Typ 'List <dynamisch>' ist kein Subtyp vom Typ 'Uint8List

Question

Ich habe ein Flatter-Plugin namens verwendet device_apps, um die Anwendungsinformationen auf meinem Android-Gerät zu installieren.

Es wird ein List<Application>Symbol zurückgegeben, das angezeigt wird, wenn ich das Objekt von Anwendung auf umwandle ApplicationWithIcon.

Aber das Symbol, das es wiederholt, ist ein Uint8-Listentyp und ich möchte es lokal speichern und später in Image.memory () verwenden.

Wenn ich es direkt verwende, ohne es lokal zu speichern, funktioniert es einwandfrei als Image.memory (app.icon). Aber wenn ich das Symbol in einer JSON-Datei gespeichert und dann verwendet habe, wird der Fehler angezeigt:

Typ 'Liste' ist kein Subtyp vom Typ 'Uint8List'

Wie kann ich es lokal speichern und dann verwenden?

import 'dart:async';
import 'dart:convert';
import 'dart:ffi';
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:device_apps/device_apps.dart';
import 'package:app_settings/app_settings.dart';
import 'package:flutter/services.dart' show rootBundle;

void main() {
  runApp(
    MaterialApp(
      title: 'Reading and Writing Files',
      home: MyApp(),
    ),
  );
}

const String dataFile = 'data1.json';

class MyApp extends StatefulWidget {
  @override
  _AppState createState() => _AppState();
}

class _AppState extends State<MyApp> {
  String data;

  File _filePath;
  bool _fileExists = false;
  String jsonString;

  List<dynamic> _json = [];
  List<dynamic> _jsonshow = [];

  List<Application> appsDetail;

  void checkFile() async {
    // chek if file exists
    String dir = (await getApplicationDocumentsDirectory()).path;
    String savePath = '$dir/$dataFile';

//for a directory: await Directory(savePath).exists();
    if (await File(savePath).exists()) {
      print("File exists");
    } else {
      print("File don't exists");
    }
  }

  Future<String> get _localPath async {
    final directory = await getApplicationDocumentsDirectory();
    print(directory.path);
    return directory.path;
  }

  Future<File> get _localFile async {
    final path = await _localPath;
    return File('$path/$dataFile');
  }

  void appDetail() async {
    print("Getting app informations using 'device_apps' : ");
    List<Application> apps = await DeviceApps.getInstalledApplications(
      includeSystemApps: true,
      includeAppIcons: true,
      onlyAppsWithLaunchIntent: true,
    );
    print("Printing apps detail from appDetail() Funtion  apps : ");
    // for (int i = 0; i < apps.length; i++) print(apps[i]);

    print(apps);

    appsDetail = apps;

    for (int i = 0; i < apps.length; i++) {
      ApplicationWithIcon icon = apps[i] as ApplicationWithIcon;

      print(icon.icon.runtimeType);

      // print(apps[i]);
      _json.add({
        "totalApps": apps.length,
        "appName": apps[i].appName,
        "apkFilePath": apps[i].apkFilePath,
        "packageName": apps[i].packageName,
        "versionName": apps[i].versionName,
        "versionCode": apps[i].versionCode,
        "dataDir": apps[i].dataDir,
        "systemApp": apps[i].systemApp,
        "installTimeMillis": apps[i].installTimeMillis,
        "updateTimeMillis": apps[i].updateTimeMillis,
        "icon": icon.icon,

        // "category": apps[i].category
      });
    }

    print(_json);
  }

  void writeJsonfile() async {
    print("Writing json file : ");

    _filePath = await _localFile;

    print("json before encoding : ");
    print("$_json"); jsonString = jsonEncode(_json); print("jsonString after encoding : "); print(jsonString); _filePath.writeAsString( jsonEncode(jsonString), ); } Future<List<Object>> Apps() async { print("Reading Json file"); _filePath = await _localFile; _fileExists = await _filePath.exists(); print('0. File exists? $_fileExists');

    if (_fileExists) {
      try {
        String jsonString = await _filePath.readAsString();
        _json = jsonDecode(jsonString);
        print('printing json file after reading : ');
        print(_json);
        return _json;
      } catch (e) {
        // Print exception errors
        print('Tried reading _file error: $e');
        // If encountering an error, return null
      }
    } else {}
  }

  @override
  void initState() {
    super.initState();
    appDetail();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(title: Text('Reading and Writing data')),
        body: Column(
          children: <Widget>[
            IconButton(icon: Icon(Icons.ac_unit), onPressed: Apps),
            _json.length >= 1
                ? GridView.builder(
                    shrinkWrap: true,
                    physics: ScrollPhysics(),
                    scrollDirection: Axis.vertical,
                    itemCount: _json.length,
                    gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                        crossAxisCount: 5, childAspectRatio: 2.0),
                    itemBuilder: (BuildContext context, int index) {
                      return Column(
                        children: <Widget>[
                          Expanded(child: Text(_json[index]["appName"])),
                          Expanded(child: Image.memory(_json[index]["icon"])),
                        ],
                      );
                    })
                : Text("No Data Found"),
          ],
        ));
  }
}

Answer 1

Ich habe eine dumme Lösung gefunden und weiß nicht, warum das funktioniert!

Einfach _json[index]['icon']in eine Variable einfügen und dann in Image.memory () verwenden.

var icon = `_json[index]['icon']` ;

Image.memory(icon)

Hier ist der vollständige Code:

import 'dart:async';
import 'dart:convert';
import 'dart:ffi';
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:device_apps/device_apps.dart';
import 'package:app_settings/app_settings.dart';
import 'package:flutter/services.dart' show rootBundle;

void main() {
  runApp(
    MaterialApp(
      title: 'Reading and Writing Files',
      home: MyApp(),
    ),
  );
}

const String dataFile = 'data1.json';

class MyApp extends StatefulWidget {
  @override
  _AppState createState() => _AppState();
}

class _AppState extends State<MyApp> {
  String data;

  File _filePath;
  bool _fileExists = false;
  String jsonString;

  List<dynamic> _json = [];
  List<dynamic> _jsonshow = [];

  List<Application> appsDetail;

  void checkFile() async {
    // chek if file exists
    String dir = (await getApplicationDocumentsDirectory()).path;
    String savePath = '$dir/$dataFile';

//for a directory: await Directory(savePath).exists();
    if (await File(savePath).exists()) {
      print("File exists");
    } else {
      print("File don't exists");
    }
  }

  Future<String> get _localPath async {
    final directory = await getApplicationDocumentsDirectory();
    print(directory.path);
    return directory.path;
  }

  Future<File> get _localFile async {
    final path = await _localPath;
    return File('$path/$dataFile');
  }

  void appDetail() async {
    print("Getting app informations using 'device_apps' : ");
    List<Application> apps = await DeviceApps.getInstalledApplications(
      includeSystemApps: true,
      includeAppIcons: true,
      onlyAppsWithLaunchIntent: true,
    );
    print("Printing apps detail from appDetail() Funtion  apps : ");
    // for (int i = 0; i < apps.length; i++) print(apps[i]);

    print(apps);

    appsDetail = apps;

    for (int i = 0; i < apps.length; i++) {
      ApplicationWithIcon icon = apps[i] as ApplicationWithIcon;

      print(icon.icon.runtimeType);

      // print(apps[i]);
      _json.add({
        "totalApps": apps.length,
        "appName": apps[i].appName,
        "apkFilePath": apps[i].apkFilePath,
        "packageName": apps[i].packageName,
        "versionName": apps[i].versionName,
        "versionCode": apps[i].versionCode,
        "dataDir": apps[i].dataDir,
        "systemApp": apps[i].systemApp,
        "installTimeMillis": apps[i].installTimeMillis,
        "updateTimeMillis": apps[i].updateTimeMillis,
        "icon": icon.icon,

        // "category": apps[i].category
      });
    }

    print(_json);
  }

  void writeJsonfile() async {
    print("Writing json file : ");

    _filePath = await _localFile;

    print("json before encoding : ");
    print("$_json"); jsonString = jsonEncode(_json); print("jsonString after encoding : "); print(jsonString); _filePath.writeAsString( jsonEncode(jsonString), ); } Future<List<Object>> Apps() async { print("Reading Json file"); _filePath = await _localFile; _fileExists = await _filePath.exists(); print('0. File exists? $_fileExists');

    if (_fileExists) {
      try {
        String jsonString = await _filePath.readAsString();
        _json = jsonDecode(jsonString);
        print('printing json file after reading : ');
        print(_json);
        return _json;
      } catch (e) {
        // Print exception errors
        print('Tried reading _file error: $e');
        // If encountering an error, return null
      }
    } else {}
  }

  @override
  void initState() {
    super.initState();
    appDetail();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(title: Text('Reading and Writing data')),
        body: Column(
          children: <Widget>[
            IconButton(icon: Icon(Icons.ac_unit), onPressed: Apps),
            _json.length >= 1
                ? GridView.builder(
                    shrinkWrap: true,
                    physics: ScrollPhysics(),
                    scrollDirection: Axis.vertical,
                    itemCount: _json.length,
                    gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                        crossAxisCount: 5, childAspectRatio: 2.0),
                    itemBuilder: (BuildContext context, int index) {
                      print("Checking");
                      print(_json[index]["icon"].runtimeType);
                      var icon = _json[index]["icon"];
                      return Column(
                        children: <Widget>[
                          Expanded(child: Text(_json[index]["appName"])),
                          Expanded(child: Image.memory(icon)),
                        ],
                      );
                    })
                : Text("No Data Found"),
          ],
        ));
  }
}