'How to prevent Bluetooth Disconnected when moving Fragment
I make a POS in android. I want to make a printing in my apps. To do printing I'm using bluetooth printer. Then, I had success make the bluetooth connection and I make it in one fragment. But every time I move to another fragment the bluetooth connction will be disconnected. How can I prevent bluetooth disconnect when moving fragment?
SettingFragment.Java
/**
* A simple {@link Fragment} subclass.
*/
public class SettingFragment extends Fragment {
public static final int MESSAGE_STATE_CHANGE = 1;
public static final int MESSAGE_READ = 2;
public static final int MESSAGE_WRITE = 3;
public static final int MESSAGE_DEVICE_NAME = 4;
public static final int MESSAGE_TOAST = 5;
public static final int MESSAGE_CONNECTION_LOST = 6;
public static final int MESSAGE_UNABLE_CONNECT = 7;
private String mConnectedDeviceName = null;
// Key names received from the BluetoothService Handler
public static final String DEVICE_NAME = "device_name";
public static final String TOAST = "toast";
// Intent request codes
private static final int REQUEST_CONNECT_DEVICE = 1;
private static final int REQUEST_ENABLE_BT = 2;
private BluetoothAdapter mBluetoothAdapter = null;
private BluetoothService mService = null;
private static final String CHINESE = "GBK";
SessionManagement sessionManagement;
DatabaseHandler db;
TextView tvConnected;
Button btnScan;
Button btnTest;
public SettingFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootview = inflater.inflate(R.layout.fragment_setting, container, false);
getActivity().setTitle("Setting");
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
btnScan = (Button)rootview.findViewById(R.id.btnScan);
btnTest = (Button) rootview.findViewById(R.id.btnTest);
tvConnected = (TextView) rootview.findViewById(R.id.tvPrinterConnect);
if (!mBluetoothAdapter.isEnabled()) {
Intent enableIntent = new Intent(
BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
// Otherwise, setup the session
} else {
if (mService == null)
KeyListenerInit();
}
return rootview;
}
@SuppressLint("HandlerLeak")
private final Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MESSAGE_STATE_CHANGE:
if (DEBUG)
Log.i(TAG, "MESSAGE_STATE_CHANGE: " + msg.arg1);
switch (msg.arg1) {
case BluetoothService.STATE_CONNECTED:
//btnScan.setText(getText(R.string.Connecting));
btnScan.setEnabled(false);
break;
case BluetoothService.STATE_CONNECTING:
Toast.makeText((MainActivity)getContext(),R.string.title_connecting,Toast.LENGTH_SHORT).show();
break;
case BluetoothService.STATE_LISTEN:
case BluetoothService.STATE_NONE:
Toast.makeText((MainActivity)getContext(),R.string.title_not_connected,Toast.LENGTH_SHORT).show();
break;
}
break;
case MESSAGE_WRITE:
break;
case MESSAGE_READ:
break;
case MESSAGE_DEVICE_NAME:
// save the connected device's name
mConnectedDeviceName = msg.getData().getString(DEVICE_NAME);
Toast.makeText(getActivity(),
"Connected to " + mConnectedDeviceName,
Toast.LENGTH_SHORT).show();
tvConnected.setText("Connected to "+mConnectedDeviceName );
break;
case MESSAGE_TOAST:
Toast.makeText(getActivity(),
msg.getData().getString(TOAST), Toast.LENGTH_SHORT)
.show();
break;
case MESSAGE_CONNECTION_LOST:
Toast.makeText(getActivity(), "Device connection was lost",
Toast.LENGTH_SHORT).show();
tvConnected.setText("Not Connect to Any Device");
// editText.setEnabled(false);
// sendButton.setEnabled(false);
break;
case MESSAGE_UNABLE_CONNECT:
Toast.makeText(getActivity(), "Unable to connect device",
Toast.LENGTH_SHORT).show();
break;
}
}
};
@Override
public void onStart() {
super.onStart();
// If Bluetooth is not on, request that it be enabled.
// setupChat() will then be called during onActivityResult
if (!mBluetoothAdapter.isEnabled()) {
Intent enableIntent = new Intent(
BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
// Otherwise, setup the session
} else {
if (mService == null)
KeyListenerInit();
}
}
@Override
public synchronized void onResume() {
super.onResume();
if (mService != null) {
if (mService.getState() == BluetoothService.STATE_NONE) {
// Start the Bluetooth services
mService.start();
}
}
}
@Override
public synchronized void onPause() {
super.onPause();
if (DEBUG)
Log.e(TAG, "- ON PAUSE -");
}
@Override
public void onStop() {
super.onStop();
if (DEBUG)
Log.e(TAG, "-- ON STOP --");
}
@Override
public void onDestroy() {
super.onDestroy();
// Stop the Bluetooth services
if (mService != null)
mService.stop();
if (DEBUG)
Log.e(TAG, "--- ON DESTROY ---");
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (DEBUG)
Log.d(TAG, "onActivityResult " + resultCode);
switch (requestCode) {
case REQUEST_CONNECT_DEVICE:{
// When DeviceListActivity returns with a device to connect
if (resultCode == Activity.RESULT_OK) {
// Get the device MAC address
String address = data.getExtras().getString(
DeviceListActivity.EXTRA_DEVICE_ADDRESS);
// Get the BLuetoothDevice object
if (BluetoothAdapter.checkBluetoothAddress(address)) {
BluetoothDevice device = mBluetoothAdapter
.getRemoteDevice(address);
// Attempt to connect to the device
mService.connect(device);
}
}
break;
}
case REQUEST_ENABLE_BT:{
// When the request to enable Bluetooth returns
if (resultCode == Activity.RESULT_OK) {
// Bluetooth is now enabled, so set up a session
KeyListenerInit();
} else {
// User did not enable Bluetooth or an error occured
Log.d(TAG, "BT not enabled");
Toast.makeText(getActivity(), R.string.bt_not_enabled_leaving,
Toast.LENGTH_SHORT).show();
getActivity().onBackPressed();
}
break;
}
}
}
private void KeyListenerInit() {
btnScan.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent serverIntent = new Intent(getActivity(), DeviceListActivity.class);
startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE);
}
});
mService = new BluetoothService(getActivity(), mHandler);
}
}
BluetoothService.JAVA
public class BluetoothService {
// Debugging
private static final String TAG = "BluetoothService";
private static final boolean DEBUG = true;
// Name for the SDP record when creating server socket
private static final String NAME = "ZJPrinter";
//UUID must be this
// Unique UUID for this application
private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
// Member fields
private BluetoothAdapter mAdapter;
private Handler mHandler;
private AcceptThread mAcceptThread;
private ConnectThread mConnectThread;
private ConnectedThread mConnectedThread;
private int mState;
// Constants that indicate the current connection state
public static final int STATE_NONE = 0; // we're doing nothing
public static final int STATE_LISTEN = 1; // now listening for incoming connections
public static final int STATE_CONNECTING = 2; // now initiating an outgoing connection
public static final int STATE_CONNECTED = 3; // now connected to a remote device
public static String ErrorMessage = "No_Error_Message";
/**
* Constructor. Prepares a new BTPrinter session.
* @param context The UI Activity Context
* @param handler A Handler to send messages back to the UI Activity
*/
public BluetoothService(Context context, Handler handler) {
mAdapter = BluetoothAdapter.getDefaultAdapter();
mState = STATE_NONE;
mHandler = handler;
}
/**
* Set the current state of the connection
* @param state An integer defining the current connection state
*/
private synchronized void setState(int state) {
if (DEBUG) Log.d(TAG, "setState() " + mState + " -> " + state);
mState = state;
// Give the new state to the Handler so the UI Activity can update
mHandler.obtainMessage(SettingFragment.MESSAGE_STATE_CHANGE, state, -1).sendToTarget();
}
/**
* Return the current connection state. */
public synchronized int getState() {
return mState;
}
/**
* Start the service. Specifically start AcceptThread to begin a
* session in listening (server) mode. Called by the Activity onResume() */
public synchronized void start() {
if (DEBUG) Log.d(TAG, "start");
// Cancel any thread attempting to make a connection
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
// Cancel any thread currently running a connection
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
// Start the thread to listen on a BluetoothServerSocket
if (mAcceptThread == null) {
mAcceptThread = new AcceptThread();
mAcceptThread.start();
}
setState(STATE_LISTEN);
}
/**
* Start the ConnectThread to initiate a connection to a remote device.
* @param device The BluetoothDevice to connect
*/
public synchronized void connect(BluetoothDevice device) {
if (DEBUG) Log.d(TAG, "connect to: " + device);
// Cancel any thread attempting to make a connection
if (mState == STATE_CONNECTING) {
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
}
// Cancel any thread currently running a connection
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
// Start the thread to connect with the given device
mConnectThread = new ConnectThread(device);
mConnectThread.start();
setState(STATE_CONNECTING);
}
/**
* Start the ConnectedThread to begin managing a Bluetooth connection
* @param socket The BluetoothSocket on which the connection was made
* @param device The BluetoothDevice that has been connected
*/
public synchronized void connected(BluetoothSocket socket, BluetoothDevice device) {
if (DEBUG) Log.d(TAG, "connected");
// Cancel the thread that completed the connection
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
// Cancel any thread currently running a connection
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
// Cancel the accept thread because we only want to connect to one device
if (mAcceptThread != null) {mAcceptThread.cancel(); mAcceptThread = null;}
// Start the thread to manage the connection and perform transmissions
mConnectedThread = new ConnectedThread(socket);
mConnectedThread.start();
// Send the name of the connected device back to the UI Activity
Message msg = mHandler.obtainMessage(SettingFragment.MESSAGE_DEVICE_NAME);
Bundle bundle = new Bundle();
bundle.putString(SettingFragment.DEVICE_NAME, device.getName());
msg.setData(bundle);
mHandler.sendMessage(msg);
setState(STATE_CONNECTED);
}
/**
* Stop all threads
*/
public synchronized void stop() {
if (DEBUG) Log.d(TAG, "stop");
setState(STATE_NONE);
if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;}
if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;}
if (mAcceptThread != null) {mAcceptThread.cancel(); mAcceptThread = null;}
}
/**
* Write to the ConnectedThread in an unsynchronized manner
* @param out The bytes to write
* @see ConnectedThread#write(byte[])
*/
public void write(byte[] out) {
// Create temporary object
ConnectedThread r;
// Synchronize a copy of the ConnectedThread
synchronized (this) {
if (mState != STATE_CONNECTED) return;
r = mConnectedThread;
}
r.write(out);
}
/**
* Indicate that the connection attempt failed and notify the UI Activity.
*/
private void connectionFailed() {
setState(STATE_LISTEN);
// Send a failure message back to the Activity
Message msg = mHandler.obtainMessage(SettingFragment.MESSAGE_TOAST);
Bundle bundle = new Bundle();
bundle.putString(SettingFragment.TOAST, "Unable to connect device");
msg.setData(bundle);
mHandler.sendMessage(msg);
}
/**
* Indicate that the connection was lost and notify the UI Activity.
*/
private void connectionLost() {
//setState(STATE_LISTEN);
// Send a failure message back to the Activity
Message msg = mHandler.obtainMessage(SettingFragment.MESSAGE_TOAST);
Bundle bundle = new Bundle();
bundle.putString(SettingFragment.TOAST, "Device connection was lost");
msg.setData(bundle);
mHandler.sendMessage(msg);
}
/**
* This thread runs while listening for incoming connections. It behaves
* like a server-side client. It runs until a connection is accepted
* (or until cancelled).
*/
private class AcceptThread extends Thread {
// The local server socket
private final BluetoothServerSocket mmServerSocket;
public AcceptThread() {
BluetoothServerSocket tmp = null;
// Create a new listening server socket
try {
tmp = mAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID);
} catch (IOException e) {
Log.e(TAG, "listen() failed", e);
}
mmServerSocket = tmp;
}
@Override
public void run() {
if (DEBUG) Log.d(TAG, "BEGIN mAcceptThread" + this);
setName("AcceptThread");
BluetoothSocket socket = null;
// Listen to the server socket if we're not connected
while (mState != STATE_CONNECTED) {
try {
// This is a blocking call and will only return on a
// successful connection or an exception
socket = mmServerSocket.accept();
} catch (IOException e) {
Log.e(TAG, "accept() failed", e);
break;
}
// If a connection was accepted
if (socket != null) {
synchronized (BluetoothService.this) {
switch (mState) {
case STATE_LISTEN:
case STATE_CONNECTING:
// Situation normal. Start the connected thread.
connected(socket, socket.getRemoteDevice());
break;
case STATE_NONE:
case STATE_CONNECTED:
// Either not ready or already connected. Terminate new socket.
try {
socket.close();
} catch (IOException e) {
Log.e(TAG, "Could not close unwanted socket", e);
}
break;
}
}
}
}
if (DEBUG) Log.i(TAG, "END mAcceptThread");
}
public void cancel() {
if (DEBUG) Log.d(TAG, "cancel " + this);
try {
mmServerSocket.close();
} catch (IOException e) {
Log.e(TAG, "close() of server failed", e);
}
}
}
/**
* This thread runs while attempting to make an outgoing connection
* with a device. It runs straight through; the connection either
* succeeds or fails.
*/
private class ConnectThread extends Thread {
private final BluetoothSocket mmSocket;
private final BluetoothDevice mmDevice;
public ConnectThread(BluetoothDevice device) {
mmDevice = device;
BluetoothSocket tmp = null;
// Get a BluetoothSocket for a connection with the
// given BluetoothDevice
try {
tmp = device.createRfcommSocketToServiceRecord(MY_UUID);
} catch (IOException e) {
Log.e(TAG, "create() failed", e);
}
mmSocket = tmp;
}
@Override
public void run() {
Log.i(TAG, "BEGIN mConnectThread");
setName("ConnectThread");
// Always cancel discovery because it will slow down a connection
mAdapter.cancelDiscovery();
// Make a connection to the BluetoothSocket
try {
// This is a blocking call and will only return on a
// successful connection or an exception
mmSocket.connect();
} catch (IOException e) {
connectionFailed();
// Close the socket
try {
mmSocket.close();
} catch (IOException e2) {
Log.e(TAG, "unable to close() socket during connection failure", e2);
}
// Start the service over to restart listening mode
BluetoothService.this.start();
return;
}
// Reset the ConnectThread because we're done
synchronized (BluetoothService.this) {
mConnectThread = null;
}
// Start the connected thread
connected(mmSocket, mmDevice);
}
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
Log.e(TAG, "close() of connect socket failed", e);
}
}
}
/**
* This thread runs during a connection with a remote device.
* It handles all incoming and outgoing transmissions.
*/
private class ConnectedThread extends Thread {
private final BluetoothSocket mmSocket;
private final InputStream mmInStream;
private final OutputStream mmOutStream;
public ConnectedThread(BluetoothSocket socket) {
Log.d(TAG, "create ConnectedThread");
mmSocket = socket;
InputStream tmpIn = null;
OutputStream tmpOut = null;
// Get the BluetoothSocket input and output streams
try {
tmpIn = socket.getInputStream();
tmpOut = socket.getOutputStream();
} catch (IOException e) {
Log.e(TAG, "temp sockets not created", e);
}
mmInStream = tmpIn;
mmOutStream = tmpOut;
}
@Override
public void run() {
Log.i(TAG, "BEGIN mConnectedThread");
int bytes;
// Keep listening to the InputStream while connected
while (true) {
try {
byte[] buffer = new byte[256];
// Read from the InputStream
bytes = mmInStream.read(buffer);
if(bytes>0)
{
// Send the obtained bytes to the UI Activity
mHandler.obtainMessage(SettingFragment.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
}
else
{
Log.e(TAG, "disconnected");
connectionLost();
//add by chongqing jinou
if(mState != STATE_NONE)
{
Log.e(TAG, "disconnected");
// Start the service over to restart listening mode
BluetoothService.this.start();
}
break;
}
} catch (IOException e) {
Log.e(TAG, "disconnected", e);
connectionLost();
//add by chongqing jinou
if(mState != STATE_NONE)
{
// Start the service over to restart listening mode
BluetoothService.this.start();
}
break;
}
}
}
/**
* Write to the connected OutStream.
* @param buffer The bytes to write
*/
public void write(byte[] buffer) {
try {
mmOutStream.write(buffer);
mmOutStream.flush();//清空缓存
/* if (buffer.length > 3000) //
{
byte[] readata = new byte[1];
SPPReadTimeout(readata, 1, 5000);
}*/
Log.i("BTPWRITE", new String(buffer,"GBK"));
// Share the sent message back to the UI Activity
mHandler.obtainMessage(SettingFragment.MESSAGE_WRITE, -1, -1, buffer)
.sendToTarget();
} catch (IOException e) {
Log.e(TAG, "Exception during write", e);
}
}
public void cancel() {
try {
mmSocket.close();
} catch (IOException e) {
Log.e(TAG, "close() of connect socket failed", e);
}
}
}
}
Sources
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