back_button_interceptor 4.2.4

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pub package

back_button_interceptor #

In simple cases, when you need to intercept the Android back-button, you usually add WillPopScope to your widget tree. However, when developing stateful widgets that interact with the back button, it's more convenient to use the BackButtonInterceptor.

You may add functions to be called when the back button is tapped. These functions may perform some useful work, and then, if any of them return true, the default button process (usually popping a Route) will not be fired.

In more detail: All added functions are called, in order. If any function returns true, the combined result is true, and the default button process will NOT be fired. Only if all functions return false (or null), the combined result is false, and the default button process will be fired.

Optionally, you may provide a z-index. Functions with a valid z-index will be called before functions with a null z-index, and functions with larger z-index will be called first. When they have the same z-index, functions added last are called first.

Each function gets the boolean stopDefaultButtonEvent that indicates the current combined result from all the previous functions. So, if some function doesn't want to fire if some other previous function already fired, it can do:

if (stopDefaultButtonEvent) return false;

The same result may be obtained if the optional ifNotYetIntercepted parameter is true. Then the function will only be called if all previous functions returned false (that is, if stopDefaultButtonEvent is false).

Note: After you've finished you MUST remove each function by calling the remove() method. Alternatively, you may also provide a name when adding a function, and then later remove it by calling the removeByName(name) method.

Note: If any of your interceptors throws an error, a message will be printed to the console, but the error will not be thrown. You can change the treatment of errors by changing the static errorProcessing field.

Note: If your functions need to know the current route in the navigator, you may use the helper static method BackButtonInterceptor.getCurrentNavigatorRouteName(context).

Import the package #

Add back_button_interceptor as a dependency in your pubspec.yaml. Then, import it:

import 'package:back_button_interceptor/back_button_interceptor.dart';

Examples #

Intercepting #

void initState() {

void dispose() {

bool myInterceptor(bool stopDefaultButtonEvent) {
   print("BACK BUTTON!"); // Do some stuff.
   return true;

Named function and z-index #

void initState() {
   BackButtonInterceptor.add(myInterceptor, zIndex:2, name:"SomeName");

void dispose() {

bool myInterceptor(bool stopDefaultButtonEvent) {
   print("BACK BUTTON!"); // Do some stuff.
   return true;

Runnable Examples #

  1. main

    Intercepts the back-button and prints a string to the console.

  2. main_complex_example

    The first screen has a button which opens a second screen. The second screen has 3 red squares. By tapping the Android back-button (or the "pop" button) each square turns blue, one by one. Only when all squares are blue, tapping the back-button once more will return to the previous screen.

  3. main_complex_example_test

    This package is test friendly, and this examples shows how to test the back button.

Testing #

For testing purposes, the BackButtonInterceptor.popRoute() method may be called directly, to simulate pressing the back button. The list of all fired functions and their results is
recorded in the BackButtonInterceptor.results static variable.

Debugging #

In complex cases, to make it easier for you to debug your interceptors, you may print them to the console, with their names and z-indexes, by doing:


See also: #

The Flutter packages I've authored:

My Medium Articles:

My article in the official Flutter documentation:

Marcelo Glasberg:

[4.2.4] - 2020/05/19 #

  • Docs improvement.

[4.2.3] - 2019/12/18 #

  • BackButtonInterceptor.describe() to help debug complex interceptors.

[4.2.2] - 2019/10/28 #

  • Stack removal.

[4.1.1] - 2019/08/13 #

  • Docs improvement.

[4.0.6] - 2019/04/23 #

  • More testing features.

[4.0.5] - 2019/04/22 #

  • Small fix.

[4.0.4] - 2019/04/17 #

  • Testing features.

[4.0.2] - 2019/04/02 #

  • Helper methods to get the current route name, and the current route stack.

[4.0.1] - 2019/03/09 #

  • Functions added last are fired first. Parameters ifNotYetIntercepted and zIndex.

[3.0.0] - 2019/03/03 #

  • Prevents silent errors swallowing.

[2.0.2] - 2019/02/22 #

  • Fixed dart version.

[2.0.0] - 2019/01/02 #

  • Multiple interceptors.

[1.0.0] - 2019/01/02 #

  • Tested thoroughly. Single interceptor.


import 'package:back_button_interceptor/back_button_interceptor.dart';
import 'package:flutter/material.dart';

void main() async => runApp(MaterialApp(home: Demo()));

class Demo extends StatefulWidget {
  DemoState createState() => new DemoState();

class DemoState extends State<Demo> {
  void initState() {

  void dispose() {

  bool myInterceptor(bool stopDefaultButtonEvent) {
    print("BACK BUTTON!"); // Do some stuff.
    return true;

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Back Button Interceptor Example')),
      body: Container(color:,

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:

  back_button_interceptor: ^4.2.4

2. Install it

You can install packages from the command line:

with Flutter:

$ flutter pub get

Alternatively, your editor might support flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:

import 'package:back_button_interceptor/back_button_interceptor.dart';
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Learn more about scoring.

We analyzed this package on Jul 14, 2020, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.8.4
  • pana: 0.13.15
  • Flutter: 1.17.5

Analysis suggestions

Package not compatible with SDK dart


  • back_button_interceptor that is a package requiring null.

Health suggestions

Fix lib/src/merge_sort.dart. (-0.50 points)

Analysis of lib/src/merge_sort.dart reported 1 hint:

line 5 col 68: 'CastError' is deprecated and shouldn't be used. Use TypeError instead.

Format lib/src/back_button_interceptor.dart.

Run flutter format to format lib/src/back_button_interceptor.dart.


Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.8.0 <3.0.0
flutter 0.0.0
Transitive dependencies
collection 1.14.12 1.14.13
meta 1.1.8 1.2.2
sky_engine 0.0.99
typed_data 1.1.6 1.2.0
vector_math 2.0.8 2.1.0-nullsafety
Dev dependencies