Flutter Read/Write File Example – with path_provider and dart:io

In this tutorial, we’re gonna build a Flutter App that can read file and write data to file for later use. To do this, we need to combine path_provider plugin with dart:io library.

Flutter App Overview

Our Flutter App has a Text field, when we click on Write to File button, the String in Text field will be written to text.txt file (appending text) and display on Screen.


Everytime we launch the App, it read text.txt file and show contents inside.
We can also clear content of the file by Clear Contents button.

Read/Write Files

Find Local Path

We need a place to write data on disk and read it again when the app loads.
>> So we use path_provider plugin to access Documents directory (on iOS, this corresponds to NSDocumentDirectory, on Android, this is the AppData directory).

Reference to File

To create a reference to the File full location (in our case, the text.txt file), we use File class from the dart:io library.

Write data to File

We will write a string to a file using File writeAsString() method. It returns a Future<File> that completes with this File object once the entire operation has completed.

By default, writeAsString() creates the file and truncates the file if it already exists.
>> To append data to existing file, we pass FileMode.append mode as second parameter.

Read data from File

We use File readAsString() method to read the entire contents as a string. It returns a Future<String> that completes with the string once contents has been read.

Complete Code

Source Code


By grokonez | July 13, 2018.

Related Posts

Got Something To Say:

Your email address will not be published. Required fields are marked *