在Android中将数据写入蓝牙LE特性 [英] Writing data to Bluetooth LE characteristic in Android
问题描述
尽管已经提出了类似的问题，但它略有不同.我知道如何将数据传递到连接的BLE设备，但我认为我在做错事，需要帮助. 下面的代码包含了我的类中扩展BroadcastReceiver的所有方法.
Although similar questions have been asked but it's slightly different. I know how to pass data to a connected BLE device but I think I'm doing something wrong for which I need help. The code below contains all the methods from my class that is extending BroadcastReceiver.
- 我扫描并连接到"PEN_ADDRESS"指定的设备.
- 在"onServicesDiscovered"方法中，我寻找一个服务，其"UUID"包含"abcd".
- 然后，我遍历此服务的特征，并在其"UUID"中查找带有特定字符串的三个特征.
- 第三个特征是可写特征，其中我试图通过调用方法writeCharac(mGatt，writeChar1,123);来写数据. 上面传递的数据123只是一个伪数据.
- I scan and connect to a device specified by `PEN_ADDRESS`.
- In `onServicesDiscovered` method I look for a service whose `UUID` contains `abcd`.
- Then I loop through the characteristics of this services and look for three characteristics with specific strings in their `UUID`.
- The third characteristic is a writable characteristic in which I'm trying to write data by calling the method `writeCharac(mGatt,writeChar1,123);` The data `123` passed above is just a dummy data.
我尝试编写此特性时调试了代码，但是在将断点放入writeCharac方法中时，发现status值为false，表明写入未成功.
我在这里想念什么吗?请帮忙！
I debugged my code while trying writing to this characteristic but on putting breakpoints inside the writeCharac method, I found that the status value is false, indicating that the write was not successful.
Am I missing something here? Please do help!
public class BackgroundReceiverFire extends BroadcastReceiver {
Context context;
private BluetoothAdapter mBluetoothAdapter;
private BluetoothGatt mGatt;
private BluetoothLeService mBluetoothLeService;
private boolean mScanning;
private final String TAG = "READING: ";
private BluetoothDevice mDevice;
private Handler mHandler;
private static final int REQUEST_ENABLE_BT = 1;
private final String PEN_ADDRESS = "FB:23:AF:42:5C:56";
// Stops scanning after 10 seconds.
private static final long SCAN_PERIOD = 10000;
public void onReceive(Context context, Intent intent) {
this.context = context;
Toast.makeText(context, "Started Scanning", LENGTH_SHORT).show();
initializeBluetooth();
startScan();
}
private void initializeBluetooth() {
mHandler = new Handler();
// Use this check to determine whether BLE is supported on the device. Then you can
// selectively disable BLE-related features.
// Initializes a Bluetooth adapter. For API level 18 and above, get a reference to
// BluetoothAdapter through BluetoothManager.
final BluetoothManager bluetoothManager =
(BluetoothManager) context.getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
// Checks if Bluetooth is supported on the device.
if (mBluetoothAdapter == null) {
Toast.makeText(this.context, "No Bluetooth", LENGTH_SHORT).show();
return;
}
}
private void startScan() {
scanLeDevice(true);
}
private void stopScan() {
scanLeDevice(false);
}
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);
mScanning = true;
//Scanning for the device
mBluetoothAdapter.startLeScan(mLeScanCallback);
} else {
mScanning = false;
mBluetoothAdapter.stopLeScan(mLeScanCallback);
}
}
private BluetoothAdapter.LeScanCallback mLeScanCallback =
new BluetoothAdapter.LeScanCallback() {
@Override
public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {
if (device.getAddress().matches(PEN_ADDRESS)) {
connectBluetooth(device);
Toast.makeText(context, "Device Found: " + device.getAddress(), Toast.LENGTH_LONG).show();
}
}
};
private void connectBluetooth(BluetoothDevice insulinPen) {
if (mGatt == null) {
Log.d("connectToDevice", "connecting to device: " + insulinPen.toString());
mDevice = insulinPen;
mGatt = insulinPen.connectGatt(context, true, gattCallback);
scanLeDevice(false);// will stop after first device detection
}
}
private void enableBluetooth() {
if (!mBluetoothAdapter.isEnabled()) {
mBluetoothAdapter.enable();
}
scanLeDevice(true);
}
private void disableBluetooth() {
if (mBluetoothAdapter.isEnabled()) {
mBluetoothAdapter.disable();
}
}
private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
@Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
Log.i("onConnectionStateChange", "Status: " + status);
switch (newState) {
case BluetoothProfile.STATE_CONNECTED:
gatt.discoverServices();
break;
case BluetoothProfile.STATE_DISCONNECTED:
Log.e("gattCallback", "STATE_DISCONNECTED");
Log.i("gattCallback", "reconnecting...");
BluetoothDevice mDevice = gatt.getDevice();
mGatt = null;
connectBluetooth(mDevice);
break;
default:
Log.e("gattCallback", "STATE_OTHER");
break;
}
}
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
mGatt = gatt;
List<BluetoothGattService> services = mGatt.getServices();
Log.i("onServicesDiscovered", services.toString());
Iterator<BluetoothGattService> serviceIterator = services.iterator();
while(serviceIterator.hasNext()){
BluetoothGattService bleService = serviceIterator.next();
if(bleService.getUuid().toString().contains("abcd")){
//Toast.makeText(context,"Got the service",Toast.LENGTH_SHORT);
BluetoothGattCharacteristic readChar1 = bleService.getCharacteristics().get(0);
for (BluetoothGattDescriptor descriptor : readChar1.getDescriptors()) {
descriptor.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
mGatt.writeDescriptor(descriptor);
mGatt.setCharacteristicNotification(readChar1, true);
}
//mGatt.readCharacteristic(readChar1);
BluetoothGattCharacteristic readChar2 = bleService.getCharacteristics().get(1);
for (BluetoothGattDescriptor descriptor : readChar2.getDescriptors()) {
descriptor.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
mGatt.writeDescriptor(descriptor);
mGatt.setCharacteristicNotification(readChar2, true);
}
//mGatt.readCharacteristic(readChar2);
BluetoothGattCharacteristic writeChar1 = bleService.getCharacteristics().get(2);
for (BluetoothGattDescriptor descriptor : writeChar1.getDescriptors()) {
descriptor.setValue( BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
mGatt.writeDescriptor(descriptor);
mGatt.setCharacteristicNotification(writeChar1, true);
}
writeCharac(mGatt,writeChar1,123);
}
}
//gatt.readCharacteristic(therm_char);
}
public void writeCharac(BluetoothGatt gatt, BluetoothGattCharacteristic charac, int value ){
if (mBluetoothAdapter == null || gatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
/*
BluetoothGattCharacteristic charac = gattService
.getCharacteristic(uuid);
*/
if (charac == null) {
Log.e(TAG, "char not found!");
}
int unixTime = value;
String unixTimeString = Integer.toHexString(unixTime);
byte[] byteArray = hexStringToByteArray(unixTimeString);
charac.setValue(byteArray);
boolean status = mGatt.writeCharacteristic(charac);
if(status){
Toast.makeText(context,"Written Successfully",Toast.LENGTH_SHORT).show();
}else{
Toast.makeText(context,"Error writing characteristic",Toast.LENGTH_SHORT).show();
}
}
public byte[] hexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len/2];
for(int i = 0; i < len; i+=2){
data[i/2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16));
}
return data;
}
public void onCharacteristicRead(BluetoothGatt gatt,
BluetoothGattCharacteristic
characteristic, int status) {
Log.i("onCharacteristicRead", characteristic.toString());
String characteristicValue = characteristic.getValue().toString();
Log.d("CHARACTERISTIC VALUE: ", characteristicValue);
gatt.disconnect();
}
public void onCharacteristicChanged(BluetoothGatt gatt,
BluetoothGattCharacteristic
characteristic) {
String value = characteristic.getValue().toString();
Log.d(TAG,value);
}
};
推荐答案
尽管BLE API本质上是异步的，但实际的信号传输不可避免地是同步的.开始任何连接/写入/读取操作之前，您必须等待上一个对回调的连接/写入/读取调用.
Although the BLE API is asynchronous in nature, the actual signal transmission is inevitably synchronous. You have to wait for the previous connect/write/read call to callback before starting any connecting/writing/reading operation.
在代码onServicesDiscovered(BluetoothGatt gatt, int status)函数中，在尝试编写特征之前，您两次调用mGatt.writeDescriptor(descriptor). API正忙于写入描述符，因此将拒绝启动您的写入请求，并为您的mGatt.writeCharacteristic(charac)调用返回false.
In your code onServicesDiscovered(BluetoothGatt gatt, int status) function, you called mGatt.writeDescriptor(descriptor) twice before trying to write the characteristic. The API will refuse to start your write request as it is being busy writing the descriptor, and return false for your mGatt.writeCharacteristic(charac) call.
因此，只需等待writeDescriptor回调后再调用writeCharacteristic.这种性质没有得到很好的记录，但是您可以在此处和
So just wait for the writeDescriptor to callback before calling writeCharacteristic. This nature is not well documented but you can find some source here and here.
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