Taste of Android :: Part-11

In Part-10, we demostrated a simple alarm application using the Android Service. We had to use an AsyncTask to avoid blocking the main UI Thread and cancel the AsyncTask and stop the Service once the alarm was trigger at the desired time (hour and minute). A simpler and easier way to acheive the same would be to use the Android framework class android.app.IntentService. The reason IntentService is simpler and easier is because it automatically creates a background processing thread to handle the alarm task and stops the service once the alarm is triggered.

In order to use IntentService, we need to extend the android.app.IntentService class and override the following method:

Default Constructor :: Need to implement the default constructor and call its superclasswith the name of the IntentService
onHandleIntent() :: method that will be executed in the background thread. This is where we place the code for the service task that will be long running and time consuming

We will now demonstrate this concept of using IntentService by creating a new Android application named DroidAlarmService2.

This application is essentially similar to DroidAlarmService except that it uses IntentService and we will use Notification instead of the Toast to alert the user when the alarm is triggered.

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


<string name="textview">textview</string>
<string name="timepicker">timepicker</string>
<string name="button1">button1</string>
<string name="button2">button2</string>



<string name="app_name">DroidAlarmService2</string>
<string name="simple_alarm">Simple Alarm</string>
<string name="set_alarm">Set Alarm</string>
<string name="cancel_alarm">Cancel Alarm</string>

</resources>

package com.polarsparc.android.droidalarmservice2;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.Messenger;
import android.view.View;
import android.widget.Button;
import android.widget.TimePicker;

public class TimePickActivity2 extends Activity {

private int pickedHour;
private int pickedMinute;

private Handler handler;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.activity_time_pick);

handler = new Handler() {
@Override
public void handleMessage(Message msg) {
Button set = (Button) findViewById(R.id.button1);
set.setEnabled(true);

Button cancel = (Button) findViewById(R.id.button2);
cancel.setEnabled(false);
}
};

TimePicker picker = (TimePicker) findViewById(R.id.timepicker);
pickedHour = picker.getCurrentHour();
pickedMinute = picker.getCurrentMinute();
picker.setOnTimeChangedListener(new TimePicker.OnTimeChangedListener() {
@Override
public void onTimeChanged(TimePicker view, int hour, int minute) {
pickedHour = hour;
pickedMinute = minute;
}
});

final Button set = (Button) findViewById(R.id.button1);
set.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
set.setEnabled(false);

Button cancel = (Button) findViewById(R.id.button2);
cancel.setEnabled(true);

Intent intent = new Intent(getBaseContext(), MyAlarmService2.class);
intent.putExtra("pickedHour", pickedHour);
intent.putExtra("pickedMinute", pickedMinute);
intent.putExtra("Messenger", new Messenger(handler));

startService(intent);
}
});

final Button cancel = (Button) findViewById(R.id.button2);
cancel.setEnabled(false);
cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
cancel.setEnabled(false);

Button set = (Button) findViewById(R.id.button1);
set.setEnabled(true);

stopService(new Intent(getBaseContext(), MyAlarmService2.class));
}
});
}

}

package com.polarsparc.android.droidalarmservice2;

import android.app.IntentService;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.Message;
import android.os.Messenger;
import android.util.Log;

import java.util.Calendar;

public class MyAlarmService2 extends IntentService {

private static String TAG = "MyAlarmService2";

private boolean loop = true;

private NotificationManager notificationManager = null;

private Messenger messenger = null;

public MyAlarmService2() {
super("MyAlarmService2");
}

@Override
protected void onHandleIntent(Intent intent) {
final int REQUEST_CODE = 0;
final int NOTIFICATION_ID = 1;

final String TITLE = "Wake Up Alarm @ %02d:%02d";
final String TEXT = "Alarm Service!";

int pickedHour = intent.getIntExtra("pickedHour", -1);
int pickedMinute = intent.getIntExtra("pickedMinute", -1);

Bundle extras = intent.getExtras();

messenger = (Messenger) extras.get("Messenger");

notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

Log.i(TAG, "MyAlarmService2 - onHandleIntent() :: pickedHour = " +
pickedHour + ", pickedMinute = " + pickedMinute);

if (pickedHour >= 0 && pickedMinute >= 0 && notificationManager != null && messenger != null) {
while (loop) {
try {
// Sleep for 1 second
Thread.sleep(1000);

if (! loop) {
break;
}

Calendar cal = Calendar.getInstance();

int curHour = cal.get(Calendar.HOUR_OF_DAY);
int curMinute = cal.get(Calendar.MINUTE);

if (curHour == pickedHour && curMinute == pickedMinute) {
Log.i(TAG, "MyAlarmService2 - onHandleIntent() :: Alarm triggered !!!");

sendHandlerMessage();

Context context = getApplicationContext();

Intent notifyIntent = new Intent(this, TimePickActivity2.class);

PendingIntent pendingIntent = PendingIntent.getActivity(context, REQUEST_CODE,
notifyIntent, Intent.FLAG_ACTIVITY_NEW_TASK);

Notification notification = new Notification.Builder(context)
.setContentTitle(String.format(TITLE, pickedHour, pickedMinute))
.setContentText(TEXT)
.setSmallIcon(R.drawable.my_alarm)
.setContentIntent(pendingIntent)
.getNotification();
notification.defaults |= Notification.DEFAULT_SOUND;
notification.flags |= Notification.FLAG_AUTO_CANCEL;

notificationManager.notify(NOTIFICATION_ID, notification);

break;
}
}
catch (Throwable t) {
Log.e(TAG, "MyAlarmService2 - onHandleIntent() :: exception !!!", t);
}
}
}
}

@Override
public void onDestroy() {
loop = false;

Log.i(TAG, "MyAlarmService2 - onDestroy() called !!!");
}

private void sendHandlerMessage() {
Message msg = Message.obtain();

try {
messenger.send(msg);
}
catch (Throwable t) {
Log.e(TAG, "MyAlarmService2 - sendHandlerMessage() :: exception !!!", t);
}
}

}

Here is how this custom alarm timer will work:

In the activity named TimePickActivity2, the user will pick an appropriate time (hour and minute) for the alarm and press the Set Alarm button
On pressing the Set Alarm button in the activity TimePickActivity2, an Intent is created to start the service named MyAlarmService2 with the associated data (selected hour and minute). Also, the Set Alarm button is disabled and the Cancel Alarm button is enabled
On pressing the Cancel Alarm button in the activity TimePickActivity2 will stop the service MyAlarmService2 and cancel the logic to trigger the alarm. Also, the Cancel Alarm button is disabled and the Set Alarm button is enabled
Calling the startService() method and passing the created Intent will start the service MyAlarmService2 in the background
When the service MyAlarmService2 starts, the onHandleIntent() method is invoked. Note that the logic in this method is processed in a background thread that is automatically created and managed
When the service MyAlarmService2 starts, the onHandleIntent() method is invoked. Note that this method is processed in a background thread that is automatically created and managed
Notice we start a Handler in the OnCreate() method of TimePickActivity2. On receiving a Message, the Cancel Alarm button is disabled and the Set Alarm button is enabled
At the selected hour and minute, the code logic in the onHandleIntent() method of the service MyAlarmService2 will create an Android Notification and dispatch it via the Android system NotificationManager. In addition, it will trigger a Message to the Handler in TimePickActivity2
Notification in Android is used to alert a user when some important event occurs. Unlike the Toast message which appears on the screen for a brief period and disappears, a Notification is a persistent message that appears on the status or notification bar located at the top of the screen on the device. To dispatch an Android Notification, we do the following:

To send notifications, we need an instance of the Android framework class android.app.NotificationManager, which can be obtained from the Context (Activity or Service) by invoking the method getSystemService()
We will need an instance of the Android Intent. This allows the Android system to launch any desired application Activity when the user selects this notification. In our case we will stay with TimePickActivity2
We also need an instance of the Android framework class android.app.PendingIntent. A PendingIntent is a token that you give to NotificationManager or any other application, which allows the other application to use your application's permissions to execute a predefined piece of code
Finally, we need to create an instance of the Android framework class android.app.Notification by using the Notification.Builder
To send the notification, we need to call the notify() on the NotificationManager

Finally, modify the contents of the AndroidManifest.xml file to look like the one shown in the listing 11.6 below:

Listing-11.6

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.polarsparc.android.droidalarmservice2"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="14" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        
        <activity
            android:name="com.polarsparc.android.droidalarmservice2.TimePickActivity2"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        
        <service android:name=".MyAlarmService2" />
        
    </application>

</manifest>

We are now ready to test our DroidAlarmService2 application on the virtual Android device we created in Part-1. We will create a Run Configuration for DroidAlarmService2 as we did in Part-2 for DroidTipCalculator.