從特徵寫入和讀取

一旦連線到 Gatt 伺服器，你就可以通過寫入和讀取伺服器的特性來與它進行互動。要做到這一點，首先你必須瞭解此伺服器上可用的服務以及每個服務中可用的特徵：

 @Override
 public void onConnectionStateChange(BluetoothGatt gatt, int status,
        int newState) {
    if (newState == BluetoothProfile.STATE_CONNECTED) {
        Log.i(TAG, "Connected to GATT server.");
        gatt.discoverServices();

    }
. . .

 @Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
             List<BluetoothGattService> services = gatt.getServices();
                for (BluetoothGattService service : services) {
                    List<BluetoothGattCharacteristic> characteristics = service.getCharacteristics();
                    for (BluetoothGattCharacteristic characteristic : characteristics) { 
                        ///Once you have a characteristic object, you can perform read/write
                        //operations with it         
                    }
                 }
              }
            }

基本的寫操作如下：

characteristic.setValue(newValue);
characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
gatt.writeCharacteristic(characteristic);

寫入過程完成後，將呼叫 BluetoothGattCallback 的 onCharacteristicWrite 方法：

    @Override
    public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
        super.onCharacteristicWrite(gatt, characteristic, status);
        Log.d(TAG, "Characteristic " + characteristic.getUuid() + " written);
    }

基本的寫操作如下：

gatt.readCharacteristic(characteristic);

寫入過程完成後，將呼叫 BluetoothGattCallback 的 onCharacteristicRead 方法：

@Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
  super.onCharacteristicRead(gatt, characteristic, status);
  byte[] value = characteristic.getValue();
  }