src/com/projectara/araepm/MainActivity.java

package com.projectara.araepm;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.io.IOException;
import android.os.Handler;
import android.util.Log;

public class MainActivity extends Activity
    implements EpmController.EpmChangeCallback {

    private static final String TAG = "araepm";

    private static String EPM_ATTACHED;
    private static String EPM_DETACHED;

    private static String EPM_ATTACHING;
    private static String EPM_DETACHING;

    private static String EPM_STATUS_OK;
    private static String EPM_STATUS_ERROR;
    private static String EPM_STATUS_TIMEOUT;

    private TextView statusText;
    private EditText portNumber;
    private Handler handler;
    private Button[] buttons;

    private EpmController epmController;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        portNumber = (EditText)findViewById(R.id.portNumber);
        statusText = (TextView)findViewById(R.id.statusText);

        EPM_ATTACHED = getString(R.string.epm_attached);
        EPM_DETACHED = getString(R.string.epm_detached);

        EPM_ATTACHING = getString(R.string.epm_attaching);
        EPM_DETACHING = getString(R.string.epm_detaching);

        EPM_STATUS_OK = getString(R.string.epm_status_ok);
        EPM_STATUS_ERROR = getString(R.string.epm_status_error);
        EPM_STATUS_TIMEOUT = getString(R.string.epm_status_timeout);

        buttons = new Button[2];
        buttons[0] = (Button)findViewById(R.id.attachButton);
        buttons[1] = (Button)findViewById(R.id.detachButton);

        handler = new Handler();
    }

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

    @Override
    protected void onStart(){
        Log.d(TAG, "onstart");
        super.onStart();
        epmController = new EpmController(this, this);
        epmController.start();
    }

    @Override
    protected void onStop() {
        Log.d(TAG, "onstop");
        super.onStop();
        epmController.stop();
        epmController = null;
    }

    private void disableStateChanges() {
        for (int i = 0; i < buttons.length; i++) {
            buttons[i].setClickable(false);
        }
    }

    private void enableStateChanges() {
        for (int i = 0; i < buttons.length; i++) {
            buttons[i].setClickable(true);
        }
    }

    private int getPortNumber() {
        String s = portNumber.getText().toString();
        try {
            return Integer.parseInt(s);
        } catch (NumberFormatException nfe) {
            // Can't happen; portNumber only allows numeric input
            Log.wtf(TAG, "non-numeric text " + s + " in portNumber");
            return -1;
        }
    }

    private void doAttachDetach(boolean attach) {
        int port = getPortNumber();
        if (port < 0) {
            return;
        }
        Log.d(TAG,
              (attach ? "Attaching" : "Detaching") + " EPM on port " + port);
        disableStateChanges();
        if (attach) {
            statusText.setText(String.format(EPM_ATTACHING, port));
            epmController.attachEpm(port);
        } else {
            statusText.setText(String.format(EPM_DETACHING, port));
            epmController.detachEpm(port);
        }
    }

    public void attachEpm(View view) {
        doAttachDetach(true);
    }

    public void detachEpm(View view) {
        doAttachDetach(false);
    }

    @Override
    public void onEpmChangeFinished(EpmController.EpmState attemptedState,
                                    EpmController.EpmChangeStatus changeStatus,
                                    int changedPort) {
        final EpmController.EpmState attempted = attemptedState;
        final EpmController.EpmChangeStatus status = changeStatus;
        final int port = changedPort;
        handler.post(new Runnable() {
                @Override
                public void run() {
                    String newStatus;
                    String s;

                    enableStateChanges();

                    switch (attempted) {
                    case EPM_ATTACH:
                        s = EPM_ATTACHED;
                        break;
                    case EPM_DETACH:
                        s = EPM_DETACHED;
                        break;
                    default:
                        Log.wtf(TAG, "can't happen");
                        return;
                    }

                    String statusFormat;
                    switch (status) {
                    case EPM_OK:
                        statusFormat = EPM_STATUS_OK;
                        break;
                    case EPM_ERROR:
                        statusFormat = EPM_STATUS_ERROR;
                        break;
                    case EPM_TIMEOUT:
                        statusFormat = EPM_STATUS_TIMEOUT;
                        break;
                    default:
                        Log.wtf(TAG, "can't happen");
                        return;
                    }
                    statusText.setText(String.format(statusFormat, s, port));
                }
            });
    }
}