android - Not able to read a characteristic value from BLE device -

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i need write , read characteristic value android ble device. i'm able write not read. here how i'm writing : 

public void writecustomcharacteristic(int value) {     if (mbluetoothadapter == null || mbluetoothgatt == null) {         log.w(tag, "bluetoothadapter not initialized");         return;     }     /*check if service available on device*/     bluetoothgattservice mcustomservice = mbluetoothgatt.getservice(uuid.fromstring("<my service uuid>"));     if(mcustomservice == null){         log.w(tag, "custom ble service not found");         return;     }     /*get read characteristic 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 write characteristic");     }else{         log.w(tag, "success write characteristic");     } }

and operation success if use 

 mwritecharacteristic.setwritetype(bluetoothgattcharacteristic.write_type_no_response);

if use other write types rather write_type_no_response not triggering oncharacteristicwrite() callback method.

here how i'm reading characteristic :

 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 active notification on characteristic, clear                 // first doesn't update data field on 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 being null                  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() returns null. i'm going wrong?


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