What is an Intent in Android?

An Intent is an "intention" to perform an action; in other words,

a messaging object you can use to request an action from another app component

An Intent is basically a message to say you did or want something to happen. Depending on the intent, apps or the OS might be listening for it and will react accordingly. Think of it as a blast email to a bunch of friends, in which you tell your friend John to do something, or to friends who can do X ("intent filters"), to do X. The other folks will ignore the email, but John (or friends who can do X) will react to it.

To listen for an broadcast intent (like the phone ringing, or an SMS is received), you implement a broadcast receiver, which will be passed the intent. To declare that you can handle another's app intent like "take picture", you declare an intent filter in your app's manifest file.

If you want to fire off an intent to do something, like pop up the dialer, you fire off an intent saying you will.

What is an Intent ?

An Intent is basically a message that is passed between components (such as Activities, Services, Broadcast Receivers, and Content Providers). So, it is almost equivalent to parameters passed to API calls. The fundamental differences between API calls and invoking components via intents are:

• API calls are synchronous while intent-based invocations are asynchronous.
• API calls are compile-time binding while intent-based calls are run-time binding.

Of course, Intents can be made to work exactly like API calls by using what are called explicit intents, which will be explained later. But more often than not, implicit intents are the way to go and that is what is explained here.

One component that wants to invoke another has to only express its intent to do a job. And any other component that exists and has claimed that it can do such a job through intent-filters, is invoked by the Android platform to accomplish the job. This means, neither components are aware of each other's existence but can still work together to give the desired result for the end-user.

This invisible connection between components is achieved through the combination of intents, intent-filters and the Android platform.

This leads to huge possibilities like:

• Mix and match or rather plug and play of components at runtime.
• Replacing the inbuilt Android applications with custom developed applications.
• Component level reuse within and across applications.
• Service orientation to the most granular level, if I may say.

Here are additional technical details about Intents from the Android documentation.

An intent is an abstract description of an operation to be performed. It can be used with startActivity to launch an Activity, broadcastIntent to send it to any interested BroadcastReceiver components, and startService(Intent) or bindService(Intent, ServiceConnection, int) to communicate with a Background Service.

An Intent provides a facility for performing late runtime binding between the code in different applications. Its most significant use is in the launching of activities, where it can be thought of as the glue between activities. It is basically a passive data structure holding an abstract description of an action to be performed. The primary pieces of information in an intent are:

• action The general action to be performed, such as ACTION_VIEW, ACTION_EDIT, ACTION_MAIN, etc.
• data The data to operate on, such as a person record in the contacts database, expressed as a Uri.

Learn more

• Lars Vogel's tutorial
• ProgrammerGuru article
• Common intents