关于android：无法从BLE设备读取特征值

Not able to read a characteristic value from BLE device

我需要向 Android BLE 设备写入和读取特征值。我能写但不能读。这是我的写作方式：

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public void writeCustomCharacteristic(int value) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG,"BluetoothAdapter not initialized");
return;
}
/*check if the service is available on the device*/
BluetoothGattService mCustomService = mBluetoothGatt.getService(UUID.fromString("<MY SERVICE UUID>"));
if(mCustomService == null){
Log.w(TAG,"Custom BLE Service not found");
return;
}
/*get the read characteristic from the service*/
BluetoothGattCharacteristic mWriteCharacteristic = mCustomService.getCharacteristic(UUID.fromString("<MY CHARACTERSTIC UUID>"));
mWriteCharacteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
mWriteCharacteristic.setValue(value,BluetoothGattCharacteristic.FORMAT_UINT8,0);
if(!mBluetoothGatt.writeCharacteristic(mWriteCharacteristic)){
Log.w(TAG,"Failed to write characteristic");
}else{
Log.w(TAG,"Success to write characteristic");
}
}

如果我使用

这个操作是成功的

1	mWriteCharacteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);

如果我使用任何其他写入类型而不是 WRITE_TYPE_NO_RESPONSE 那么它不会触发 onCharacteristicWrite() 回调方法。

这是我阅读特征的方式：

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private boolean readCharacteristics(int groupPosition,int childPosition){
try{
if (mGattCharacteristics != null) {
final BluetoothGattCharacteristic characteristic = mGattCharacteristics.get(2).get(2);
final int charaProp = characteristic.getProperties();
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;
}
mBluetoothLeService.readCharacteristic(characteristic);
}
if ((charaProp | BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
mNotifyCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicNotification(characteristic, true);
}
waitSometime(100);
if ((charaProp | BluetoothGattCharacteristic.PROPERTY_INDICATE) > 0) {
mNotifyCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicIndication(characteristic, true);
}
waitSometime(100);
if ((charaProp | BluetoothGattCharacteristic.PROPERTY_WRITE) > 0) {

byte[] value = characteristic.getValue(); //this is being NULL always

if (mNotifyCharacteristic != null) {
mBluetoothLeService.setCharacteristicNotification(mNotifyCharacteristic, true);
mNotifyCharacteristic = null;
}
mBluetoothLeService.writeCharacteristic(characteristic, value);
if(value!=null&&value.length>0) {
Toast.makeText(DeviceControlActivity.this,"success reading data",Toast.LENGTH_LONG).show();
}else{
Toast.makeText(DeviceControlActivity.this,"error reading data",Toast.LENGTH_LONG).show();
}
}
/* if ((charaProp | BluetoothGattCharacteristic.PROPERTY_INDICATE) > 0) {
mNotifyCharacteristic = characteristic;
//characteristic.setWriteType();
mBluetoothLeService.setCharacteristicIndication(
characteristic, true);
byte[] value=characteristic.getValue();
}*/
return true;
}
}catch (Exception e){
e.printStackTrace();
}
return false;
}

characteristic.getValue() 始终返回 null。我哪里错了？

这是我的看法：

你需要弄清楚你将获得什么样的特征数据？其中一些需要先设置指示或通知！喜欢：

一个。获取特征的描述符

1 2	BluetoothGattDescriptor descriptor = gattCharacteristic.getDescriptors().get(0); //Usually is Client_Characteristic_Configuration

乙。根据特性，设置描述符的property()为true。

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if ((gattCharacteristic.PROPERTY_NOTIFY)> 0 ){
if (descriptor != null) {
descriptor.setValue((BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE));
}
}
else if((gattCharacteristic.PROPERTY_INDICATE) >0 ){
if(descriptor != null){
descriptor.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
}
}

c。将值发送到远程 BLE 设备。

1	gatt.writeDescriptor(descriptor);

之后，你可以在回调函数中获取数据：

1	onCharacteristicChanged

至少以上对我有用！
希望能帮到人~

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/tech/268981.html

关于android：无法从BLE设备读取特征值

Not able to read a characteristic value from BLE device

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