My android application prints only 1 ticket every 5 seconds

Question

Firstly, thank you for your time reading my question. I'm still a noob when it comes to programming in Java and I am grateful for any advice or assistance.

The App

I wrote a small android application that prints out jobcard tickets via a bluetooth printer.

The Problem

My application can only print one ticket every 5 seconds, meaning if a second jobcard is captured within 5 seconds the application does not print a ticket.

What I want

I really want the application to consecutively print out a ticket for every jobcard captured.

I think I got lost in the details with AsyncTasks,Threads (Bluetooth comms) etc. and when to use what class.

Any guidelines on best practices how to use these classes are more than welcome. I have pasted some of the source code below which I suspect might be the root of the problem.

Equipment :

Zebra RW420 Printer (Zebra SDK)

What the log says :

03-06 20:17:04.328: W/BluetoothAdapter(25552): getBluetoothService() called with no BluetoothManagerCallback 03-06 20:17:04.328: W/BluetoothAdapter(25552): getBluetoothService() called with no BluetoothManagerCallback 03-06 20:17:04.386: D/dalvikvm(25552): GC_CONCURRENT freed 133K, 9% free 4079K/4468K, paused 17ms+23ms, total

Source Code :

MainScreen.java

public class MainScreen extends Activity {

submitBtn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub                                              
               //Do printing
                    String tpl = "Hello World!";
                    new PrintTask().execute(tpl);                    
            }
        });       
   }

//Async Printing Task
private class PrintTask extends AsyncTask<String, Integer, String> {
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                uiHelper.showLoadingDialog("Printing, please wait...");                                 
            }

            @Override
            protected String doInBackground(String... params) {
                String msg = params[0];                                 
                print(msg);                                                                 
                publishProgress(1);                 
                return "All Done!";
            }

            @Override
            protected void onProgressUpdate(Integer... values) {
                super.onProgressUpdate(values);
                uiHelper.updateLoadingDialog("Printing jobcard " + values[0]);              
            }

            @Override
            protected void onPostExecute(String result) {
                super.onPostExecute(result);
                uiHelper.dismissLoadingDialog();
                finish(); //close the window
            }
        }

    public void print(String tpl) {
        final String msg = tpl;     
        //runOnUiThread(new Runnable()
        new Thread(new Runnable() {
            public void run() {                                                             
                Looper.prepare();
                printer_ob.printMessage(msg);               
                Looper.loop();
                Looper.myLooper().quit();                
            }
        }).start();                     
    }

}

The ZebraPrinter helper class I use :

public class ZebraPrinterHelper {
    Context context;
    private ZebraPrinterConnection zebraPrinterConnection;
    private RadioButton btRadioButton;
    private ZebraPrinter printer;
    private TextView statusField;
    private EditText macAddress, ipDNSAddress, portNumber;
    private Button testButton;  

    public ZebraPrinterHelper(Context c) {
        context = c;
    }

    public ZebraPrinter connect() {

        zebraPrinterConnection = null;      
        zebraPrinterConnection = new BluetoothPrinterConnection(SettingsHelper.getBluetoothAddress(context));               

        try {
            zebraPrinterConnection.open();          
        } catch (ZebraPrinterConnectionException e) {       
            Toast.makeText(context, "Comm Error! Disconnecting", 500).show();
            DemoSleeper.sleep(1000);
            disconnect();
        }
        ZebraPrinter printer = null;

        if (zebraPrinterConnection.isConnected()) {
            try {
                printer = ZebraPrinterFactory.getInstance(zebraPrinterConnection);
                //setStatus("Determining Printer Language", Color.YELLOW);
                PrinterLanguage pl = printer.getPrinterControlLanguage();
                //    setStatus("Printer Language " + pl, Color.BLUE);
            } catch (ZebraPrinterConnectionException e) {
                //"Unknown Printer Language");
                Toast.makeText(context, "Error, Unknown printer language", 500).show();
                DemoSleeper.sleep(1000);
                printer = null;
                DemoSleeper.sleep(1000);
                disconnect();
            } catch (ZebraPrinterLanguageUnknownException e) {
                //setStatus("Unknown Printer Language", Color.RED);
                Toast.makeText(context, "Error, Unknown printer language", 500).show();             
                printer = null;
                DemoSleeper.sleep(1000);
                disconnect();
            }
        }

        return printer;         
    }

    private void writeMessage(byte[] message) {
        //message in bytes      
        try {           
            zebraPrinterConnection.write(message);              
            DemoSleeper.sleep(1500);
            if (zebraPrinterConnection instanceof BluetoothPrinterConnection) {
                String friendlyName = ((BluetoothPrinterConnection) zebraPrinterConnection).getFriendlyName();                  
                DemoSleeper.sleep(500);
            }
        } catch (ZebraPrinterConnectionException e) {
            //helper.showErrorDialogOnGuiThread("Error:" + e.getMessage());
            Log.d("Error",e.getMessage());
        } finally {
            disconnect();
        }
    }



        public void printMessage(String message) {
            byte[] msg = null;          
            msg = message.getBytes();

            //check connections

            printer = connect();
            if (printer != null) {
                writeMessage(msg);
            } else {
                disconnect();
            }

        }

        public void disconnect() {
            try {           
                if (zebraPrinterConnection != null) {
                    zebraPrinterConnection.close();
                }               
            } catch (ZebraPrinterConnectionException e) {
                //setStatus("COMM Error! Disconnected", Color.RED);
            } finally {

            }
        }
    }

Answer 1

I think you will have to use a IntentService rather than a AsyncTask. IntentServices handle asynchronous requests and also has built in features for queuing. Have a look at this link for more info on IntentServices.