I am new to the programming in android studio, I am generating an interface to connect a Bluetooh printer with the help of the included SDK but when calling the method that made the connection I generated the following error, an expert that could guide.
E/AndroidRuntime: FATAL EXCEPTION: main
Process: mx.prodeco.printnew, PID: 4653
java.lang.NullPointerException: Attempt to invoke interface method 'void net.posprinter.posprinterface.IMyBinder.connectBtPort(java.lang.String, net.posprinter.posprinterface.UiExecute)' on a null object reference
at mx.prodeco.printnew.MainActivity.connetBle(MainActivity.java:213)
at mx.prodeco.printnew.MainActivity.onClick(MainActivity.java:124)
at android.view.View.performClick(View.java:5647)
at android.view.View$PerformClick.run(View.java:22462)
at android.os.Handler.handleCallback(Handler.java:754)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:163)
at android.app.ActivityThread.main(ActivityThread.java:6361)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
this is the code:
public class MainActivity extends Activity implements OnClickListener {
public static String DISCONNECT="com.posconsend.net.disconnetct";
//IMyBinder interface，All methods that can be invoked to connect and send data are encapsulated within this interface
public static IMyBinder binder;
//bindService connection
ServiceConnection conn= new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
//Bind successfully
binder= (IMyBinder) iBinder;
Log.e("binder","connected");
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
Log.e("disbinder","disconnected");
}
};
public static boolean ISCONNECT;
Button BTCon,//connection button
BTDisconnect,//disconnect button
BtposPrinter,
BtSb;// start posprint button
EditText showET;// show edittext
CoordinatorLayout container;
private View dialogView;
BluetoothAdapter bluetoothAdapter;
private ArrayAdapter<String> adapter1
,adapter2;
private ListView lv1,lv2;
private ArrayList<String> deviceList_bonded=new ArrayList<String>();//bonded list
private ArrayList<String> deviceList_found=new ArrayList<String>();//found list
private Button btn_scan; //scan button
private LinearLayout LLlayout;
AlertDialog dialog;
String mac;
int pos ;
private DeviceReceiver myDevice;
@Override
protected void onCreate(Bundle savedInstanceState) {
Log.i("bluetooth", "onCreate...");
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//bind service，get ImyBinder object
Intent intent=new Intent(this,PosprinterService.class);
bindService(intent, conn, BIND_AUTO_CREATE);
//init view
initView();
//setlistener
setlistener();
}
private void initView(){
Log.i("bluetooth", "initView...");
BTCon= (Button) findViewById(R.id.buttonConnect);
BTDisconnect= (Button) findViewById(R.id.buttonDisconnect);
BtposPrinter= (Button) findViewById(R.id.buttonPosPrinter);
BtSb= (Button) findViewById(R.id.buttonSB);
showET= (EditText) findViewById(R.id.showET);
}
private void setlistener(){
Log.i("bluetooth", "setlistener...");
BTCon.setOnClickListener(this);
BTDisconnect.setOnClickListener(this);
BtSb.setOnClickListener(this);
//BTpos.setOnClickListener(this);
}
@Override
public void onClick(View view) {
Log.i("bluetooth", "onClick...");
switch (view.getId()){
case R.id.buttonConnect:{
//bluetooth connection
connetBle();
break;
}
case R.id.buttonSB:{
setBluetooth();
BTCon.setText(getString(R.string.connect));
break;
}
case R.id.buttonDisconnect:{
if (ISCONNECT){
binder.disconnectCurrentPort(new UiExecute() {
@Override
public void onsucess() {
showSnackbar(getString(R.string.toast_discon_success));
showET.setText("");
BTCon.setText(getString(R.string.connect));
}
@Override
public void onfailed() {
showSnackbar(getString(R.string.toast_discon_faile));
}
});
}else {
showSnackbar(getString(R.string.toast_present_con));
}
break;
}
default:
break;
}
}
private void connetBle(){
Log.i("bluetooth", "connetBle...");
String bleAdrress=showET.getText().toString();
Log.i("bluetooth", ""+bleAdrress+"...");
if (bleAdrress.equals(null)||bleAdrress.equals("")){
showSnackbar(getString(R.string.bleselect));
}else {
binder.connectBtPort(bleAdrress, new UiExecute() {
@Override
public void onsucess() {
ISCONNECT=true;
showSnackbar(getString(R.string.con_success));
BTCon.setText(getString(R.string.con_success));
binder.write(DataForSendToPrinterPos80.openOrCloseAutoReturnPrintState(0x1f), new UiExecute() {
@Override
public void onsucess() {
binder.acceptdatafromprinter(new UiExecute() {
@Override
public void onsucess() {
}
@Override
public void onfailed() {
ISCONNECT=false;
showSnackbar(getString(R.string.con_has_discon));
}
});
}
@Override
public void onfailed() {
}
});
}
@Override
public void onfailed() {
ISCONNECT=false;
showSnackbar(getString(R.string.con_failed));
}
});
}
}
public void setBluetooth(){
Log.i("bluetooth", "setBluetooth...");
bluetoothAdapter=BluetoothAdapter.getDefaultAdapter();
if (!bluetoothAdapter.isEnabled()){
//open bluetooth
Intent intent=new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(intent, Conts.ENABLE_BLUETOOTH);
}else {
showblueboothlist();
}
}
private void showblueboothlist() {
Log.i("bluetooth", "showbluetoothlist...");
if (!bluetoothAdapter.isDiscovering()) {
bluetoothAdapter.startDiscovery();
}
LayoutInflater inflater=LayoutInflater.from(this);
dialogView=inflater.inflate(R.layout.printer_list, null);
adapter1=new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, deviceList_bonded);
lv1=(ListView) dialogView.findViewById(R.id.listView1);
btn_scan=(Button) dialogView.findViewById(R.id.btn_scan);
LLlayout=(LinearLayout) dialogView.findViewById(R.id.ll1);
lv2=(ListView) dialogView.findViewById(R.id.listView2);
adapter2=new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, deviceList_found);
lv1.setAdapter(adapter1);
lv2.setAdapter(adapter2);
dialog=new AlertDialog.Builder(this).setTitle("BLE").setView(dialogView).create();
dialog.show();
myDevice=new DeviceReceiver(deviceList_found,adapter2,lv2);
//register the receiver
IntentFilter filterStart=new IntentFilter(BluetoothDevice.ACTION_FOUND);
IntentFilter filterEnd=new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(myDevice, filterStart);
registerReceiver(myDevice, filterEnd);
setDlistener();
findAvalibleDevice();
}
private void setDlistener() {
Log.i("bluetooth", "setDlistener...");
// TODO Auto-generated method stub
btn_scan.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
LLlayout.setVisibility(View.VISIBLE);
//btn_scan.setVisibility(View.GONE);
}
});
//boned device connect
lv1.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
// TODO Auto-generated method stub
try {
if(bluetoothAdapter!=null&&bluetoothAdapter.isDiscovering()){
bluetoothAdapter.cancelDiscovery();
}
String msg=deviceList_bonded.get(arg2);
mac=msg.substring(msg.length()-17);
String name=msg.substring(0, msg.length()-18);
//lv1.setSelection(arg2);
dialog.cancel();
showET.setText(mac);
//Log.i("TAG", "mac="+mac);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
//found device and connect device
lv2.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
// TODO Auto-generated method stub
try {
if(bluetoothAdapter!=null&&bluetoothAdapter.isDiscovering()){
bluetoothAdapter.cancelDiscovery();
}
String msg=deviceList_found.get(arg2);
mac=msg.substring(msg.length()-17);
String name=msg.substring(0, msg.length()-18);
//lv2.setSelection(arg2);
dialog.cancel();
showET.setText(mac);
Log.i("TAG", "mac="+mac);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
/*
find avaliable device
*/
private void findAvalibleDevice() {
Log.i("bluetooth", "findAvalibleDevice...");
// TODO Auto-generated method stub
Set<BluetoothDevice> device=bluetoothAdapter.getBondedDevices();
deviceList_bonded.clear();
if(bluetoothAdapter!=null&&bluetoothAdapter.isDiscovering()){
adapter1.notifyDataSetChanged();
}
if(device.size()>0){
//already
for(Iterator<BluetoothDevice> it = device.iterator(); it.hasNext();){
BluetoothDevice btd=it.next();
deviceList_bonded.add(btd.getName()+'\n'+btd.getAddress());
adapter1.notifyDataSetChanged();
}
}else{
deviceList_bonded.add("No can be matched to use bluetooth");
adapter1.notifyDataSetChanged();
}
}
/**
* show the massage
* @param showstring content
*/
private void showSnackbar(String showstring){
Snackbar.make(container, showstring,Snackbar.LENGTH_LONG)
.setActionTextColor(getResources().getColor(R.color.button_unable)).show();
}
@Override
protected void onDestroy() {
super.onDestroy();
binder.disconnectCurrentPort(new UiExecute() {
@Override
public void onsucess() {
}
@Override
public void onfailed() {
}
});
unbindService(conn);
}
}