# Android ActivityControlSurface attachToActivity signature change

> attachToActivity activity parameter changed to ExclusiveAppComponent instead of Activity.




:::important
These breaking change docs are accurate, as of the release
under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

The [breaking change index file](/release/breaking-changes)
lists the docs created for each release.
:::


## Summary

:::note
If you use standard Android embedding Java classes like
[`FlutterActivity`][] or [`FlutterFragment`][],
and don't manually embed a [`FlutterView`][]
inside your own custom `Activity` (this should be uncommon),
you can stop reading.
:::

A new [`ActivityControlSurface`][] method:

```java
void attachToActivity(
    @NonNull ExclusiveAppComponent<Activity> exclusiveActivity,
    @NonNull Lifecycle lifecycle);
```

is replacing the now deprecated method:

```java
void attachToActivity(@NonNull Activity activity, @NonNull Lifecycle lifecycle);
```

The existing deprecated method with the `Activity`
parameter was removed in Flutter 2.

## Context

In order for custom Activities to also supply the `Activity`
lifecycle events Flutter plugins expect using the
[`ActivityAware`][] interface, the [`FlutterEngine`][]
exposed a [`getActivityControlSurface()`][] API.

This allows custom Activities to signal to the engine
(with which it has a `(0|1):1` relationship) that
it was being attached or detached from the engine.

:::note
This lifecycle signaling is done automatically when you
use the engine's bundled [`FlutterActivity`][]
or [`FlutterFragment`][], which should be the most
common case.
:::

However, the previous API had the flaw that it didn't
enforce exclusion between activities connecting to
the engine, thus enabling `n:1` relationships between
the activity and the engine,
causing lifecycle cross-talk issues.

## Description of change

After [Issue #21272][], instead of attaching your activity
to the [`FlutterEngine`][] by using the:

```java
void attachToActivity(@NonNull Activity activity, @NonNull Lifecycle lifecycle);
```

API, which is now deprecated, instead use:

```java
void attachToActivity(
    @NonNull ExclusiveAppComponent<Activity> exclusiveActivity,
    @NonNull Lifecycle lifecycle);
```

An `ExclusiveAppComponent<Activity>` interface
is now expected instead of an `Activity`.
The `ExclusiveAppComponent<Activity>` provides a callback
in case your exclusive activity is being replaced by
another activity attaching itself to the `FlutterEngine`.

```java
void detachFromActivity();
```

API remains unchanged and you're still expected
to call it when your custom
activity is being destroyed naturally.

## Migration guide

If you have your own activity holding a
[`FlutterView`][], replace calls to:

```java
void attachToActivity(@NonNull Activity activity, @NonNull Lifecycle lifecycle);
```

with calls to:

```java
void attachToActivity(
    @NonNull ExclusiveAppComponent<Activity> exclusiveActivity,
    @NonNull Lifecycle lifecycle);
```

on the [`ActivityControlSurface`][] that you obtained by calling
[`getActivityControlSurface()`][] on the [`FlutterEngine`][].

Wrap your activity with an `ExclusiveAppComponent<Activity>`
and implement the callback method:

```java
void detachFromFlutterEngine();
```

to handle your activity being replaced by another
activity being attached to the [`FlutterEngine`][].
Generally, you want to perform the same detaching operations
as performed when the activity is being naturally destroyed.

## Timeline

Landed in version: 1.23.0-7.0.pre<br>
In stable release: 2.0.0

## References

Motivating bug: [Issue #66192][]—Non exclusive
UI components attached to the FlutterEngine causes
event crosstalk


[`ActivityAware`]: https://api.flutter.dev/javadoc/io/flutter/embedding/engine/plugins/activity/ActivityAware.html
[`ActivityControlSurface`]: https://api.flutter.dev/javadoc/io/flutter/embedding/engine/plugins/activity/ActivityControlSurface.html
[`FlutterActivity`]: https://api.flutter.dev/javadoc/io/flutter/embedding/android/FlutterActivity.html
[`FlutterEngine`]: https://api.flutter.dev/javadoc/io/flutter/embedding/engine/FlutterEngine.html
[`FlutterFragment`]: https://api.flutter.dev/javadoc/io/flutter/embedding/android/FlutterFragment.html
[`FlutterView`]: https://api.flutter.dev/javadoc/io/flutter/view/FlutterView.html
[`getActivityControlSurface()`]: https://api.flutter.dev/javadoc/io/flutter/embedding/engine/FlutterEngine.html#getActivityControlSurface--
[Issue #66192]: https://github.com/flutter/flutter/issues/66192.
[Issue #21272]: https://github.com/flutter/engine/pull/21272