純手寫實現極簡方式 BLE 開發，並適度封裝。實現掃描、連接、發送、接收等功能
下面帶大家從 0 實現基本的 BLE 開發。文末提供 git 完整源碼。
權限
進行藍牙相關操作，需要使用到藍牙權限，在AndroidManifest.xml清單文件中添加相應權限
<uses-feature
android:name="android.hardware.bluetooth_le"
android:required="true" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
在 android6.0 以後，藍牙BLE還需要需要獲得位置權限
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
這個位置權限，需要動態申請
/**
* 請求位置權限
*
* @param activity 上下文
* @return boolean
*/
public static boolean isGrantLocationPermission(Activity activity) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && activity.checkSelfPermission(
Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
activity.requestPermissions(new String[]{
Manifest.permission.ACCESS_FINE_LOCATION,
Manifest.permission.ACCESS_COARSE_LOCATION,
}, GROUP_LOCATION);
return false;
}
return true;
}
初始化藍牙 Adapter
final BluetoothManager bluetoothManager =
(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
if (bluetoothManager != null){
mBluetoothAdapter = bluetoothManager.getAdapter();
}
判斷藍牙是否可用或者是否開啓，如果藍牙關閉，那麼開啓藍牙
if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, 1);
}
掃描
掃描過程中，需要對掃描結果進行回調，在 onLeScan(）方法中對掃描的結果進行相關處理
private BluetoothDevice mDevice;
final BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() {
@Override
public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
Log.d("haha", "onLeScan: " + device.getName() + " : " + rssi);
String name = device.getName();
if (name != null) {
deviceName.setText(name);
if (name.equals("test_ble")) {// 或者比較 mac 地址
mDevice = device;
mBluetoothAdapter.stopLeScan(mLeScanCallback);
}
}
}
};
由於藍牙掃描耗時耗電，所以在進行掃描的時候，注意自定義一個合適的掃描時間，在實際的開發和項目應用過程中，自己選擇合適的時間。定義好藍牙掃描回調，開始掃描藍牙，掃描到想要的藍牙，就可以停止掃描
private void scanLeDevice(final boolean enable) {
if (enable) {
// Stops scanning after a pre-defined scan period.
// 預先定義停止藍牙掃描的時間（因爲藍牙掃描需要消耗較多的電量）
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
mScanning = false;
mBluetoothAdapter.stopLeScan(mLeScanCallback);
}
}, 30000);
mScanning = true;
// 定義一個回調接口供掃描結束處理
mBluetoothAdapter.startLeScan(mLeScanCallback);
} else {
mScanning = false;
mBluetoothAdapter.stopLeScan(mLeScanCallback);
}
}
通過獲取的 mBluetoothAdapter 調用 startLeScan() 傳入 mLeScanCallback 參數，即可進行藍牙掃描。
BluetoothGattCallback 實現
GATT 是用於發送和接收的通用規範， BLE 之間的文件數據傳輸基於 GATT，因此在進行連接之前，需要進行Gatt接口回調。
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
if (connectChangedListener != null) {
connectChangedListener.onConnected();
}
mConnectionState = STATE_CONNECTED;
sendBroadcast(connectSuccess, "連接成功");
mBluetoothGatt.discoverServices();
} else if (newState == BluetoothProfile.STATE_DISCONNECTED
|| status != BluetoothGatt.GATT_SUCCESS) {
if (connectChangedListener != null) {
connectChangedListener.onDisconnected();
sendBroadcast(connectFail, "連接失敗");
}
mConnectionState = STATE_DISCONNECTED;
// 重置
gatt.close();
close();
// 重連操作 todo
connect(MAC);
}
Log.d(TAG, "連接狀態:" + mConnectionState);
}
@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
Log.d(TAG, "onServicesDiscovered: " + "發現服務 : status = " + status);
//成功
isServiceConnected = true;
if (mBluetoothGatt != null) {
BluetoothGattService gattService = mBluetoothGatt.getService(serviceUuid);
BluetoothGattCharacteristic characteristic = gattService
.getCharacteristic(notifyUuid);
boolean b = mBluetoothGatt.setCharacteristicNotification(characteristic, true);
if (b) {
List<BluetoothGattDescriptor> descriptors = characteristic.getDescriptors();
for (BluetoothGattDescriptor descriptor : descriptors) {
boolean b1 = descriptor
.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
if (b1) {
mBluetoothGatt.writeDescriptor(descriptor);
Log.d(TAG, "描述 UUID :" + descriptor.getUuid().toString());
}
}
Log.d(TAG, "startRead: " + "監聽接收數據開始");
}
}
} else {
Log.w(TAG, "onServicesDiscovered : 發現服務異常 status = " + status);
}
}
@Override
public void onCharacteristicChanged(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic) {
Log.d(TAG, "onCharacteristicChanged: 接收數據成功,value =" + HexUtil
.bytesToHexString(characteristic.getValue()));
// parseData(characteristic);
sendBroadcast(notifyAction, HexUtil.bytesToHexString(characteristic.getValue()));
}
@Override
public void onDescriptorWrite(BluetoothGatt gatt,
BluetoothGattDescriptor descriptor, int status) {
super.onDescriptorWrite(gatt, descriptor, status);
Log.d(TAG, "onDescriptorWrite: " + "設置成功");
}
@Override
public void onCharacteristicWrite(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicWrite(gatt, characteristic, status);
Log.d(TAG, "onCharacteristicWrite: " + "發送數據成功，value = " + HexUtil
.bytesToHexString(characteristic.getValue()));
sendBroadcast(writeSuccessAction, HexUtil.bytesToHexString(characteristic.getValue()));
}
};
通過status對當前連接進行判斷，當status != BluetoothGatt.GATT_SUCCESS時，可以進行Gatt的重置操作，嘗試重連。當newState == BluetoothProfile.STATE_CONNECTED時，此時連接成功。
連接
/**
* Connects to the GATT server hosted on the Bluetooth LE device.
*
* @param address The device address of the destination device.
*/
public void connect(final String address) {
if (mBluetoothAdapter == null || address == null) {
Log.w(TAG, " --------- BluetoothAdapter not initialized or unspecified address. --------- ");
return;
}
final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
Log.w(TAG, " --------- Device not found. Unable to connect. --------- ");
return;
}
mBluetoothGatt = device.connectGatt(context, true, mGattCallback);
Log.d(TAG, " --------- Trying to create a new connection. --------- ");
mConnectionState = STATE_CONNECTING;
}
發現服務
在連接成功後，可以通過 Gatt 進行 discoverServices()
if (newState == BluetoothProfile.STATE_CONNECTED) {
if (connectChangedListener != null) {
connectChangedListener.onConnected();
}
mConnectionState = STATE_CONNECTED;
sendBroadcast(connectSuccess, "連接成功");
mBluetoothGatt.discoverServices();
}
在 mGattCallback 回調添加 Servicest 的相關回調
//發現服務回調。
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
Log.d("haha", "onServicesDiscovered: " + "發現服務 : " + status);
if (status == BluetoothGatt.GATT_SUCCESS) {
//成功
}
}
讀寫開關
當返回的 status == BluetoothGatt.GATT_SUCCESS 時，進行讀寫以及通知相關的操作， 調用 writeDescriptor()，注意設置 setValue 爲 ENABLE_NOTIFICATION_VALUE，否則可能後續讀取不到數據。
@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
Log.d(TAG, "onServicesDiscovered: " + "發現服務 : status = " + status);
//成功
isServiceConnected = true;
if (mBluetoothGatt != null) {
BluetoothGattService gattService = mBluetoothGatt.getService(serviceUuid);
BluetoothGattCharacteristic characteristic = gattService.getCharacteristic(notifyUuid);
boolean b = mBluetoothGatt.setCharacteristicNotification(characteristic, true);
if (b) {
List<BluetoothGattDescriptor> descriptors = characteristic.getDescriptors();
for (BluetoothGattDescriptor descriptor : descriptors) {
boolean b1 = descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
if (b1) {
mBluetoothGatt.writeDescriptor(descriptor);
Log.d(TAG, "描述 UUID :" + descriptor.getUuid().toString());
}
}
Log.d(TAG, "startRead: " + "監聽接收數據開始");
}
}
} else {
Log.w(TAG, "onServicesDiscovered : 發現服務異常 status = " + status);
}
}
設置成功，會在 onDescriptorWrite 方法進行回調，注意 服務 UUID， 特徵值UUID，通知 UUID，可以詢問公司固件端的開發人員，和開發人員配合修改。
@Override
public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status{
super.onDescriptorWrite(gatt, descriptor, status);
Log.d(TAG, "onDescriptorWrite: " + "設置成功");
}
發送數據
/**
* 發送數據
*
* @param value 指令
* @param writeCallback 發送回調
*/
public void writeBuffer(String value, OnWriteCallback writeCallback) {
if ((mBluetoothGatt != null) && (isServiceConnected)) {
BluetoothGattService gattService = mBluetoothGatt.getService(serviceUuid);
BluetoothGattCharacteristic characteristic = gattService.getCharacteristic(writeUuid);
characteristic.setValue(HexUtil.hexStringToBytes(value));
characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
boolean b = mBluetoothGatt.writeCharacteristic(characteristic);
if (b) {
if (writeCallback != null) {
writeCallback.onSuccess();
}
} else {
sendBroadcast(writeFailedAction, "發送失敗");
}
}
}
讀取數據
讀取數據在 onCharacteristicChanged 方法中，注意進制間的轉換。
@Override
public void onCharacteristicChanged(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic) {
Log.d(TAG, "onCharacteristicChanged: 接收數據成功,value =" + HexUtil
.bytesToHexString(characteristic.getValue()));
// parseData(characteristic);
sendBroadcast(notifyAction, HexUtil.bytesToHexString(characteristic.getValue()));
}
斷開操作
/**
* After using a given BLE device, the app must call this method to ensure resources are
* released properly.
*/
public void close() {
if (mBluetoothGatt == null) {
return;
}
mBluetoothGatt.disconnect();
mBluetoothGatt.close();
mBluetoothGatt = null;
}
注意事項
- BLE 實現android 4.3 以後 google 才提供了支持，所以Ble項目只可運行在 API 18 以上的手機；Android 6.0 以上，Ble 服務還需要定位權限，並且需要動態申請，否則使用不了。不使用時，還應注意對藍牙進行關閉或斷開操作，由於 Ble 連接屬於獨佔操作，有設備連接上了，其它設備是無法進行任何操作的。
- 一定要進行讀寫開關操作，注意 descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE)，否則可能讀取不到數據。
遇到的問題
Android BLE 藍牙onCharacteristicChanged 方法不調用
參考裏面的終結回答。本文用的就是這種方式。
源碼
參考 & 感謝
