Develop Reference

Android Notification Sound Causes Media Volume to Duck (Lower) & It Never Comes Back

I just converted one of my apps to target Android API 9 (was targeting API 8); now when notifications are sent out, the volume of media is lowered and never comes back to full volume.
The app uses WebView to play media files. This was not happening prior to targeting API 9. I had to convert the app into level 9 so that I could upload to the Google Play Store. I am running a Samsung S7 which was originally designed for API level 6 (with the OS upgraded to 8.0), not sure if that has something to do with the issue. Another detail is that I use Xamarin.Android for development, not sure if that matters either.
Additionally, I forced the notifications to play a blank sound (a very short[couple ms] blank mp3) in the same build that I converted the app to target API 9:
var channelSilent = new Android.App.NotificationChannel(CHANNEL_ID, name + " Silent", Android.App.NotificationImportance.High)
{
Description = description
};
var alarmAttributes = new Android.Media.AudioAttributes.Builder()
.SetContentType(Android.Media.AudioContentType.Sonification)
.SetUsage(Android.Media.AudioUsageKind.Notification).Build()
//blank is blank mp3 file with nothing in it, a few ms in duration
var uri = Android.Net.Uri.Parse("file:///Assets/blank.mp3")
channelSilent.SetSound(uri, alarmAttributes);
...so it could also be the blank sound that is causing the ducking to malfunction, not the API change. Is there something to do with notification sound ducking that could be causing the issue? Is there any other way to mute a notification with Xamarin.Android other than playing a blank sound? That is one route I think would be worth trying to fix this issue.
Here is the code I am using to generate notifications:
private static List<CustomNotification> _sentNotificationList = new List<CustomNotification>();
private static NotificationManagerCompat _notificationManager;
public async void SendNotifications(List<CustomNotification> notificationList)
{
await Task.Run(() =>
{
try
{
var _ctx = Android.App.Application.Context;
if (_notificationManager == null)
{
_notificationManager = Android.Support.V4.App.NotificationManagerCompat.From(_ctx);
}
if (notificationList.Count == 0)
{
return;
}
int notePos = 0;
foreach (var note in notificationList)
{
var resultIntent = new Intent(_ctx, typeof(MainActivity));
var valuesForActivity = new Bundle();
valuesForActivity.PutInt(MainActivity.COUNT_KEY, _count);
valuesForActivity.PutString("URL", note._noteLink);
resultIntent.PutExtras(valuesForActivity);
var resultPendingIntent = PendingIntent.GetActivity(_ctx, MainActivity.NOTIFICATION_ID, resultIntent, PendingIntentFlags.UpdateCurrent);
resultIntent.AddFlags(ActivityFlags.SingleTop);
var alarmAttributes = new Android.Media.AudioAttributes.Builder()
.SetContentType(Android.Media.AudioContentType.Sonification)
.SetUsage(Android.Media.AudioUsageKind.Notification).Build();
//I am playing this blank sound to prevent android from spamming sounds as the notifications get sent out
var uri = Android.Net.Uri.Parse("file:///Assets/blank.mp3");
//if the notification is the first in our batch then use this
//code block to send the notifications with sound
if (!_sentNotificationList.Contains(note) && notePos == 0)
{
var builder = new Android.Support.V4.App.NotificationCompat.Builder(_ctx, MainActivity.CHANNEL_ID + 1)
.SetAutoCancel(true)
.SetContentIntent(resultPendingIntent) // Start up this activity when the user clicks the intent.
.SetContentTitle(note._noteText) // Set the title
.SetNumber(1) // Display the count in the Content Info
.SetSmallIcon(Resource.Drawable.bitchute_notification2)
.SetContentText(note._noteType)
.SetPriority(NotificationCompat.PriorityMin);
MainActivity.NOTIFICATION_ID++;
_notificationManager.Notify(MainActivity.NOTIFICATION_ID, builder.Build());
_sentNotificationList.Add(note);
notePos++;
}
//if the notification isn't the first in our batch, then use this
//code block to send the notifications without sound
else if (!_sentNotificationList.Contains(note))
{
var builder = new Android.Support.V4.App.NotificationCompat.Builder(_ctx, MainActivity.CHANNEL_ID)
.SetAutoCancel(true) // Dismiss the notification from the notification area when the user clicks on it
.SetContentIntent(resultPendingIntent) // Start up this activity when the user clicks the intent.
.SetContentTitle(note._noteText) // Set the title
.SetNumber(1) // Display the count in the Content Info
.SetSmallIcon(Resource.Drawable.bitchute_notification2)
.SetContentText(note._noteType)
.SetPriority(NotificationCompat.PriorityHigh);
MainActivity.NOTIFICATION_ID++;
_notificationManager.Notify(MainActivity.NOTIFICATION_ID, builder.Build());
_sentNotificationList.Add(note);
notePos++;
}
ExtStickyService._notificationsHaveBeenSent = true;
}
}
catch
{
}
});
}
In my MainActivity I've created two different notification channels: one is silent; the other uses default notification setting for the device:
void CreateNotificationChannel()
{
var alarmAttributes = new Android.Media.AudioAttributes.Builder()
.SetContentType(Android.Media.AudioContentType.Sonification)
.SetUsage(Android.Media.AudioUsageKind.Notification).Build();
var uri = Android.Net.Uri.Parse("file:///Assets/blank.mp3");
if (Build.VERSION.SdkInt < BuildVersionCodes.O)
{
// Notification channels are new in API 26 (and not a part of the
// support library). There is no need to create a notification
// channel on older versions of Android.
return;
}
var name = "BitChute";
var description = "BitChute for Android";
var channelSilent = new Android.App.NotificationChannel(CHANNEL_ID, name + " Silent", Android.App.NotificationImportance.High)
{
Description = description
};
var channel = new Android.App.NotificationChannel(CHANNEL_ID + 1, name, Android.App.NotificationImportance.High)
{
Description = description
};
channel.LockscreenVisibility = NotificationVisibility.Private;
//here is where I set the sound for the silent channel... this could be the issue?
var notificationManager = (Android.App.NotificationManager)GetSystemService(NotificationService);
channelSilent.SetSound(uri, alarmAttributes);
notificationManager.CreateNotificationChannel(channel);
notificationManager.CreateNotificationChannel(channelSilent);
}
Full source: https://github.com/hexag0d/BitChute_Mobile_Android_BottomNav/tree/APILevel9
EDIT: something really interesting is that if I pulldown the system ui bar, the volume goes back to normal. Very strange workaround but it might help diagnose the cause.
DOUBLE EDIT: I used .SetSound(null, null) instead of using the blank .mp3 and the ducking works fine now. See comments

Bluetooth BLE Battery Level - C#

I have an specific issue about the Bluetooth BLE API on Windows 10.
At the moment I'm programming a tool on C# (Visual Studio) which connects itself to a given BLE - Device. Currently the connection works perfect and I can read out the ServiceUUIDs and the CharacterUUIDs.
The main Problem is after I try to read the value of the Character its always returns me 00. I heard that implementing a notification will change that and I followed these instructions but they didn't help me.
(Here are the Specifications from bluetooth.com:)
My Code:
//connect to BluetoothDevice
var device = await BluetoothLEDevice.FromIdAsync(address);
//get UUID of Services
var services = await device.GetGattServicesAsync();
if (services != null)
{
foreach (var servicesID in services.Services)
{
//if there is a service thats same like the Battery Service
if (servicesID.Uuid.ToString() == BluetoothBLE.Constants.BATTERY_SERVICE)
{
//updateServiceList is like a console logging in my tool
updateServiceList($"Service: {servicesID.Uuid}");
var characteristics = await servicesID.GetCharacteristicsAsync();
foreach (var character in characteristics.Characteristics)
{
if (Constants.BATTERY_LEVEL == character.Uuid.ToString())
{
updateServiceList("C - UUID: "+ character.Uuid.ToString());
GattReadResult result = await character.ReadValueAsync();
if (result.Status == GattCommunicationStatus.Success)
{
var reader = DataReader.FromBuffer(result.Value);
byte[] input = new byte[reader.UnconsumedBufferLength];
reader.ReadBytes(input);
System.Diagnostics.Debug.WriteLine(BitConverter.ToString(input));
}
}
}
}
After Running my Code, the system logs 00. The characterUUID for battery level (0x2A19, from https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.characteristic.battery_level.xml) was read successfully but the value is strange..

DeviceConnectionChangeTrigger - Value does not fall within the expected range

I'm developing an UWP app for Desktop and Mobile. I'd like using DeviceConnectionChangeTrigger to identify when my BT device is in range, but when i try using it, I cannot register background task cause it keeps return System.ArgumentException "Value does not fall within the expected range." when executing "Register" method of BackgroundTaskBuilder.
code is very simple
var current = BackgroundExecutionManager.GetAccessStatus();
if (current == BackgroundAccessStatus.Unspecified || current == BackgroundAccessStatus.Denied)
{
var result = await BackgroundExecutionManager.RequestAccessAsync();
if (result == BackgroundAccessStatus.Denied || result == BackgroundAccessStatus.Unspecified)
throw new Exception("You cannot register Access");
}
//I tested it with BT and BTLE device but no luck
//var devices = await DeviceInformation.FindAllAsync(BluetoothLEDevice.GetDeviceSelector());
var devices = await DeviceInformation.FindAllAsync(BluetoothDevice.GetDeviceSelector());
var device = devices.FirstOrDefault();
if (device == null) throw new Exception("Device not found");
var trigger = await DeviceConnectionChangeTrigger.FromIdAsync(device.Id);
//trigger.MaintainConnection = true;
var builder = new BackgroundTaskBuilder
{
Name = "BluetoothConnectionWatcher",
TaskEntryPoint = typeof(BluetoothConnectionWatcherTask).FullName
};
builder.SetTrigger(trigger);
//error on next line!
var r = builder.Register();
My project has Bluetooth capabilities and one background task registered with Bluetooth property flagged.
All Bluetooth functionalities work well and I can communicate with devices without problem.
I tried several BT and BTLE device and for all of them seems I have the same problem.
I tried on Desktop and Mobile version of Windows 10 (both last fast insider build). Same problem.
The device.Id returned by code is similar to "Bluetooth#Bluetooth00:1a:7d:da:71:0a-fc:58:fa:4c:17:0a" for every BT device i tried (of course 2nd MAC address change based on device...)
Any advice?
Thanks in advance

As far as I know, with BLE you should use the Triggers designed for it. Thus if it is characteristics change you would want to get knowledge about, then you should use GattCharacteristicNotificationTrigger, and example on using it can be found from my blog.
Then if it just BLE device availability, and you can detect yours via scanrecord data, then do use the BluetoothLEAdvertisementWatcherTrigger instead. My Friend Juhana has example fro this in his blog.

Recording Audio and Playing sound at the same time - C# - Windows Phone 8.1

I am trying to record audio and play it directly (I want to hear my voice in the headphone without saving it) however the MediaElement and the MediaCapture seems non to work at the same time.
I initialized my MediaCapture so:
_mediaCaptureManager = new MediaCapture();
var settings = new MediaCaptureInitializationSettings();
settings.StreamingCaptureMode = StreamingCaptureMode.Audio;
settings.MediaCategory = MediaCategory.Other;
settings.AudioProcessing = AudioProcessing.Default;
await _mediaCaptureManager.InitializeAsync(settings);
However I don't really know how to proceed; I am wonderign if one of these ways could work (I tryied implement them without success, and I have not found examples):
Is there a way to use StartPreviewAsync() recording Audio, or it only works for Videos? I noticed that I get the following error:"The specified object or value does not exist" while setting my CaptureElement Source; it only happens if I write "settings.StreamingCaptureMode = StreamingCaptureMode.Audio;" while everyting works for .Video.
How can I record to a stream using StartRecordToStreamAsync(); I mean, how have I to initialize the IRandomAccessStream and read from it? Can I write on a stream while I keep reading for it?
I read that changing AudioCathegory of the MediaElement and the MediaCathegory of the MediaCapture to Communication there is a possibility it could work. However, while my code works (it just have to record and save in a file) with the previous setting, it don't works if I wrote "settings.MediaCategory = MediaCategory.Communication;" instead of "settings.MediaCategory = MediaCategory.Other;". Can you tell me why?
Here is my current program that just record, save and play:
private async void CaptureAudio()
{
try
{
_recordStorageFile = await KnownFolders.VideosLibrary.CreateFileAsync(fileName, CreationCollisionOption.GenerateUniqueName);
MediaEncodingProfile recordProfile = MediaEncodingProfile.CreateWav(AudioEncodingQuality.Auto);
await _mediaCaptureManager.StartRecordToStorageFileAsync(recordProfile, this._recordStorageFile);
_recording = true;
}
catch (Exception e)
{
Debug.WriteLine("Failed to capture audio:"+e.Message);
}
}
private async void StopCapture()
{
if (_recording)
{
await _mediaCaptureManager.StopRecordAsync();
_recording = false;
}
}
private async void PlayRecordedCapture()
{
if (!_recording)
{
var stream = await _recordStorageFile.OpenAsync(FileAccessMode.Read);
playbackElement1.AutoPlay = true;
playbackElement1.SetSource(stream, _recordStorageFile.FileType);
playbackElement1.Play();
}
}
If you have any suggestion I'll be gratefull.
Have a good day.

Would you consider targeting Windows 10 instead? The new AudioGraph API allows you to do just this, and the Scenario 2 (Device Capture) in the SDK sample demonstrates it well.
First, the sample populates all output devices into a list:
private async Task PopulateDeviceList()
{
outputDevicesListBox.Items.Clear();
outputDevices = await DeviceInformation.FindAllAsync(MediaDevice.GetAudioRenderSelector());
outputDevicesListBox.Items.Add("-- Pick output device --");
foreach (var device in outputDevices)
{
outputDevicesListBox.Items.Add(device.Name);
}
}
Then it gets to building the AudioGraph:
AudioGraphSettings settings = new AudioGraphSettings(AudioRenderCategory.Media);
settings.QuantumSizeSelectionMode = QuantumSizeSelectionMode.LowestLatency;
// Use the selected device from the outputDevicesListBox to preview the recording
settings.PrimaryRenderDevice = outputDevices[outputDevicesListBox.SelectedIndex - 1];
CreateAudioGraphResult result = await AudioGraph.CreateAsync(settings);
if (result.Status != AudioGraphCreationStatus.Success)
{
// TODO: Cannot create graph, propagate error message
return;
}
AudioGraph graph = result.Graph;
// Create a device output node
CreateAudioDeviceOutputNodeResult deviceOutputNodeResult = await graph.CreateDeviceOutputNodeAsync();
if (deviceOutputNodeResult.Status != AudioDeviceNodeCreationStatus.Success)
{
// TODO: Cannot create device output node, propagate error message
return;
}
deviceOutputNode = deviceOutputNodeResult.DeviceOutputNode;
// Create a device input node using the default audio input device
CreateAudioDeviceInputNodeResult deviceInputNodeResult = await graph.CreateDeviceInputNodeAsync(MediaCategory.Other);
if (deviceInputNodeResult.Status != AudioDeviceNodeCreationStatus.Success)
{
// TODO: Cannot create device input node, propagate error message
return;
}
deviceInputNode = deviceInputNodeResult.DeviceInputNode;
// Because we are using lowest latency setting, we need to handle device disconnection errors
graph.UnrecoverableErrorOccurred += Graph_UnrecoverableErrorOccurred;
// Start setting up the output file
FileSavePicker saveFilePicker = new FileSavePicker();
saveFilePicker.FileTypeChoices.Add("Pulse Code Modulation", new List<string>() { ".wav" });
saveFilePicker.FileTypeChoices.Add("Windows Media Audio", new List<string>() { ".wma" });
saveFilePicker.FileTypeChoices.Add("MPEG Audio Layer-3", new List<string>() { ".mp3" });
saveFilePicker.SuggestedFileName = "New Audio Track";
StorageFile file = await saveFilePicker.PickSaveFileAsync();
// File can be null if cancel is hit in the file picker
if (file == null)
{
return;
}
MediaEncodingProfile fileProfile = CreateMediaEncodingProfile(file);
// Operate node at the graph format, but save file at the specified format
CreateAudioFileOutputNodeResult fileOutputNodeResult = await graph.CreateFileOutputNodeAsync(file, fileProfile);
if (fileOutputNodeResult.Status != AudioFileNodeCreationStatus.Success)
{
// TODO: FileOutputNode creation failed, propagate error message
return;
}
fileOutputNode = fileOutputNodeResult.FileOutputNode;
// Connect the input node to both output nodes
deviceInputNode.AddOutgoingConnection(fileOutputNode);
deviceInputNode.AddOutgoingConnection(deviceOutputNode);
Once all of that is done, you can record to a file while at the same time playing the recorded audio like so:
private async Task ToggleRecordStop()
{
if (recordStopButton.Content.Equals("Record"))
{
graph.Start();
recordStopButton.Content = "Stop";
}
else if (recordStopButton.Content.Equals("Stop"))
{
// Good idea to stop the graph to avoid data loss
graph.Stop();
TranscodeFailureReason finalizeResult = await fileOutputNode.FinalizeAsync();
if (finalizeResult != TranscodeFailureReason.None)
{
// TODO: Finalization of file failed. Check result code to see why, propagate error message
return;
}
recordStopButton.Content = "Record";
}
}

Example of QRCode ZXing

I need to create a qrreader with windows phone.
Xzing examples only print to video the qr string captured,
I need an example of how to understand if this string is a vcard and, consequently, save it in contact, or if it is a link and open it in the browser.
private void ScanPreviewBuffer()
{
try
{
_photoCamera.GetPreviewBufferY(_luminance.PreviewBufferY);
var binarizer = new HybridBinarizer(_luminance);
var binBitmap = new BinaryBitmap(binarizer);
var result = _reader.decode(binBitmap);
Dispatcher.BeginInvoke(() => CheckQr(result.Text));
}
catch { }
}
private void CheckQr(string qrString)
{
VibrateController vibrate = VibrateController.Default;
vibrate.Start(TimeSpan.FromMilliseconds(500));
MessageBox.Show(qrString);
/* CONTROLS HERE */
}

Obviously you have to start by parsing the qrString content to get what you want, i think we'll both agree on that point ;)
So the main issues are :
Determining formats (url or vcard)
Parsing them (if needed)
Using them to trigger wanted actions
1. About vCard
To determine if you qrString holds a vCard, maybe you could just try to match (with string.Contains or string.StartsWith methods) the vCard header which is BEGIN:VCARD and always seems to be the same from one version to another (see wikipedia).
For Windows Phone 7, there's no builtin features to parse vCards, so you have to do it by yourself or you could try to use the vCard library For Windows Phone. It would be used this way :
byte[] byteArray = Encoding.UTF8.GetBytes(qrString);
using (StreamReader reader = new StreamReader(new MemoryStream(byteArray)))
{
vCard card = new vCard(reader);
// access here card.PropertyFromvCard to get the information you need
}
There's not so much documentation about it, but sources are available on codeplex, so you'll probably find all the property names and samples you need.
For Windows Phone 8, the builtin ContactInformation.ParseVcardAsync method could help you to parse your qrString content (here is an official tutorial)
Then you need to finally create your contact :
If you're developping your App on Windows Phone 7, there's no way to create a contact directly from your application. You need to use the "save contact task" and pre-populate the fields you need. Here's an example :
SaveContactTask saveContactTask = new SaveContactTask();
saveContactTask.Completed += new EventHandler<SaveContactResult>(saveContactTask_Completed);
saveContactTask.FirstName = "John"; // card.PropertyFromvCard and so on...
saveContactTask.LastName = "Doe";
saveContactTask.MobilePhone = "2065550123";
saveContactTask.Show();
If you're developping on Windows Phone 8 (and it doesn't seem to be the case given your question tags), you can create a Custom contact store and write directly into it
2. About URLs
To know if you're dealing with an URL or not, i would advice you to follow suggestions coming with this SO answer. To make a long story short, here's the code you could use or at least something similar :
static bool IsValidUrl(string qrString)
{
Uri uri;
return Uri.TryCreate(urlString, UriKind.Absolute, out uri)
&& (uri.Scheme == Uri.UriSchemeHttp
|| uri.Scheme == Uri.UriSchemeHttps
|| uri.Scheme == Uri.UriSchemeFtp
|| uri.Scheme == Uri.UriSchemeMailto
/*...*/);
}
And finally to open your URL into a web browser (if it is a valid one of course), you could use the WebBrowser task or embed a true WebBrowser into your application with the WebBrowser control and make good use of it.

ZXing has a class called ResultParser with a static method parseResult.
The ResultParser supports some common content formats like vCard, vEvent, URL, etc.
It gives you as a result an instance of AddressBookParsedResult for vCard content back.
ParsedResult parsedResult = ResultParser.parseResult(result);