I am working on a BLE project (Android application) using Android 4.3 API, i have used sample BLE app it is only reading characteristics in DeviceControlActivity.activity, but i want to write characteristics and send it to BLE chip on clicking a button. How can I write data on chip cc2540 .. Basically i don't know the step by step procedure to write characteristics.
write i can only see the name and id of device with following piece of code in DeviceControlActivity
private final ExpandableListView.OnChildClickListener servicesListClickListner =
new ExpandableListView.OnChildClickListener() {
@Override
public boolean onChildClick(ExpandableListView parent, View v, int groupPosition,
int childPosition, long id) {
if (mGattCharacteristics != null) {
final BluetoothGattCharacteristic characteristic =
mGattCharacteristics.get(groupPosition).get(childPosition);
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);
showDialog("reading");
}
if ((charaProp | BluetoothGattCharacteristic.PROPERTY_WRITE) > 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.writeCharacteristic(characteristic);
showDialog("writing");
//characteristic.setValue(bytes);
//characteristic.setValue("testing");
//characteristic.setWriteType(BluetoothGattCharacteristic.PERMISSION_WRITE);
}
if ((charaProp | BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
mNotifyCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicNotification(
characteristic, true);
}
byte[] value = {0x00, (byte) (0xB9) , 0x0D, (byte) (0x90), 0x2F};
if(!characteristic.setValue(value))
{
Log.w(TAG, "Couldn't set characteristic's local value");
//return;
}
characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
/*if(!writeCharacteristic.writeCharacteristic(characteristic))
{
Log.w(TAG, "Couldn't write characteristic");
}*/
return true;
}
return false;
}
};
The following code is write characteristic using byte[] data:
public boolean writeCharacteristic(){
//check mBluetoothGatt is available
if (mBluetoothGatt == null) {
Log.e(TAG, "lost connection");
return false;
}
BluetoothGattService Service = mBluetoothGatt.getService(your Services);
if (Service == null) {
Log.e(TAG, "service not found!");
return false;
}
BluetoothGattCharacteristic charac = Service
.getCharacteristic(your characteristic);
if (charac == null) {
Log.e(TAG, "char not found!");
return false;
}
byte[] value = new byte[1];
value[0] = (byte) (21 & 0xFF);
charac.setValue(value);
boolean status = mBluetoothGatt.writeCharacteristic(charac);
return status;
}
Please note that the logic OR in:
if ((charaProp | BluetoothGattCharacteristic.PROPERTY_READ) > 0)" in the original post should be a logic AND for the permission check to work. Same for the second charaProp comparison. Otherwise bot statements are true regardless of the actual permission flag.
The following code is write characteristic using string data in utf-8 format:
public void writeCharacteristic(BluetoothGattCharacteristic characteristic,
String data) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w(TAG, "BluetoothAdapter not initialized");
return;
}
Log.i(TAG, "characteristic " + characteristic.toString());
try {
Log.i(TAG, "data " + URLEncoder.encode(data, "utf-8"));
characteristic.setValue(URLEncoder.encode(data, "utf-8"));
// TODO
mBluetoothGatt.writeCharacteristic(characteristic);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
Hope it helps!
public boolean writeCharacteristic(byte value[],int type){
//check mBluetoothGatt is available
if (mBluetoothGatt == null) {
Log.e(TAG, "lost connection");
return false;
}
BluetoothGattService Service = mBluetoothGatt.getService(UUID_SIMPLESERVICE);
if (Service == null) {
Log.e(TAG, "service not found!");
//////////NO service found...........
return false;
}
BluetoothGattCharacteristic charac1 = null;
boolean status1 = false;
if(type==1) {
charac1 = Service.getCharacteristic(UUID_PORT1);
charac1.setValue(value);
status1 = mBluetoothGatt.writeCharacteristic(charac1);
Log.v("________BLESERVICE____", "___WRITE CHARATERISTICS STATUS:_________"+status1);
onReliableWriteCompleted(status1);
}
if (charac1 == null) {
Log.e(TAG, "char not found!");
return false;
}
Log.v("___TYPE___","______________________"+type);
return status1;
}
来源：https://stackoverflow.com/questions/20043388/working-with-ble-android-4-3-how-to-write-characteristics