I'm a new android developer and I'm trying to send a data using BLE 4.3, based on Gatt android sample project.
I use characteristics to put the data that i want to transmit.
When I try to transmit, I use the third service in the list of DeviceControlActivity of the project, appears a text dialog to introduce text. When I press OK, the idea is that start the transmission, but I obtain a NullPointerException error.
I don't know why appears this error and how can I solve this.
This is my full code, if this is useful
package com.example.blem;
public class DeviceControlActivity extends Activity {
public static final String EXTRAS_DEVICE_NAME = "DEVICE_NAME";
public static final String EXTRAS_DEVICE_ADDRESS = "DEVICE_ADDRESS";
private TextView mConnectionState;
private TextView mDataField;
private TextView mRssiField;
private String mDeviceName;
private String mDeviceAddress;
private ExpandableListView mGattServicesList;
private BluetoothLeService mBluetoothLeService;
private ArrayList<ArrayList<BluetoothGattCharacteristic>> mGattCharacteristics =
new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
private boolean mConnected = false;
private BluetoothGattCharacteristic mNotifyCharacteristic;
private BluetoothGattCharacteristic mWriteCharacteristic;
Button Escritor;
byte hello []={0};
private final String LIST_NAME = "NAME";
private final String LIST_UUID = "UUID";
BluetoothGattCharacteristic characteristic;
public BluetoothGatt mBluetoothGatt;
// Code to manage Service lifecycle.
private final ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName componentName, IBinder service) {
mBluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();
if (!mBluetoothLeService.initialize()) {
Log.e("Unable to initialize Bluetooth");
finish();
}
// Automatically connects to the device upon successful start-up initialization.
mBluetoothLeService.connect(mDeviceAddress);
mBluetoothLeService.setBLEServiceCb(mDCServiceCb);
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
mBluetoothLeService = null;
}
};
// If a given GATT characteristic is selected, check for supported features. This sample
// demonstrates 'Read' and 'Notify' features. See
// http://d.android.com/reference/android/bluetooth/BluetoothGatt.html for the complete
// list of supported characteristic features.
private final ExpandableListView.OnChildClickListener servicesListClickListner =
new ExpandableListView.OnChildClickListener() {
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
@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.
Log.d("BluetoothGattCharacteristic has PROPERTY_READ, so send read request");
if (mNotifyCharacteristic != null) {
mBluetoothLeService.setCharacteristicNotification(
mNotifyCharacteristic, false);
mNotifyCharacteristic = null;
}
mBluetoothLeService.readCharacteristic(characteristic);
}
if ((charaProp & BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
Log.d("BluetoothGattCharacteristic has PROPERTY_NOTIFY, so send notify request");
mNotifyCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicNotification(
characteristic, true);
}
if (((charaProp & BluetoothGattCharacteristic.PROPERTY_WRITE) |
(charaProp & BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE)) > 0) {
Log.d("BluetoothGattCharacteristic has PROPERY_WRITE | PROPERTY_WRITE_NO_RESPONSE");
mWriteCharacteristic = characteristic;
// popup an dialog to write something.
showCharactWriteDialog();
}
return true;
}
return false;
}
};
private void showCharactWriteDialog() {
DialogFragment newFrame = new BleCharacterDialogFragment();
newFrame.show(getFragmentManager(), "blewrite");
}
private void clearUI() {
mGattServicesList.setAdapter((SimpleExpandableListAdapter) null);
mDataField.setText(R.string.no_data);
}
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.gatt_services_characteristics);
final Intent intent = getIntent();
mDeviceName = intent.getStringExtra(EXTRAS_DEVICE_NAME);
mDeviceAddress = intent.getStringExtra(EXTRAS_DEVICE_ADDRESS);
// Sets up UI references.
((TextView) findViewById(R.id.device_address)).setText(mDeviceAddress);
mGattServicesList = (ExpandableListView) findViewById(R.id.gatt_services_list);
mGattServicesList.setOnChildClickListener(servicesListClickListner);
mConnectionState = (TextView) findViewById(R.id.connection_state);
mDataField = (TextView) findViewById(R.id.data_value);
mRssiField = (TextView) findViewById(R.id.signal_rssi);
//Escritor = (Button) findViewById(R.id.escrito);
/*Escritor.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
characteristic.setValue(new byte[] {(byte) 0xFF});
writeCharacteristicValue(characteristic);
Toast.makeText(getApplicationContext(), "Se envío el dato",
Toast.LENGTH_SHORT).show();
return;
}
});*/
getActionBar().setTitle(mDeviceName);
getActionBar().setDisplayHomeAsUpEnabled(true);
Intent gattServiceIntent = new Intent(this, BluetoothLeService.class);
bindService(gattServiceIntent, mServiceConnection, BIND_AUTO_CREATE);
}
@Override
protected void onResume() {
super.onResume();
//registerReceiver(mGattUpdateReceiver, makeGattUpdateIntentFilter());
if (mBluetoothLeService != null) {
final boolean result = mBluetoothLeService.connect(mDeviceAddress);
Log.d("Connect request result=" + result);
}
}
@Override
protected void onPause() {
super.onPause();
//unregisterReceiver(mGattUpdateReceiver);
}
@Override
protected void onDestroy() {
super.onDestroy();
unbindService(mServiceConnection);
mBluetoothLeService = null;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.gatt_services, menu);
if (mConnected) {
menu.findItem(R.id.menu_connect).setVisible(false);
menu.findItem(R.id.menu_disconnect).setVisible(true);
} else {
menu.findItem(R.id.menu_connect).setVisible(true);
menu.findItem(R.id.menu_disconnect).setVisible(false);
}
return true;
}
@TargetApi(Build.VERSION_CODES.ECLAIR)
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case R.id.menu_connect:
mBluetoothLeService.connect(mDeviceAddress);
return true;
case R.id.menu_disconnect:
mBluetoothLeService.disconnect();
return true;
case android.R.id.home:
onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}
private void updateConnectionState(final int resourceId) {
runOnUiThread(new Runnable() {
@Override
public void run() {
mConnectionState.setText(resourceId);
}
});
}
private void displayData(String data) {
if (data != null) {
mDataField.setText(data);
}
}
private void displayRssi(String rssi) {
if (rssi != null) {
//Log.d("-- dispaly Rssi: " + rssi);
mRssiField.setText(rssi);
}
}
// Demonstrates how to iterate through the supported GATT Services/Characteristics.
// In this sample, we populate the data structure that is bound to the ExpandableListView
// on the UI.
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
private void displayGattServices(List<BluetoothGattService> gattServices) {
Log.d("displayGATTServices");
if (gattServices == null) return;
String uuid = null;
String unknownServiceString = getResources().getString(R.string.unknown_service);
String unknownCharaString = getResources().getString(R.string.unknown_characteristic);
ArrayList<HashMap<String, String>> gattServiceData = new ArrayList<HashMap<String, String>>();
ArrayList<ArrayList<HashMap<String, String>>> gattCharacteristicData
= new ArrayList<ArrayList<HashMap<String, String>>>();
mGattCharacteristics = new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
// Loops through available GATT Services.
for (BluetoothGattService gattService : gattServices) {
HashMap<String, String> currentServiceData = new HashMap<String, String>();
uuid = gattService.getUuid().toString();
currentServiceData.put(
LIST_NAME, SampleGattAttributes.lookup(uuid, unknownServiceString));
currentServiceData.put(LIST_UUID, uuid);
gattServiceData.add(currentServiceData);
ArrayList<HashMap<String, String>> gattCharacteristicGroupData =
new ArrayList<HashMap<String, String>>();
List<BluetoothGattCharacteristic> gattCharacteristics =
gattService.getCharacteristics();
ArrayList<BluetoothGattCharacteristic> charas =
new ArrayList<BluetoothGattCharacteristic>();
// Loops through available Characteristics.
for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
charas.add(gattCharacteristic);
HashMap<String, String> currentCharaData = new HashMap<String, String>();
uuid = gattCharacteristic.getUuid().toString();
currentCharaData.put(
LIST_NAME, SampleGattAttributes.lookup(uuid, unknownCharaString));
currentCharaData.put(LIST_UUID, uuid);
gattCharacteristicGroupData.add(currentCharaData);
}
mGattCharacteristics.add(charas);
gattCharacteristicData.add(gattCharacteristicGroupData);
}
SimpleExpandableListAdapter gattServiceAdapter = new SimpleExpandableListAdapter(
this,
gattServiceData,
android.R.layout.simple_expandable_list_item_2,
new String[] {LIST_NAME, LIST_UUID},
new int[] { android.R.id.text1, android.R.id.text2 },
gattCharacteristicData,
android.R.layout.simple_expandable_list_item_2,
new String[] {LIST_NAME, LIST_UUID},
new int[] { android.R.id.text1, android.R.id.text2 }
);
mGattServicesList.setAdapter(gattServiceAdapter);
}
private DCServiceCb mDCServiceCb = new DCServiceCb();
public class DCServiceCb implements BluetoothLeService.BLEServiceCallback {
@Override
public void displayRssi(final int rssi) {
runOnUiThread(new Runnable() {
@Override
public void run() {
DeviceControlActivity.this.displayRssi(String.valueOf(rssi));
}
}
);
}
@Override
public void displayData(final String data) {
runOnUiThread(new Runnable() {
@Override
public void run() {
DeviceControlActivity.this.displayData(data);
}
});
}
@Override
public void notifyConnectedGATT() {
runOnUiThread(new Runnable() {
@Override
public void run() {
mConnected = true;
updateConnectionState(R.string.connected);
invalidateOptionsMenu();
}
});
}
@Override
public void notifyDisconnectedGATT() {
runOnUiThread(new Runnable() {
@Override
public void run() {
mConnected = false;
updateConnectionState(R.string.disconnected);
invalidateOptionsMenu();
clearUI();
}
});
}
@Override
public void displayGATTServices() {
Log.d("displayGATTServices.");
runOnUiThread(new Runnable() {
@Override
public void run() {
if (mBluetoothLeService != null) {
DeviceControlActivity.this.displayGattServices(
mBluetoothLeService.getSupportedGattServices());
}
}
});
}
}
@SuppressLint("ValidFragment")
public class BleCharacterDialogFragment extends DialogFragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.write_charact_dialog, container, false);
final EditText ed = (EditText) v.findViewById(R.id.charact_value);
Button ok = (Button) v.findViewById(R.id.dialog_confirm);
Button cancel = (Button) v.findViewById(R.id.dialog_cancel);
ok.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
characteristic.setValue(hello);
//characteristic.setValue("FF");
//characteristic.setValue(new byte[] {(byte) 0xFF});
writeCharacteristicValue(characteristic);
Toast.makeText(getApplicationContext(), "Se envío el dato",
Toast.LENGTH_SHORT).show();
dismiss();
return;
}
});
cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dismiss();
}
});
return v;
}
}
public void writeCharacteristicValue(BluetoothGattCharacteristic characteristica)
{
byte[] value= {(byte) 0xFF};
characteristica.setValue(bytesToHex(value));
boolean status = mBluetoothGatt.writeCharacteristic(characteristica);
}
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
public String bytesToHex(byte[] bytes)
{
char[] hexChars = new char[bytes.length * 2];
int v;
for ( int j = 0; j < bytes.length; j++ )
{
v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
}
Can someone tell what I'm doing wrong?
Thanks for advance
