Java – Android starts activities through background services

My goal is to have the UDP packet receiving application run continuously when it starts in the background, processing messages and displaying them as long as it receives valid packets.

After some research, I did the following.

1. Broadcast Receiver class – Start the service at startup (mstart.java).
2. A service class used to monitor UDP packets (UDP.java).
3. The Display class displays the message as text (RMSGS.java).
4. GlobalState.Java for global variables.

I wrote a standalone application with a

UDP application with a ListView and it worked fine. So I know it’s okay.

When I compile the runtime, the code service starts at boot time and then crashes. For debugging, I took the UDP packet receive part. After the UDP class receives the packet, it will produce two array lists, which are saved in the Global class and obtained by the Display class.

    This code is working now, I found mistake I have made and corrected it.

Now I have to modify to receive UDP packets.

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.WAKE_LOCK"/>
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.QUICKBOOT_POWERON"/>
<application
    android:name="com.mmm.rmsg.GlobalState"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:largeHeap="true"
    android:theme="@style/AppTheme" >
    <activity
        android:name=". MsgView"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
           <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <receiver android:enabled="true" android:exported="true"
        android:name=".mstart"
        android:permission="android.permission.RECEIVE_BOOT_COMPLETED">
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED"/>
            <action android:name="android.intent.action.QUICKBOOT_POWERON"/>
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </receiver>
    <service android:name=".udp"
      />
    </application>
<uses-permission android:name="android.permission.INTERNET"/>

Broadcast receiver class

 package com.mmm.rmsg;
 import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class mstart extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {

Toast.makeText(context, "Intent detcted.", Toast.LENGTH_LONG).show();

Intent pushIntent = new Intent(context, udp.class);
    context.startService(pushIntent);
  }

}

Class of service

  package com.mmm.rmsg;
  import android.app.Service;
  import android.content.Context;
  import android.content.Intent;
  import android.os.IBinder;
  import android.os.PowerManager;
  import android.widget.Toast;
  import java.util.ArrayList;

import static android.os.PowerManager.PARTIAL_WAKE_LOCK;

public class udp extends Service {

private static final String LOG_TAG =udp.class.getSimpleName();

GlobalState gs = (GlobalState)getApplication();

@Override
 public IBinder onBind(Intent arg0){

return  null;
}

@Override public int onStartCommand(Intent intent, int flags, int startId) {

setWakeLock();
    Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();

new Thread(new Server()).start();

return START_STICKY;

}

private void setWakeLock(){

PowerManager.WakeLock mWakeLock;
    PowerManager powerManager = (PowerManager)getSystemService(Context.POWER_SERVICE);
    mWakeLock=powerManager.newWakeLock(PARTIAL_WAKE_LOCK, LOG_TAG);
}

public class Server implements Runnable {

@Override
    public void run() {

ArrayList<String> list = new ArrayList<>();
        ArrayList<String> clist = new ArrayList<>();
         here udp packets are recvd & processed into 2 list arrays

list.add(0, "MAIN FAIL");
        list.add(1,"BOILER HEATER 20C");
        list.add(2, "COOLING NEED ATT");

clist.add(0, "6");
        clist.add(1,"1");
        clist.add(2, "5");

GlobalState gs = (GlobalState)getApplication();

gs.setGmlist(list);
          gs.setGclist(clist);

call();

}

}

public void call() {

Intent dialogIntent = new Intent(getBaseContext(), MsgView.class);
    dialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    startActivity(dialogIntent);

}

}

Global classes

   package com.mmm.rmsg;

import java.util.ArrayList;
  import android.app.Application;

public class GlobalState extends Application
  {
    private ArrayList<String> Gmlist = new ArrayList<>();
    private ArrayList<String> Gclist = new ArrayList<>();
    private boolean chk = true;
    private boolean cchk = true;

public ArrayList<String> getGmlist() {

chk = Gmlist.isEmpty();

if(chk==true)
    {
        Gmlist.add(0,"No Calls");
    }

return Gmlist;
  }

public ArrayList<String> getGclist() {
      cchk = Gclist.isEmpty();

if(cchk==true)
    {
        Gclist.add(0,"0");
    }

return Gclist;
}

public void setGmlist(ArrayList<String> Gmlit) {

for (int i = 0; i < Gmlit.size(); i++) {
            this. Gmlist.add(i, Gmlit.get(i));
        }

}

public void setGclist(ArrayList<String> Gclit) {

for (int i = 0; i < Gclit.size(); i++) {
        this. Gmlist.add(i, Gclit.get(i));
      }

}

}

Display class

    package com.mmm.rmsg;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.widget.ListView;
    import android.content.Context;
    import android.graphics.Color;
    import android.widget.ArrayAdapter;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.TextView;
    import java.util.ArrayList;
    import java.util.Arrays;

public class MsgView extends AppCompatActivity {

ListView listView ;
        ArrayList<String> mlist = new ArrayList<>();
        ArrayList<String> plist = new ArrayList<>();

@Override
        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_msg_view);

 Get ListView object from xml
            listView = (ListView) findViewById(R.id.list);

GlobalState gs = (GlobalState) getApplication();

mlist= gs.getGmlist();
                plist= gs.getGclist();

String[] msgArray = mlist.toArray(new String[mlist.size()]);
                Arrays.toString(msgArray);
                String[] clrArray = plist.toArray(new String[plist.size()]);
                Arrays.toString(clrArray);

listView.setAdapter(new ColorArrayAdapter(this, android. R.layout.simple_list_item_1, msgArray,clrArray));

}

public class ColorArrayAdapter extends ArrayAdapter<Object>{
            private String[] list;
            private String[] p;
            public ColorArrayAdapter(Context context, int textViewResourceId,
                             Object[] objects, Object[] obj) {
            super(context, textViewResourceId, objects);
            list = new String[objects.length];
            for (int i = 0; i < list.length; i++)
                list[i] = (String) objects[i];

p = new String[objects.length];
                for (int i = 0; i < p.length; i++)
                p[i] = (String) obj[i];
    }

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = (TextView)super.getView(position, convertView, parent);

String c;
        for(int x=0; x< list.length; x++)
        {
            c=chk(x,p);

if("R".equals(c) && position==x ) {
                view.setBackgroundColor(Color.RED);
            }
            else
            if("Y".equals(c) && position==x) {
                view.setBackgroundColor(Color.YELLOW);
            }
            else
            if("G".equals(c) && position==x) {
                view.setBackgroundColor(Color.GREEN);
           }

}
            return view;
        }

}

public  String chk(int idx, String[] table){

String res;
    if("6".equals(table[idx]) || "7".equals(table[idx])  || "8".equals(table[idx])) {
        res = "R";
    }
    else
    if("4".equals(table[idx])  || "5".equals(table[idx])) {
        res = "Y";
    }
    else
    if("1".equals(table[idx])|| "2".equals(table[idx]) || "3".equals(table[idx]) ) {
        res = "G";
    }
    else{
        res = "W";
    }

return res;
    }

@Override
        public boolean onCreateOptionsMenu(Menu menu) {
     Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_msg_view, menu);
        return true;
    }

@Override
        public boolean onOptionsItemSelected(MenuItem item) {
         Handle action bar item clicks here. The action bar will
             automatically handle clicks on the Home/Up button, so long
         as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
            }

return super.onOptionsItemSelected(item);
        }

@Override
        protected void onDestroy(){
            super.onDestroy();

}
    }

You haven’t started your topic yet. You can do this:

Thread initBkgThread = new Thread(new Runnable() {

public void run() {
            udp();
        }
    });
initBkgThread .start();