Android 蓝牙4.0（BLE）开发实现对蓝牙的写入数据和读取数据

由于最近学校组织了一个移动APP（安卓）设计大赛，自己也学习安卓有一段时间了，就跟同学商量一起去参加试试，一拍即合，然后我们就开始想idea，因为最近可穿戴设备比较火，我们也就想试试。经过商量，我负责Android上位机的开发，同学负责下位机的开发。

上位机的开发主要是低功耗蓝牙BLE的开发，然后就开始找资料，各种找，最后谷歌官方提供的demo还有其他网友基于官方demo修改的demo，结合网上的博客对demo进行理解。刚开始是觉得看起来有点费劲，各种广播，跳来跳去的，刚开始就晕菜了。但是经过三四天的理解，算是把官方的demo理解了。

代码基本上都是官方的demo，只是通过修改获得自己想要的结果，下面就简单介绍一下自己的理解。

一、扫描BLE设备activity

检查该设备是否支持BLE设备，谷歌在Android4.3才开始支持BLE设备（晕死，很长一段时间都没有一台4.3的设备，看着程序修改了也不能测试！）。

 if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
            Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
            finish();
        }

初始化获得一个bluetoothManager，并检测设备是否支持蓝牙

final BluetoothManager bluetoothManager =
                (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        mBluetoothAdapter = bluetoothManager.getAdapter();

// Checks if Bluetooth is supported on the device.
        if (mBluetoothAdapter == null) {
            Toast.makeText(this, R.string.error_bluetooth_not_supported, Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

扫描BLE设备，然后添加到listView里面。

private void scanLeDevice(final boolean enable) {
        if (enable) {
            // Stops scanning after a pre-defined scan period.
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    mScanning = false;
                    mBluetoothAdapter.stopLeScan(mLeScanCallback);
                    invalidateOptionsMenu();
                }
            }, SCAN_PERIOD);

            mScanning = true;
            mBluetoothAdapter.startLeScan(mLeScanCallback);
        } else {
            mScanning = false;
            mBluetoothAdapter.stopLeScan(mLeScanCallback);
        }
        invalidateOptionsMenu();
    }

二、蓝牙控制的服务BluetoothLeService

在这个服务里面有一个很重要的回调函数BluetoothGattCallback()，蓝牙的数据读取和状态改变都会回调这个函数。

private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
        @Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            String intentAction;
          //收到设备notify值 （设备上报值）
            if (newState == BluetoothProfile.STATE_CONNECTED) {
                intentAction = ACTION_GATT_CONNECTED;
                mConnectionState = STATE_CONNECTED;
                broadcastUpdate(intentAction);
                Log.i(TAG, "Connected to GATT server.");
                // Attempts to discover services after successful connection.
                Log.i(TAG, "Attempting to start service discovery:" +
                        mBluetoothGatt.discoverServices());

            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                intentAction = ACTION_GATT_DISCONNECTED;
                mConnectionState = STATE_DISCONNECTED;
                Log.i(TAG, "Disconnected from GATT server.");
                broadcastUpdate(intentAction);
            }
        }

        @Override
        public void onServicesDiscovered(BluetoothGatt gatt, int status) {
            if (status == BluetoothGatt.GATT_SUCCESS) {
                broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
            } else {
                Log.w(TAG, "onServicesDiscovered received: " + status);
                System.out.println("onServicesDiscovered received: " + status);
            }
        }

        @Override
        public void onCharacteristicRead(BluetoothGatt gatt,
                                         BluetoothGattCharacteristic characteristic,
                                         int status) {
        	//读取到值，在这里读数据
            if (status == BluetoothGatt.GATT_SUCCESS) {
                broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
            }
        }

        @Override
        public void onCharacteristicChanged(BluetoothGatt gatt,
                                            BluetoothGattCharacteristic characteristic) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }
    };

在官方的demo中还使用到广播，可能是因为人大神写的，要严谨些。我一开始看的时候就得这有点麻烦，跳转的多麻烦。

private void broadcastUpdate(final String action) {
        final Intent intent = new Intent(action);
        sendBroadcast(intent);
    }

    private void broadcastUpdate(final String action,
                                 final BluetoothGattCharacteristic characteristic) {
        final Intent intent = new Intent(action);

        // This is special handling for the Heart Rate Measurement profile.  Data parsing is
        // carried out as per profile specifications:
        // http://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml
        if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
            int flag = characteristic.getProperties();
            int format = -1;
            if ((flag & 0x01) != 0) {
                format = BluetoothGattCharacteristic.FORMAT_UINT16;
                Log.d(TAG, "Heart rate format UINT16.");
            } else {
                format = BluetoothGattCharacteristic.FORMAT_UINT8;
                Log.d(TAG, "Heart rate format UINT8.");
            }
            final int heartRate = characteristic.getIntValue(format, 1);
            Log.d(TAG, String.format("Received heart rate: %d", heartRate));
            intent.putExtra(EXTRA_DATA, String.valueOf(heartRate));
        } else {
            // For all other profiles, writes the data formatted in HEX.对于所有的文件，写入十六进制格式的文件
        	//这里读取到数据
            final byte[] data = characteristic.getValue();
            for (int i = 0; i < data.length; i++) {
				System.out.println("data......" + data[i]);
			}
            if (data != null && data.length > 0) {
                final StringBuilder stringBuilder = new StringBuilder(data.length);
                for(byte byteChar : data)
                	//以十六进制的形式输出
                    stringBuilder.append(String.format("%02X ", byteChar));
               // intent.putExtra(EXTRA_DATA, new String(data) + "\n" + stringBuilder.toString());
                intent.putExtra(EXTRA_DATA, new String(data));
            }
        }
        sendBroadcast(intent);
    }

发送了广播之后就肯定有广播接收器，这个是在控制蓝牙的activity中，后面再说。

还有几个重要的函数比如readCharacteristic(BluetoothGattCharacteristic characteristic)函数，读取蓝牙中数据。

public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return;
        }
        mBluetoothGatt.readCharacteristic(characteristic);
    }

有readCharacteristic(BluetoothGattCharacteristic characteristic)函数，当然就有writeCharacteristic(BluetoothGattCharacteristic characteristic)，向蓝牙中写入数据。

  public void writeCharacteristic(BluetoothGattCharacteristic characteristic) {
        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return;
        }
        mBluetoothGatt.writeCharacteristic(characteristic);
    }

另外在这个service中还有其他的一些函数例如初始化initialize()函数、连接蓝牙函数connect(final String address)、断开蓝牙连接函数disconnect()等。
三、蓝牙控制DeviceControlActivity

扫描到蓝牙设备之后就是对蓝牙进行自己需要的控制，比如写数据，读数据，获取设备信息，设备电量等。

在Service中讲到有一个广播，广播接收器就在这个activity中，通过不同的action做出相应的操作。

注册的几种事件

 private static IntentFilter makeGattUpdateIntentFilter() {
        final IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_CONNECTED);
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_DISCONNECTED);
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED);
        intentFilter.addAction(BluetoothLeService.ACTION_DATA_AVAILABLE);
        return intentFilter;
    }

// Handles various events fired by the Service.处理服务所激发的各种事件
    // ACTION_GATT_CONNECTED: connected to a GATT server.连接一个GATT服务
    // ACTION_GATT_DISCONNECTED: disconnected from a GATT server.从GATT服务中断开连接
    // ACTION_GATT_SERVICES_DISCOVERED: discovered GATT services.查找GATT服务
    // ACTION_DATA_AVAILABLE: received data from the device.  This can be a result of read
    //                        or notification operations.从服务中接受数据
    private final BroadcastReceiver mGattUpdateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            final String action = intent.getAction();
            if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action)) {
                mConnected = true;
                updateConnectionState(R.string.connected);
                invalidateOptionsMenu();
            } else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {
                mConnected = false;
                updateConnectionState(R.string.disconnected);
                invalidateOptionsMenu();
                clearUI();
            } 
            //发现有可支持的服务
            else if (BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED.equals(action)) {
            	//写数据的服务和characteristic
            	mnotyGattService = mBluetoothLeService.getSupportedGattServices(UUID.fromString("0000ffe5-0000-1000-8000-00805f9b34fb"));
                characteristic = mnotyGattService.getCharacteristic(UUID.fromString("0000ffe9-0000-1000-8000-00805f9b34fb"));
                //读数据的服务和characteristic
                readMnotyGattService = mBluetoothLeService.getSupportedGattServices(UUID.fromString("0000ffe0-0000-1000-8000-00805f9b34fb"));
                readCharacteristic = readMnotyGattService.getCharacteristic(UUID.fromString("0000ffe4-0000-1000-8000-00805f9b34fb"));
            } 
            //显示数据
            else if (BluetoothLeService.ACTION_DATA_AVAILABLE.equals(action)) {
            	//将数据显示在mDataField上
            	String data = intent.getStringExtra(BluetoothLeService.EXTRA_DATA);
            	System.out.println("data----" + data);
                displayData(data);
            }
        }
    };    

在发现了有可支持的服务之后会回调Service中的onServicesDiscovered()函数，并发送广播，在官方的demo中发现了可用的Service之后，就查找该BLE设备支持的所有服务和characteristic，在这里不需要查找所有的服务，只需要向蓝牙写数据和读取数据的 Service和characteristic的UUID即可。通过查询低功耗蓝牙（BLE）的数据手册可以得到所需要的UUID。

有了这两个Service和characteristic的UUID，就可以对蓝牙发送数据，并发出通知（当写数据发生改变时发出）。

//写数据的服务和characteristic
            	mnotyGattService = mBluetoothLeService.getSupportedGattServices(UUID.fromString("0000ffe5-0000-1000-8000-00805f9b34fb"));
                characteristic = mnotyGattService.getCharacteristic(UUID.fromString("0000ffe9-0000-1000-8000-00805f9b34fb"));
                //读数据的服务和characteristic
                readMnotyGattService = mBluetoothLeService.getSupportedGattServices(UUID.fromString("0000ffe0-0000-1000-8000-00805f9b34fb"));
                readCharacteristic = readMnotyGattService.getCharacteristic(UUID.fromString("0000ffe4-0000-1000-8000-00805f9b34fb"));

得到这两个Service和characteristic就可以向蓝牙发送数据了。

private void read() {
    	//mBluetoothLeService.readCharacteristic(readCharacteristic);
    	//readCharacteristic的数据发生变化，发出通知
    	mBluetoothLeService.setCharacteristicNotification(readCharacteristic, true);
    	//Toast.makeText(this, "读成功", Toast.LENGTH_SHORT).show();
	}

检测readCharacteristic的数据发生变化，发出通知。

向蓝牙发送数据。

read();
				
                final int charaProp = characteristic.getProperties();
                
                //如果该char可写
                if ((charaProp | BluetoothGattCharacteristic.PROPERTY_READ) > 0) {
                    // If there is an active notification on a characteristic, clear
                    // it first so it doesn't update the data field on the user interface.
                    if (mNotifyCharacteristic != null) {
                        mBluetoothLeService.setCharacteristicNotification( mNotifyCharacteristic, false);
                        mNotifyCharacteristic = null;
                    }
                    //读取数据，数据将在回调函数中
                    //mBluetoothLeService.readCharacteristic(characteristic);
                    byte[] value = new byte[20];
                    value[0] = (byte) 0x00;
                    if(edittext_input_value.getText().toString().equals("")){
                    	Toast.makeText(getApplicationContext(), "请输入！", Toast.LENGTH_SHORT).show();
                    	return;
                    }else{
                    	WriteBytes = edittext_input_value.getText().toString().getBytes();
                    	characteristic.setValue(value[0],BluetoothGattCharacteristic.FORMAT_UINT8, 0);
                        characteristic.setValue(WriteBytes);
                        mBluetoothLeService.writeCharacteristic(characteristic);
                        Toast.makeText(getApplicationContext(), "写入成功！", Toast.LENGTH_SHORT).show();
                    }
                }
                if ((charaProp | BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
                    mNotifyCharacteristic = characteristic;
                    mBluetoothLeService.setCharacteristicNotification(characteristic, true);
                }
                edittext_input_value.setText("");
			}

一旦数据发生改变，就会发出通知，通知发出后就会调用下面的函数并发出广播。

 @Override
        public void onCharacteristicChanged(BluetoothGatt gatt,
                                            BluetoothGattCharacteristic characteristic) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }

在广播接收器中接收到广播后，把数据显示在EditText上。下面是测试的两张图片。

demo下载地址：BLE 读写