runOnUiThread Undefined for Class

Question

I'm trying to throw and alert dialog on the UI thread from my background thread but I'm having problems with runOnUiThread being undefined. I have tried FindLocation.this.runOnUiThread and runOnUiThread but both seem to throw the same error The method runOnUiThread(new Runnable(){}) is undefined for the type new LocationListener(){} (or ...the type FindLocation). Any ideas why? Here is a snippet of my FindLocation.java class. This is called by my main activity.

public class FindLocation extends Thread {

public boolean inJurisdiction;
public boolean AlertNotice = false;
private LocationManager locManager;
private LocationListener locListener;

Context ctx;
public String userId;

public FindLocation(Context ctx) {
     this.ctx = ctx;
}

 public void start(String userId) {
        this.userId = userId;
        super.start();

      }

@Override
public void run() {
     Looper.prepare();
    final String usr = userId;  

    //get a reference to the LocationManager
    locManager = (LocationManager) ctx.getSystemService(Context.LOCATION_SERVICE);

    //checked to receive updates from the position
    locListener = new LocationListener() {
        public void onLocationChanged(Location loc) {

            String lat = String.valueOf(loc.getLatitude()); 
            String lon = String.valueOf(loc.getLongitude());

            Double latitude = loc.getLatitude();
            Double longitude = loc.getLongitude();

            if (latitude >= 39.15296 && longitude >= -86.547546 && latitude <= 39.184901 && longitude <= -86.504288 || inJurisdiction != false) {
                Log.i("Test", "Yes");  

                inJurisdiction = true;

                FindLocation.this.runOnUiThread(new Runnable() { ///****error here****
                    public void run() {
                        AlertDialog.Builder alert = new AlertDialog.Builder(ctx);
                        alert.setTitle("Sent");
                        alert.setMessage("You will be contacted shortly.");
                        alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                           public void onClick(DialogInterface dialog, int which) {
                           }
                        });
                    }
                });

Answer 1

Since runOnUIThread() is method of Activity, you can pass reference to calling activity in constructor.

...
Context ctx;
Activity act;
public String userId;
...

public FindLocation(Context ctx, Activity act) {
    this.ctx = ctx;
    this.act = act;
}

and use runOnUIThread() like

act.runOnUiThread(new Runnable() {...});

However I believe it's unsafe and you need to take precautions to make sure your Activity is still there when you are calling runOnUiThread

Answer 2

Another better approach..

No need to create constructor for getting Activity.

Just typecast the context to Activity class.

((Activity)context).runOnUiThread(new Runnable()
    {
        public void run()
        { 
             Toast.makeText(context, toast, Toast.LENGTH_SHORT).show();
        }
    });

Answer 3

runOnUIThread() is a method belonging to Activity.. SO you cannot call it from a Thread.

So instead of Context take Activity instance in its Constructor and call it using that.. something like

activity.runOnUIThread();