Differences between Intent and PendingIntent

Question

I read through some articles. All seem to do the same thing and I was wondering what is the difference between starting the service as below:

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

or below:

Calendar cal = Calendar.getInstance(); Intent intent = new Intent(this, MyService.class); PendingIntent pintent = PendingIntent.getService(this, 0, intent, 0); AlarmManager alarm = (AlarmManager)getSystemService(Context.ALARM_SERVICE); alarm.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), 30*1000, pintent);  

As I read through, these two do the same thing, if in the service you return a parameter START_STICKY;

Answer 1

Intent

An Android Intent is an object carrying an intent, i.e. a message from one component to another component either inside or outside of the application. Intents can communicate messages among any of the three core components of an application -- Activities, Services, and BroadcastReceivers.

The intent itself, an Intent object, is a passive data structure. It holds an abstract description of an operation to be performed.

For example: say you have an Activity that needs to launch an email client and send an email. To do this, your Activity would send an Intent with the action ACTION_SEND, along with the appropriate chooser, to the Android Intent Resolver:

Intent intent = new Intent(Intent.ACTION_SENDTO); intent.setData(Uri.parse("mailto:")); // only email apps should handle this 

The specified chooser gives the proper interface for the user to pick how to send your email data.

EXPLICIT INTENTS

// Explicit Intent by specifying its class name    Intent i = new Intent(this, TargetActivity.class);    i.putExtra("Key1", "ABC");    i.putExtra("Key2", "123");  // Starts TargetActivity    startActivity(i); 

IMPLICIT INTENTS

// Implicit Intent by specifying a URI    Intent i = new Intent(Intent.ACTION_VIEW,     Uri.parse("http://www.example.com"));  // Starts Implicit Activity    startActivity(i);  

Pending Intent

A PendingIntent is a token that you give to a foreign application (e.g. NotificationManager, AlarmManager, Home Screen AppWidgetManager, or other 3rd party applications), which allows the foreign application to use your application's permissions to execute a predefined piece of code.

By giving a PendingIntent to another application, you are granting it the right to perform the operation you have specified as if the other application was yourself (with the same permissions and identity). As such, you should be careful about how you build the PendingIntent: almost always, for example, the base Intent you supply should have the component name explicitly set to one of your own components, to ensure it is ultimately sent there and nowhere else.

Example for Pending Intent : http://android-pending-intent.blogspot.in/

Source : Android Intents and Android Pending Intents

Hope this helps.

Answer 2

PendingIntent is a wrapper of Intent. The foreign app that receives the PendingIntent, doesn't know the content of Intent which is wrapped by PendingIntent. The mission of foreign app is to send back the intent to owner when some conditions are met (For example: alarm with schedule, or notification with click...). The conditions are given by owner but processed by foreign app (For example: alarm, notification).

If foreign app sent intent to your app, mean that foreign app know about the content of the intent. and foreign app make decision to send intent then your app must process intent to meet some conditions => your app get performance resource of system.