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Android - ArrayList containing Bluetooth devices remains empty

I am trying to discover all available bluetooth devices and pass to another activity.
However even when looking at the Android Docs, I am unable to figure out why I cannot discover any devices and my ArrayList remains empty.
OnClick execute this:
mBluetoothAdapter.startDiscovery();
My broadcast listener also works but nothing is every returned and ArrayList remains empty.
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
mDeviceList.add(device);
showToast("Found device " + device.getName());
}
if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR);
if (state == BluetoothAdapter.STATE_ON) {
showToast("Enabled");
showEnabled();
}
}
if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
mDeviceList = new ArrayList<>();
mProgressDlg.show();
}
if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
mProgressDlg.dismiss();
Intent newIntent = new Intent(MainScreen.this, DeviceListActivity.class);
if (mDeviceList.isEmpty()){
Log.d("onReceive: ", "EMPTY");
}
newIntent.putParcelableArrayListExtra("device.list", mDeviceList);
startActivity(newIntent);
}
}
};
GIST

Answered my own question.
The fix was to turn location on with app permissions.
Apparently this is required for Android Marshmallow

How to call onReceive method in another method?

Currently I developed a new method to discover bluetooh ready connections. Here is my code:
private void DiscoverOBDConnection() {
BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
mBluetoothAdapter.startDiscovery();
BroadcastReceiver mReceiver;
// Create a BroadcastReceiver for ACTION_FOUND
final List<String> discoverableDevicesList = new ArrayList<String>();
mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
short rssi = intent.getShortExtra(BluetoothDevice.EXTRA_RSSI, Short.MIN_VALUE);
discoverableDevicesList.add(device.getName() + "\n" + device.getAddress() + "\n" + rssi);
String discoveredDeviceName = device.getName();
discoverableDevicesList.add(discoveredDeviceName);
}
}
};
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
context.registerReceiver(mReceiver,filter); // Don't forget to unregister during onDestroy
}
I just do not know how to call the onreceive method from another method. Could you help me to learn how to implement and discover the ready to connect bluetooth devices?

You can just send broadcast
Intent i = new Intent(BluetoothDevice.ACTION_FOUND);
sendBroadcast(i);
Or call it directly
mReceiver.onReceive(this, new Intent(BluetoothDevice.ACTION_FOUND));

BroadCast Receiver Battery Status error

i'm trying to use in my project a broadcast receiver which listens to battery status of charging/not charging and throw a toast in each of the options .
every time i change the charger status in the app ,the app crash.
(if i start the app with the charger connected it's show me the right toast
but when i uncharge the phone the app crashes)
here is the code
thanks in advance
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = this.registerReceiver(null, ifilter);
int status = batteryStatus.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING ||
status == BatteryManager.BATTERY_STATUS_FULL;
if(isCharging==true){
Toast.makeText(this, "Charging", Toast.LENGTH_SHORT).show();
}
else{
Toast.makeText(this, "Charger not connected", Toast.LENGTH_SHORT).show();
UPDATE
i'm having an hard time to understand what i suppose to do.
i'm pretty new so be patient with me :)
here is the code i made
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
checkBatteryState(null);
public void checkBatteryState(View sender) {
IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
Intent batteryStatus = registerReceiver(null, filter);
int chargeState = batteryStatus.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
String strState;
switch (chargeState) {
case BatteryManager.BATTERY_STATUS_CHARGING:
case BatteryManager.BATTERY_STATUS_FULL:
strState = "charging";
Toast.makeText(this, strState, Toast.LENGTH_LONG).show();
break;
default:
strState = "not charging";
Toast.makeText(this, strState, Toast.LENGTH_LONG).show();
}
}
}

http://www.vogella.com/tutorials/AndroidBroadcastReceiver/article.html
is this what you're using?
Maybe you haven't ensured your Intent is sticky.
My advice would be not to use a registerreceiver with a null argument.
Try this method for creating a broadcastreceiver:
How to send data to another app which is not started
put your Toasts in the onReceive() function.

The code is not actually registering a receiver, just getting a sticky broadcast. If the broadcast has never been sent the this will return null which will cause a NPE in the remaining code.

How do I send scanresults from broadcastreceiver to service

I have a broadcastreceiver created in my Service class.
It is set to react to this action: WifiManager.SCAN_RESULTS_AVAILABLE_ACTION
So basically everytime I do a method call of wifi.startScan(); , and the results become available, the broadcastreceiver's onReceive method does its thing.
My issue is that I need to process those scan results and its likely not good practice to do so much in the broadcastreceiver. I want to do all the calculations back in my service class but I need to somehow access the ScanResults.
Any sort of help with this? As it is much needed.
Here is a simplified version of my code conveying the purpose of my broadcastreceiver:
Snippet from my Service class:
IntentFilter i = new IntentFilter();
i.addAction(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION); //reacts to the scan results being available
registerReceiver(mybroadcast,i);
wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
if(!wifi.isWifiEnabled()){ // if wifi is not enabled
toast = Toast.makeText(getApplicationContext(), "Wifi is off. Please turn it on.", Toast.LENGTH_LONG);
toast.show();
//wifi.setWifiEnabled(true);
//startActivity(backIntent);
}
else
{
wifi.startScan(); //what the receiver is going to react to
}
Code for my receiver:
private final BroadcastReceiver mybroadcast = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
//gets the scan results
wifi = (WifiManager) mContext.getSystemService(Context.WIFI_SERVICE);
List<ScanResult> scans = wifi.getScanResults();
// do some work here...
}
}

You can try adding an handler to service for ex:
private final Handler handler = new Handler() {
public void handleMessage(Message msg) {
String aResponse = msg.getData().getString("message");
if ((null != aResponse)) {
// ALERT MESSAGE
Toast.makeText(getBaseContext(),
"Server Response: " + aResponse, Toast.LENGTH_SHORT)
.show();
} else {
// ALERT MESSAGE
Toast.makeText(getBaseContext(),
"Not Got Response From Server.", Toast.LENGTH_SHORT)
.show();
}
}
};
And send a message to it in OnReceive of your BroadcastReceiver:
Message msgObj = handler.obtainMessage();
Bundle b = new Bundle();
b.putString("message", msg);
msgObj.setData(b);
handler.sendMessage(msgObj);

how to get Bluetooth name of peer device in Android?

how is it possible to get the Bluetooth information (name, Mac address,...) of the peer device that the android device is connected to that via Bluetooth ?

You can use the following code to get all remote devices :)
private void discoveryDevice(){
// Register the BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestroy
mBluetoothAdapter.startDiscovery();
}
// Create a BroadcastReceiver for ACTION_FOUND
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
Log.d(TAG, "device " + device.getName() + "\n" + device.getAddress());
}
}
};
It's really good for you to get the name of remote device throught the code:
Log.d(TAG, "device " + device.getName() + "\n" + device.getAddress());

I can't test this code at this moment but maybe can give an idea to how you can get the name and others parameters of bluetooth.
static BluetoothSocket socket ;
public static boolean btCon(Context ctx){
Method m;
try {
BluetoothDevice devc = BluetoothAdapter.getDefaultAdapter().getRemoteDevice(MAC_ADRS);
m = devc.getClass().getMethod("createRfcommSocket", new Class[]{int.class});
socket = (BluetoothSocket)m.invoke(devc, Integer.valueOf(1));
socket.connect();
String name = devc.getName();/* or */ String name2 = devc.getName().toString();
Log.i("Test","Name: "+name);
Log.i("Test","Name 2: "+name2);
return true;
}catch(Exception e)
{
return false;
}
}