I am using flutter_blue plugin to scan for BLE device i have a pressure monitoring device which broadcasts BLE signal when there is a change in pressure. i want to receive these values in my flutter app then send them to Firestore.
Everything works fine when the app is in foreground but it does not works when app is in background.
Below is my scanner function
void scanner() {
flutterBlue.startScan(timeout: Duration(days: 5));
flutterBlue.scanResults.listen((results) {
if (results != null && results.length > 0) {
for (var i = 0; i < results.length; i++) {
bool checkpoint1 = results[i].device.id.toString() == frontDevice;
bool checkpoint2 = results[i].device.id.toString() == rearDevice;
if (checkpoint1) {
first = results[i].advertisementData.manufacturerData;
}
if (checkpoint2) {
second = results[i].advertisementData.manufacturerData;
}
if (results.length - 1 == i) {
if (first != null && second != null) {
deviceData(first, second);
}
}
}
}
});
}
If you want to run something on background mode[when app is minimized] then you have to drill down to platform specific solutions. At-least for iOS Isolate or any other solution will not work because iOS pauses app after few seconds when user minimized app.
For iOS that you need to enable BackgroundMode to make iOS aware that you are using specific services and you need a privision to running app on background. Only few things can be run on background and Bluetooth is one of the thing. You need to setup few things in iOS project. Here you will find details: https://developer.apple.com/library/archive/documentation/NetworkingInternetWeb/Conceptual/CoreBluetooth_concepts/CoreBluetoothBackgroundProcessingForIOSApps/PerformingTasksWhileYourAppIsInTheBackground.html#//apple_ref/doc/uid/TP40013257-CH7-SW7
For Android you may use Foreground Services to keep running your Bluetooth related stuff.[Note that I have very basic knowledge about Android. There could be better suggestion]
For Android, there are some limitations like if you try to write Characteristics from thread except Main Thread then you may get exception. Here are few important notes about it: https://github.com/xabre/xamarin-bluetooth-le
Refer to "Caution! Important remarks / API limitations" section specially.
Note for iOS: As far as I understand Isolate can run code snippet on background thread but can not run something when app is minimzed and iOS is pausing execution of source code.
If you start a background service, then please do it cross platform, unless you need this service to run while the app is running (not as a background fetch, meaning the app is in the foreground, but is running not on the main thread).
Please use this package here if you need to run the flutter_blue plugin. If you try to run any other plugins, it will fail:
https://pub.dev/packages/flutter_isolate
Also if you need this to run as a background fetch, then please use this plugin here:
https://pub.dev/packages/background_fetch
Related
I want to make a Flutter application which runs in the background and never stops. I tried so many methods for instance background process, foreground process, Notification and so on but I couldn't find any workable solution.
Can anyone help me with this?
Try this package
https://pub.dev/packages/flutter_background
Request permission to run in background
bool hasPermissions = await FlutterBackground.hasPermissions;
Then to run it in background use
bool success = await FlutterBackground.enableBackgroundExecution();
Please note this works only in android
I'm quite new into flutter and coding in general. I'm trying to build a meditation app, that plays a bell every 30/60/120... seconds, depends on user input. My code works perfectly fine on Android device, but when running on iOS, it plays bell only once and doesn't play anymore. Any suggestions please? Thank you!
if (((widget.meditation.notification) != 0) &&
((_time % widget.meditation.notification) == 0)) {
print('notification $_time');
audioCache.play('audio/bell.wav');
}
Finally I found solution, simply everytime .release() must be called.
By default, the player will be release once the playback is finished or the stop method is called.
This is because on Android, a MediaPlayer instance can be quite resource-heavy, and keep it unreleased would cause performance issues if you play lots of different audios.
On iOS and macOS this doesn't apply, so release does nothing.
A try to start a screen recording with RPScreenRecorder. I got the following error:
Recording interrupted by multitasking and content resizing
func startRecording() {
let recorder = RPScreenRecorder.shared()
recorder.startRecording(handler: { (error) in
if let unwrappedError = error {
print(unwrappedError.localizedDescription)
} else {
}
})
}
Before iOS 12.0 everything worked fine. From the update I get the error above.
My app has been rejected from App store for the same reason. So far the only workaround is to reboot the device.
I had a similar problem and here is how I solved it.
go to project then targets then capability switch on Background mode then enable audio and VOIP. It should work
I've done a lot of research on the errors and posted the solution Here.
For now my screen recording feature is bug free. But who knows what comes with the new OS updates
We've been rejected same issue several times.
But we found a senario to re-produce as bellow,
We reported it on Resolution Center in App Store Connect, then passed.
connect iOS(12.4) device to host launched XCode 10.3
(regardless of opened related project)
cold boot iOS device.
launch app and start recording video ASAP(until 30sec after booted)
Now iOS13, we don't face this error at the above senario.
In an iOS app you can set application.idleTimerDisabled = YES to prevent the phone from auto locking.
I need to do this in mobile safari for a game like Doodle Jump where the user may not touch the screen for an extended period of time. Is there any documented method or hack to do this?
(Update)
They seem to be doing it somehow in this site http://www.uncoveryourworld.com. Visit from your iphone and when you get to the buildings/street scene with music playing in the background just leave your phone alone. It never goes to sleep.
(Update 2)
I've spent some time taking a closer look at how they might be keeping the phone from going to sleep. I've done a barebones test and it seems that the way they are looping the audio in the street scene is what keeps it from going to sleep. If you'd like to test this just put a simple audio player that loops on your page and click play:
<audio src="loop.mp3" onended="this.play();" controls="controls" autobuffer></audio>
Everywhere I searched it is being said that this isn't possible, so it is nice to see there is at least some way to do it even if a bit of a hack. Otherwise a browser based game with doodle-jump style play would not be possible. So you could have a loop in your game/app if appropriate or just play a silent loop.
NoSleep.js seems to work in iOS 11 and it reportedly works on Android as well.
Old answer
This is a simple HTML-only method to do that: looping inline autoplaying videos (it might also work in Android Chrome 53+)
<video playsinline muted autoplay loop src="https://rawgit.com/bower-media-samples/big-buck-bunny-480p-30s/master/video.mp4" height=60></video>
See the same demo on CodePen (includes a stopwatch)
Notes
Avoid loading a big video just for this. Perhaps make a short, tiny, black-only video or use
To make it fully work, the videos needs to be always in the viewport or you need to start its playback via JS: video.play()
Edit: This work around no longer works. It is not currently possible to prevent the phone from sleeping in safari.
Yes, you can prevent the phone to sleep using an audio loop. The trick won't start automatically, you will have to play it when the visitor touches the screen.
<audio loop src="http://www.sousound.com/music/healing/healing_01.mp3"></audio>
Test page: tap play and the display will stay on but it will dim on some devices, like an iPhone with iOS 7.
Note: be careful using this trick because it will stop any music that the visitors might be using—and it will annoy them.
No, you can't do this, unfortunately. The only way to achieve this is by making a UIWebView-application and setting the variable you provided there.
https://stackoverflow.com/a/7477438/267892
[edit] random bug behavior, sometimes lockscreen media controls showing, sometimes not
Years later, updated my code
Easy steps :
unlock audio context
create silent sound
loop it and play forever
keep tab active
Working on Safari iOs 15.3.1, tab & browser in background, screen off
// unlock audio context
let ctx = null;
// create silent sound
let bufferSize = 2 * ctx.sampleRate,
emptyBuffer = ctx.createBuffer(1, bufferSize, ctx.sampleRate),
output = emptyBuffer.getChannelData(0);
// fill buffer
for(let i = 0; i < bufferSize; i++)
output[i] = 0;
// create source node
let source = ctx.createBufferSource();
source.buffer = emptyBuffer;
source.loop = true;
// create destination node
let node = ctx.createMediaStreamDestination();
source.connect(node);
// dummy audio element
let audio = document.createElement("audio");
audio.style.display = "none";
document.body.appendChild(audio);
// set source and play
audio.srcObject = node.stream;
audio.play();
// background exec enabled
Even if this approach might not be suitable in every case, you can prevent your phone from locking by reloading the page using Javascript.
// This will trigger a reload after 30 seconds
setTimeout(function(){
self.location = self.location
}, 30000);
Please note that I tested this with iOS7 beta 3
You can stop sleeping and screen dimming in iOS Safari by faking a refresh every 20–30 seconds
var stayAwake = setInterval(function () {
location.href = location.href; //try refreshing
window.setTimeout(window.stop, 0); //stop it soon after
}, 30000);
Please use this code responsibly, don't use it "just because". If it's only needed for a bit, disable it.
clearInterval(stayAwake); //allow device sleep again when not needed
Tested in Safari iOS 7, 7.1.2, and 8.1, but it may not work in UIWebView browsers like Chrome for iOS or the Facebook app.
Demo: http://jsbin.com/kozuzuwaya/1
bfred.it's answer works if you replace the audio-tag with a enter code here -tag - but only if the page is open in iOS10+ Safari AND the user has started the video. You can hide the video with CSS.
Also, I suspect that this feature will also be removed at some point.
This is based on nicopowa's answer, which saves a PWA from being suspended by iOS. (Playing an infinite loop of nothing keeps the app running - even with the screen turned off.)
In order to also make sure that it's triggered by user interaction,
the only thing to change is instead of
let ctx = null
put
let ctx = new AudioContext()
Hello I am planning to develop a simple iPhone game. I would like to be able to distinguish between a genuine crash, and the user killing the app ( by double tapping home screen and long-clicking it to kill it) .
Can someone please shed some light on what exactly happens when the user kill the app through the multitasking bar.
If your app is in the background and suspended when the user kills it, it will receive no notification. This accounts for the majority of cases.
If your app is currently running in the background (there are only very specific categories of apps that can do that), then it receives applicationWillTerminate.
Indeed, Apple is very clear as to the fact that you should save any relevant data before entering the background. Have a look at this (chapter "Responding to Application Termination"):
Even if you develop your application using iOS SDK 4 and later, you must still be prepared for your application to be killed without any notification. The user can kill applications explicitly using the multitasking UI. In addition, if memory becomes constrained, the system might remove applications from memory to make more room. If your application is currently suspended, the system kills your application and removes it from memory without any notice. However, if your application is currently running in the background state (in other words, not suspended), the system calls the applicationWillTerminate: method of your application delegate. Your application cannot request additional background execution time from this method.
EDIT:
about the "saying sorry" thing...
you can certainly do that on the next launch. simply store a key in NSUserDefaults and remove it when the app enters the background (I hope all this sounds familiar to you, otherwise look into the UIApplicationDelegate protocol).
when the app starts up, you check the key; if it is there, then the app was not closed by the user; if the app is not there, then the user at least moved the app to the background and did not experience any sudden termination...
For iOS6 and later there is a way to do this. A side effect of State Restoration is that it will delete the state when there is either a crash during restore or a user manually kills the app. You can use this to your advantage to detect a user manually killing the app.
From the documentation:
Be aware that the system automatically deletes an app’s preserved state when the user force quits the app. Deleting the preserved state information when the app is killed is a safety precaution. (The system also deletes preserved state if the app crashes at launch time as a similar safety precaution.) If you want to test your app’s ability to restore its state, you should not use the multitasking bar to kill the app during debugging. Instead, use Xcode to kill the app or kill the app programmatically by installing a temporary command or gesture to call exit on demand.
The following code assumes that you already have a BOOL for crash detection called _didCrashInLastSession. There are different approaches for getting this value such as this 3rd party library. In your code call the method [self getLaunchType] to see which type of launch you are dealing with and act on that accordingly. Put the following in your AppDelegate.m:
typedef NS_ENUM(NSInteger, LaunchType) {
LaunchTypeUnknown,
LaunchTypeNewInstall,
LaunchTypeNormalLaunch,
LaunchTypeCrashedLastSession,
LaunchTypeUserManualQuit,
};
static BOOL hadStateToRestore = NO;
static NSString * const kAppHasEverRunKey = #"appHasEverRun";
- (BOOL)application:(UIApplication *)application shouldSaveApplicationState:(NSCoder *)coder
{
// Called when going into the background
[[NSUserDefaults standardUserDefaults] setBool:YES forKey:kAppHasEverRunKey];
[[NSUserDefaults standardUserDefaults] synchronize];
return YES;
}
- (BOOL)application:(UIApplication *)application shouldRestoreApplicationState:(NSCoder *)coder
{
// Called on start up
hadStateToRestore = YES;
return YES;
}
- (LaunchType)getLaunchType
{
if (_didCrashInLastSession) {
return LaunchTypeCrashedLastSession;
}
if (![[NSUserDefaults standardUserDefaults] boolForKey:kAppHasEverRunKey]) {
return LaunchTypeNewInstall;
}
if (!hadStateToRestore) {
return LaunchTypeUserManualQuit;
}
return LaunchTypeNormalLaunch;
}
Update: At least one 3rd party SDK breaks this technique: Urban Airship.
You can do it through your device also.
Connect your device to your machine.
Run xcode and go to organizer.
There select your device and device logs.
There you can also see crash logs of your app or game.