低功耗蓝牙
传统蓝牙
蓝牙发展至今经历了8个版本的更新。1.1、1.2、2.0、2.1、3.0、4.0、4.1、4.2。那么在1.x~3.0之间的我们称之为传统蓝牙,4.x开始的蓝牙我们称之为低功耗蓝牙也就是蓝牙ble,当然4.x版本的蓝牙也是向下兼容的。
Android手机必须系统版本4.3及以上才支持BLE API。通过GATT协议进行BLE设备之间的通信。
优点:传输速度更快,覆盖范围更广,安全性更高,延迟更短,耗电极低等等优点
BLE分为三部分:Service,Characteristic,Descriptor。这三部分都用UUID作为唯一标识符
一个BLE终端可以包含多个Service(服务)
一个Service可以包含多个Characteristic(特征)
一个Characteristic包含一个value和多个Descriptor(描述符),一个Descriptor包含一个Value。
Characteristic是比较重要的,是手机与BLE终端交换数据的关键,读取设置数据等操作都是操作Characteristic的相关属性
接下来讲解开发步骤
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
// 检查当前手机是否支持ble 蓝牙,如果不支持退出程序
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
finish();
}
通过以下两种方式获取
BluetoothManager bluetoothManager =(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
BluetoothAdapter mBluetoothAdapter = bluetoothManager.getAdapter();
或
BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
//如果mBluetoothAdapter == null,说明设备不支持蓝牙
if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
switch (requestCode) {
case REQUEST_ENABLE:
if (resultCode == Activity.REQUEST_ENABLE_BT) {
Toast.makeText(this, "蓝牙已启用", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(this, "蓝牙未启用", Toast.LENGTH_SHORT).show();
}
break;
}
}
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);
}
}, SCAN_PERIOD); //10秒后停止搜索
mScanning = true;
mBluetoothAdapter.startLeScan(mLeScanCallback); //开始搜索
} else {
mScanning = false;
mBluetoothAdapter.stopLeScan(mLeScanCallback);//停止搜索
}
}
private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() {
@Override
public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
runOnUiThread(new Runnable() {
@Override
public void run() {
//在这里可以把搜索到的设备保存起来
//device.getName();获取蓝牙设备名字
//device.getAddress();获取蓝牙设备mac地址
}
});
}
};
代码里建了一个service,里面封装了连接,读写设备等操作。连接是通过获取到的mac地址去进行连接操作就可以了。
BluetoothGatt()下的方法:
connect() :连接远程设备。
discoverServices() : 搜索连接设备所支持的service。
disconnect():断开与远程设备的GATT连接。
close():关闭GATT Client端。
readCharacteristic(characteristic) :读取指定的characteristic。
setCharacteristicNotification(characteristic, enabled) :指定characteristic值变化时,发出通知。
getServices() :获取远程设备所支持的services。
public boolean connect(final String address) {
if (mBluetoothAdapter == null || address == null) {
Log.w(TAG,"BluetoothAdapter not initialized or unspecified address.");
return false;
}
// Previously connected device. Try to reconnect. (先前连接的设备。 尝试重新连接)
if (mBluetoothDeviceAddress != null&& address.equals(mBluetoothDeviceAddress)&& mBluetoothGatt != null) {
Log.d(TAG,"Trying to use an existing mBluetoothGatt for connection.");
if (mBluetoothGatt.connect()) {
mConnectionState = STATE_CONNECTING;
return true;
} else {
return false;
}
}
final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
Log.w(TAG, "Device not found. Unable to connect.");
return false;
}
// We want to directly connect to the device, so we are setting the
// autoConnect
// parameter to false.
mBluetoothGatt = device.connectGatt(this, false, mGattCallback); //该函数才是真正的去进行连接
Log.d(TAG, "Trying to create a new connection.");
mBluetoothDeviceAddress = address;
mConnectionState = STATE_CONNECTING;
return true;
}
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
@Override //当连接上设备或者失去连接时会回调该函数
public void onConnectionStateChange(BluetoothGatt gatt, int status,int newState) {
if (newState == BluetoothProfile.STATE_CONNECTED) { //连接成功
mBluetoothGatt.discoverServices(); //连接成功后就去找出该设备中的服务 private BluetoothGatt mBluetoothGatt;
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) { //连接失败
}
}
@Override //当设备是否找到服务时,会回调该函数
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) { //找到服务了
//在这里可以对服务进行解析,寻找到你需要的服务
} else {
Log.w(TAG, "onServicesDiscovered received: " + status);
}
}
@Override //当读取设备时会回调该函数
public void onCharacteristicRead(BluetoothGatt gatt,BluetoothGattCharacteristic characteristic, int status) {
System.out.println("onCharacteristicRead");
if (status == BluetoothGatt.GATT_SUCCESS) {
//读取到的数据存在characteristic当中,可以通过characteristic.getValue();函数取出。然后再进行解析操作。
//int charaProp = characteristic.getProperties();if ((charaProp | BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0)表示可发出通知。 判断该Characteristic属性
}
}
@Override //当向设备Descriptor中写数据时,会回调该函数
public void onDescriptorWrite(BluetoothGatt gatt,BluetoothGattDescriptor descriptor, int status) {
System.out.println("onDescriptorWriteonDescriptorWrite = " + status + ", descriptor =" + descriptor.getUuid().toString());
}
@Override //设备发出通知时会调用到该接口
public void onCharacteristicChanged(BluetoothGatt gatt,BluetoothGattCharacteristic characteristic) {
if (characteristic.getValue() != null) {
System.out.println(characteristic.getStringValue(0));
}
System.out.println("--------onCharacteristicChanged-----");
}
public void onReadRemoteRssi(BluetoothGatt gatt, int rssi, int status) {
System.out.println("rssi = " + rssi);
}
@Override //当向Characteristic写数据时会回调该函数
public void onCharacteristicWrite(BluetoothGatt gatt,BluetoothGattCharacteristic characteristic, int status) {
System.out.println("--------write success----- status:" + status);
};
}
public List<BluetoothGattService> getSupportedGattServices() {
if (mBluetoothGatt == null)
return null;
return mBluetoothGatt.getServices(); //此处返回获取到的服务列表
}
private void displayGattServices(List<BluetoothGattService> gattServices) {
if (gattServices == null)
return;
for (BluetoothGattService gattService : gattServices) { // 遍历出gattServices里面的所有服务
List<BluetoothGattCharacteristic> gattCharacteristics = gattServices.getCharacteristics();
for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) { // 遍历每条服务里的所有Characteristic
if (gattCharacteristic.getUuid().toString().equalsIgnoreCase(需要通信的UUID)) {
// 有哪些UUID,每个UUID有什么属性及作用,一般硬件工程师都会给相应的文档。我们程序也可以读取其属性判断其属性。
// 此处可以可根据UUID的类型对设备进行读操作,写操作,设置notification等操作
// BluetoothGattCharacteristic gattNoticCharacteristic 假设是可设置通知的Characteristic
// BluetoothGattCharacteristic gattWriteCharacteristic 假设是可读的Characteristic
// BluetoothGattCharacteristic gattReadCharacteristic 假设是可写的Characteristic
}
}
}
}
public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic, boolean enabled) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID
.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
if (descriptor != null) {
System.out.println("write descriptor");
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);
}
}
public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.readCharacteristic(characteristic);
}
public void wirteCharacteristic(BluetoothGattCharacteristic characteristic) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.writeCharacteristic(characteristic);
}