Flutter常用libs

Flutter 学习

1. dio 网络请求

2. fluttertoast 显示Toast

   import 'package:fluttertoast/fluttertoast.dart';
      
   Fluttertoast.showToast(
           msg: "This is Center Short Toast",
           toastLength: Toast.LENGTH_SHORT,
           gravity: ToastGravity.CENTER,
           timeInSecForIos: 1,
           backgroundColor: Colors.red,
           textColor: Colors.white,
           fontSize: 16.0
       );
      
   

3. url_launcher 打开web view

   import 'package:flutter/material.dart';
   import 'package:url_launcher/url_launcher.dart';
      
   void main() {
     runApp(Scaffold(
       body: Center(
         child: RaisedButton(
           onPressed: _launchURL,
           child: Text('Show Flutter homepage'),
         ),
       ),
     ));
   }
      
   _launchURL() async {
     const url = 'https://flutter.dev';
     if (await canLaunch(url)) {
       await launch(url);
     } else {
       throw 'Could not launch $url';
     }
   }
      
      
   

4. path_provider 文件路径

   Directory tempDir = await getTemporaryDirectory();
   String tempPath = tempDir.path;
      
   Directory appDocDir = await getApplicationDocumentsDirectory();
   String appDocPath = appDocDir.path;
      
   

5. image_picker 图片选择库

      var image = await ImagePicker.pickImage(source: ImageSource.camera);
      
   

6. sqflite sqlite

   import 'package:sqflite/sqflite.dart';
   var db = await openDatabase('my_db.db');
   await db.close();
   // Get a location using getDatabasesPath
   var databasesPath = await getDatabasesPath();
   String path = join(databasesPath, 'demo.db');
      
   // Delete the database
   await deleteDatabase(path);
      
   // open the database
   Database database = await openDatabase(path, version: 1,
       onCreate: (Database db, int version) async {
     // When creating the db, create the table
     await db.execute(
         'CREATE TABLE Test (id INTEGER PRIMARY KEY, name TEXT, value INTEGER, num REAL)');
   });
      
   // Insert some records in a transaction
   await database.transaction((txn) async {
     int id1 = await txn.rawInsert(
         'INSERT INTO Test(name, value, num) VALUES("some name", 1234, 456.789)');
     print('inserted1: $id1');
     int id2 = await txn.rawInsert(
         'INSERT INTO Test(name, value, num) VALUES(?, ?, ?)',
         ['another name', 12345678, 3.1416]);
     print('inserted2: $id2');
   });
      
   // Update some record
   int count = await database.rawUpdate(
       'UPDATE Test SET name = ?, VALUE = ? WHERE name = ?',
       ['updated name', '9876', 'some name']);
   print('updated: $count');
      
   // Get the records
   List<Map> list = await database.rawQuery('SELECT * FROM Test');
   List<Map> expectedList = [
     {'name': 'updated name', 'id': 1, 'value': 9876, 'num': 456.789},
     {'name': 'another name', 'id': 2, 'value': 12345678, 'num': 3.1416}
   ];
   print(list);
   print(expectedList);
   assert(const DeepCollectionEquality().equals(list, expectedList));
      
   // Count the records
   count = Sqflite
       .firstIntValue(await database.rawQuery('SELECT COUNT(*) FROM Test'));
   assert(count == 2);
      
   // Delete a record
   count = await database
       .rawDelete('DELETE FROM Test WHERE name = ?', ['another name']);
   assert(count == 1);
      
   // Close the database
   await database.close();
      
   

7. cached_network_image 图片缓存库

   CachedNetworkImage(
           imageUrl: "http://via.placeholder.com/350x150",
           placeholder: (context, url) => new CircularProgressIndicator(),
           errorWidget: (context, url, error) => new Icon(Icons.error),
        ),
      
   Image(image: new CachedNetworkImageProvider(url))
      
   CachedNetworkImage(
     imageUrl: "http://via.placeholder.com/200x150",
     imageBuilder: (context, imageProvider) => Container(
       decoration: BoxDecoration(
         image: DecorationImage(
             image: imageProvider,
             fit: BoxFit.cover,
             colorFilter:
                 ColorFilter.mode(Colors.red, BlendMode.colorBurn)),
       ),
     ),
     placeholder: (context, url) => CircularProgressIndicator(),
     errorWidget: (context, url, error) => Icon(Icons.error),
   ),
      
   

8. package_info pack信息

9. import 'package:package_info/package_info.dart';
      
   PackageInfo packageInfo = await PackageInfo.fromPlatform();
      
   String appName = packageInfo.appName;
   String packageName = packageInfo.packageName;
   String version = packageInfo.version;
   String buildNumber = packageInfo.buildNumber;
   

10. webview_flutter

11. flutter_swiper

12. photo_view

13. import 'package:photo_view/photo_view.dart';
    @override
    Widget build(BuildContext context) {
      return Container(
        child: PhotoView(
          imageProvider: AssetImage("assets/large-image.jpg"),
        )
      );
    }
    

15. flutter_easyrefresh

16. shared_preferences

    import 'package:flutter/material.dart';
    import 'package:shared_preferences/shared_preferences.dart';
        
    void main() {
      runApp(MaterialApp(
        home: Scaffold(
          body: Center(
          child: RaisedButton(
            onPressed: _incrementCounter,
            child: Text('Increment Counter'),
            ),
          ),
        ),
      ));
    }
        
    _incrementCounter() async {
      SharedPreferences prefs = await SharedPreferences.getInstance();
      int counter = (prefs.getInt('counter') ?? 0) + 1;
      print('Pressed $counter times.');
      await prefs.setInt('counter', counter);
    }
    

17. permission_handler

    import 'package:permission_handler/permission_handler.dart';
    ///requesting permission
    Map<PermissionGroup, PermissionStatus> permissions = await PermissionHandler().requestPermissions([PermissionGroup.contacts]);
        
    ///Checking permission
    PermissionStatus permission = await PermissionHandler().checkPermissionStatus(PermissionGroup.contacts);
        
    ///check service status
    ServiceStatus serviceStatus = await PermissionHandler().checkServiceStatus(PermissionGroup.location);
    

    ###