android - BluetoothGattCallback only calls onConnectionStateChange -

my device.connectgatt() triggers onconnectionstatechage. status 0, , connection established. tested on 4.4 , 5.1 system - same result. code:

private final bluetoothgattcallback mycallback = new bluetoothgattcallback() {     @override     public void onconnectionstatechange(bluetoothgatt gatt, int status, int newstate) {         super.onconnectionstatechange(gatt, status, newstate);          //bluetoothgattcharacteristic tempchar = null;         //tempchar.setvalue("test");          if(status == 0) {             gatt.connect();             //gatt.disconnect();           }     }      @override     public void onservicesdiscovered(bluetoothgatt gatt, int status) {         super.onservicesdiscovered(gatt, status);     }      @override     public void oncharacteristicread(bluetoothgatt gatt, bluetoothgattcharacteristic characteristic, int status) {         super.oncharacteristicread(gatt, characteristic, status);     }      @override     public void oncharacteristicwrite(bluetoothgatt gatt, bluetoothgattcharacteristic characteristic, int status) {         super.oncharacteristicwrite(gatt, characteristic, status);         // try send data device         characteristic.setvalue("test");         gatt.writecharacteristic(characteristic);     }      @override     public void oncharacteristicchanged(bluetoothgatt gatt, bluetoothgattcharacteristic characteristic) {         super.oncharacteristicchanged(gatt, characteristic);       }      @override     public void ondescriptorread(bluetoothgatt gatt, bluetoothgattdescriptor descriptor, int status) {         super.ondescriptorread(gatt, descriptor, status);     }      @override     public void ondescriptorwrite(bluetoothgatt gatt, bluetoothgattdescriptor descriptor, int status) {         super.ondescriptorwrite(gatt, descriptor, status);      }      @override     public void onreliablewritecompleted(bluetoothgatt gatt, int status) {         super.onreliablewritecompleted(gatt, status);     }      @override     public void onreadremoterssi(bluetoothgatt gatt, int rssi, int status) {         super.onreadremoterssi(gatt, rssi, status);     }      @override     public void onmtuchanged(bluetoothgatt gatt, int mtu, int status) {         super.onmtuchanged(gatt, mtu, status);     }      @override     protected object clone() throws clonenotsupportedexception {         return super.clone();     }      @override     public boolean equals(object o) {         return super.equals(o);     }      @override     protected void finalize() throws throwable {         super.finalize();     }      @override     public int hashcode() {         return super.hashcode();     }      @override     public string tostring() {         return super.tostring();     } }; 

i added break-point calls , 1 gets hit onconnectionstatechange. supposed work this? write either characteristic or description , push ble module? also, ble module (hc-10 controlled arduino) sending data out (tested different app) ... expect hit oncharacteristiconchage method well. missing ?

upon connection, android not aware of services or characteristics on device.

hence, must discoverservices() once connected:

@override public void onconnectionstatechange(bluetoothgatt gatt, int status, int newstate) {     if (newstate == bluetoothprofile.state_connected) {         gatt.discoverservices();     } } 

once callback, can write:

@override public void onservicesdiscovered(bluetoothgatt gatt, int status) {     if (status == bluetoothgatt.gatt_success) {         bluetoothgattcharacteristic writechar = mbluetoothgatt.getservice(myserviceuuid)                     .getcharacteristic(mywritecharuuid);         byte[] data = new byte[10];         writechar.setvalue(data);         gatt.writecharacteristic(writechar);     } }