如何从MainActivity类中的另一个类调用setText？

Question

I am trying to setText in my MainActivity but I do not know how can I get it work. I know that activitys are not instantiated so I dont know how can I set the string to the variable in the MainActivity.

I appreciate any help

 public class MainActivity extends ActionBarActivity { TextView textLat; TextView textLong; TextView textWifi; TextView textTime; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textLat = (TextView) findViewById(R.id.textLat); textLong = (TextView) findViewById(R.id.textLong); textWifi = (TextView) findViewById(R.id.textWifi); textTime = (TextView) findViewById(R.id.textTime); } } 

 public class ConnectionBroadcast extends BroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { if (intent.getAction().equals( android.net.ConnectivityManager.CONNECTIVITY_ACTION)) { //code } else if (intent.getAction().equals( android.net.wifi.WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)) { //code textWifi.setText(a.toString()); } } } 

Answer 1

String tw = textWifi.toString(); //do this in MainActivity Class
textWifi.setText(tw); // in your subclass

Answer 2

public class MainActivity extends ActionBarActivity {

TextView textLat;
    TextView textLong;
    TextView textWifi;
    TextView textTime;

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

        textLat = (TextView) findViewById(R.id.textLat);
        textLong = (TextView) findViewById(R.id.textLong);
        textWifi = (TextView) findViewById(R.id.textWifi);
        textTime = (TextView) findViewById(R.id.textTime);



    }

    private BroadcastReceiver receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
           if (intent.getAction().equals(
                android.net.ConnectivityManager.CONNECTIVITY_ACTION)) {
            //code

        } else if (intent.getAction().equals(
                android.net.wifi.WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)) {
            //code
                textWifi.setText(a.toString());
            }
        }
    };

    @Override
    protected void onResume() {
        IntentFilter filter = new IntentFilter();
        filter.addAction(android.net.wifi.WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
        registerReceiver(receiver, filter);
        super.onResume();
    }

    @Override
    protected void onPause() {
        unregisterReceiver(receiver);
        super.onPause();
    }
}

Answer 3

public class MainActivity extends ActionBarActivity implements ConnectionBroadcast.Listener {

    private TextView textLat;
    private TextView textLong;
    private TextView textWifi;
    private TextView textTime;

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

        textLat = (TextView) findViewById(R.id.textLat);
        textLong = (TextView) findViewById(R.id.textLong);
        textWifi = (TextView) findViewById(R.id.textWifi);
        textTime = (TextView) findViewById(R.id.textTime);

        ConnectionBroadcast.getInstance().register(this);
    }

    @Override
    public void onConnect() {

    }

    @Override
    public void onScan() {
        textWifi.setText(a.toString());
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        ConnectionBroadcast.getInstance().unRegister(this);
    }
}

Defines ConnectionBroadcast class as a singleton and communicate with other classes by interface.

public class ConnectionBroadcast extends BroadcastReceiver {

    private List<Listener> listeners = new ArrayList<>();

    private ConnectionBroadcast() {

    }

    private static class SingleHolder {
        private static ConnectionBroadcast instance = new ConnectionBroadcast();
    }

    public static ConnectionBroadcast getInstance() {
        return SingleHolder.instance;
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(android.net.ConnectivityManager.CONNECTIVITY_ACTION)) {
            synchronized (listeners) {
                for (Listener l : listeners) {
                    l.onConnect();
                }
            }
        } else if (intent.getAction().equals(
            android.net.wifi.WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)) {
            synchronized (listeners) {
                for (Listener l : listeners) {
                    l.onScan();
                }
            }
        }
    }

    public void register(Listener listener) {
        synchronized (listeners) {
            if (listeners.contains(listener)) {
                return;
            }
            listeners.add(listener);
        }
    }

    public void unRegister(Listener listener) {
        synchronized (listeners) {
            if (listeners.contains(listener)) {
                listeners.remove(listener);
            }
        }
    }

    public interface Listener {
        public void onConnect();
        public void onScan();
    }
}