For example, to extract the data values passed to ActivityB: Bundle extras = getIntent().getExtras() The getIntent() method of the Activity class returns the intent that started the activity, whilst the getExtras() method (of the Intent class) returns a Bundle object for that intent containing the data. The data is received at the target activity as part of a Bundle object which can be obtained via a call to getIntent().getExtras(). I.putExtra("myString", "This is a message for ActivityB")
ANDROID STUDIO INTENT METHODS CODE
The following code extends the previous example to add String and integer values with the keys “myString” and “myInt” respectively to the intent: Intent i = new Intent(this, ActivityB.class) Data must be added in the form of key-value pairs. For example, the following code fragment issues an intent for the activity with the class name ActivityB to be launched: Intent i = new Intent(this, ActivityB.class) ĭata may be transmitted to the receiving activity by adding it to the intent object before it is started via calls to the putExtra() method of the intent object. A call is then made to the startActivity() method, passing through the intent object as an argument. This approach is most common when launching an activity residing in the same application as the sending activity (since the Java class name is known to the application developer).Īn explicit intent is issued by creating a new instance of the Intent class, passing through the activity context and the component name of the activity to be launched. Intents are categorized as either explicit or implicit.Īn explicit intent requests the launch of a specific activity by referencing the component name (which is actually the Java class name) of the target activity. Though not covered until later chapters, it is also worth highlighting the fact that, in addition to launching activities, intents are also used to launch and communicate with services and broadcast receivers. Similarly, the receiving activity may also be configured to return results data to the sending activity when the required tasks are completed. In the previously outlined scenario, for example, the sending activity would need to send the URL of the web page to be displayed to the second activity. Intents also allow for the transfer of data from the sending activity to the receiving activity. The runtime system will match the request to available activities on the device and either launch the activity that matches or, in the event of multiple matches, allow the user to decide which activity to use.
ANDROID STUDIO INTENT METHODS ANDROID
Rather than the application having to contain a second activity to perform this task, the code can simply send an intent to the Android runtime requesting the services of any activity that has registered the ability to display a web page. Consider, for example, an activity contained within an application that requires a web page to be loaded and displayed to the user. Intents also, however, go beyond this concept by allowing an activity to request the services of any other appropriately registered activity on the device for which permissions are configured. An activity can, for example, issue an intent to request the launch of another activity contained within the same application.
Intents () are the messaging system by which one activity is able to launch another activity. Prior to working through some Android Studio based example implementations of intents in the following chapters, the goal of this chapter is to provide an overview of intents in the form of explicit intents and implicit intents together with an introduction to intent filters. As outlined briefly in the chapter entitled The Anatomy of an Android Studio Android Application, this is achieved primarily using Intents. An area that has yet to be covered in extensive detail, however, is the mechanism by which one activity can trigger the launch of another activity. Purchase the fully updated Android Studio Chipmunk Edition of this publication in eBook ($29.99) or Print ($46.99) formatĪndroid Studio Chipmunk Essentials - Java Edition Print and eBook (PDF) editions contain 94 chapters and over 800 pagesīy this stage of the book, it should be clear that Android applications are comprised, among other things, of one or more activities. You are currently reading the Android Studio 1.x - Android 5 Edition of this book.
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