App always crashes on hot restart #970
Comments
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Later, I discovered that JNI crashes hard whenever closing the flutter engine (??) I discovered this because my app has a background If it fires at the same time I use the app, it launches it's own flutterEngine, does some stuff, and then closes it... which crashes the whole app: I see the same crash when i swipe away my app (well, then it's not the problem obviously 😂) Any useful details: I am using And I, of course, don't |
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About your original issue: You're doing _manager = android.BluetoothManager.fromRef(
ctx
.getSystemService(android.Context.BLUETOOTH_SERVICE.toJString())
.reference,
);to simplify, let's write it like: bar = Bar.fromRef(foo.reference);Here, both bar = foo.castTo(Bar.type);This will create a new reference for bar = foo.castTo(Bar.type, releaseOriginal: true);This way, the same underlying reference is used for So, in your case, do: _manager = ctx.getSystemService(android.Context.BLUETOOTH_SERVICE.toJString())
.castTo(android.BluetoothManager.type, releaseOriginal: true); |
thank you!!
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Oh it works now!!! Both of my issues are gone ✌️ Big thanks again! |
@HosseinYousefi Does this issue arise due to us using inheritance over composition? More specifically I see that we have class JReference implements Finalizable {}
class JObject extends JReference {}
class JArray extends JObject {}
class X extends JObject {}It would seem more natural to model this as composition and attach finalizers to class JReference implements Finalizable {}
class JObject {
final JReference _reference;
}
class JArray extends JObject {}
class X extends JObject {}Though since we do allow eager releasing, any re-use of the reference must be made explicit - so developers have to decide (and know) whether reference is shared or not, and thereby be cautions about when to release. |
Yes, this exact problem will be solved, and I will change this in the next version (also to allow sharing of |
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Looking forward to sending jobjects between Isolates because it will allow me for async read/writes to bluetooth - right now I'm literally doing while(true) {
if(available > 0) {
...
}
await Future.delayed(10ms); // free the main Isolate
} |
You can send them between isolates. It's just a bit manual right now: For example, using this helper method: Future<R> runOnIsolate<T extends JObject, R>(
T object, R Function(T object) callback) async {
final type = object.$type;
final address = object.reference.address;
return Isolate.run(() {
final ref = Jni.env.NewGlobalRef(Pointer.fromAddress(address));
final sentObject = type.fromRef(ref) as T;
return callback(sentObject);
});
}And then you can run something on a different isolate like: final str = 'hello'.toJString();
await runOnIsolate(str, (object) {
print(object);
}); // prints hello |
While hot-reload works fine, hot-restarting crashes my app every time with
JNI DETECTED ERROR IN APPLICATION: JNI ERROR (app bug): jobject is an invalid global reference: 0x30c6 (deleted reference at index 390) in call to DeleteGlobalRefI will obviously show my code, but I think it's details are not useful because I suspect I must be "not properly freeing Java references" in
dispose()es or something like that - so, I'm opening this issue as a request to add some universal notes about when and why to call.release()🙏My main "plugin" file: https://github.com/TheLastGimbus/the_last_bluetooth/blob/60013e4959cb1f0ecd8c2d9f2e1daea81f4a60bd/lib/the_last_bluetooth.dart
My example's main.dart that uses it: https://github.com/TheLastGimbus/the_last_bluetooth/blob/60013e4959cb1f0ecd8c2d9f2e1daea81f4a60bd/example/lib/main.dart
The gigantic stack trace: https://pastebin.com/TRa3kyVu
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