intentfilter

IntentFilter is a component of Android's intent resolution mechanism. It describes the kinds of intents a component can respond to and is used when declaring components in the manifest or when registering receivers at runtime. An intent filter defines three aspects an intent must satisfy to be delivered to the component: actions, categories, and data.

Actions specify the operation the intent represents, such as viewing or sending data. Categories provide additional constraints, commonly including DEFAULT. Data describes what kind of data the intent carries, which can be specified as a MIME type or as a data URI with components such as scheme, host, port, and path. A data filter may require any combination of these elements, and matching occurs only if the intent’s data aligns with the filter’s data constraints.

Declaration and usage: In the manifest, an intent filter is nested inside a component tag (activity, service, or broadcast receiver) using elements for action, category, and data. Filters can also be created programmatically at runtime and registered with a component via a system call, using an IntentFilter object that is populated with actions, categories, and data specifications.

Matching and resolution: When an implicit intent is sent, the system compares the intent’s action, categories, and data against all registered filters. Only filters that match all specified fields are considered. If multiple filters match, the system may rely on filter priority, explicit declarations, or user selection through a chooser to determine the handling component.

Notes: IntentFilter plays a central role in enabling inter-app communication and flexible routing of intents, while preserving component boundaries and security by ensuring that only appropriately declared handlers can respond to specific actions and data types.