Question

I create an gpsservice, a main activity with two buttons and a list activity. I’d like to get the gpsservie data when the gps data is obtained, so I create a gps receiver in the main activity to get the data. When I click the button in the main activity, it turns to the list activity. I’d like to transfer the obtained data to the list activity by using intent() when the button is clicked. the problem is that when I click the button, there is nothing shown in the listview.

the key codes of GPS service :

LocationListener locationListener = new LocationListener() {
        public void onLocationChanged(Location location) {
            additem(location);
            addgeo(location);
            //String latLongString = "Lat:" + location.getLatitude() + "\nLong:" + location.getLongitude();
            Intent intent= new Intent("com.example.geotask.gpsdata");
            intent.putIntegerArrayListExtra("lat", (ArrayList<Integer>) lat);
            intent.putIntegerArrayListExtra("lon", (ArrayList<Integer>) lon);
            intent.putStringArrayListExtra("data", (ArrayList<String>) position);
            //intent.putExtra("data", latLongString);
            sendBroadcast(intent);    }

the main activity code:

public class MainActivity extends Activity {

    public  ArrayList<String> position1 = new ArrayList<String>(); 
    public  ArrayList<Long> time=new ArrayList<Long>();
    public  ArrayList<Integer> lat1= new ArrayList<Integer>(); 
    public  ArrayList<Integer> lon1= new ArrayList<Integer>(); 
    private BroadcastReceiver gpsreceiver;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        IntentFilter intentFilter=new IntentFilter("com.example.geotask.gpsdata");
        gpsreceiver=new BroadcastReceiver()
        {
            @Override 
            public void onReceive(Context context, Intent intent)
            {
             ArrayList<String> position1=intent.getStringArrayListExtra("data");
             ArrayList<Integer> lat1=intent.getIntegerArrayListExtra("lat");
            ArrayList<Integer> lon1=intent.getIntegerArrayListExtra("lon");
            }

        };
        this.registerReceiver(gpsreceiver, intentFilter);

        final Button listbutton=(Button) findViewById(R.id.button2);
        listbutton.setOnClickListener(new OnClickListener(){
            public void onClick(View v){
                Intent intent =new Intent();
                intent.setClass(MainActivity.this, list.class);
                intent.putStringArrayListExtra("data", (ArrayList<String>) position1);
                startActivity(intent);

            }
        });
        }

the list activity:

public class list extends Activity{ 
    static ArrayList<listdetails> details = new ArrayList<listdetails>();
   // private BroadcastReceiver gpsreceiver;

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.list); 
        ListView listView; 
        listView = (ListView)findViewById(R.id.listView1);
        Intent intent=getIntent();
        List<String> ex=intent.getStringArrayListExtra("data");
        customlist Adapter = new customlist(details, this);
        listView.setAdapter(Adapter);
        listdetails Detail = new listdetails();
            for(int i=0;i<ex.size();i++)
            {
                Detail.setIcon(R.drawable.ic_launcher);
                Detail.setPlace(ex.get(i));
                Detail.setTime("2012.12.2");
                details.add(Detail);

            }

            }

Answer 1

You are duplicating your variables in onReceive(). This means that the ArrayList variables get destroyed once onReceive() completes. Your onReceive() should look like:

        @Override 
        public void onReceive(Context context, Intent intent)
        {
          position1=intent.getStringArrayListExtra("data");
          lat1=intent.getIntegerArrayListExtra("lat");
         lon1=intent.getIntegerArrayListExtra("lon");
        }

This ensures that you are now modifying the global ArrayLists. Also, you may need to declare the global ArrayLists as final since Java might treat your new BroadCastReceiver as an anonymous inner class.