如何在传递数据之前知道蓝牙设备是否仍然连接到笔记本电脑？我使用 blue-cove 编写了一个 java 程序lib 通过笔记本电脑发现和传递数据。第一次传数据后，如何在下次传数据前检查设备是否还连接着笔记本电脑？

我看到了类似的问题。但是他们问了如何查看连接到android的蓝牙设备状态。

最佳答案

您可以按照一系列步骤创建一个异步任务来验证连接，同时在设备之间搜索和共享文件。

函数 deviceDiscovered() 和 inquiryCompleted() 是在发现设备和查询完成时执行的函数。

如果设备断开连接，您将从 inqueryCompleted 方法收到通知并在行中处理它:

try {
                    synchronized(lock){
                        lock.wait();
                    }
                }

                catch (InterruptedException e) {
                    e.printStackTrace();
                }

在InterruptedException中你可以处理这个错误。

package bt;

import java.io.OutputStream;
import java.util.ArrayList;

import javax.bluetooth.DataElement;
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.obex.ClientSession;
import javax.obex.HeaderSet;
import javax.obex.Operation;
import javax.obex.ResponseCodes;

import bt.BTListener.MyDeviceListenerFilter;

public class MyDiscoveryListener implements DiscoveryListener{

    private static Object lock=new Object();
    public ArrayList<RemoteDevice> devices;

    public MyDiscoveryListener() {
        devices = new ArrayList<RemoteDevice>();
    }

    public static void main(String[] args) {

        MyDiscoveryListener listener =  new MyDiscoveryListener();

        try{
            LocalDevice localDevice = LocalDevice.getLocalDevice();
            DiscoveryAgent agent = localDevice.getDiscoveryAgent();
            agent.startInquiry(DiscoveryAgent.GIAC, listener);

            try {
                synchronized(lock){
                    lock.wait();
                }
            }
            catch (InterruptedException e) {
                e.printStackTrace();
                return;
            }


            System.out.println("Device Inquiry Completed. ");


            UUID[] uuidSet = new UUID[1];
            uuidSet[0]=new UUID(0x1105); //OBEX Object Push service

            int[] attrIDs =  new int[] {
                    0x0100 // Service name
            };

            for (RemoteDevice device : listener.devices) {
                agent.searchServices(
                        attrIDs,uuidSet,device,listener);


                try {
                    synchronized(lock){
                        lock.wait();
                    }
                }
                catch (InterruptedException e) {
                    e.printStackTrace();
                    return;
                }


                System.out.println("Service search finished.");
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }



    @Override
    public void deviceDiscovered(RemoteDevice btDevice, DeviceClass arg1) {
        String name;
        try {
            name = btDevice.getFriendlyName(false);
        } catch (Exception e) {
            name = btDevice.getBluetoothAddress();
        }

        devices.add(btDevice);
        System.out.println("device found: " + name);

    }

    @Override
    public void inquiryCompleted(int arg0) {
        synchronized(lock){
            lock.notify();
        }
    }

    @Override
    public void serviceSearchCompleted(int arg0, int arg1) {
        synchronized (lock) {
            lock.notify();
        }
    }

    @Override
    public void servicesDiscovered(int transID, ServiceRecord[] servRecord) {
        for (int i = 0; i < servRecord.length; i++) {
            String url = servRecord[i].getConnectionURL(ServiceRecord.NOAUTHENTICATE_NOENCRYPT, false);
            if (url == null) {
                continue;
            }
            DataElement serviceName = servRecord[i].getAttributeValue(0x0100);
            if (serviceName != null) {
                System.out.println("service " + serviceName.getValue() + " found " + url);

                if(serviceName.getValue().equals("OBEX Object Push")){
                    sendMessageToDevice(url);                
                }
            } else {
                System.out.println("service found " + url);
            }


        }
    }

    private static void sendMessageToDevice(String serverURL){
        try{
            System.out.println("Connecting to " + serverURL);

            ClientSession clientSession = (ClientSession) Connector.open(serverURL);
            HeaderSet hsConnectReply = clientSession.connect(null);
            if (hsConnectReply.getResponseCode() != ResponseCodes.OBEX_HTTP_OK) {
                System.out.println("Failed to connect");
                return;
            }

            HeaderSet hsOperation = clientSession.createHeaderSet();
            hsOperation.setHeader(HeaderSet.NAME, "Hello.txt");
            hsOperation.setHeader(HeaderSet.TYPE, "text");

            //Create PUT Operation
            Operation putOperation = clientSession.put(hsOperation);

            // Send some text to server
            byte data[] = "Hello World !!!".getBytes("iso-8859-1");
            OutputStream os = putOperation.openOutputStream();
            os.write(data);
            os.close();

            putOperation.close();

            clientSession.disconnect(null);

            clientSession.close();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }

}

关于java - 检查连接的蓝牙设备状态，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34326400/