V/FA (28362): Inactivity, disconnecting from the service
════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following assertion was thrown building:
A non-null String must be provided to a Text widget.
'package:flutter/src/widgets/text.dart':
Failed assertion: line 298 pos 10: 'data != null'

i used to codes and settings:
-----> contacts_service: ^0.3.10

`import 'dart:math';

import 'package:contacts_service/contacts_service.dart';
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
@OverRide
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Contacts'),
);
}
}

class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);

final String title;

@OverRide
_MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
List contacts = [];
List contactsFiltered = [];
Map<String, Color> contactsColorMap = new Map();
TextEditingController searchController = new TextEditingController();

@OverRide
void initState() {
super.initState();
getAllContacts();
searchController.addListener(() {
filterContacts();
});
}

String flattenPhoneNumber(String phoneStr) {
return phoneStr.replaceAllMapped(RegExp(r'^(+)|\D'), (Match m) {
return m[0] == "+" ? "+" : "";
});
}

getAllContacts() async {
List colors = [
Colors.green,
Colors.indigo,
Colors.yellow,
Colors.orange
];
int colorIndex = 0;
List _contacts = (await ContactsService.getContacts()).toList();
_contacts.forEach((contact) {
Color baseColor = colors[colorIndex];
contactsColorMap[contact.displayName] = baseColor;
colorIndex++;
if (colorIndex == colors.length) {
colorIndex = 0;
}
});
setState(() {
contacts = _contacts;
});
}

filterContacts() {
List _contacts = [];
_contacts.addAll(contacts);
if (searchController.text.isNotEmpty) {
_contacts.retainWhere((contact) {
String searchTerm = searchController.text.toLowerCase();
String searchTermFlatten = flattenPhoneNumber(searchTerm);
String contactName = contact.displayName.toLowerCase();
bool nameMatches = contactName.contains(searchTerm);
if (nameMatches == true) {
return true;
}

    if (searchTermFlatten.isEmpty) {
      return false;
    }

    var phone = contact.phones.firstWhere((phn) {
      String phnFlattened = flattenPhoneNumber(phn.value);
      return phnFlattened.contains(searchTermFlatten);
    }, orElse: () => null);

    return phone != null;
  });

  setState(() {
    contactsFiltered = _contacts;
  });
}

}

@OverRide
Widget build(BuildContext context) {
bool isSearching = searchController.text.isNotEmpty;
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Container(
padding: EdgeInsets.all(20),
child: Column(
children: [
Container(
child: TextField(
controller: searchController,
decoration: InputDecoration(
labelText: 'Search',
border: new OutlineInputBorder(
borderSide: new BorderSide(
color: Theme.of(context).primaryColor
)
),
prefixIcon: Icon(
Icons.search,
color: Theme.of(context).primaryColor
)
),
),
),
Expanded(
child: ListView.builder(
shrinkWrap: true,
itemCount: isSearching == true ? contactsFiltered.length : contacts.length,
itemBuilder: (context, index) {
Contact contact = isSearching == true ? contactsFiltered[index] : contacts[index];

              var baseColor = contactsColorMap[contact.displayName] as dynamic;

              Color color1 = baseColor[800];
              Color color2 = baseColor[400];

              return ListTile(
                  title: Text(contact.displayName),
                  subtitle: Text(
                      contact.phones.elementAt(0).value
                  ),
                  leading: (contact.avatar != null && contact.avatar.length > 0) ?
                  CircleAvatar(
                    backgroundImage: MemoryImage(contact.avatar),
                  ) :
                  Container(
                      decoration: BoxDecoration(
                          shape: BoxShape.circle,
                          gradient: LinearGradient(
                              colors: [
                                color1,
                                color2,
                              ],
                              begin: Alignment.bottomLeft,
                              end: Alignment.topRight
                          )
                      ),
                      child: CircleAvatar(
                          child: Text(
                              contact.initials(),
                              style: TextStyle(
                                  color: Colors.white
                              )
                          ),
                          backgroundColor: Colors.transparent
                      )
                  )
              );
            },
          ),
        )
      ],
    ),
  ),
);

}
}`

No contacts exits.

Hi!
I'm having an issue when trying to build the app on android. This is the log:

Launching lib\main.dart on Nokia 7 2 in debug mode...
Running Gradle task 'assembleDebug'...
Running Gradle task 'assembleDebug'... Done 17.5s
√ Built build\app\outputs\apk\debug\app-debug.apk.
Installing build\app\outputs\apk\app.apk... 4.8s
D/FlutterActivity(23291): Using the launch theme as normal theme.
D/FlutterActivityAndFragmentDelegate(23291): Setting up FlutterEngine.
D/FlutterActivityAndFragmentDelegate(23291): No preferred FlutterEngine was provided. Creating a new FlutterEngine for this FlutterFragment.
D/FlutterActivityAndFragmentDelegate(23291): Attaching FlutterEngine to the Activity that owns this Fragment.
D/FlutterView(23291): Attaching to a FlutterEngine: io.flutter.embedding.engine.FlutterEngine@78b24b1
D/FlutterActivityAndFragmentDelegate(23291): Executing Dart entrypoint: main, and sending initial route: /
E/AndroidRuntime(23291): FATAL EXCEPTION: pool-2-thread-1
E/AndroidRuntime(23291): Process: com.example.contacts_app, PID: 23291
E/AndroidRuntime(23291): java.lang.RuntimeException: An error occurred while executing doInBackground()
E/AndroidRuntime(23291): at android.os.AsyncTask$4.done(AsyncTask.java:399)
E/AndroidRuntime(23291): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
E/AndroidRuntime(23291): at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
E/AndroidRuntime(23291): at java.util.concurrent.FutureTask.run(FutureTask.java:271)
E/AndroidRuntime(23291): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
E/AndroidRuntime(23291): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
E/AndroidRuntime(23291): at java.lang.Thread.run(Thread.java:919)
E/AndroidRuntime(23291): Caused by: java.lang.SecurityException: Permission Denial: opening provider com.android.providers.contacts.ContactsProvider2 from ProcessRecord{37be599 23291:com.example.contacts_app/u0a223} (pid=23291, uid=10223) requires android.permission.READ_CONTACTS or android.permission.WRITE_CONTACTS
E/AndroidRuntime(23291): at android.os.Parcel.createException(Parcel.java:2071)
E/AndroidRuntime(23291): at android.os.Parcel.readException(Parcel.java:2039)
E/AndroidRuntime(23291): at android.os.Parcel.readException(Parcel.java:1987)
E/AndroidRuntime(23291): at android.app.IActivityManager$Stub$Proxy.getContentProvider(IActivityManager.java:5054)
E/AndroidRuntime(23291): at android.app.ActivityThread.acquireProvider(ActivityThread.java:6602)
E/AndroidRuntime(23291): at android.app.ContextImpl$ApplicationContentResolver.acquireUnstableProvider(ContextImpl.java:2725)
E/AndroidRuntime(23291): at android.content.ContentResolver.acquireUnstableProvider(ContentResolver.java:2120)
E/AndroidRuntime(23291): at android.content.ContentResolver.query(ContentResolver.java:930)
E/AndroidRuntime(23291): at android.content.ContentResolver.query(ContentResolver.java:881)
E/AndroidRuntime(23291): at android.content.ContentResolver.query(ContentResolver.java:837)
E/AndroidRuntime(23291): at flutter.plugins.contactsservice.contactsservice.ContactsServicePlugin.getCursor(ContactsServicePlugin.java:229)
E/AndroidRuntime(23291): at flutter.plugins.contactsservice.contactsservice.ContactsServicePlugin.access$200(ContactsServicePlugin.java:44)
E/AndroidRuntime(23291): at flutter.plugins.contactsservice.contactsservice.ContactsServicePlugin$GetContactsTask.doInBackground(ContactsServicePlugin.java:170)
E/AndroidRuntime(23291): at flutter.plugins.contactsservice.contactsservice.ContactsServicePlugin$GetContactsTask.doInBackground(ContactsServicePlugin.java:149)
E/AndroidRuntime(23291): at android.os.AsyncTask$3.call(AsyncTask.java:378)
E/AndroidRuntime(23291): at java.util.concurrent.FutureTask.run(FutureTask.java:266)
E/AndroidRuntime(23291): ... 3 more
E/AndroidRuntime(23291): Caused by: android.os.RemoteException: Remote stack trace:
E/AndroidRuntime(23291): at com.android.server.am.ActivityManagerService.getContentProviderImpl(ActivityManagerService.java:6954)
E/AndroidRuntime(23291): at com.android.server.am.ActivityManagerService.getContentProvider(ActivityManagerService.java:7374)
E/AndroidRuntime(23291): at android.app.IActivityManager$Stub.onTransact(IActivityManager.java:2078)
E/AndroidRuntime(23291): at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:2765)
E/AndroidRuntime(23291): at android.os.Binder.execTransactInternal(Binder.java:1021)
E/AndroidRuntime(23291):
Lost connection to device.
I/Process (23291): Sending signal. PID: 23291 SIG: 9
Syncing files to device Nokia 7 2...
Could not update files on device: HttpException: Connection closed before full header was received, uri =
http://127.0.0.1:53042/7bMByz4HsY4=/
Syncing files to device Nokia 7 2...

Error in main.dart on line no 21 and 169 respectively.

Hi again!
I'm just a newbie learning flutter. So try to run the code on ios device also and see this error: