Develop Reference

Flutter/Dart UDP multicast send from iOS not receiving on Android

With this setup, I've been able to get two android phones to send and receive UDP broadcasts. I can also use this setup to send a UDP broadcast from a physical Android device to an iPhone.
However, my problem is that it doesn't seem to work the other way around. The send function is ran on the iPhone, and the receive function is being run on the Android phone. The Android phone never gets the broadcast. It seems like something is wrong with the iPhone's sending function. Here's the setup:
The Android side that has worked for me before:
const port = 37069;
const address = '224.0.0.1';
void receive() async {
final socket = await RawDatagramSocket.bind(address, port);
socket.multicastHops = 1;
socket.broadcastEnabled = true;
socket.writeEventsEnabled = true;
socket.listen((RawSocketEvent event) {
print("still listening...");
final packet = socket.receive();
print("The packet was $packet");
print("It came from ${packet?.address}");
});
}
and this is the iPhone side, that seems to be the problem. I'm not getting errors, so I'm wondering if there are any permissions in the Info.plist file that need to be added?
void broadcast() {
// for the iphone
RawDatagramSocket.bind(address, port).then((RawDatagramSocket socket) {
socket.multicastLoopback = false;
socket.broadcastEnabled = true;
socket.readEventsEnabled = true;
for (int i = 0; i < 150; i++) {
socket.send("Sent #$i".codeUnits, InternetAddress(address), port);
print("sent $i");
}
socket.close();
});
}
I've tested this same setup in my project, and it has worked in the following situations:
Android -> Android
Android -> iOS
but, iOS -> Android doesn't work. When I run the app, I can see that the iPhone is indeed sending the data, but the Android isn't receiving anything. Is the Android side the problem? What am I doing wrong?

I ended up using a package called Bonsoir to achieve what I wanted to.
It lets you broadcast and receive network services, and I'm pretty sure its the same underlying technology as household programs like Airplay and Google Casting. It's also very reliable and simple to use.
To send a certain string, I passed in a string argument in the form of a dictionary into the attributes attribute within the BonsoirService class.
The package can be found here.

How to send BLE advertisements from Android to Unity on HoloLens v2

I have already successfully used BLE advertising to broadcast information from one android device and receive it on another. Now I want the observer to be a Unity-app running on the HoloLens v2. The HoloLens does not need to connect to the android-device as I am aware that this does not seem to be supported. I am looking for a broadcaster -> observer solution.
As mentioned, I already have the broadcaster written and it works fine with android -> android. Now I have implemented my observer in Unity, largely inspired by this article, and it looks like this:
#if ENABLE_WINMD_SUPPORT
using System;
using Windows.Devices.Bluetooth.Advertisement;
#endif
public class DemoManager : MonoBehaviour
{
[SerializeField] private StatusDisplay statusDisplay;
private void Awake()
{
#if ENABLE_WINMD_SUPPORT
StartWatcher();
#else
statusDisplay.Display("UWP APIs are not supported on this platform!");
#endif
}
#if ENABLE_WINMD_SUPPORT
private void StartWatcher()
{
void OnAdvertisementReceived(object sender, BluetoothLEAdvertisementReceivedEventArgs eventArgs)
{
statusDisplay.Display("Advertisement received!");
}
try {
BluetoothLEAdvertisementWatcher watcher = new BluetoothLEAdvertisementWatcher();
watcher.AdvertisementFilter.Advertisement.ManufacturerData.Add(GetManufacturerData());
watcher.Received += OnAdvertisementReceived;
watcher.Start();
statusDisplay.Display("Watcher started!");
} catch (Exception e){
statusDisplay.Display($"Watcher could not start! Error: {e.Message}");
}
}
private BluetoothLEManufacturerData GetManufacturerData()
{
var manufacturerData = new BluetoothLEManufacturerData();
manufacturerData.CompanyId = 1234;
return manufacturerData;
}
#endif
}
The StatusDisplay script is used for displaying text in a thread-safe way. The company-id 1234 is also used by the broadcaster.
My app has bluetooth capabilities (enabled both in the Unity-editor and in the built solution)
All looks very promising, but sadly the advertisement never seems to be received, or at the very least I am getting no corresponding status message.
Does anybody have any ide what might be wrong? Does anyone have any experience with this problem?

We tested the Bluetooth.Advertisement API and works well on the HoloLens. I found that you assigned the CompanyId(a 16-bit unsigned integer) property a signed decimal number, but we usually provide a hexadecimal number as a Bluetooth LE company identifier code. Could you double-check this point both in your watcher and publisher? For example, it should look like 0xFFFE. Besides, more information about how to use the Bluetooth Advertisement API to send and receive Bluetooth Low Energy advertisements please see:Bluetooth advertisement sample

The problem was not with the Unity-side. My advertisement was malformed. I tested my advertisements with a observer that I also wrote myself on Android. So I accounted for the incorrect formatting there, but of course, the C# Advertisement-watcher did not.

process input from voice recognition

I'm starting my final year project. I will do an android application, which will take commands from the user, and then process the input in order to show results.
My question is, what ways can I use to process the input( what I mean by input here is the data or text after transferring speech to text)?
I have found some ways to do that like matching the input with data stored already(template matching), but Im looking for something more better and smarter that that (and if there are any suggested references).
Thanks

I would suggest you start with a very basic and clearly defined set of keyword rules of your own:
#Override
public void onResults(final Bundle results) {
final ArrayList<String> heardVoice = results.getStringArrayList(SpeechRecognizer.RESULTS_RECOGNITION);
if(heardVoice != null && !heardVoice.isEmpty()) {
for(String result: heardVoice){
if(result.contains("bluetooth")){
if(result.contains("on")){
// turn on bluetooth
break;
} else if(result.contains("off")){
// turn off bluetooth
break;
}
}
}
}
}
Once you've understood these basic keyword parameters, you can then look to using a Natural Language Processing (NLP) model and the performance of your code.
There are many examples out there, but the Apache OpenNLP is a good place to start, with comprehensive documentation.

TransactionTooLargeEception when trying to get a list of applications installed

As part of my app I get a list of apps installed on the device by using ApplicationPackageManager.getInstalledApplications but for some users I get crash reports saying that
TransactionTooLargeException at android.osBinderProxy.tranasact(Native Method)
Can anyone think why I'd get this?

I've found that this was solved on Android 5.1 (proof here, search for "Fix package manager TransactionTooLargeExceptions") as it was reported on multiple places:
https://code.google.com/p/android/issues/detail?id=95749
https://code.google.com/p/android/issues/detail?id=93717
https://code.google.com/p/android/issues/detail?id=69276
However, I wanted to solve this for pre-5.1, so I've come up with a solution (and suggested Google to put it on the support library, here) . Here's a short code version of what I've suggested:
public static List<PackageInfo> getInstalledPackages(Context context,int flags)
{
final PackageManager pm=context.getPackageManager();
try
{
return pm.getInstalledPackages(flags);
}
catch(Exception ignored)
{
//we don't care why it didn't succeed. We'll do it using an alternative way instead
}
// use fallback:
Process process;
List<PackageInfo> result=new ArrayList<>();
BufferedReader bufferedReader=null;
try
{
process=Runtime.getRuntime().exec("pm list packages");
bufferedReader=new BufferedReader(new InputStreamReader(process.getInputStream()));
String line;
while((line=bufferedReader.readLine())!=null)
{
final String packageName=line.substring(line.indexOf(':')+1);
final PackageInfo packageInfo=pm.getPackageInfo(packageName,flags);
result.add(packageInfo);
}
process.waitFor();
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
if(bufferedReader!=null)
try
{
bufferedReader.close();
}
catch(IOException e)
{
e.printStackTrace();
}
}
return result;
}
What it does it to try using the official way first, and then, if failed, it fetches the package names using ADB command, and get the information of each of the apps, one after another.
It is much slower than the official one, but it didn't crash for me. I've tested it on Android emulators (2.3.x till 5.0.x, including), and on real devices too.
The time it took on my device (Galaxy S3 with custom rom of Android 5.1) is 1375-2012 ms (on 197 apps total) compared to 37-65 ms using the official way .
EDIT: people claim here that it's not fixed on Android 5.1 . I hope that it got fixed on Android 6 .

This exception is kind of difficult to reproduce under normal circumstances. You will get this exception when there IPC memory is exhausted when transferring data. This can occur in both cases, where a service is trying to place data to client or a client is sending data to service. Most probably some of your users might have installed huge number of application, which results in a data size greater than 1MB (which is the size of IPC buffer).
I am afraid in this case, you will not be do anything better. But if you are doing something like, applyBatch, you can separate one large transaction to multiple smaller transactions.
Also have a look at this thread What to do on TransactionTooLargeException

Android - Communicate with Bluetooth subsystem (BlueZ)

I'm looking for a way to do periodic bluetooth inquiry's from my Android Smartphone (HTC Desire with Android 4.0.1). The Device is rooted and it is a custom Rom installed so that I have full privileges.
I already wrote a shellscript, which uses hcitool, hciconfig and hcidump to do the inquiry's. That works fine so far, but it is a little to slow for me. I guess that's because of my dirty workaround of using an android-app to execute a shellscript from linux.
Although I got problems by killing the executed processes via my App.
So I'd like to find a way to inquire BT Devices from the Android API.
I found out that there is no possibility 'til now to do this, but i read about the bluez API which is possibly able to fit my requests.
Does anyone have any links, tips or advises for me?
I haven't found anything useful :/
Thanks in advance.
Edit (2012-09-28):
Okay, I think I'm a little closer to the solution now.
I downloaded the source of blueZ library from: bluez.org
Then i put the important files (hci.h, bluetooth.h, hcilib.h and their sourcefiles) into the jni folder of my android project and compiled them into my shared library.
I wrote a JNI Wrapper around the function
hci_inquiry(int dev_id, int len, int nrsp, const uint8_t *lap,inquiry_info **ii, long flags)
and followed the advises of this book to do my inquiry. Everything fine 'til here.
But when I start the inquiry, the function
dev_id = hci_get_route(NULL);
always returns -1, and I can't continue.
Bluetooth is activated, and i already tried to grant root access to my application. Not better :(
Anything I did wrong until here? Isn't it allowed to use BlueZ HCI commands from a android app?
I mean JBlueZ doesn't do anything else is it?
My native code looks like this:
inquiry_info *ii = NULL;
int max_rsp, num_rsp;
int dev_id, sock, len, flags;
int i;
char addr[19] = { 0 };
char name[248] = { 0 };
dev_id = hci_get_route(NULL);
if (dev_id < 0 ) {
LOGI("ERROR ON finding Device ID");
return;
}
sock = hci_open_dev( dev_id );
if (sock < 0) {
LOGI("ERROR ON opening socket");
return;
}
len = 8;
max_rsp = 255;
flags = IREQ_CACHE_FLUSH;
ii = (inquiry_info*)malloc(max_rsp * sizeof(inquiry_info));
num_rsp = hci_inquiry(dev_id, len, max_rsp, NULL, &ii, flags);
//##################################################################################
LOGI("INQUIRY Executed!!!");
(*env)->CallVoidMethod(env, obj, callBackID, num_rsp);
free(ii);
close(sock);
Thank you for any help.