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）。

<span style="font-size:18px;">//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"));</span>

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