Home Widget

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

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" >
    <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.

iOS

Add a Widget to your App in Xcode

Add a widget extension by going File > New > Target > 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 > +

(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.

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")

Usage

Setup

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)

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

Clicking

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

<intent-filter>
    <action android:name="es.antonborri.home_widget.action.LAUNCH" />
</intent-filter>

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 Click

Android allows interactive elements in HomeScreenWidgets. This allows to for example add a refresh button on a widget. With home_widget you can use this by following these steps:

Android/Native Part

1. Add the necessary Receiver and Service to you AndroidManifest.xml file

   <receiver android:name="es.antonborri.home_widget.HomeWidgetBackgroundReceiver">
       <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)

Dart

4. 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")
   void backgroundCallback(Uri data) {
     // do something with data
     ...
   }

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

5. Register the callback function by calling

   HomeWidget.registerBackgroundCallback(backgroundCallback);

Using images of Flutter widgets

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

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: Size(width: 400, height: 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
       }

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)
          }
      }
   }