我想在 J2ME 应用程序中使用蓝牙在打印机上打印一些数据。我可以完美地打印数据，但完成打印功能后，打印机会自动关闭。我的意思是与设备的连接丢失，当我关闭应用程序时，它会自动打开。我不明白为什么打印一次后连接丢失。如果有人有任何想法，请帮助我。谢谢。
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package com.mobifin;
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*/
import com.sun.lwuit.Command;
import com.sun.lwuit.Component;
import com.sun.lwuit.Dialog;
import com.sun.lwuit.Display;
import com.sun.lwuit.Font;
import com.sun.lwuit.Form;
import com.sun.lwuit.Label;
import com.sun.lwuit.List;
import com.sun.lwuit.TextArea;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.list.ListCellRenderer;
import com.sun.lwuit.plaf.Border;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.Vector;
import javax.bluetooth.BluetoothStateException;
import javax.bluetooth.DeviceClass;
import javax.bluetooth.DiscoveryAgent;
import javax.bluetooth.DiscoveryListener;
import javax.bluetooth.LocalDevice;
import javax.bluetooth.RemoteDevice;
import javax.bluetooth.ServiceRecord;
import javax.bluetooth.UUID;
import javax.microedition.io.Connector;
import javax.microedition.io.StreamConnection;
/**
*
* @author riddhi.barbhaya
*/
public class PrintScreen extends Form implements ActionListener, ListCellRenderer, DiscoveryListener {
String title;
Form form, info;
MobifinMidlet parent;
Command cmd_exit = new Command("Exit", 1);
Command cmd_Print = new Command("Print", 1);
LocalDevice bluetooth;
String blueStr;
List activeDevice = new List();
List activeServices = new List();
DiscoveryAgent disAgent;
Vector deviceFound;
private ServiceRecord[] servicesFound = null;
private boolean Dflag;
private String connectionURL;
private boolean srviceDisFlag;
private DataInputStream ioDataInputStream;
StreamConnection sc;
// private Command cmdinfo, select;
Display display;
Label lbl = new Label("Searching for devices...");
Label l1;
int device = 0;
String msg;
public PrintScreen(MobifinMidlet parent, String title, String message) {
this.title = title;
this.setTitle(title);
this.parent = parent;
this.msg = message;
this.addComponent(lbl);
activeDevice.setListCellRenderer(this);
this.addCommandListener(this);
this.addComponent(activeDevice);
this.addComponent(activeServices);
try {
bluetooth = LocalDevice.getLocalDevice();
} catch (BluetoothStateException ex) {
ex.printStackTrace();
}
blueStr = bluetooth.getFriendlyName();
disAgent = bluetooth.getDiscoveryAgent();
deviceFound = new Vector();
try {
disAgent.startInquiry(DiscoveryAgent.GIAC, this);
} catch (BluetoothStateException ex) {
ex.printStackTrace();
showMessageDialog("Exception", "Exception in start app");
}
if (Dflag) {
disAgent.cancelInquiry(this);
}
}
public void dosearchServies(RemoteDevice device) {
int[] attributes = {0x100, 0x101, 0x102};
UUID[] uuids;
UUID RFCOMM_UUID = new UUID(0x1101); // RFCOMM service
uuids = new UUID[1];
uuids[0] = RFCOMM_UUID;
disAgent = bluetooth.getDiscoveryAgent();
try {
disAgent.searchServices(null, uuids, device, this);
} catch (Exception e) {
e.printStackTrace();
// showMessageDialog("Error", "Error");
}
}
public void deviceDiscovered(RemoteDevice btDevice, DeviceClass cod) {
try {
String deviceaddress = null;
try {
deviceaddress = btDevice.getBluetoothAddress();//btDevice.getFriendlyName(true);
System.out.println("Device Address is>>" + deviceaddress);
} catch (Exception ex) {
ex.printStackTrace();
}
String str;
str = btDevice.getFriendlyName(true);
activeDevice.addItem(str);
deviceFound.addElement(btDevice);
System.out.println("----");
// dosearchServies(btDevice);
} catch (IOException ex) {
showMessageDialog("Exception", "Exception in device discovered");
ex.printStackTrace();
}
}
public void showMessageDialog(String title, String message) {
Dialog dialog = new Dialog("Alert");
dialog.setScrollable(false);
dialog.setIsScrollVisible(false);
dialog.setTimeout(2000); // set timeout milliseconds
dialog.setPreferredH(100);
dialog.setPreferredW(100);
TextArea textarea = new TextArea(2, 30, TextArea.UNEDITABLE) {
public int getRows() {
if (isGrowByContent()) {
return getLines();
} else {
return super.getRows();
}
}
};
textarea.getStyle().setBorder(Border.createLineBorder(0));
textarea.getStyle().setFont(Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_MEDIUM));
textarea.getStyle().setBorder(Border.createLineBorder(0));
textarea.setGrowByContent(true);
textarea.setFocusable(false);
textarea.setIsScrollVisible(false);
textarea.setText(message);
dialog.setTitle(title);
dialog.addComponent(textarea);
dialog.show(0, 120, 10, 10, true);
}
public void actionPerformed(ActionEvent ae) {
Command c = ae.getCommand();
String str;
if (c.equals(cmd_exit)) {
MainMenu mainmenu = new MainMenu("Menu", parent);
mainmenu.show();
}
else if (c.equals(cmd_Print)) {
try {
device = activeDevice.getSelectedIndex();
dosearchServies((RemoteDevice) deviceFound.elementAt(device));
} catch (Exception e) {
showMessageDialog("Exception", "Exception in command print");
e.printStackTrace();
}
}
}
private synchronized int a(int p) {
int i = p;
notifyAll();
return i;
}
public Component getListCellRendererComponent(List list, Object value, int i, boolean isSelected) {
Label l = new Label(value.toString());
if (isSelected == true) {
l.setFocus(true);
l.setGap(0);
l.getStyle().setFont(Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_BOLD, Font.SIZE_MEDIUM));
} else {
l.setFocus(false);
l.setGap(0);
l.getStyle().setFont(Font.createSystemFont(Font.FACE_SYSTEM, Font.STYLE_BOLD, Font.SIZE_MEDIUM));
return l;
}
return l;
}
public Component getListFocusComponent(List list) {
return null;
}
public void serviceSearchCompleted(int i, int i1) {
switch (i) {
case DiscoveryListener.SERVICE_SEARCH_COMPLETED:
srviceDisFlag = true;
break;
case DiscoveryListener.SERVICE_SEARCH_DEVICE_NOT_REACHABLE:
break;
case DiscoveryListener.SERVICE_SEARCH_ERROR:
break;
case DiscoveryListener.SERVICE_SEARCH_NO_RECORDS:
break;
case DiscoveryListener.SERVICE_SEARCH_TERMINATED:
break;
}
this.setTitle("Select Device For printing Selection");
int service = activeServices.getSelectedIndex();
connectionURL = servicesFound[service].getConnectionURL(0, false);
printmethod(connectionURL);
}
public void inquiryCompleted(int discType) {
if (discType != DiscoveryListener.INQUIRY_COMPLETED) {
} else {
this.removeComponent(lbl);
this.addCommand(cmd_Print);
this.addCommand(cmd_exit);
revalidate();
}
Dflag = true;
try {
} catch (Exception ex) {
ex.printStackTrace();
}
}
public void printmethod(String connection_u) {
try {
try {
StreamConnection connection = (StreamConnection) Connector.open(connection_u);
byte[] buffer = new byte[100];
InputStream is = connection.openInputStream();
OutputStream os = connection.openOutputStream();
OutputStreamWriter ow = new OutputStreamWriter(os, "US-ASCII");
InputStreamReader ir = new InputStreamReader(is, "US-ASCII");
ow.write(msg);
ow.flush();
ow.close();
connection.close();
showMessageDialog("", "Please Wait Printing is in Progress");
MainMenu menu=new MainMenu("Menu", parent);
menu.show();
System.out.println("-4-");
System.out.println("-5-");
} catch (Exception e) {
System.out.println("Error " + e);
showMessageDialog("Exception", e.toString());
}
int i2 = 0;
System.out.println("-0-");
}
public void servicesDiscovered(int i, ServiceRecord[] srs) {
servicesFound = srs;
}
public void addText(String text) {
TextArea t = new TextArea(2, 30, TextArea.UNEDITABLE) {
public int getRows() {
if (isGrowByContent()) {
return getLines();
} else {
return super.getRows();
}
}
};
t.getStyle().setBorder(Border.createLineBorder(0));
t.setGrowByContent(true);
t.setText(text);
this.addComponent(t);
}
}