蓝牙开发经验小结——自动文件传输（OBEX）

场景：控制端——普通手机；被控制端——XX设备（无屏幕、无法用户操作、有系统权限）
网上关于文件传输实现的文章较少，没有发现满足我需求的资料，于是我索性深入到系统源码里头，研究了系统蓝牙（com.android.bluetooth不同的平台包名可能有差异）是如何实现文件收发的，然后再设计出自己的实现方案。
对于已经实现了蓝牙socket通讯（BluetoothChatService和BluetoothUtil）的小伙伴们，很容易想到的文件传输方式是采用文件流，1.通过socket获取输入输出流来处理传输（分别使用getInputStream()和getOutputStream()）。2.用read(byte[])和write(byte[])来实现读写。然而实际上并没有那么简单，如“数据包截断”问题，以及传输过程中穿插其他信令交互的问题等等。如果基于蓝牙socket，通过文件流的形式传输，要做到比较可靠，其实就相当于你要实现OBEX协议（对象交换）的具体内容，复杂度和工作量还是不小的。
请注意，普通手机端，由于可以用户操作，依据通用API直接调用com.android.bluetooth的文件传输功能即可，这里说的是XX设备端，由于无法交互，需要程序自动确认传输的实现方式。
直接上代码吧，XX设备端，发送文件的处理：

    /**     * 通过系统的蓝牙文件传输功能，基于OBEX协议，向外发送文件     * @param file     * @param destination     */    public void sendFileByBluetooth(File file, String destination) {                String uri = "file://" + file.getAbsolutePath();        Intent sharingIntent = new Intent(android.content.Intent.ACTION_SEND);        sharingIntent.setType("*/*");        sharingIntent.setComponent(new ComponentName("com.android.bluetooth", "com.android.bluetooth.opp.BluetoothOppLauncherActivity"));        sharingIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse(uri));        App.getInstance().startActivity(sharingIntent);        //以上代码看上去和第三方应用调用蓝牙发送没什么太多区别        //下面的代码，就是直接跳过原本需要用户手动操作的步骤了        //稍等片刻,提高发送成功率的关键        try {            Thread.sleep(500);        }catch (InterruptedException e){            e.printStackTrace();            logd(e);        }        Intent intent = new Intent(BluetoothDevicePicker.ACTION_DEVICE_SELECTED);//需要系统应用uid=1000，才可以发送        intent.putExtra(BluetoothDevice.EXTRA_DEVICE, getBTDevice(destination));        intent.setClassName("com.android.bluetooth", "com.android.bluetooth.opp.BluetoothOppReceiver");        App.getInstance().sendBroadcast(intent);//这一段发送了一个定向广播，告诉com.android.bluetooth已经选择了一个设备//下面这一段，就是要把弹出的蓝牙选择界面自动去除（模拟按下返回键）        new Thread(new Runnable() {//自动去掉蓝牙选择的界面            @Override            public void run() {                boolean cover = false;//被遮挡                while (true) {                    if (!isAppOnForeground(App.getInstance(), App.getInstance().getPackageName())) {                        try {                            Instrumentation inst = new Instrumentation();                            inst.sendKeyDownUpSync(KeyEvent.KEYCODE_BACK);                        } catch (Exception e) {                            e.printStackTrace();                        }                        cover = true;                    }                    if (cover && isAppOnForeground(App.getInstance(), App.getInstance().getPackageName())) {                        logd("break");                        break;                    } else {                        try {                            Thread.sleep(500);                        } catch (InterruptedException e) {                            e.printStackTrace();                            logd(e);                        }                    }                }            }        }).start();    }

XX设备端，接收文件的处理：
（使用了ContentObserver ，至于为什么可查看源码，这里不多解释）

    String sendFileName = "";    File targetFileReceive = null;    File targetFileSend = null;    boolean transferFlag = false;    private ContentObserver btObserver = new ContentObserver(mHandler) {//用于自动确认并接收蓝牙文件        @Override        public void onChange(boolean selfChange) {            super.onChange(selfChange);            logd("btObserver onChange.");//需要申请权限android.permission.ACCESS_BLUETOOTH_SHARE，并且需要同Bluetooth的签名，即系统签名            if(!transferFlag){                return;            }            Cursor cursor = App.getInstance().getContentResolver().query(BluetoothShare.CONTENT_URI, null, null, null, BluetoothShare._ID);            if(cursor == null){                logd("cursor null.");                return;            }            cursor.moveToLast();//直接跳至最后一条记录（最新记录）            int id = cursor.getInt(cursor.getColumnIndex(BluetoothShare._ID));            int direction = cursor.getInt(cursor.getColumnIndex(BluetoothShare.DIRECTION));            int user_confirm = cursor.getInt(cursor.getColumnIndex(BluetoothShare.USER_CONFIRMATION));            String fileName = cursor.getString(cursor.getColumnIndex(BluetoothShare.FILENAME_HINT));            StringBuilder stringBuilder = new StringBuilder();            if (direction == BluetoothShare.DIRECTION_INBOUND && user_confirm == BluetoothShare.USER_CONFIRMATION_PENDING) {                stringBuilder.append("a new incoming file confirm,");                if (!TextUtils.isEmpty(sendFileName) && sendFileName.equals(fileName)) {                    if (fileName != null) {                        targetFileReceive = new File(FileConfig.FILE_BLUETOOTH, fileName);                        if(targetFileReceive.exists()){//避免有重名的文件，先删除                            targetFileReceive.delete();                        }                    }                    ContentValues mUpdateValues = new ContentValues();                    mUpdateValues.put(BluetoothShare.USER_CONFIRMATION, BluetoothShare.USER_CONFIRMATION_CONFIRMED);                    App.getInstance().getContentResolver().update(BluetoothShare.CONTENT_URI, mUpdateValues, null, null);                    stringBuilder.append("confirm it.");                    startBTTransferMonitering(id, direction);//开始监控接收过程                } else {                    stringBuilder.append("refuse it.");                    ContentValues mUpdateValues = new ContentValues();                    mUpdateValues.put(BluetoothShare.USER_CONFIRMATION, BluetoothShare.USER_CONFIRMATION_DENIED);                    App.getInstance().getContentResolver().update(BluetoothShare.CONTENT_URI, mUpdateValues, null, null);                }                logd(stringBuilder.append("id = ").append(id).toString());//打印该条记录            } else if (direction == BluetoothShare.DIRECTION_OUTBOUND && user_confirm == BluetoothShare.USER_CONFIRMATION_AUTO_CONFIRMED) {                logd(stringBuilder.append("a new outcoming file request:").append("id = ").append(id));//打印该条记录                startBTTransferMonitering(id, direction);//开始监控发送过程            }            for (int i = 0; i < 3 && !cursor.isBeforeFirst(); i++) {//打印最后三条记录                logd(buildBtCursorInfo(cursor));                cursor.moveToPrevious();            }            if (cursor != null) {                cursor.close();            }        }    };    private String buildBtCursorInfo(Cursor cursor){        if(cursor == null){            return null;        }        StringBuilder stringBuilder = new StringBuilder();        int id = cursor.getInt(cursor.getColumnIndex(BluetoothShare._ID));        String uri = cursor.getString(cursor.getColumnIndex(BluetoothShare.URI));        String fileName = cursor.getString(cursor.getColumnIndex(BluetoothShare.FILENAME_HINT));        String data = cursor.getString(cursor.getColumnIndex(BluetoothShare._DATA));        String mineType = cursor.getString(cursor.getColumnIndex(BluetoothShare.MIMETYPE));        int direction = cursor.getInt(cursor.getColumnIndex(BluetoothShare.DIRECTION));        String destination = cursor.getString(cursor.getColumnIndex(BluetoothShare.DESTINATION));        int visibility = cursor.getInt(cursor.getColumnIndex(BluetoothShare.VISIBILITY));        int user_confirm = cursor.getInt(cursor.getColumnIndex(BluetoothShare.USER_CONFIRMATION));        int status = cursor.getInt(cursor.getColumnIndex(BluetoothShare.STATUS));        int total_bytes = cursor.getInt(cursor.getColumnIndex(BluetoothShare.TOTAL_BYTES));        int current_bytes = cursor.getInt(cursor.getColumnIndex(BluetoothShare.CURRENT_BYTES));        int timeStamp = cursor.getInt(cursor.getColumnIndex(BluetoothShare.TIMESTAMP));        int media_scanned = cursor.getInt(cursor.getColumnIndex("scanned"));        stringBuilder.append(BluetoothShare._ID).append(" = ").append(id).append(",")                .append(BluetoothShare.URI).append(" = ").append(uri).append(",")                .append(BluetoothShare.FILENAME_HINT).append(" = ").append(fileName).append(",")                .append(BluetoothShare._DATA).append(" = ").append(data).append(",")                .append(BluetoothShare.MIMETYPE).append(" = ").append(mineType).append(",")                .append(BluetoothShare.DIRECTION).append(" = ").append(direction).append(",")                .append(BluetoothShare.DESTINATION).append(" = ").append(destination).append(",")                .append(BluetoothShare.VISIBILITY).append(" = ").append(visibility).append(",")                .append(BluetoothShare.USER_CONFIRMATION).append(" = ").append(user_confirm).append(",")                .append(BluetoothShare.STATUS).append(" = ").append(status).append(",")                .append(BluetoothShare.TOTAL_BYTES).append(" = ").append(total_bytes).append(",")                .append(BluetoothShare.CURRENT_BYTES).append(" = ").append(current_bytes).append(",")                .append(BluetoothShare.TIMESTAMP).append(" = ").append(timeStamp).append(",")                .append("scanned").append(" = ").append(media_scanned);        return stringBuilder.toString();    }    private void startBTTransferMonitering(final int id, final int direction){        new Thread(new Runnable() {            @Override            public void run() {                logt("bt Transfer Monitor Thread start.");                Cursor cursor = null;                long start = System.currentTimeMillis();                boolean success = false;                while (true){                    cursor = App.getInstance().getContentResolver().query(BluetoothShare.CONTENT_URI, null, null, null, BluetoothShare._ID);                    if(cursor == null){                        logt("bt transfer monitering failed, cursor null.");                        break;                    } else {                        for(cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()){                            if(cursor.getInt(cursor.getColumnIndex(BluetoothShare._ID)) == id){                                break;                            }                        }                        //logt(buildBtCursorInfo(cursor));                        int status = cursor.getInt(cursor.getColumnIndex(BluetoothShare.STATUS));                        if (BluetoothShare.isStatusCompleted(status)) {                            if (BluetoothShare.isStatusSuccess(status)) {                                success = true;                                logt("Status Success.");                            } else if (BluetoothShare.isStatusError(status)) {                                if (BluetoothShare.isStatusClientError(status)) {                                    logt("Status Client Error.");                                } else if (BluetoothShare.isStatusServerError(status)) {                                    logt("Status Server Error.");                                } else {                                    logt("Status Error");                                }                            } else {                                logt("Status Completed.");                            }                            break;                        } else if (BluetoothShare.isStatusInformational(status)) {                            //logt("Status Informational.");                        } else if (BluetoothShare.isStatusSuspended(status)) {                            logt("Status Suspended.");                        } else {                            logt("Status = " + status);                        }                    }                    if(System.currentTimeMillis() - start >= 10*60*1000){//十分钟超时                        break;                    }                    try{                        Thread.sleep(500);                    }catch (InterruptedException e){                        e.printStackTrace();                        logt(e);                    }                }                if (cursor != null) {                    cursor.close();                }                if (direction == BluetoothShare.DIRECTION_OUTBOUND) {//发送文件结束                    String res = buildBtMessage(success ? TcpConfig.BT_COPY_FILE : TcpConfig.BT_DELETE_FILE, targetFileSend.getName());                    if (!TextUtils.isEmpty(res)) {                        sendMessage(res);                    }                    if (targetFileSend != null && targetFileSend.exists()) {//删除压缩包                        targetFileSend.delete();                        targetFileSend = null;                    }                } else {//接收文件结束                    if (targetFileReceive != null && targetFileReceive.exists()) {//把目标文件（apk升级包）剪切至Download目录                        if (success) {                            ShellUtil.execCommand("cp " + targetFileReceive.getAbsolutePath() + " " + FileConfig.FILE_DOWNLOAD + targetFileReceive.getName(), false);                            //FileUtil.copyFile(targetFileReceive.getAbsolutePath(), FileConfig.FILE_DOWNLOAD + targetFileReceive.getName(), false);                        }                        sendMessage(buildBtMessage(TcpConfig.BT_SEND_APK, success ? "成功" : "失败"));                        targetFileReceive.delete();                        targetFileReceive = null;                    }                }                logt("bt Transfer Monitor Thread quit. Duration time = "                        + getSimpleFormat(System.currentTimeMillis() - start));            }            private void logt(Object o) {                logd("Thread_" + Thread.currentThread().getId() + ":" + o);            }        }).start();    }    public String getSimpleFormat(long cost){        if (cost >= 60 * 60 * 1000) {            return String.valueOf(UniversalUtil.getDoubleFomat((float) cost / (60 * 60 * 1000), 3)) + " h";        } else if (cost >= 60 * 1000) {            return String.valueOf(UniversalUtil.getDoubleFomat((float) cost / (60 * 1000), 3)) + " min";        } else if(cost>=1000){            return String.valueOf(UniversalUtil.getDoubleFomat((float) cost / 1000, 3)) + " s";        } else {            return String.valueOf(cost) + "ms";        }    }

以上实现方案，纯属自行研究结果，如有更优方案，欢迎交流指教。
根据实测经验，蓝牙传输的速率，相比于热点连接，会慢很多。