btimageclient.java

一个利用手机上的bluetooth来开发的小程序 也是很经典的例子

                isDownloadCanceled = false;

                // ok, wait for download or need to wait for next search
                try {
                    wait();
                } catch (InterruptedException e) {
                    System.err.println("Unexpected interuption: " + e);
                    return;
                }

                // check the component is destroyed
                if (isClosed) {
                    return;
                }

                // this means "go to begining"
                if (imageNameToLoad == null) {
                    break;
                }

                // load selected image data
                Image img = loadImage();

                // FIXME: this never happen - monitor is taken...
                if (isClosed) {
                    return;
                }

                if (isDownloadCanceled) {
                    continue; // may be next image to be download
                }

                if (img == null) {
                    parent.informLoadError("Can't load image: "
                            + imageNameToLoad);
                    continue; // may be next image to be download
                }

                // ok, show image to user
                parent.showImage(img);

                // may be next image to be download
                continue;
            }
        }
    }

    /**
     * Search for bluetooth devices.
     *
     * @return false if should end the component work.
     */
    private boolean searchDevices() {

        // ok, start a new search then
        state = DEVICE_SEARCH;
        devices.removeAllElements();

        try {
            discoveryAgent.startInquiry(DiscoveryAgent.GIAC, this);
        } catch (BluetoothStateException e) {
            System.err.println("Can't start inquiry now: " + e);
            parent.informSearchError("Can't start device search");
            return true;
        }

        try {
            wait(); // until devices are found
        } catch (InterruptedException e) {
            System.err.println("Unexpected interuption: " + e);
            return false;
        }

        // this "wake up" may be caused by 'destroy' call
        if (isClosed) {
            return false;
        }

        // no?, ok, let's check the return code then
        switch (discType) {
        case INQUIRY_ERROR:
            parent.informSearchError("Device discovering error...");

            // fall through

        case INQUIRY_TERMINATED:

            // make sure no garbage in found devices list
            devices.removeAllElements();

            // nothing to report - go to next request
            break;

        case INQUIRY_COMPLETED:
            if (devices.size() == 0) {
                parent.informSearchError("No devices in range");
            }

            // go to service search now
            break;
        default:

            // what kind of system you are?... :(
            System.err.println("system error:"
                    + " unexpected device discovery code: " + discType);
            destroy();
            return false;
        }
        return true;
    }

    /**
     * Search for proper service.
     *
     * @return false if should end the component work.
     */
    private boolean searchServices() {
        state = SERVICE_SEARCH;
        records.removeAllElements();
        searchIDs = new int[devices.size()];
        boolean isSearchStarted = false;

        for (int i = 0; i < devices.size(); i++) {
            RemoteDevice rd = (RemoteDevice) devices.elementAt(i);

            try {
                searchIDs[i] = discoveryAgent.searchServices(attrSet, uuidSet,
                        rd, this);
            } catch (BluetoothStateException e) {
                System.err.println("Can't search services for: "
                        + rd.getBluetoothAddress() + " due to " + e);
            }
            isSearchStarted = true;
        }

        // at least one of the services search should be found
        if (!isSearchStarted) {
            return true;
        }

        try {
            wait(); // until services are found
        } catch (InterruptedException e) {
            System.err.println("Unexpected interuption: " + e);
            return false;
        }

        // this "wake up" may be caused by 'destroy' call
        if (isClosed) {
            return false;
        }

        // actually, no services were found
        if (records.size() == 0) {
            parent.informSearchError("No proper services were found");
        }
        return true;
    }

    /**
     * Gets the collection of the images titles (names)
     * from the services, prepares a hashtable to match
     * the image name to a services list, presents the images names
     * to user finally.
     *
     * @return false if no names in found services.
     */
    private boolean presentUserSearchResults() {
        base.clear();

        for (int i = 0; i < records.size(); i++) {
            ServiceRecord sr = (ServiceRecord) records.elementAt(i);

            // get the attribute with images names
            DataElement de = sr.getAttributeValue(IMAGES_NAMES_ATTRIBUTE_ID);

            if (de == null) {
                System.err.println("Unexpected service - missed attribute");
                continue;
            }

            // get the images names from this attribute
            Enumeration en = (Enumeration) de.getValue();

            while (en.hasMoreElements()) {
                de = (DataElement) en.nextElement();
                String name = (String) de.getValue();

                // name may be stored already
                Object obj = base.get(name);

                // that's either the ServiceRecord or Vector
                if (obj != null) {
                    Vector v;

                    if (obj instanceof ServiceRecord) {
                        v = new Vector();
                        v.addElement(obj);
                    } else {
                        v = (Vector) obj;
                    }
                    v.addElement(sr);
                    obj = v;
                } else {
                    obj = sr;
                }
                base.put(name, obj);
            }
        }
        return parent.showImagesNames(base);
    }

    /**
     * Loads selected image data.
     */
    private Image loadImage() {
        if (imageNameToLoad == null) {
            System.err.println("Error: imageNameToLoad=null");
            return null;
        }

        // ok, get the list of service records
        ServiceRecord[] sr = null;
        Object obj = base.get(imageNameToLoad);

        if (obj == null) {
            System.err.println("Error: no record for: " + imageNameToLoad);
            return null;
        } else if (obj instanceof ServiceRecord) {
            sr = new ServiceRecord[] { (ServiceRecord) obj };
        } else {
            Vector v = (Vector) obj;
            sr = new ServiceRecord[v.size()];

            for (int i = 0; i < v.size(); i++) {
                sr[i] = (ServiceRecord) v.elementAt(i);
            }
        }

        // now try to load the image from each services one by one
        for (int i = 0; i < sr.length; i++) {
            StreamConnection conn = null;
            String url = null;

            // the process may be canceled
            if (isDownloadCanceled) {
                return null;
            }

            // first - connect
            try {
                url = sr[i].getConnectionURL(
                        ServiceRecord.NOAUTHENTICATE_NOENCRYPT, false);
                conn = (StreamConnection) Connector.open(url);
            } catch (IOException e) {
                System.err.println("Note: can't connect to: " + url);

                // ignore
                continue;
            }

            // then open a steam and write a name
            try {
                OutputStream out = conn.openOutputStream();
                out.write(imageNameToLoad.length()); // length is 1 byte
                out.write(imageNameToLoad.getBytes());
                out.close();
            } catch (IOException e) {
                System.err.println("Can't write to server for: " + url);

                // close stream connection
                try {
                    conn.close();
                } catch (IOException ee) {} // ignore
                continue;
            }

            // then open a steam and read an image
            byte[] imgData = null;

            try {
                InputStream in = conn.openInputStream();

                // read a length first
                int length = in.read() << 8;
                length |= in.read();

                if (length <= 0) {
                    throw new IOException("Can't read a length");
                }

                // read the image now
                imgData = new byte[length];
                length = 0;

                while (length != imgData.length) {
                    int n = in.read(imgData, length, imgData.length - length);

                    if (n == -1) {
                        throw new IOException("Can't read a image data");
                    }
                    length += n;
                }
                in.close();
            } catch (IOException e) {
                System.err.println("Can't read from server for: " + url);
                continue;
            } finally {

                // close stream connection anyway
                try {
                    conn.close();
                } catch (IOException e) {} // ignore
            }

            // ok, may it's a chance
            Image img = null;

            try {
                img = Image.createImage(imgData, 0, imgData.length);
            } catch (Exception e) {

                // may be next time
                System.err.println("Error: wrong image data from: " + url);
                continue;
            }
            return img;
        }
        return null;
    }
} // end of class 'BTImageClient' definition