Flutter app run Cannot invoke method toInteger() on null object - flutter

Question

I am new to Flutter. I have just cloned a project on GitHub that I have to work on. So running the project first in my android studio brings me the following error:
FAILURE: Build failed with an exception.
Where:
Build file 'C:\Users\19ngu\AndroidStudioProjects\damufasta\android\app\build.gradle' line: 29
What went wrong:
A problem occurred evaluating project ':app'.
Cannot invoke method toInteger() on null object
I have already resolved the dependencies and pointed the project SDK and module to the latest API as directed from checking other responses. So I was expecting it to run successfully.
This is the app\build.gradle file content:
def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
localPropertiesFile.withReader('UTF-8') { reader ->
localProperties.load(reader)
}
}
def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
throw GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}
def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
flutterVersionCode = '1'
}
def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
flutterVersionName = '1.0'
}
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
android {
compileSdkVersion localProperties.getProperty('flutter.compileSdkVersion').toInteger()
ndkVersion flutter.ndkVersion
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
kotlinOptions {
jvmTarget = '1.8'
}
sourceSets {
main.java.srcDirs += 'src/main/kotlin'
}
defaultConfig {
// TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
applicationId "com.example.damufasta"
// You can update the following values to match your application needs.
// For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-build-configuration.
minSdkVersion localProperties.getProperty('flutter.minSdkVersion').toInteger()
targetSdkVersion localProperties.getProperty('flutter.targetSdkVersion').toInteger()
versionCode flutterVersionCode.toInteger()
versionName flutterVersionName
}
buildTypes {
release {
// TODO: Add your own signing config for the release build.
// Signing with the debug keys for now, so `flutter run --release` works.
signingConfig signingConfigs.debug
}
}
}
flutter {
source '../..'
}
dependencies {
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

Answer 1

Set min sdk at 21 :
minSdkVersion = 21 Line 44 build.gradle

Answer 2

In case this happens, one of the likely problems as mentioned by the responders is the missing value of the minSdkVersion in the local.properties file.
So first check if the values are present, if not add them.
If they are present then ensure that the minSdkVersion is 21.
This has worked for me.