Monday, 31 August 2015

How to make app auto run in background daily to fetch data from internet?

How to make app auto run in background daily to fetch data from internet?


I am developing a web crawler using Android. Currently my crawler crawls the web using async task every time the app starts, which takes a long time.
I want my app to update its database daily in the background, without needing to launch the MainActivity interface. After doing some research, I found the following classes can help me:
  1. Service
  2. AlarmManager
Can someone shed some light for me, I'm new to Android programming. Thanks



source: http://stackoverflow.com/questions/4459058/alarm-manager-example

This is working code. It wakes CPU every 10 minutes until the phone turns off.
Add to Manifest.xml:
...
<uses-permission android:name="android.permission.WAKE_LOCK"></uses-permission>
...
<receiver android:process=":remote" android:name=".Alarm"></receiver>
...
Code in your class:
package YourPackage; 
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.PowerManager;
import android.widget.Toast;
 
public class Alarm extends BroadcastReceiver 
{     
    @Override 
    public void onReceive(Context context, Intent intent) 
    {    
        PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
        PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "");
        wl.acquire();
 
        // Put here YOUR code. 
        Toast.makeText(context, "Alarm !!!!!!!!!!", Toast.LENGTH_LONG).show(); // For example
 
        wl.release();
    } 
 
    public void SetAlarm(Context context)
    { 
        AlarmManager am =( AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
        Intent i = new Intent(context, Alarm.class);
        PendingIntent pi = PendingIntent.getBroadcast(context, 0, i, 0);
        am.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 1000 * 60 * 10, pi); // Millisec * Second * Minute
    } 
 
    public void CancelAlarm(Context context)
    { 
        Intent intent = new Intent(context, Alarm.class);
        PendingIntent sender = PendingIntent.getBroadcast(context, 0, intent, 0);
        AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
        alarmManager.cancel(sender);
    } 
} 
Set Alarm from Service:
package YourPackage; 
 
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
 
public class YourService extends Service
{ 
    Alarm alarm = new Alarm();
    public void onCreate() 
    { 
        super.onCreate();        
    } 
 
    @Override 
    public int onStartCommand(Intent intent, int flags, int startId) 
    { 
        alarm.SetAlarm(this);
        return START_STICKY;
    } 
 
   @Override         
   public void onStart(Intent intent, int startId)
    { 
        alarm.SetAlarm(this);
    } 
 
    @Override 
    public IBinder onBind(Intent intent) 
    { 
        return null; 
    } 
} 
If you want set alarm repeating at phone boot time:
Add permission to Manifest.xml:
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"></uses-permission>
...
<receiver android:name=".AutoStart">
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED"></action>
    </intent-filter>
</receiver>
...
And create new class:
package YourPackage; 
 
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
 
public class AutoStart extends BroadcastReceiver
{    
    Alarm alarm = new Alarm();
    @Override 
    public void onReceive(Context context, Intent intent)
    {    
        if (intent.getAction().equals(Intent.ACTION_BOOT_COMPLETED))
        { 
            alarm.SetAlarm(context);
        } 
    } 
} 
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1 
How this setAlarm method will be called. If i would like to call it from service class ? Is it automatically called? –  Srizan Sagar Jan 20 '12 at 4:26
14 
This is very helpful, but a few things: 1. It might be better to use am.setInexactRepeating(...) so the phone isn't needlessly woken up because of the service. Other programmers should take note of this fact. 2. Instead of creating a new Alarm in AutoStart upon receiving theRECEIVE_BOOT_COMPLETED intent, it might make more sense to start YourService fromAutoStart, as shown here: stackoverflow.com/a/5439320/198348 –  Ehtesh Choudhury Jun 6 '12 at 17:31 
4 
I think acquiring the lock on the onReceive method is not mandatory since android will do it for you. See here: developer.android.com/reference/android/app/AlarmManager.html –  Ran Jun 13 '13 at 6:08
7 
WakeLock not needed in a BroadcastReceiver. Android uses its own one util broadcastReceiver finishes. – Jorge Fuentes Gonz├ílez Jul 2 '13 at 10:26
3 
Great answer, but is better extend from WakefulBroadcastReceiver instead of BroadcastReceiver, WakefulBroadcastReceiver manages the wake lock itself. See link for more info. –  icastell Mar 27 '14 at 8:28 

I tried the solution from XXX and while it did initially work, at some point it stopped working. The onReceive never got called again. I spent hours trying to figure out what it could be. What I came to realize is that the Intent for whatever mysterious reason was no longer being called. To get around this, I discovered that you really do need to specify an action for the receiver in the manifest. Example:
<receiver android:name=".Alarm" android:exported="true">
    <intent-filter>
        <action android:name="mypackage.START_ALARM" >
        </action>
    </intent-filter>
</receiver> 
Note that the name is ".Alarm" with the period. In XXX's SetAlarm method, create the Intent as follows:
Intent i = new Intent("mypackage.START_ALARM");
The START_ALARM message can be whatever you want it to be. I just gave it that name for demonstration purposes.
I have not seen receivers defined in the manifest without an intent filter that specifies the action. Creating them the way XXX has specified it seems kind of bogus. By specifying the action name, Android will be forced to create an instance of the BroadcastReceiver using the class that corresponds to the action. If you rely upon context, be aware that Android has several different objects that are ALL called context and may not result in getting your BroadcastReceiver created. Forcing Android to create an instance of your class using only the action message is far better than relying upon some iffy context that may never work.
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