Perform Long-Running Tasks in a Service
Description
The following code shows how to Perform Long-Running Tasks in a Service. You will simulate the service of downloading a file from the Internet.
Example
Populate the MyService.java file with the following code:
package com.java2s.myapplication3.app;
// ww w .ja va 2 s . co m
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.widget.Toast;
public class MyService extends Service {
@Override
public IBinder onBind(Intent arg0) {
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
try {
int result = DownloadFile(new URL("http://www.your server.com/somefile.pdf"));
Toast.makeText (getBaseContext(),
"Downloaded " + result + " bytes",
Toast.LENGTH_LONG).show();
} catch (MalformedURLException e) {
e.printStackTrace();
}
return START_STICKY;
}
private int DownloadFile(URL url) {
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return 100;
}
@Override
public void onDestroy() {
super.onDestroy();
Toast.makeText (this, "Service Destroyed", Toast.LENGTH_LONG).show();
}
}
In the AndroidManifest.xml file, add the following statement:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.java2s.Services"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="14" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name=".ServicesActivity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".MyService" />
</application>
</manifest>
Main layout xml file
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<Button android:id="@+id/btnStartService"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Start Service"
android:onClick="startService"/>
<Button android:id="@+id/btnStopService"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Stop Service"
android:onClick="stopService" />
</LinearLayout>
Main Activity Java code
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
/*from w ww . jav a 2 s . c o m*/
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void startService(View view) {
startService(new Intent(getBaseContext(), MyService.class));
}
public void stopService(View view) {
stopService(new Intent(getBaseContext(),MyService.class));
}
}
Note
Clicking the Start Service button will start the service. To stop the service, click the Stop Service button.
The activity is frozen for a few seconds before the Toast class displays the "Downloaded 100 bytes" message.
Note 2
The service runs on the same thread as your activity. In this case, because the service is suspended for five seconds, so is the activity.