Systemwarnungsfenster

system_alert_window

A flutter plugin to show Truecaller like overlay window, over all other apps along with callback events. Android Go or Android 11 & above, this plugin shows notification bubble, in other android versions, it shows an overlay window.

Android

Demo

1. Clip of example app and 2. Working of button click in the background

      

Manifest

  //Permissions
  <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
  <uses-permission android:name="android.permission.FOREGROUND_SERVICE " />
  <uses-permission android:name="android.permission.WAKE_LOCK" />


      <application
          //Linking the previously added application class
          android:name=".Application"
          android:label="system_alert_window_example"
          android:icon="@mipmap/ic_launcher">

Android 10 & below, Android GO (API 27)

Uses 'draw on top' permission and displays it as a overlay window

Android 11 & above

With SystemWindowPrefMode.OVERLAY, system alert windows uses 'overlay functionality' wherever it's supported. In that mode, it will show as bubbles if the 'display over other apps' is not supported. With SystemWindowPrefMode.DEFAULT/SystemWindowPrefMode.BUBBLE, User has to allow 'All conversations can bubble' in the notification settings of the app. Uses Android Bubble APIs to show the overlay window inside a notification bubble.

Edge-to-edge content and window insets are handled automatically inside the bubble container — wrap your overlay widget with SafeArea to avoid content being obscured by system bars.

Android GO (API 29)

User has to manually enable bubbles from the developer options. Uses Android Bubble APIs to show the overlay window inside a notification bubble.

IOS

Displays as a notification in the notification center [Help Needed]

Example

Show Overlay

Request overlay permission

  await SystemAlertWindow.requestPermissions;

Inside main.dart create an entry point for your Overlay widget;

// overlay entry point
@pragma("vm:entry-point")
void overlayMain() {
  runApp(const MaterialApp(
    debugShowCheckedModeBanner: false,
    home: Material(child: Text("My overlay"))
  ));
}


 //Open overLay content

//  - Optional arguments:
/// `gravity` Position of the window and default is [SystemWindowGravity.CENTER]
/// `width` Width of the window and default is [Constants.MATCH_PARENT]
/// `height` Height of the window and default is [Constants.WRAP_CONTENT]
/// `notificationTitle` Notification title, applicable in case of bubble
/// `notificationBody` Notification body, applicable in case of bubble
/// `prefMode` Preference for the system window. Default is [SystemWindowPrefMode.DEFAULT]
/// `layoutParamFlags` List of List of WindowManager.LayoutParams. This is not applicable for bubbles.
await SystemAlertWindow.showSystemWindow();

/// update the overlay flag while the overlay in action
///   - Optional arguments:
/// `gravity` Position of the window and default is [SystemWindowGravity.CENTER]
/// `width` Width of the window and default is [Constants.MATCH_PARENT]
/// `height` Height of the window and default is [Constants.WRAP_CONTENT]
/// `notificationTitle` Notification title, applicable in case of bubble
/// `notificationBody` Notification body, applicable in case of bubble
/// `prefMode` Preference for the system window. Default is [SystemWindowPrefMode.DEFAULT]
/// `layoutParamFlags` List of List of WindowManager.LayoutParams. This is not applicable for bubbles.
await FlutterOverlayWindow.updateSystemWindow();

 // closes overlay if open
await SystemAlertWindow.closeSystemWindow();

 // broadcast data to overlay app from main app
await SystemAlertWindow.sendMessageToOverlay("Hello from the other side");

 //streams message from main app to overlay.
SystemAlertWindow.overlayListener.listen((event) {
log("Current Event: $event");
});

Isolate communication

Use this snippet, if you want the callbacks on your main thread

Create an isolate_manager.dart

import 'dart:isolate';

import 'dart:ui';

class IsolateManager{

  static const FOREGROUND_PORT_NAME = "foreground_port";

  static SendPort lookupPortByName() {
    return IsolateNameServer.lookupPortByName(FOREGROUND_PORT_NAME);
  }

  static bool registerPortWithName(SendPort port) {
    assert(port != null, "'port' cannot be null.");
    removePortNameMapping(FOREGROUND_PORT_NAME);
    return IsolateNameServer.registerPortWithName(port, FOREGROUND_PORT_NAME);
  }

  static bool removePortNameMapping(String name) {
    assert(name != null, "'name' cannot be null.");
    return IsolateNameServer.removePortNameMapping(name);
  }

}

While initializing system alert window in your code

    await SystemAlertWindow.checkPermissions;
    ReceivePort _port = ReceivePort();
    IsolateManager.registerPortWithName(_port.sendPort);
    _port.listen((message) {
          log("message from OVERLAY: $message");
          print("Do what ever you want here. This is inside your application scope");
    });

Use this to send data to isolate mentioned above

void callBackFunction(String tag) {
  print("Got tag " + tag);
  SendPort port = IsolateManager.lookupPortByName();
  port.send(tag);
}