实现一个Android APP主要需求：

1、APP连接蓝牙转以太网的转接板给底板配置广播信息；

2、广播板的状态能通过蓝牙转接板透传给APP；

蓝牙搜索，发现这些之前一个app都做过，但是读写数据没有做，关键点是：

1、GATT连接；

2、服务特征UUID/读特征UUID 配置特征UUID/写特征UUID，这几个特征UUID 最好是找厂家确认。

要接收到蓝牙的数据，关键是读配置Enable功能：setBleNotification方法，网上这块有很多方法，最后生效的是下面的方法。

@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
    if (status == BluetoothGatt.GATT_SUCCESS) {
        // services are discoverd
        Log.d(TAG, "onServicesDiscovered: GATT_SUCCESS");
        mBluetoothGatt = gatt;
    }

    List<BluetoothGattService> list = gatt.getServices();
    for(BluetoothGattService service: list){
        serviceUid = service.getUuid();
        for(BluetoothGattCharacteristic characteristic : service.getCharacteristics()){
            //获取到相应的服务UUID和特征UUID
            characterUid = characteristic.getUuid();
            if (characterUid.toString().contains("8e32")){
                //readd
                characterReadUid = characterUid;
                m_bluetoothGattCharacteristic_read = characteristic;
                gatt.setCharacteristicNotification(characteristic, true);
            }
            if (characterUid.toString().contains("8e40")){
                //write
                characterWriteUid = characterUid;
            }
            if (characterUid.toString().contains("2902")){
                //read config
                characterReadConfigUid = characterUid;
            }
        }
        if (serviceUid.toString().contains("8e20")){
            break;
        }
    }
    gatt.requestMtu(200);
}

//关键是这个方法，网上的说法很多，但是最后生效的还是下面的方法
private void setBleNotification(){

            if (characterReadConfigUid == null){
                characterReadConfigUid = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
            }
            BluetoothGattService service = mBluetoothGatt.getService(serviceUid);
            if(m_bluetoothGattCharacteristic_read != null) {

                List<BluetoothGattDescriptor> descriptors = m_bluetoothGattCharacteristic_read.getDescriptors();
                Log.v(TAG, "len:"+descriptors.size());
                // 遍历设置 BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE 值 , 并写出
                for(BluetoothGattDescriptor descriptor : descriptors) {
                    descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
                    mBluetoothGatt.writeDescriptor(descriptor);
                }
//                BluetoothGattDescriptor descriptor = m_bluetoothGattCharacteristic_read.getDescriptor(characterReadConfigUid);
//                descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
//                mBluetoothGatt.writeDescriptor(descriptor);
//                descriptor.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
//                mBluetoothGatt.writeDescriptor(descriptor);
                mBluetoothGatt.readCharacteristic(m_bluetoothGattCharacteristic_read);
            }
        }

3、写完成的回调；

写需要设置最大MTU，否则大于MTU的字符串发不出去

@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
    if (status == BluetoothGatt.GATT_SUCCESS) {
        // services are discoverd
        Log.d(TAG, "onServicesDiscovered: GATT_SUCCESS");
        mBluetoothGatt = gatt;
    }
    gatt.requestMtu(200);
}
@Override
public void onMtuChanged(BluetoothGatt gatt, int mtu, int status) {
    Log.v(TAG, "onMtuChanged:"+status + ",mtu:"+mtu);
    if(status == BluetoothGatt.GATT_SUCCESS){
        setBleNotification();
    }
}

4、读数据的回调函数；onCharacteristicChanged 蓝牙收到数据的回调方法，网上有说是onCharacteristicRead方法，实际是这个。

@Override
public void onCharacteristicChanged(BluetoothGatt gatt,
                                    BluetoothGattCharacteristic characteristic) {

    if (characteristic.getUuid().equals(characterReadUid)) {
        //step 7-1:读取出characteristic的value值
        // 收到的数据
        byte[] receiveByte = characteristic.getValue();
        String res = new String(receiveByte);
        Log.i(TAG, "=====>2 value =" + res + ",len:" + receiveByte.length);
        if (notifyCallback != null){
            notifyCallback.notifyMessage(res);
        }
    }
}

5、蓝牙转接板居然还有一个NAT的问题，蓝牙转接板主动转发过来的UDP包，必须使用相同的端口回过去，否则转接板收不到包。

6、主要代码：

GattCommnucationManage.java代码

import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattDescriptor;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothProfile;
import android.content.Context;
import android.util.Log;

import java.util.List;
import java.util.UUID;

import top.keepempty.MyApplication;

public class GattCommnucationManager {

    static GattCommnucationManager instanceGattMgr = new GattCommnucationManager();
    private BluetoothDevice selectBleDevice;
    private Context mContext;
    public static final String  TAG = "GattCommnucationManager";
    BluetoothGatt mBluetoothGatt;
    private UUID  serviceUid;
    private UUID characterUid;
    private UUID characterReadUid;
    private UUID characterReadConfigUid;
    private UUID characterWriteUid;
    private BleMessageNotify notifyCallback;

    private GattCommnucationManager(){
    }
    public static GattCommnucationManager getInstance(){
        if (instanceGattMgr == null){
            instanceGattMgr = new GattCommnucationManager();
        }
        return instanceGattMgr;
    }

    public void registerInterface(BleMessageNotify callback){
        notifyCallback = callback;
    }

    public void setDevice(BluetoothDevice device){
        mContext = MyApplication.getInstance();
        if (selectBleDevice != null && mBluetoothGatt != null){
            mBluetoothGatt.disconnect();
            mBluetoothGatt.close();
            mBluetoothGatt = null;
        }
        selectBleDevice = device;

        connectSelectDevice();
    }

    public void connectSelectDevice(){
        if (selectBleDevice == null){
            return;
        }
        mBluetoothGatt = selectBleDevice.connectGatt(mContext, false, mGattCallback);
    }

    //关闭蓝牙和Gatt输入通道 避免出现Gatt 133状态错误

    public void closeBlueToothGatt(){
        if (mBluetoothGatt == null){
            return;
        }
        mBluetoothGatt.disconnect();
        mBluetoothGatt.close();

        mBluetoothGatt = null;
        selectBleDevice = null;

    }
    /**
     * 向设备发送数据
     * @param value
     * @return
     */
    public boolean writeRXCharacteristic(byte[] value) {
        if (mBluetoothGatt == null){
            return false;
        }
        BluetoothGattService rxService = mBluetoothGatt.getService(serviceUid);
        if (rxService == null) {
            //Service not supported
            Log.d(TAG, "writeRXCharacteristic: Service not supported");
            return false;
        }
        BluetoothGattCharacteristic rxChar = rxService.getCharacteristic(characterWriteUid);
        if (rxChar == null) {
            // service not supported
            Log.d(TAG, "writeRXCharacteristic: Service not supported");
            return false;
        }
        rxChar.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
        rxChar.setValue(value);
        Log.d(TAG, "writeRXCharacteristic: "+String.valueOf(rxChar));
        return mBluetoothGatt.writeCharacteristic(rxChar);
    }

    public  final UUID DEVICE_INFO_SERVICE_UUID = UUID.fromString("00001800-0000-1000-8000-00805f9b34fb");
    //Charcteristic UUID
    public  final UUID VID_PID_CHARACTERISTIC_UUID = UUID.fromString("00002a00-0000-1000-8000-00805f9b34fb");

    BluetoothGattCharacteristic m_bluetoothGattCharacteristic_read;

    /**
     * 连接成功或者失败的回调函数
     */
    public final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
        @Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            Log.d(TAG, "onConnectionStateChange: "+newState);

            if (newState == BluetoothProfile.STATE_CONNECTED) {
                //bluetooth is connected so discover services
                Log.d(TAG, "onConnectionStateChange: "+mBluetoothGatt.getDevice().getName());
                mBluetoothGatt.discoverServices();

            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                //Bluetooth is disconnected
                Log.d(TAG, "onConnectionStateChange: disconnected");
                mBluetoothGatt = null;
            }
        }

        private void setBleNotification(){

            if (characterReadConfigUid == null){
                characterReadConfigUid = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
            }
            BluetoothGattService service = mBluetoothGatt.getService(serviceUid);
            if(m_bluetoothGattCharacteristic_read != null) {

                List<BluetoothGattDescriptor> descriptors = m_bluetoothGattCharacteristic_read.getDescriptors();
                Log.v(TAG, "len:"+descriptors.size());
                // 遍历设置 BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE 值 , 并写出
                for(BluetoothGattDescriptor descriptor : descriptors) {
                    descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
                    mBluetoothGatt.writeDescriptor(descriptor);
                }
//                BluetoothGattDescriptor descriptor = m_bluetoothGattCharacteristic_read.getDescriptor(characterReadConfigUid);
//                descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
//                mBluetoothGatt.writeDescriptor(descriptor);
//                descriptor.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
//                mBluetoothGatt.writeDescriptor(descriptor);
                mBluetoothGatt.readCharacteristic(m_bluetoothGattCharacteristic_read);
            }
        }

        @Override
        public void onMtuChanged(BluetoothGatt gatt, int mtu, int status) {
            Log.v(TAG, "onMtuChanged:"+status + ",mtu:"+mtu);
            if(status == BluetoothGatt.GATT_SUCCESS){
                setBleNotification();
            }
        }
        @Override
        public void onServicesDiscovered(BluetoothGatt gatt, int status) {
            if (status == BluetoothGatt.GATT_SUCCESS) {
                // services are discoverd
                Log.d(TAG, "onServicesDiscovered: GATT_SUCCESS");
                mBluetoothGatt = gatt;
            }

            List<BluetoothGattService> list = gatt.getServices();
            for(BluetoothGattService service: list){
                serviceUid = service.getUuid();
                for(BluetoothGattCharacteristic characteristic : service.getCharacteristics()){
                    //获取到相应的服务UUID和特征UUID
                    characterUid = characteristic.getUuid();
                    if (characterUid.toString().contains("8e32")){
                        //readd
                        characterReadUid = characterUid;
                        m_bluetoothGattCharacteristic_read = characteristic;
                        gatt.setCharacteristicNotification(characteristic, true);
                    }
                    if (characterUid.toString().contains("8e40")){
                        //write
                        characterWriteUid = characterUid;
                    }
                    if (characterUid.toString().contains("2902")){
                        //read config
                        characterReadConfigUid = characterUid;
                    }
                }
                if (serviceUid.toString().contains("8e20")){
                    break;
                }
            }
            gatt.requestMtu(200);
        }
        @Override
        public void onCharacteristicRead(BluetoothGatt gatt,
                                         BluetoothGattCharacteristic characteristic,
                                         int status) {
            if (status == BluetoothGatt.GATT_SUCCESS) {
                String value = "";
                if (characteristic.getUuid().equals(characterReadUid))
                {
                    //step 7-1:读取出characteristic的value值
                    // 收到的数据
                    byte[] receiveByte = characteristic.getValue();
                    Log.i(TAG, "=====>读取到 value =" +String.valueOf(receiveByte) + ",len:"+receiveByte.length);
                    //step 7-2:此处为ascii表字符，需转换为十进制ascii值
                    //再将十进制ascii值，转换为十六进制
                    //String VID = changeAsciiTo16(value.charAt(0));
                    //String PID = changeAsciiTo16(value.charAt(value.length() - 1));
                    //设备VID、PID读取成功，handle更新主线程界面UI
                    //Log.i(TAG, characteristic.getUuid()+",VID:"+VID+",PID:"+PID);

                }

            }
        }

        @Override
        public void onCharacteristicChanged(BluetoothGatt gatt,
                                            BluetoothGattCharacteristic characteristic) {

            if (characteristic.getUuid().equals(characterReadUid)) {
                //step 7-1:读取出characteristic的value值
                // 收到的数据
                byte[] receiveByte = characteristic.getValue();
                String res = new String(receiveByte);
                Log.i(TAG, "=====>2 value =" + res + ",len:" + receiveByte.length);
                if (notifyCallback != null){
                    notifyCallback.notifyMessage(res);
                }
            }
        }

        @Override
        public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
            super.onCharacteristicWrite(gatt, characteristic, status);

            if (status == BluetoothGatt.GATT_SUCCESS) {
                mBluetoothGatt.readCharacteristic(m_bluetoothGattCharacteristic_read);
            }
        }
    };

    static public interface BleMessageNotify {
        void notifyMessage(String msg);
    }

}