Android Tutorial Android Bluetooth / BluetoothAdmin Tutorial

Better implementation based on B4XPages:

[B4XPages] Bluetooth Chat Example

Updated implementation, based on B4XPages of https://www.b4x.com/android/forum/threads/android-bluetooth-bluetoothadmin-tutorial.14768/#content. The code is much simpler compared to the previous example. Note that you can call Serial.Listen without making the device discoverable. This is useful...

www.b4x.com

Tutorial was rewritten in April 2018.
We will create a chat example between two Android devices.

All the non-UI code is implemented in a class named BluetoothManager. It is initialized in Service_Create of the starter service.

It is always better to implement communication related code in a service or a class initialized from a service. This way the communication state is not affected by the activities more complicated state.

The activities call the class methods directly. Calling the activities subs is done with CallSub. Remember that CallSub doesn't do anything if the activity is paused.

The first activity, the main activity, shows two buttons. One for searching other devices and one for listening for connections.

Searching other devices requires a "dangerous" permissions (see the runtime permissions tutorial for more information).
Note that you need to add the permission in the manifest editor:

AddPermission(android.permission.ACCESS_FINE_LOCATION)

Sub btnSearchForDevices_Click
   rp.CheckAndRequest(rp.PERMISSION_ACCESS_FINE_LOCATION)
   Wait For Activity_PermissionResult (Permission As String, Result As Boolean)
   If Result = False Then
       ToastMessageShow("No permission...", False)
       Return
   End If
   Starter.Manager.SearchForDevices
End Sub

The second button sends an intent to the OS to make the device discoverable and then calls Serial.Listen.

Once a connection is established:
1. AsyncStreams is initialized in prefix mode (see the AsyncStreams tutorial for more information).
2. The ChatActivity is started.

Notes

- In this example we send text messages. Use B4XSerializator to send more complex types.

 

[georgestheking]

Hi,

I try to compile the bluetooth program using Basic4Android 1.9 but I get compilation errors !!!!!

Any update ?

Georges

 

[Erel]

Which errors?

 

[maleche]

Help!
This is the error in Log I recived any time I try sending "ATZ" using the Bluetooth example. I changed to AsyncStreams per this post and still unable to send without lock ups.

java.lang.OutOfMemoryError at anywheresoftware.ba.randomaccessfile.AsyncStreams$AIN.run(AsyncStreams.java:168)
at java.lang.Thread.run(Thread.java:1019)
** Activity (chatactivity) Pause, UserClosed = true **

I just need to send via Bluetooth. any other examples to try?
Thanks!
DM

 

[Erel]

This error usually happens when you use AsyncStreams in prefix mode and don't implement the protocol correctly in the other side.

AsyncStreams Tutorial

 

[fdx12345]

Not running

When I run the example I keep getting a pause at line 26: If admin.IsEnabled=Flase. When I click continue, every thing is greyed out and nothing works.

I am running Basic4Android program as an administrator and my account (my pc) is type administrator.

Bill

 

[Erel]

You should check the logs and post the full error message.

 

[balistreri1]

Hello Erel,

Bluetooth serial example bug report:
Sending 8 characters works fine.

Sending 9 or more characters results in extra
garbage data ahead of the actual data.

Key data is entered into a TextEdit called txtinput
and then sent out with the following button click

Sub btnSend_Click
AStream.Write(txtInput.Text.GetBytes("UTF8"))
txtInput.SelectAll
txtInput.RequestFocus
LogMessage("Me", txtInput.Text)
End Sub

Any help???

 

[walterf25]

Bluetooth help

Hi all, i finally got my RN-41 bluetooth Module to communicate with my Motorola Photon, i'm using the Erel's latest example, now i have another issue, while running this example i can send data and i see that i receive it on the other side, i'm basically just using a windows terminal to see what i send from the phone, now the problem is that when i want to reply from the terminal to the phone, i get an error that says.
"An error has occured in sub:
java.lang.Exception: Sub astreams_newdata was not found."

below is the log i get from the phone

FireFly-A09F:00:06:66:43:A0:9F
connected: true
java.lang.Exception: Sub astreams_newdata was not found.
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:142)
at anywheresoftware.b4a.BA$2.run(BA.java:244)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3806)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
java.lang.Exception: Sub astreams_newdata was not found.

any ideas why this is happening, just to clarify i got it working by using this

serial1.ConnectInsecure(admin,connectedDevice.Mac,1)

and this

AStream.Initialize(Main.Serial1.InputStream, Main.Serial1.OutputStream, "AStreams")

any help will be greatly appreciated guys.

Thanks,
:sign0085:

 

[walterf25]

Bluetooth help

I'm sorry everyone, for some reason the

AStream.Initialize(Main.Serial1.InputStream, Main.Serial1.OutputStream, "AStreams")

'AStreams event was misspelled, i corrected to this

Sub AStreams_NewData (Buffer() As Byte)
   LogMessage("You", BytesToString(Buffer, 0, Buffer.Length, "UTF8"))
End Sub

now i have another question, when i send data back from the terminal to the phone, i don't receive all the characters in one line, i get one character per line, is there a way to receive the characters collect them in an array and then display them in the text box?

thanks,
Walter

 

[Erel]

This is exactly the purpose of "prefix" mode. Each message is prefixed with the message length and the library is responsible pass complete messages.

In regular mode the event is raised whenever there is data available. Your device probably sends the characters one after another. You will need to collect the data in your code.

 

[walterf25]

Bluetooth help

I see, thanks a lot for that info Erel, now i understand a little better the whole bluetooth communication deal, i was actually able to program a microcontroller and read an analog voltage and display the voltage on my android phone last night, I will try to post some pictures when i get a chance, B4Android rocks.

cheers,
Walter

 

[hpk2000]

serial.ConnectInsecure doubt

hi, how can I use the method? especially de Port argument. Don't know what to put there.

 

[Erel]

For some reason you appear as an unlicensed user in the forum. Please contact [email protected] in order to fix it.

 

[CSP]

Bluetooth program error

Will this example run on Android 1.6? The code runs perfect on my Droids, but on my Motorola Blur, I get this error on app execution:

Sorry! The application Bluetooth Example (process anywheresoftware.b4a.samples.bluetooth) has stopped unexpectedly. Please try again. (force close)

I've tried enabling bluetooth, disabling it, re-enabling it, resetting the phone, etc, all to no avail.

 

[Erel]

Bluetooth APIs (the native APIs) are only available on Android 2.0 and above.

 

[luke2012]

Bluetooth file transfer

Hi!
It's possible to send a file between two paired devices ?

 

[Erel]

Yes. Instead of sending text you can send bytes.

 

[mclightning]

why i dont have access to this file, even though i just registered...

 

[Erel]

Some of the files are only available to licensed users. Contact [email protected] if you have bought Basic4android.

 

[PD5DJ]

Hi Erel

I have some issues using the Asyncstreams,

Also caused by the fact im very new to this..

But neverteless I cant get my situation working..

I want to receive the following sentences from an embedded device.

Header = $
Stopper = #
Variable = 1234

$1234#

I have made a similar code for my embedded work, and that works fine..

This is what i made with Astreams_newdata.
I looks like I am missing a lot of characters sended in..

What I want is full control over all the characters 1 by 1 coming in, without missing some.

:sign0163:

Sub AStreams_NewData (D() As Byte)
  
   Dd = BytesToString(D,0,1,"UTF-8")
   
   Dim Bytecounter As Byte
   Dim Cmaxchar As Byte :Cmaxchar = 20
   Dim Buffer As String
   Dim Dd As String
   
   If Connected Then
   
      If Bytecounter < Cmaxchar Then
   
         Bytecounter = Bytecounter + 1
      
         If Dd = "#" Then
            Buffer = ""
            Bytecounter = 0
            Label1.Text = Buffer
            
         
            Else If Dd = "$" Then
         
               Buffer= ""
               Bytecounter = 0
            Else
         
               Buffer = Buffer & Dd
                              
               If Bytecounter > 19 Then
                  Buffer = ""
                  Bytecounter = 0
               End If
            
         End If
      End If
   End If
   
End Sub