I am writing an Android app to print text on a bluetooth thermal printer. Here is the complete code
The app works fine in the debug mode but when I generate a signed APK and install it on the device, it does not respond at all.
I have tried different solution suggested on stackoverflow but non of them worked.
This is my main activity
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import com.lvrenyang.io.IOCallBack;
import java.lang.ref.WeakReference;
public class MainActivity extends AppCompatActivity {
private Handler mHandler; // Our main handler that will receive callback notifications
// #defines for identifying shared types between calling functions
private final static int REQUEST_ENABLE_BT = 1; // used to identify adding bluetooth names
private static String TAG = "MAIN_ACTIVITY";
private Activity activity;
private Button btnConnect;
private String name = "MTP-II";
private String mac_address = "02:15:44:31:49:05";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Get the activity
this.activity = this;
//Button from the XML view
btnConnect = findViewById(R.id.btnConnect);
//Start the Init Work Service Async task
new InitWorkService().execute();
//Set onClickListener for test print button
btnConnect.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
try {
//Check if name and address are set
if (name != "null" && mac_address != "null" && mac_address.contains(":")) {
if (!WorkService.workThread.isConnected()) {
WorkService.workThread.connectBt(mac_address);
//Sleep for 3 seconds
try {
Thread.sleep(3000);
} catch (Exception e) {
}
}
//Check if connected
if (WorkService.workThread.isConnected()) {
//Collect data in background Thread
new PrintData().execute();
} else {
Toast.makeText(activity, Global.toast_notconnect, Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(activity, "Please setup printer first!", Toast.LENGTH_LONG).show();
}
}
catch(Exception e){
Log.e(TAG, e.getMessage(), e.fillInStackTrace());}
}
});
}
/**
* Background Async Task
* */
private class InitWorkService extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
protected String doInBackground(String... args){
try{
WorkService.cb = new IOCallBack() {
public void OnOpen() {
if (null != mHandler) {
Message msg = mHandler.obtainMessage(Global.MSG_IO_ONOPEN);
mHandler.sendMessage(msg);
}
}
public void OnClose() {
if (null != mHandler) {
Message msg = mHandler.obtainMessage(Global.MSG_IO_ONCLOSE);
mHandler.sendMessage(msg);
}
}
};
}
catch(Exception e){
Log.e(TAG, e.getMessage(), e.fillInStackTrace());
}
return null;
}
protected void onPostExecute(String file_url){
try {
mHandler = new MHandler(MainActivity.this);
WorkService.addHandler(mHandler);
if (null == WorkService.workThread) {
Intent intent = new Intent(activity, WorkService.class);
startService(intent);
}
}
catch (Exception e) {
Log.e(TAG, e.getMessage(), e.fillInStackTrace());
Toast.makeText(activity, "Unable to initiate the WorkService!", Toast.LENGTH_LONG).show();
}
}
}
/**
* Background Async Task
* */
class PrintData extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
protected String doInBackground(String... args){
try{
int nTextAlign=1;
String text = "Test message!\r\n\r\n\r\n";
String encoding = "UTF-8";
byte[] hdrBytes = {0x1c, 0x26, 0x1b, 0x39, 0x01};
Bundle dataAlign = new Bundle();
Bundle dataTextOut = new Bundle();
Bundle dataHdr = new Bundle();
dataHdr.putByteArray(Global.BYTESPARA1, hdrBytes);
dataHdr.putInt(Global.INTPARA1, 0);
dataHdr.putInt(Global.INTPARA2, hdrBytes.length);
dataAlign.putInt(Global.INTPARA1, nTextAlign);
dataTextOut.putString(Global.STRPARA1, text);
dataTextOut.putString(Global.STRPARA2, encoding);
WorkService.workThread.handleCmd(Global.CMD_POS_WRITE,dataHdr);
WorkService.workThread.handleCmd(Global.CMD_POS_SALIGN,dataAlign);
WorkService.workThread.handleCmd(Global.CMD_POS_STEXTOUT,dataTextOut);
}catch(Exception e){
Log.e(TAG, e.getMessage(), e.fillInStackTrace());
}
return null;
}
protected void onPostExecute(String file_url){}
}
@Override
protected void onUserLeaveHint()
{
Log.d("onUserLeaveHint","Home button pressed");
super.onUserLeaveHint();
//Unregister bluetooth receiver
try{unregisterReceiver(bluetoothReceiver);}catch(Exception e){}
//Disconnect bt connection
try{WorkService.workThread.disconnectBt();}catch(Exception e){}
// remove the handler
try{WorkService.delHandler(mHandler);}catch(Exception e){}
mHandler = null;
}
/**
* Broadcast receiver for bluetooth state changes
*/
private final BroadcastReceiver bluetoothReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent)
{
final String action = intent.getAction();
if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED))
{
final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,BluetoothAdapter.ERROR);
switch (state)
{
case BluetoothAdapter.STATE_OFF:
// closeConnection();//Close on going connection and disable button
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
break;
case BluetoothAdapter.STATE_ON:
break;
}
}
}
};
private static class MHandler extends Handler {
WeakReference<MainActivity> mActivity;
MHandler(MainActivity activity) {
mActivity = new WeakReference<>(activity);
}
@Override
public void handleMessage(Message msg) {
MainActivity theActivity = mActivity.get();
switch (msg.what) {
case Global.CMD_POS_STEXTOUTRESULT:
case Global.CMD_POS_WRITERESULT: {
int result = msg.arg1;
Toast.makeText(
theActivity,
(result == 1) ? Global.toast_success
: Global.toast_fail, Toast.LENGTH_SHORT).show();
Log.v(TAG, "Result: " + result);
break;
}
}
}
}
}
Does your app manifest declare permissions for bluetooth to be used?
https://developer.android.com/guide/topics/connectivity/bluetooth#Permissions
In order to use Bluetooth features in your application, you must declare two permissions. The first of these is BLUETOOTH. You need this permission to perform any Bluetooth communication, such as requesting a connection, accepting a connection, and transferring data.
The other permission that you must declare is either ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION. A location permission is required because Bluetooth scans can be used to gather information about the location of the user. This information may come from the user's own devices, as well as Bluetooth beacons in use at locations such as shops and transit facilities.
如果它只在你签署 apk 时发生,看起来你必须更新你的 proguard 规则,以排除打印机库类或类似的
One reason for the application not responding is that you stop the main thread for 3 seconds on line 60 in the click listener of the button. Replace the onCreate() method with the code below
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Get the activity
this.activity = this;
//Button from the XML view
btnConnect = findViewById(R.id.btnConnect);
//Start the Init Work Service Async task
new InitWorkService().execute();
final ExecutorService es = Executors.newFixedThreadPool(1);
//Set onClickListener for test print button
btnConnect.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
btnConnect.setEnabled(false);
es.submit(new Runnable() {
@Override
public void run() {
connect();
}
});
}
});
}
private void connect() {
try {
//Check if name and address are set
if (name != null && mac_address != null && mac_address.contains(":")) {
if (!WorkService.workThread.isConnected()) {
WorkService.workThread.connectBt(mac_address);
//Sleep for 3 seconds
try {
Thread.sleep(3000);
} catch (Exception e) {
}
}
//Check if connected
if (WorkService.workThread.isConnected()) {
//Collect data in background Thread
new PrintData().execute();
} else {
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
Toast.makeText(activity, Global.toast_notconnect, Toast.LENGTH_SHORT).show();
}
});
}
} else {
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
Toast.makeText(activity, "Please setup printer first!", Toast.LENGTH_LONG).show();
}
});
}
} catch (Exception e) {
Log.e(TAG, e.getMessage(), e.fillInStackTrace());
}
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
btnConnect.setEnabled(true);
}
});
}
Now the connection part executes in a new thread and only the UI operations go on the main one.
Please note that this code is not the optimal solution because it does not take into account the activity lifecycle. If the activity is re-created while the thread sleeps, there is still a reference kept to the old activity. But it should be a starting point for you.
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