How to read a file in Flutter Application? In this post, we are going to create a simple flutter application that will read the data from the File and Write data onto the file.
For this File Read and Write operations we will use the path_provider plugin with dart io library.
We will learn
Let's get started
Step 1: Create a Flutter application
Step 2: Add required plugins in pubspec.yaml file
dependencies:
flutter:
sdk: flutter
path_provider: ^2.0.2
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Step 3: Now Create a Util class which will handle File Read and Write operations
Create a Folder in the Flutter application:
To create a folder we will use the below code
static Future<String> createFolderInAppDocDir(String folderName) async {
//Get this App Document Directory
final Directory _appDocDir = await getApplicationDocumentsDirectory();
//App Document Directory + folder name
final Directory _appDocDirFolder = Directory('${_appDocDir.path}/$folderName/');
if(await _appDocDirFolder.exists()){ //if folder already exists return path
return _appDocDirFolder.path;
}else{//if folder not exists create folder and then return its path
final Directory _appDocDirNewFolder=await _appDocDirFolder.create(recursive: true);
return _appDocDirNewFolder.path;
}
}
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To create a File will use the below code
static Future<File> getFile(String name) async {
final path = await getFilePath;
return File('$path/$name');
}
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File Util class will be like this
class FileUtils {
static String folderName="MyFiles";
static Future<String> get getFilePath async {
final directory = await getApplicationDocumentsDirectory();
final Directory _appDocDirFolder= Directory('${directory.path}/${folderName}/');
if(await _appDocDirFolder.exists()){ //if folder already exists return path
return _appDocDirFolder.path;
}else{//if folder not exists create folder and then return its path
final Directory _appDocDirNewFolder=await _appDocDirFolder.create(recursive: true);
return _appDocDirNewFolder.path;
}
}
static Future<List> getFiles()
async {
final directory = await getApplicationDocumentsDirectory();
final Directory _appDocDirFolder= Directory('${directory.path}/${folderName}/');
if(await _appDocDirFolder.exists()){ //if folder already exists return path
return _appDocDirFolder.listSync();
}
return List.empty(growable: true);
}
static Future<File> getFile(String name) async {
final path = await getFilePath;
return File('$path/$name');
}
static Future<File> saveToFile(String name,data) async {
final file = await getFile(name);
return file.writeAsString(data);
}
static Future<String> readFromFile(name) async {
try {
final file = await getFile(name);
String fileContents = await file.readAsString();
return fileContents;
} catch (e) {
return "";
}
}
static Future<String> createFolderInAppDocDir(String folderName) async {
//Get this App Document Directory
final Directory _appDocDir = await getApplicationDocumentsDirectory();
//App Document Directory + folder name
final Directory _appDocDirFolder = Directory('${_appDocDir.path}/$folderName/');
if(await _appDocDirFolder.exists()){ //if folder already exists return path
return _appDocDirFolder.path;
}else{//if folder not exists create folder and then return its path
final Directory _appDocDirNewFolder=await _appDocDirFolder.create(recursive: true);
return _appDocDirNewFolder.path;
}
}
}
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Step 4: Update main.dart file
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'dart:io';
class FileOperationsScreen extends StatefulWidget {
FileOperationsScreen() : super();
final String title = "File Operations";
@override
_FileOperationsScreenState createState() => _FileOperationsScreenState();
}
class _FileOperationsScreenState extends State {
String fileContents = "No Data";
final name_controller = TextEditingController();
final msg_controller = TextEditingController();
List listFiles=List();
var _scaffold_key=GlobalKey();
@override
void initState() {
// TODO: implement initState
super.initState();
FileUtils.getFiles().then((value) => {
setState(() {
listFiles=value;
})
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
key: _scaffold_key,
appBar: AppBar(
title: Text(widget.title),
),
body: Container(
margin: EdgeInsets.all(10),
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: [
TextField(
keyboardType: TextInputType.text,
textInputAction: TextInputAction.next,
decoration: new InputDecoration(
contentPadding:
EdgeInsets.only(left: 15, bottom: 11, top: 11, right: 15),
hintText: "File Name"),
controller: name_controller,
),
TextField(
keyboardType: TextInputType.multiline,
decoration: new InputDecoration(
contentPadding:
EdgeInsets.only(left: 15, bottom: 11, top: 11, right: 15),
hintText: "File data"),
controller: msg_controller,
),
RaisedButton(
child: Text("Save File"),
onPressed: () {
if(name_controller.text.length<=0)
{
_scaffold_key.currentState.showSnackBar(SnackBar(content: Text("Please Enter File name")));
return;
}
if(msg_controller.text.length<=10)
{
_scaffold_key.currentState.showSnackBar(SnackBar(content: Text("Please Enter File Data")));
return;
}
FileUtils.saveToFile(name_controller.text,msg_controller.text).then((value) => {
FileUtils.getFiles().then((value) => {
setState(() {
listFiles=value;
})
})
});
},
),
Card(child: Container(width:double.infinity,padding:EdgeInsets.all(10),child: Center(child: Text("List Of Files",style: TextStyle(color: Colors.green,fontSize: 20),)))),
Expanded(
child: ListView.builder(
shrinkWrap: true,
itemCount: listFiles.length,
itemBuilder: (context,index){
String path=listFiles[index].path;
String file_name= path.substring(path.lastIndexOf("/")+1);
return Card(
elevation: 10,
margin: EdgeInsets.all(10),
child: ListTile(title: Text(file_name),onTap: (){
FileUtils.readFromFile(file_name).then((contents) {
_scaffold_key.currentState.showSnackBar(SnackBar(content: Text("File Content ${contents}")));
});
},),
);
}),
),
],
),
),
);
}
}
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Step 5: Run the Application
Complete code
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'dart:io';
class FileOperationsScreen extends StatefulWidget {
FileOperationsScreen() : super();
final String title = "File Operations";
@override
_FileOperationsScreenState createState() => _FileOperationsScreenState();
}
class _FileOperationsScreenState extends State<FileOperationsScreen> {
String fileContents = "No Data";
final name_controller = TextEditingController();
final msg_controller = TextEditingController();
List listFiles=List.empty(growable: true);
var _scaffold_key=GlobalKey<ScaffoldState>();
@override
void initState() {
// TODO: implement initState
super.initState();
FileUtils.getFiles().then((value) => {
setState(() {
listFiles=value;
})
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
key: _scaffold_key,
appBar: AppBar(
title: Text(widget.title),
),
body: Container(
margin: EdgeInsets.all(10),
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
TextField(
keyboardType: TextInputType.text,
textInputAction: TextInputAction.next,
decoration: new InputDecoration(
contentPadding:
EdgeInsets.only(left: 15, bottom: 11, top: 11, right: 15),
hintText: "File Name"),
controller: name_controller,
),
TextField(
keyboardType: TextInputType.multiline,
decoration: new InputDecoration(
contentPadding:
EdgeInsets.only(left: 15, bottom: 11, top: 11, right: 15),
hintText: "File data"),
controller: msg_controller,
),
RaisedButton(
child: Text("Save File"),
onPressed: () {
if(name_controller.text.length<=0)
{
_scaffold_key.currentState!.showSnackBar(SnackBar(content: Text("Please Enter File name")));
return;
}
if(msg_controller.text.length<=10)
{
_scaffold_key.currentState!.showSnackBar(SnackBar(content: Text("Please Enter File Data")));
return;
}
FileUtils.saveToFile(name_controller.text,msg_controller.text).then((value) => {
FileUtils.getFiles().then((value) => {
setState(() {
listFiles=value;
})
})
});
},
),
Card(child: Container(width:double.infinity,padding:EdgeInsets.all(10),child: Center(child: Text("List Of Files",style: TextStyle(color: Colors.green,fontSize: 20),)))),
Expanded(
child: ListView.builder(
shrinkWrap: true,
itemCount: listFiles.length,
itemBuilder: (context,index){
String path=listFiles[index].path;
String file_name= path.substring(path.lastIndexOf("/")+1);
return Card(
elevation: 10,
margin: EdgeInsets.all(10),
child: ListTile(title: Text(file_name),onTap: (){
FileUtils.readFromFile(file_name).then((contents) {
_scaffold_key.currentState!.showSnackBar(SnackBar(content: Text("File Content ${contents}")));
});
},),
);
}),
),
],
),
),
);
}
}
class FileUtils {
static String folderName="MyFiles";
static Future<String> get getFilePath async {
final directory = await getApplicationDocumentsDirectory();
final Directory _appDocDirFolder= Directory('${directory.path}/${folderName}/');
if(await _appDocDirFolder.exists()){ //if folder already exists return path
return _appDocDirFolder.path;
}else{//if folder not exists create folder and then return its path
final Directory _appDocDirNewFolder=await _appDocDirFolder.create(recursive: true);
return _appDocDirNewFolder.path;
}
}
static Future<List> getFiles()
async {
final directory = await getApplicationDocumentsDirectory();
final Directory _appDocDirFolder= Directory('${directory.path}/${folderName}/');
if(await _appDocDirFolder.exists()){ //if folder already exists return path
return _appDocDirFolder.listSync();
}
return List.empty(growable: true);
}
static Future<File> getFile(String name) async {
final path = await getFilePath;
return File('$path/$name');
}
static Future<File> saveToFile(String name,data) async {
final file = await getFile(name);
return file.writeAsString(data);
}
static Future<String> readFromFile(name) async {
try {
final file = await getFile(name);
String fileContents = await file.readAsString();
return fileContents;
} catch (e) {
return "";
}
}
static Future<String> createFolderInAppDocDir(String folderName) async {
//Get this App Document Directory
final Directory _appDocDir = await getApplicationDocumentsDirectory();
//App Document Directory + folder name
final Directory _appDocDirFolder = Directory('${_appDocDir.path}/$folderName/');
if(await _appDocDirFolder.exists()){ //if folder already exists return path
return _appDocDirFolder.path;
}else{//if folder not exists create folder and then return its path
final Directory _appDocDirNewFolder=await _appDocDirFolder.create(recursive: true);
return _appDocDirNewFolder.path;
}
}
}
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