Flutter: simple use of counter for Provider state management

The first step inpubspec.yamlInstall dependency in

Dependencies: Flutter: SDK: Flutter provider: ^3.0.0+1Copy the code

The second step inlibCreated in theThe provider folderAnd the newcount_num_provider.dart

    import 'package:flutter/material.dart'; class CountNumProvider with ChangeNotifier { int _num = 0; int get value => _num; // Expose the private variable _num with getincrementNum() { _num++; notifyListeners(); // Update status and inform listeners}}Copy the code

The third step inmain.dartRegistered in the provider

import 'package:provider/provider.dart';
import 'package:flutter_bilibili/provider/count_num_provider.dart';

void main() {
  // AMapLocationClient.setApiKey("56383edf209ce13dc3421ea77b7a0e09");
  runApp(new MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    returnProviders: [ChangeNotifierProvider(Builder: (_) => CountNumProvider()),], child: MaterialApp( initialRoute:'/',
        onGenerateRoute: onGenerateRoute,
        title: 'I'm just a decoration.',
        debugShowCheckedModeBanner: false, theme: ThemeData(primaryColor: Color(0xffFE9900)), // home: IndexPage() ), ); }}Copy the code

Step 4 Apply to a pageprovider

import 'package:provider/provider.dart';
import 'package:flutter_bilibili/provider/count_num_provider.dart';

class StatePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    var _count = Provider.of<CountNumProvider>(context);
    return Scaffold(
        body: Center(
            child: liveWiget("${_count.value}", _count.incrementNum),
            )
        );
    }
    
    Widget liveWiget(text, cb) {
        return Container(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(text, style: TextStyle(fontSize: 20)),
              RaisedButton(
                child: Text('increase'), onPressed: cb, ) ], ), ); }}Copy the code