPermissionRationale(registrar.activity(), permission)) {
^
symbol: variable ActivityCompat
location: class SimplePermissionsPlugin
D:\Flutter\flutter.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:175: error: cannot find symbol
if (ActivityCompat.checkSelfPermission(registrar.context(), permission) == PackageManager.PERMISSION_GRANTED) {
^
symbol: variable ActivityCompat
location: class SimplePermissionsPlugin
6 errors
FAILURE: Build failed with an exception.
What went wrong:
Execution failed for task ':simple_permissions:compileDebugJavaWithJavac'.
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 45s
The Gradle failure may have been because of AndroidX incompatibilities in this Flutter app.\
Exited (sigterm)

Answer 1

I had the same error and what I did was change the version of klotin in the build.gradle file I have it as follows
buildscript {
ext.kotlin_version = '1.3.72'
repositories {
google()
jcenter()
}
dependencies {
classpath 'com.android.tools.build:gradle:3.5.0'
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
classpath 'com.google.gms:google-services:4.3.2'
}
}