Android Concepts: 2014

Android Started Service Concept and Example

Android Service Types

Started Service (Unbound)
Bound Service

For Android Service Concepts go to this blog. To get over Bound Services visit the link.

Started Service

By extending Intent Service class
By extending Service

In this post I am going to explain about Started Service by extending Service Class.

Android provides multiple API to create a Service within same or different address space than their clients. Started Service is used within the same Application which implements it i.e. inside same address space.

A service is "started" when an application component (such as an activity) starts it by calling startService(). Once started, a service can run in the background indefinitely, even if the component that started it is destroyed. Usually, a started service performs a single operation and does not return a result to the caller. For example, it might download or upload a file over the network. When the operation is done, the service should stop itself.

What Service needs ?

Extends Service
Handler and write its handleMessage()
Looper : For multiple requests to be queued
Override onCreate()
No need to override onBind()

Extends the Service

public class MyStartedService extends Service { …. }

Required Field Variables

public class MyStartedService extends Service {

MyServiceHandler mHandler;

Looper looper;

…. }

Implement The Handler for the Service

private final class MyServiceHandler extends Handler {

public MyServiceHandler(Looper looper) {

super(looper);

}

@Override

public void handleMessage(Message msg) {

// Service will do the necessary jobs using the Message

// you can stop the service here

stopSelf(msg.arg1);

}

Override onCreate() of Service Class

@Override

public void onCreate() {

HandlerThread thread = new HandlerThread("ServiceStartArguments",

Process.THREAD_PRIORITY_BACKGROUND);

thread.start();

// Get the HandlerThread's Looper and use it for our Handler

looper = thread.getLooper();

mHandler = new ServiceHandler(mServiceLooper);

}

Override onStartCommand() of Service Class

@Override

public int onStartCommand(Intent intent, int flags, int startId) {

// For each start request, send a message to start a job and deliver the

// start ID so we know which request we're stopping when we finish the job

Message msg = mServiceHandler.obtainMessage();

msg.arg1 = startId;

mServiceHandler.sendMessage(msg);

// If we get killed, after returning from here, restart

return START_STICKY;

}

Override onBind(): No need to override it because service is not Bound

@Override

public IBinder onBind(Intent intent) {

// We don't provide binding, so return null

return null;

}

What Client needs

Start the Service

Intent intent = new Intent(this, HelloService.class);

startService(intent);

Stop the Service

Once requested to stop with stopSelf() or stopService(), the system destroys the service as soon as possible.

A live example

In the sample example UI Activity class sends a request to "started service " and service gives back the reply to the client which is displayed inside the edit text area.

MyStartedService.java

package pp.startedservice;

import android.app.Service;

import android.content.Intent;

import android.os.Bundle;

import android.os.Handler;

import android.os.HandlerThread;

import android.os.IBinder;

import android.os.Looper;

import android.os.Message;

import android.widget.Toast;

public class MyStartedService extends Service {

private Looper serviceLooper;

private ServiceHandler serviceHandler;

private class ServiceHandler extends Handler{

public ServiceHandler(Looper looper) {

super(looper);

}

@Override

public void handleMessage(Message msg) {

String req=msg.getData().getString("REQ");

String dis ="Service: "+req;

// Toast.makeText(getApplicationContext(), dis,Toast.LENGTH_SHORT).show();

Intent bIntent = new Intent ("STARTED_SERVICE");

bIntent.addCategory(Intent.CATEGORY_DEFAULT);

bIntent.putExtra("RESPONSE", dis);

sendBroadcast(bIntent);

// Service stop itself after serving

// stopSelf(msg.arg1);

}

@Override

public void onCreate() {

// New thread other than UI....

HandlerThread thread = new HandlerThread("ServiceStartArguments", 7);

thread.start();

serviceLooper = thread.getLooper();

serviceHandler = new ServiceHandler(serviceLooper);

// Toast.makeText(this, "Service is created",Toast.LENGTH_SHORT).show();

};

@Override

public IBinder onBind(Intent arg0) {

// TODO Auto-generated method stub

// Not required if Service is " Started One"

return null;

}

@Override

public int onStartCommand(Intent intent, int flags, int startId){

String req = intent.getExtras().getString("REQUEST");

Bundle data=new Bundle();

data.putString("REQ", req);

Message msg = serviceHandler.obtainMessage();

msg.arg1 = startId;

msg.setData(data);

serviceHandler.sendMessage(msg);

Toast.makeText(this, "Service is started"+"\nREQUEST is : "+req,Toast.LENGTH_SHORT).show();

return START_STICKY;

}

public void onDestroy(){

Toast.makeText(this, "Service is Destroyed",Toast.LENGTH_SHORT).show();

}

MainActivity.java

package pp.startedservice;

import android.app.Service;

import android.content.Intent;

import android.os.Bundle;

import android.os.Handler;

import android.os.HandlerThread;

import android.os.IBinder;

import android.os.Looper;

import android.os.Message;

import android.widget.Toast;

public class MyStartedService extends Service {

private Looper serviceLooper;

private ServiceHandler serviceHandler;

private class ServiceHandler extends Handler{

public ServiceHandler(Looper looper) {

super(looper);

}

@Override

public void handleMessage(Message msg) {

String req=msg.getData().getString("REQ");

String dis ="Service: "+req;

// Toast.makeText(getApplicationContext(), dis,Toast.LENGTH_SHORT).show();

Intent bIntent = new Intent ("STARTED_SERVICE");

bIntent.addCategory(Intent.CATEGORY_DEFAULT);

bIntent.putExtra("RESPONSE", dis);

sendBroadcast(bIntent);

// Service stop itself after serving

// stopSelf(msg.arg1);

}

@Override

public void onCreate() {

// New thread other than UI....

HandlerThread thread = new HandlerThread("ServiceStartArguments", 7);

thread.start();

serviceLooper = thread.getLooper();

serviceHandler = new ServiceHandler(serviceLooper);

// Toast.makeText(this, "Service is created",Toast.LENGTH_SHORT).show();

};

@Override

public IBinder onBind(Intent arg0) {

// TODO Auto-generated method stub

// Not required if Service is " Started One"

return null;

}

@Override

public int onStartCommand(Intent intent, int flags, int startId){

String req = intent.getExtras().getString("REQUEST");

Bundle data=new Bundle();

data.putString("REQ", req);

Message msg = serviceHandler.obtainMessage();

msg.arg1 = startId;

msg.setData(data);

serviceHandler.sendMessage(msg);

Toast.makeText(this, "Service is started"+"\nREQUEST is : "+req,Toast.LENGTH_SHORT).show();

return START_STICKY;

}

public void onDestroy(){

Toast.makeText(this, "Service is Destroyed",Toast.LENGTH_SHORT).show();

}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:id="@+id/container"

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context="pp.messengerservice.MainActivity"

tools:ignore="MergeRootFrame"

android:background="#000000" >

<TextView

android:id="@+id/textView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_alignParentRight="true"

android:layout_alignParentTop="true"

android:text="Started Service Test"

android:textColor="#ff0000"

android:textSize="25sp" />

<RelativeLayout

android:id="@+id/control"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_alignParentLeft="true"

android:layout_marginBottom="44dp" >

<Button

android:id="@+id/button1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_marginTop="28dp"

android:onClick="sayHello"

android:text="Start Service"

android:textSize="25sp" />

<Button

android:id="@+id/button2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_alignParentRight="true"

android:layout_below="@+id/button1"

android:layout_marginTop="20dp"

android:text="Stop Service"

android:textSize="25sp" />

</RelativeLayout>

<RelativeLayout

android:id="@+id/reqrep"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_alignParentRight="true"

android:layout_below="@+id/textView1"

android:layout_marginTop="62dp" >

<EditText

android:id="@+id/editText2"

android:layout_width="wrap_content"

android:layout_height="35dp"

android:layout_alignParentLeft="true"

android:layout_alignParentRight="true"

android:layout_below="@+id/editText1"

android:layout_margin="5dp"

android:background="#f0fcf2"

android:ems="10"

android:hint="Response from Server !"

android:textColor="#ff0000" >

</EditText>

<EditText

android:id="@+id/editText1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_alignParentRight="true"

android:layout_alignParentTop="true"

android:layout_margin="3dp"

android:ems="10"

android:hint="Request Message !" />

</RelativeLayout>

AndroidManifest.xml

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

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="pp.startedservice"

android:versionCode="1"

android:versionName="1.0" >

<uses-sdk

android:minSdkVersion="15"

android:targetSdkVersion="19" />

<application

android:allowBackup="true"

android:icon="@drawable/ic_launcher"

android:label="@string/app_name"

android:theme="@style/AppTheme" >

<activity

android:name="pp.startedservice.MainActivity"

android:label="@string/app_name" >

<intent-filter>

</intent-filter>

</activity>

</application>

</manifest>

Android Concepts

Tuesday 1 July 2014

Android Started Service by extending Service