Android Question android-serialport-api

jgbozza · Apr 19, 2014

I'm using android-serialport-api library in my application in order to establish communication between one tablet as master and another devices connected over a RS485 network as slaves.
Recentely I had two tablets crashing after being turned on and coincidentaly both of them had faced troubles with power sources or cable malfunction before it happened.

Here below the logs of them:

--------- beginning of /dev/log/system

--------- beginning of /dev/log/main

** Activity (main) Create, isFirst = true **

** Activity (main) Resume **
java.lang.ExceptionInInitializerError

at java.lang.Class.classForName(Native Method)
at java.lang.Class.forName(Class.java:234)
at java.lang.Class.forName(Class.java:181)
at anywheresoftware.b4a.shell.Shell.getCorrectClassName(Shell.java:378)
at anywheresoftware.b4a.shell.Shell.createObject(Shell.java:365)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:247)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:174)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:93)
at b4a.example.main.afterFirstLayout(main.java:91)
at b4a.example.main.access$100(main.java:16)
at b4a.example.main$WaitForLayout.run(main.java:76)
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:3688)
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)
Caused by: java.lang.UnsatisfiedLinkError: Couldn't load serial_port: findLibrary returned null
at java.lang.Runtime.loadLibrary(Runtime.java:429)
at java.lang.System.loadLibrary(System.java:554)
at android_serialport_api.SerialPort.<clinit>(SerialPort.java:93)
... 22 more

AND THE OTHER ONE:

modulo485_process_globals (java line: 109)
java.lang.ExceptionInInitializerError
at jab.comboio.modulo485._process_globals(modulo485.java:109)
at jab.comboio.main.initializeProcessGlobals(main.java:703)
at jab.comboio.main.afterFirstLayout(main.java:94)
at jab.comboio.main.access$100(main.java:16)
at jab.comboio.main$WaitForLayout.run(main.java:76)
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:3688)
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)
Caused by: java.lang.UnsatisfiedLinkError: Couldn't load serial_port: findLibrary returned null
at java.lang.Runtime.loadLibrary(Runtime.java:429)
at java.lang.System.loadLibrary(System.java:554)
at android_serialport_api.SerialPort.<clinit>(SerialPort.java:93)
... 14 more

Any ideas ????

Erel · Apr 19, 2014

How did you wrap this library?

jgbozza · Apr 25, 2014

yes I did. I used it because I needed to set the baud rate programmaticaly and didnt find any way to do it with the builtin serial library

B4X:

#Region  Service Attributes 
    #StartAtBoot: false
#End Region

Sub Process_Globals
Try
    'These global variables will be declared once when the application starts.
    'These variables can be accessed from all modules.
    Dim Async As AsyncStreams
    Dim PORTA485 As SerialPort
    Dim RECEBIDO As String
Catch
    Msgbox(LastException.Message, "ERROR : SERIAL")
        Dim inten As Intent
        inten.Initialize(inten.ACTION_MAIN, "")
        inten.AddCategory("android.intent.category.MONKEY")
        inten.Flags = 0x10000000
        StartActivity(inten)
        ExitApplication   
End Try   
End Sub
Sub Service_Create
Try
    PORTA485.SetPort("/dev/ttymxc0",9600,0) 'THIS IS THE REASON WHY I USED THE android.serialport.api
    Async.Initialize(PORTA485.InputStream,PORTA485.OutputStream,"TESTE") 
    Do While Async.IsInitialized = False
    Loop
Catch 'in case of a general failure the last resort is to exit the application
        Msgbox(LastException.Message, "ERRO : SERIAL 0002")
        Dim inten As Intent
        inten.Initialize(inten.ACTION_MAIN, "")
        inten.AddCategory("android.intent.category.MONKEY")
        inten.Flags = 0x10000000
        StartActivity(inten)
        ExitApplication   
End Try
End Sub

Sub Service_Start (StartingIntent As Intent)
    Dim c As String
    c="ABCDEF"
    Async.Write(c.GetBytes("UTF8"))   
End Sub

Sub Service_Destroy

End Sub

Sub TESTE_NewData (Buffer() As Byte)
    .
    .
    .
    .
End Sub

Ferraz71 · Apr 25, 2014

this is the code inside the eclipse...

B4X:

package android_serialport_api;

//import java.io.File;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io_OutputStream;
import android.util.Log;

import anywheresoftware.b4a.BA.ShortName;
@ShortName("SerialPort")

public class SerialPort {

    private static final String TAG = "SerialPort";

    /*
    * Do not remove or rename the field mFd: it is used by native method close();
    */
    private FileDescriptor mFd;
    private FileInputStream mFileInputStream;
    private FileOutputStream mFileOutputStream;

    public void SetPort (String path, int baudrate, int flags) throws SecurityException, IOException {

        mFd = open(path, baudrate, flags);
        if (mFd == null) {
            Log.e(TAG, "native open returns null");
            throw new IOException();
        }
        mFileInputStream = new FileInputStream(mFd);
        mFileOutputStream = new FileOutputStream(mFd);
    }

    // Getters and setters
    public InputStream getInputStream() {
        return mFileInputStream;
    }

    public OutputStream getOutputStream() {
        return mFileOutputStream;
    }
  


    // JNI
    private native static FileDescriptor open(String path, int baudrate, int flags);
    public native void close();
    static {
        System.loadLibrary("serial_port");
    }
}

jgbozza · Apr 25, 2014

Erel,

The code above posted by Ferraz71 is used to compile our serial library.

The thing about this error is that the app works perfectly for weeks, even months flawlessly and all of sudden when the tablet is turned on a error message is thrown. It never happens while the app is working, only when someone turns it on.

Fortunately I got to debug the error by connecting the tablet to the B4A IDE and the logs are posted up above in this thread. Both of them seemed to be similar (lib's not found) even if the erros don't seem to be exactly the same.

I saw a thread where someone had a similar issue and you recommended they to change the code from

B4X:

System.loadLibrary("serial_port");

to

B4X:

System.load(File.Combine(File.getDirInternal(), "serial_port.so"));

probably because the android system is losing the reference to the library path.

Thank you in advance.

Erel · Apr 27, 2014

Can you upload the library jar file?

jgbozza · Apr 28, 2014

Here it goes.

Erel · Apr 28, 2014

The jar file is built correct. The important file is the one under lib\armeabi

Does it happen in Release mode as well?

jgbozza · Apr 28, 2014

Yes, the problem happens in release mode. If I upload the application again from Basic 4 Android the problem vanishes. That's why this flaw has become so hard to be debugged.
As a workaround we are willing to check if the lib file exists before the application starts. If it doesnt means that somehow the path is lost or modified, then a internal routine copies this file from an external folder to the assets folder or where the application originally points to. Speaking of which, do you know where the app looks for a lib physically in the folders tree and how it can be accessed programmaticaly in order to avoid this error by doing that workaround procedure?

Erel · Apr 29, 2014

The library should be loaded from the lib folder. This is the default path.

You can copy it from the assets folder and load it with the code you posted above. My guess is that the file location is not the real problem here.

jgbozza · Apr 29, 2014

Copying from the assets folder in startup will prevent the app from crashing ?
Yesterday one more error was thrown from another device and it has been working perfectly for almost 2 months.

What else could it be instead of file location ? Have you ever had a similar problem? Please let me know your thoughts.

Erel · Apr 29, 2014

If the problem is that it cannot find the file then it is worth trying to load it from a different folder. I never encountered such issue.

jgbozza · May 1, 2014

I've seen a lot of people having similar problems all around and apparently nobody seemed to reach a plausible solution.
I want to leave two links below where you can see for yourself.

http://stackoverflow.com/questions/...lang-unsatisfiedlinkerror-cannot-load-library
https://groups.google.com/forum/#!topic/android-ndk/9X2ejyiHNUU

If you see a light in the end of the tunnel please let us know.

jgbozza · Sep 2, 2014

Erel, Do you think that this issue is related to a forced shut-down of the tablet? I asked the operators to hold the power off button in order to shut down the device after their shift. Another workaround should be putting a power off virtual button which would close all services and close the application afterwards. Is it possible to turn off the tablet programatically?

(For instance, there is another tablet with the same software but in a steady place. It's never been shut down and the exception never happened so far)

Erel · Sep 3, 2014

Not sure. Maybe you can create another app that will try to run this one and if it fails will try to run it again in a few seconds.

jgbozza · Sep 3, 2014

Is there any example available? My feeling is that due to the forced closing of the device there is a chance of a file to get corrupted or to be allocated in a memory space that is no longer available once the tablet restarts the app after the forced shut down. Maybe we could stop the services to prevent it from happening.

Erel · Sep 4, 2014

Create an app that runs in the background all the time and starts your app with an Intent every 30 seconds. If your app is already running then nothing should happen.

jgbozza · Sep 4, 2014

Erel,

My biggest issue is the customer getting stuck by the fact that the app wont close it when the exception is thrown. Is there a way to close the application remotelly from a desktop service the same way Basic4Android does? Would it be possible to send a Debugger Software to our client or staff only to debbug our application deployed to tablets? I mean, use the Basic4Android funcionallity but without the entire programming IDE.

Erel · Sep 5, 2014

Would it be possible to send a Debugger Software to our client or staff only to debbug our application deployed to tablets? I mean, use the Basic4Android funcionallity but without the entire programming IDE.

It is technically not possible.

What happens where there is an exception?

Android Question android-serialport-api

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