Android: run main() once per process, not once per activity #161
@@ -891,13 +891,41 @@ public class MainActivity extends AppCompatActivity {
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}
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}
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/**
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* The activity going away is not the app shutting down.
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*
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* <p>The scaffold called {@code bridge.shutdown()} here, which is
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* the natural reading of onDestroy and is wrong for this app twice
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* over. Android destroys and recreates an activity for a
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* configuration change the manifest does not declare, under memory
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* pressure, and on every background if the user has "Don't keep
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* activities" on -- all **without restarting the process**. And
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* when the user really does leave, this app's reason for existing
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* in the background is that a song is playing, which is what the
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* {@code mediaPlayback} foreground service is holding the process
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* alive for. Either way, tearing the Go side down here would stop
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* the music.
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*
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* <p>It was harmless only by accident: {@code nativeShutdown} calls
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* {@code App.Quit()}, whose Android {@code destroy()} is an empty
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* method, and {@code Run()}'s deferred {@code shutdownServices()}
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* can never fire because Android's {@code platformRun} is
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* {@code select{}} and does not return. So no {@code
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* ServiceShutdown} has ever run on Android, and removing this call
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* changes nothing today -- it stops the day someone implements
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* {@code destroy()} from silently killing playback on a rotation.
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*
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* <p>There is no callback for "the process is going away"; Android
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* simply kills it. Durability on this platform is the persist
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* writers, which submit on every mutation rather than at exit.
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*
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* <p>See #52, and CLAUDE.md, "An activity is a view onto the
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* process".
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*/
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@Override
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protected void onDestroy() {
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super.onDestroy();
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unregisterSystemEventReceivers();
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if (bridge != null) {
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bridge.shutdown();
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}
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if (webView != null) {
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webView.destroy();
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}
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@@ -129,7 +129,24 @@ public class WailsBridge {
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}
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/**
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* Initialize the native Go library
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* Initialize the native Go library.
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*
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* <p><b>{@code initialized} is deliberately per-instance, and making
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* it {@code static} is the trap this comment exists for.</b> A
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* recreated activity builds a new bridge and calls this again, in a
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* process where the native library is already loaded and Go's
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* {@code main()} is already running -- so "initialise once per
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* process" looks like exactly the right rule. It is not, because
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* {@code nativeInit} does <i>two</i> things: it runs
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* {@code go mainFunc()}, and it stores the global JNI reference to
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* <i>this</i> bridge. Skip it and Go keeps executing JavaScript
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* against the destroyed activity's WebView: the app opens, renders,
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* and never receives another backend event.
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*
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* <p>So this is called every time, and the half that must not repeat
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* is latched on the Go side instead, at the top of {@code main()} --
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* which is also where the damage was ({@code os.Exit(1)}), and the
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* only place that can see it. See #52.
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*/
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public void initialize() {
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if (initialized) {
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