Intent are of two types: Explicit Intent and Implicit Intent 4 Importance of using Intents in Android Applications:.Specify a listener for when the button is clicked:.Declare a button that points to the button ID in the layout file:īutton startButton = (Button) findViewById(R.id.trigger).Put a button in the designated layout XML file:.The steps to adding a button to a given layout and assigning an action to a button press are A button press is introduced here for that purpose. To fully demonstrate multiple activities, it is useful to use a trigger event. When a user selects a contact, the Android system finds all available activities with the proper intent filter for viewing contacts and asks the user to decide which one should be used. For example, say a new application for displaying phone contacts is loaded on an Android device. When a new component is developed that meets the required implicit intent filter, it can be used in place of an Android internal intent.
Note that unlike other activities, implicit intents that reside in other applications do not need to be declared in the current application's AndroidManifest file.Īndroid utilizes implicit intents as often as possible, providing a powerful framework for modular functionality.
The system then determines the best component or components to use, even if it is in a separate application or native to the OS. If instead the requirements of an application can be specified by intent filters, an implicit intent can be used. To activate a particular component of the application, an intent naming the component explicitly is used. When the secondary activity ends, the main activity is brought to the foreground and resumed. This causes the main activity to pause while the secondary activity is active. This activity can launch another activity, usually after a trigger event. The main activity, as defined in the AndroidManifest XML file, is started when the application is started. A notepad can have three activities: view a list of notes, read a selected note, and edit a selected or new note. For example, a game can have two activities: a high scores screen and a game screen. Hence, there is often a need to deal with multiple activities. Android Developer's Cookbook, The: Building Applications with the Android SDK: Building Applications with the Android SDKĮven the simplest applications have more than one functionality.
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