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Home Widget

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HomeWidget is a Plugin to make it easier to create HomeScreen Widgets on Android and iOS. HomeWidget does not allow writing Widgets with Flutter itself. It still requires writing the Widgets with native code. However, it provides a unified Interface for sending data, retrieving data and updating the Widgets

iOS  Android

Platform Setup

In order to work correctly there needs to be some platform specific setup. Check below on how to add support for Android and iOS

iOS

Add a Widget to your App in Xcode

Add a widget extension by going File > New > Target > Widget Extension

Widget Extension

Add GroupId

You need to add a groupId to the App and the Widget Extension

Note: in order to add groupIds you need a paid Apple Developer Account

Go to your Apple Developer Account and add a new group Add this group to you Runner and the Widget Extension inside XCode Signing & Capabilities > App Groups > +

Build Targets

(To swap between your App, and the Extension change the Target)

Sync CFBundleVersion (optional)

This step is optional, this will sync the widget extension build version with your app version, so you don't get warnings of mismatch version from App Store Connect when uploading your app.

Build Phases

In your Runner (app) target go to Build Phases > + > New Run Script Phase and add the following script:

generatedPath="$SRCROOT/Flutter/Generated.xcconfig"
versionNumber=$(grep FLUTTER_BUILD_NAME $generatedPath | cut -d '=' -f2)
buildNumber=$(grep FLUTTER_BUILD_NUMBER $generatedPath | cut -d '=' -f2)
/usr/libexec/PlistBuddy -c "Set :CFBundleVersion $buildNumber" "$SRCROOT/HomeExampleWidget/Info.plist"
/usr/libexec/PlistBuddy -c "Set :CFBundleShortVersionString $versionNumber" "$SRCROOT/HomeExampleWidget/Info.plist"

Replace HomeExampleWidget with the name of the widget extension folder that you have created.

Write your Widget

Check the Example App for an Implementation of a Widget. A more detailed overview on how to write Widgets for iOS 14 can be found on the Apple Developer documentation. In order to access the Data send with Flutter can be access with

let data = UserDefaults.init(suiteName:"YOUR_GROUP_ID")
Android

Create Widget Layout inside android/app/src/main/res/layout

Create Widget Configuration into android/app/src/main/res/xml

<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
    android:minWidth="40dp"
    android:minHeight="40dp"
    android:updatePeriodMillis="86400000"
    android:initialLayout="@layout/example_layout"
    android:resizeMode="horizontal|vertical"
    android:widgetCategory="home_screen">
</appwidget-provider>

Add WidgetReceiver to AndroidManifest

<receiver android:name="HomeWidgetExampleProvider" android:exported="true">
    <intent-filter>
        <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
    </intent-filter>
    <meta-data android:name="android.appwidget.provider"
        android:resource="@xml/home_widget_example" />
</receiver>

Write your WidgetProvider

For convenience, you can extend from HomeWidgetProvider which gives you access to a SharedPreferences Object with the Data in the onUpdate method. In case you don't want to use the convenience Method you can access the Data using

import es.antonborri.home_widget.HomeWidgetPlugin
...
HomeWidgetPlugin.getData(context)

which will give you access to the same SharedPreferences

More Information

For more Information on how to create and configure Android Widgets, check out this guide on the Android Developers Page.

Usage

Setup

iOS For iOS, you need to call `HomeWidget.setAppGroupId('YOUR_GROUP_ID');` Without this you won't be able to share data between your App and the Widget and calls to `saveWidgetData` and `getWidgetData` will return an error

Save Data

In order to save Data call HomeWidget.saveWidgetData<String>('id', data)

Update a Widget

In order to force a reload of the HomeScreenWidget you need to call

HomeWidget.updateWidget(
    name: 'HomeWidgetExampleProvider',
    androidName: 'HomeWidgetExampleProvider',
    iOSName: 'HomeWidgetExample',
    qualifiedAndroidName: 'com.example.app.HomeWidgetExampleProvider',
);

The name for Android will be chosen by checking qualifiedAndroidName, falling back to <packageName>.androidName and if that was not provided it will fallback to <packageName>.name. This Name needs to be equal to the Classname of the WidgetProvider

The name for iOS will be chosen by checking iOSName if that was not provided it will fallback to name. This name needs to be equal to the Kind specified in you Widget

Retrieve Data

To retrieve the current Data saved in the Widget call HomeWidget.getWidgetData<String>('id', defaultValue: data)

Interactive Widgets

Android and iOS (starting with iOS 17) allow widgets to have interactive Elements like Buttons

Dart

  1. Write a static function that takes a Uri as an argument. This will get called when a user clicks on the View

    @pragma("vm:entry-point")
FutureOr<void> backgroundCallback(Uri data) async {
  // do something with data
  ...
}

    @pragma('vm:entry-point') must be placed above the callback function to avoid tree shaking in release mode.

  2. Register the callback function by calling

    HomeWidget.registerInteractivityCallback(backgroundCallback);
iOS

  1. Adjust your Podfile to add home_widget as a dependency to your WidgetExtension

    target 'YourWidgetExtension' do
   use_frameworks!
   use_modular_headers!

   pod 'home_widget', :path => '.symlinks/plugins/home_widget/ios'
end

  2. To be able to use plugins with the Background Callback add this to your AppDelegate's application function

    if #available(iOS 17, *) {
 HomeWidgetBackgroundWorker.setPluginRegistrantCallback { registry in
     GeneratedPluginRegistrant.register(with: registry)
 }
}

  3. Create a custom AppIntent in your App Target (Runner) and make sure to select both your App and your WidgetExtension in the Target Membership panel

    Target Membership

    In this Intent you should import home_widget and call HomeWidgetBackgroundWorker.run(url: url, appGroup: appGroup!) in the perform method. url and appGroup can be either hardcoded or set as parameters from the Widget

    import AppIntents
import Flutter
import Foundation
import home_widget

@available(iOS 16, *)
public struct BackgroundIntent: AppIntent {
   static public var title: LocalizedStringResource = "HomeWidget Background Intent"
   
   @Parameter(title: "Widget URI")
   var url: URL?
   
   @Parameter(title: "AppGroup")
   var appGroup: String?
   
   public init() {}
   
   public init(url: URL?, appGroup: String?) {
      self.url = url
      self.appGroup = appGroup
   }
   
   public func perform() async throws -> some IntentResult {
      await HomeWidgetBackgroundWorker.run(url: url, appGroup: appGroup!)
   
      return .result()
   }
}

  4. Add a Button to your Widget. This Button might be encapsulated by a Version check. Pass in an instance of the AppIntent created in the previous step

    Button(
   intent: BackgroundIntent(
     url: URL(string: "homeWidgetExample://titleClicked"), appGroup: widgetGroupId)
 ) {
   Text(entry.title).bold().font( /*@START_MENU_TOKEN@*/.title /*@END_MENU_TOKEN@*/)
 }.buttonStyle(.plain)

  5. With the current setup the Widget is now Interactive as long as the App is still in the background. If you want to have the Widget be able to wake the App up you need to add the following to your AppIntent file

    @available(iOS 16, *)
@available(iOSApplicationExtension, unavailable)
extension BackgroundIntent: ForegroundContinuableIntent {}

    This code tells the system to always perform the Intent in the App and not in a process attached to the Widget. Note however that this will start your Flutter App using the normal main entrypoint meaning your full app might be run in the background. To counter this you should add checks in the very first Widget you build inside runApp to only perform necessary calls/setups while the App is launched in the background

Android
  1. Add the necessary Receiver and Service to you AndroidManifest.xml file 
    <receiver android:name="es.antonborri.home_widget.HomeWidgetBackgroundReceiver"  android:exported="true">
    <intent-filter>
        <action android:name="es.antonborri.home_widget.action.BACKGROUND" />
    </intent-filter>
</receiver>
<service android:name="es.antonborri.home_widget.HomeWidgetBackgroundService"
    android:permission="android.permission.BIND_JOB_SERVICE" android:exported="true"/>
  2. Add a HomeWidgetBackgroundIntent.getBroadcast PendingIntent to the View you want to add a click listener to 
    val backgroundIntent = HomeWidgetBackgroundIntent.getBroadcast(
    context,
    Uri.parse("homeWidgetExample://titleClicked")
)
setOnClickPendingIntent(R.id.widget_title, backgroundIntent)

Using images of Flutter widgets

In some cases, you may not want to rewrite UI code in the native frameworks for your widgets.

Dart For example, say you have a chart in your Flutter app configured with `CustomPaint`: 
class LineChart extends StatelessWidget {
  const LineChart({
    super.key,
  });

  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: LineChartPainter(),
      child: const SizedBox(
        height: 200,
        width: 200,
      ),
    );
  }
}
Screenshot 2023-06-07 at 12 33 44 PM

Rewriting the code to create this chart on both Android and iOS might be time consuming. Instead, you can generate a png file of the Flutter widget and save it to a shared container between your Flutter app and the home screen widget.

var path = await HomeWidget.renderFlutterWidget(
  const LineChart(),
  key: 'lineChart',
  logicalSize: const Size(400, 400),
);
  • LineChart() is the widget that will be rendered as an image.
  • key is the key in the key/value storage on the device that stores the path of the file for easy retrieval on the native side
iOS To retrieve the image and display it in a widget, you can use the following SwiftUI code:

  1. In your TimelineEntry struct add a property to retrieve the path:

    struct MyEntry: TimelineEntry {
    …
    let lineChartPath: String
}

  2. Get the path from the UserDefaults in getSnapshot:

    func getSnapshot(
    ...
    let lineChartPath = userDefaults?.string(forKey: "lineChart") ?? "No screenshot available"

  3. Create a View to display the chart and resize the image based on the displaySize of the widget:

    struct WidgetEntryView : View {
  …
   var ChartImage: some View {
        if let uiImage = UIImage(contentsOfFile: entry.lineChartPath) {
            let image = Image(uiImage: uiImage)
                .resizable()
                .frame(width: entry.displaySize.height*0.5, height: entry.displaySize.height*0.5, alignment: .center)
            return AnyView(image)
        }
        print("The image file could not be loaded")
        return AnyView(EmptyView())
    }
…
}

  4. Display the chart in the body of the widget's View:

    VStack {
        Text(entry.title)
        Text(entry.description)
        ChartImage
    }
Screenshot 2023-06-07 at 12 57 28 PM
Android
  1. Add an image UI element to your xml file: 
    <ImageView
       android:id="@+id/widget_image"
       android:layout_width="200dp"
       android:layout_height="200dp"
       android:layout_below="@+id/headline_description"
       android:layout_alignBottom="@+id/headline_title"
       android:layout_alignParentStart="true"
       android:layout_alignParentLeft="true"
       android:layout_marginStart="8dp"
       android:layout_marginLeft="8dp"
       android:layout_marginTop="6dp"
       android:layout_marginBottom="-134dp"
       android:layout_weight="1"
       android:adjustViewBounds="true"
       android:background="@android:color/white"
       android:scaleType="fitCenter"
       android:src="@android:drawable/star_big_on"
       android:visibility="visible"
       tools:visibility="visible" />
  2. Update your Kotlin code to get the chart image and put it into the widget, if it exists. 
    class NewsWidget : AppWidgetProvider() {
   override fun onUpdate(
       context: Context,
       appWidgetManager: AppWidgetManager,
       appWidgetIds: IntArray,
   ) {
       for (appWidgetId in appWidgetIds) {
           // Get reference to SharedPreferences
           val widgetData = HomeWidgetPlugin.getData(context)
           val views = RemoteViews(context.packageName, R.layout.news_widget).apply {
               // Get chart image and put it in the widget, if it exists
               val imagePath = widgetData.getString("lineChart", null)
               val imageFile = File(imagePath)
               val imageExists = imageFile.exists()
               if (imageExists) {
                  val myBitmap: Bitmap = BitmapFactory.decodeFile(imageFile.absolutePath)
                  setImageViewBitmap(R.id.widget_image, myBitmap)
               } else {
                  println("image not found!, looked @: $imagePath")
               }
               // End new code
           }
           appWidgetManager.updateAppWidget(appWidgetId, views)
       }
   }
}

Launch App and Detect which Widget was clicked

To detect if the App has been initially started by clicking the Widget you can call HomeWidget.initiallyLaunchedFromHomeWidget() if the App was already running in the Background you can receive these Events by listening to HomeWidget.widgetClicked. Both methods will provide Uris, so you can easily send back data from the Widget to the App to for example navigate to a content page.

In order for these methods to work you need to follow these steps:

iOS

Add .widgetUrl to your WidgetComponent

Text(entry.message)
    .font(.body)
    .widgetURL(URL(string: "homeWidgetExample://message?message=\(entry.message)&homeWidget"))

In order to only detect Widget Links you need to add the queryParameterhomeWidget to the URL

Android Add an `IntentFilter` to the `Activity` Section in your `AndroidManifest` ``` ```

In your WidgetProvider add a PendingIntent to your View using HomeWidgetLaunchIntent.getActivity

val pendingIntentWithData = HomeWidgetLaunchIntent.getActivity(
        context,
        MainActivity::class.java,
        Uri.parse("homeWidgetExample://message?message=$message"))
setOnClickPendingIntent(R.id.widget_message, pendingIntentWithData)

Background Update

As the methods of HomeWidget are static it is possible to use HomeWidget in the background to update the Widget even when the App is in the background.

The example App is using the flutter_workmanager plugin to achieve this. Please follow the Setup Instructions for flutter_workmanager (or your preferred background code execution plugin). Most notably make sure that Plugins get registered in iOS in order to be able to communicate with the HomeWidget Plugin. In case of flutter_workmanager this achieved by adding:

WorkmanagerPlugin.setPluginRegistrantCallback { registry in
    GeneratedPluginRegistrant.register(with: registry)
}

to AppDelegate.swift

Resources, Articles, Talks

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