Android: run main() once per process, not once per activity #161

Merged
logan merged 3 commits from fix/52-android-activity-recreation-restarts-the-process into main 2026-08-20 17:18:19 +00:00
2 changed files with 49 additions and 4 deletions
Showing only changes of commit d714bd7090 - Show all commits
@@ -891,13 +891,41 @@ public class MainActivity extends AppCompatActivity {
}
}
/**
* The activity going away is not the app shutting down.
*
* <p>The scaffold called {@code bridge.shutdown()} here, which is
* the natural reading of onDestroy and is wrong for this app twice
* over. Android destroys and recreates an activity for a
* configuration change the manifest does not declare, under memory
* pressure, and on every background if the user has "Don't keep
* activities" on -- all **without restarting the process**. And
* when the user really does leave, this app's reason for existing
* in the background is that a song is playing, which is what the
* {@code mediaPlayback} foreground service is holding the process
* alive for. Either way, tearing the Go side down here would stop
* the music.
*
* <p>It was harmless only by accident: {@code nativeShutdown} calls
* {@code App.Quit()}, whose Android {@code destroy()} is an empty
* method, and {@code Run()}'s deferred {@code shutdownServices()}
* can never fire because Android's {@code platformRun} is
* {@code select{}} and does not return. So no {@code
* ServiceShutdown} has ever run on Android, and removing this call
* changes nothing today -- it stops the day someone implements
* {@code destroy()} from silently killing playback on a rotation.
*
* <p>There is no callback for "the process is going away"; Android
* simply kills it. Durability on this platform is the persist
* writers, which submit on every mutation rather than at exit.
*
* <p>See #52, and CLAUDE.md, "An activity is a view onto the
* process".
*/
@Override
protected void onDestroy() {
super.onDestroy();
unregisterSystemEventReceivers();
if (bridge != null) {
bridge.shutdown();
}
if (webView != null) {
webView.destroy();
}
@@ -129,7 +129,24 @@ public class WailsBridge {
}
/**
* Initialize the native Go library
* Initialize the native Go library.
*
* <p><b>{@code initialized} is deliberately per-instance, and making
* it {@code static} is the trap this comment exists for.</b> A
* recreated activity builds a new bridge and calls this again, in a
* process where the native library is already loaded and Go's
* {@code main()} is already running -- so "initialise once per
* process" looks like exactly the right rule. It is not, because
* {@code nativeInit} does <i>two</i> things: it runs
* {@code go mainFunc()}, and it stores the global JNI reference to
* <i>this</i> bridge. Skip it and Go keeps executing JavaScript
* against the destroyed activity's WebView: the app opens, renders,
* and never receives another backend event.
*
* <p>So this is called every time, and the half that must not repeat
* is latched on the Go side instead, at the top of {@code main()} --
* which is also where the damage was ({@code os.Exit(1)}), and the
* only place that can see it. See #52.
*/
public void initialize() {
if (initialized) {