file_edit_launcher

An API used to open/edit a file in another app.

Overview

This plugin provides and API for editing a file using a third-party app.

This plugin uses code from the open_file plugin. On the Android side the code has been hollowed out and changed to Kotlin. The IOS code was simply copied and not changerd. We also added the key functionality of editing a file. Editing Files is currently only supported on Android. For Android we're using Intents and FileProvider to open and edit files in other apps.

High Level Explination

This package exposes and API consisting of one function launchFileEditor(file) that launches the app chooser(Android) allowing the user to pick an external app to edit the file with. This edit should happen in place and happen even if the file is a application private file. When the user has finished editing the file there is a call back to notify that app that the edit has been finished.

Dart Layer: On the dart side the launchFileEditor(File file) requires a Dart File Object. The path of this file is passed across the method channel where it is passed to the native kotlin. When the response is returned we return a LauncherResult representing all the potential results.

Android Layer: First we register the method channel. When the call over the channel is consumed we extract the file path. Using the File path we first check to make sure that the file exists. If it doesnt we return and error communicating the file is missing. We then check the Build version to ask for permissions if needed. At this point we create a new Intent(Intent.ACTION_EDIT). We then get the uri provided by FileProvider so other apps can access our private files. From here we set the data and type of the intent. The final step is we launch the intent using startActivityForResult(); When the activity has finished and returned we send that back across the method channel notifying the consumer.

Getting Started

The Flutter side of this API is very symple. It consists of one function used to open and edit the desired file. Keep in mind when editing a file that it must be in a directory allowing edits.

Example

In this example we create a pdf and save it in a file. Afterwhich we open it to let the user update it.

    var dir = await getExternalStorageDirectory();
    var dirPath = dir?.absolute.path;
    var file = File("$dirPath/temp.pdf");
    var pdf = createPdf();
    await file.writeAsBytes(await pdf.save());
    
    final result = await FileEditLauncher.launchFileEditor(file);
    

When the user has finished viewing or editing a file you'll recieve a LauncherResult. Make sure to handle the errors returned here properly.

Notes

There are a few potential problems that may arise when using this plugin.

When there is conflict with other plugins about FileProvider, add code below in your /android/app/src/main/AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools"
          package="xxx.xxx.xxxxx">
    <application>
        ...
        <provider
                android:name="androidx.core.content.FileProvider"
                android:authorities="${applicationId}.fileProvider"
                android:exported="false"
                android:grantUriPermissions="true"
                tools:replace="android:authorities">
            <meta-data
                    android:name="android.support.FILE_PROVIDER_PATHS"
                    android:resource="@xml/filepaths"
                    tools:replace="android:resource" />
        </provider>
    </application>
</manifest>

TODO

IOS

Firstly if doing all this in swift is possible that would be great.

Currently the IOS version of this package only opens a file for viewing but lacks the ability to edit the file in place. The package being used atm is UIDocumentInteractionController. This package allows us to open the file but lacks the editing funcitonality(as far as I can tell). IOS has a function called openDocument that should do this for you. In not sure what this would be on the swift side.

The package must use the MethodChannel to communicate with the Flutter/dart layer. The channel you should be listening on is 'file_edit_launcher'. This channel on the dart side and android side only consist of one call being 'launch_file_editor'. This MUST be carried over to the IOS package or it obviously wont work. The call has only one argument being 'file_path' which is a String. Using the file_path we want to open the file in a 3rd-party app to edit the file and recieve a callback when they are finished and return the string 'Done Editing' when finished. Make sure this is passed as a success to the method channel.

On the Dart side we return a LauncherResult object that holds either successful = true or an error and stackTrace. There are only three errors im catching currently being 'Permission Denied, , "File Missing" , and 'File Path Null'. These strings should be passed back via the error on your method channel. We parse them on the dart side. If there are more errors that i've missed just add them to the dart side.

here is an article using objective-c describing how to do this: https://code.tutsplus.com/tutorials/ios-sdk-previewing-and-opening-documents--mobile-15130

here is the documentation on openDocument: https://developer.apple.com/documentation/appkit/nsdocumentcontroller/1515005-opendocument