Specify action and category to call system activity

1. Intent object details

Android applications include three important components: Activity, service, and broadcastreceiver. The applications start them in the same way-all of which are started by intent, intent encapsulates the intention of the program to start the program. In addition, intent is also used to exchange information with the started component.

Component Type	Start Method
Activity	Startactivity (intent) Startactivityforresult (intent, intrequestcode)
Service	Componentname startservice (intent Service) Boolean bindservice (intent service, serviceconnection Conn, int flags)
Broadcastreceiver	Sendbroadcast (intent) Sendbroadcast (intent, string receiverpermission) Sendorderedbroadcast (intent, string receiverpermission, broadcastreceiver resultreceiver, Handler scheduler, int initialcode, string initialdata, bundle initialextras) Sendorderedbroadcast (intent, string receiverpermission) Sendstickyorderedbroadcast (intent, broadcastreceiver resultreceiver, Handler scheder, int initialcode, string initialdata, bundle initialextras)

 

 

The intent object contains seven attributes: component, action, category, Data, type, extra, and flag. The component is used to specify the target component to be started, extra is used to "carry" the data to be exchanged.

2. Intent attributes and intent-filter configuration

(1) component attributes

The Component Attribute of intent needs to accept a componentname object. The application can start a specific component based on the given component class.

When a program uses the Component Attribute of Intent (specifying which component to start) to start a specific component, the <intent-filter.../> element is almost unnecessary for the started component.

(2) Action, category attribute and intent-filter configuration

The action and category attributes of intent are common strings. Action indicates an abstract "action" to be completed by the intent. category is used to add additional category information to the action. Generally, action and category.

The <intent-filter.../> element usually contains the following sub-elements:

A, 0 ~ N <action.../> sub-elements

B, 0 ~ N <category.../> sub-elements

C, 0 ~ 1 <data.../> sub-element

The configuration of <action.../> <category.../> sub-elements is very simple. You can specify the Android: Name attribute. The value of this attribute is a common string.

When <activity... /> <intent-filter... /> the sub-element contains multiple <action... /> when the sub-element (equivalent to specifying multiple strings), it indicates that the activity can respond to the intent with the action attribute value of any of the strings.

An intent object can only contain one action attribute. The program calls the setaction (string Str) method of intent to set the action attribute value. However, an intent object can contain multiple category attributes, call the addcategory (string Str) method of intent to add.

When the program creates an intent, the intent starts the component whose category attribute value is intent. category_default constant (the constant value is Android. Intent. Category. Default) by default.

(3) specify action and category to call the system activity

In fact, Android provides a large number of standard action and category constants. The standard action constants and corresponding strings used to start the activity are as follows:

 

Action constant	Corresponding string	Simple Description
Action_main	Android. Intent. Action. Main	Application Portal
Action_view	Android. Intent. Action. View	Display specified data
Action_attach_data	Android. Intent. Action. attach_data	Specify that a piece of data will be appended to other places
Action_edit	Android. Intent. Action. Edit	Edit specified data
Action_pick	Android. Intent. Action. Pick	Select an item from the list and return the selected data
Action_chooser	Android. Intent. Action. chooser	Display an activity Selector
Action_get_content	Android. Intent. Action. get_content	Let the user select data and return the selected data
Action_dial	Android. Intent. Action. Dial	Display dial panel
Action_call	Android. Intent. Action. Call	Directly call a specified user
Action_send	Android. Intent. Action. Send	Send data to others
Action_sendto	Android. Intent. Action. sendto	Send messages to others
Action_answer	Android. Intent. Action. Answer	Answer phone number
Action_insert	Android. Intent. Action. insert	Insert data
Action_delete	Android. Intent. Action. Delete	Delete data
Action_run	Android. Intent. Action. Run	Operation and Maintenance
Action_sync	Android. Intent. Action. sync	Execute Data Synchronization
Action_pick_activity	Android. Intent. Action. pick_activity	Used to select activity
Action_search	Android. Intent. Action. Search	Execute search
Action_web_search	Android. Intent. Action. web_search	Execute Web Search
Action_factory_test	Android. Intent. Action. factory_test	Factory test entry point

 

The standard category constant and corresponding strings are as follows:

 

CATEGORY constant	Corresponding string	Simple Description
Category_default	Android. Intent. Category. Default	Default category
Category_browsable	Android. Intent. Category. browsable	Specify that the activity can be safely called by the browser
Category_tab	Android. Intent. Category. Tab	Specify activity as the tab page of tabactivity
Category_launcher	Android. Intent. Category. Launcher	Activity displays the list of top-level programs
Category_info	Android. Intent. Category. Info	Used to provide package information
Category_home	Android. Intent. Category. Home	Set the activity to run with the system startup
Category_preference	Android. Intent. Category. Preference	This activity is a parameter panel
Category_test	Android. Intent. Category. Test	This activity is a test
Category_car_dock	Android. Intent. Category. car_dock	Run the activity when the mobile phone is inserted into the car base (hardware ).
Category_assist_dock	Android. Intent. Category. wash_dock	Run the activity when the mobile phone is inserted into the desktop base (hardware ).
Category_car_mode	Android. Intent. Category. car_mode	You can set this activity to be used in a vehicle-mounted environment.

 

3. Data and type attributes and intent-filter configuration

The data property is usually used to provide operation data to the Action property. The data property receives a URI object, which is usually represented by a string in the following format:

Content: // com. Android. Contracts/contacts/1

Tel: 123

The colon of the preceding two strings roughly specifies the data type, followed by the data part.

The Type attribute is used to specify the data type or MIME type specified by the data attribute. When the intent does not specify the data attribute, the type attribute takes effect, otherwise, the android system will analyze the data type based on the data property value, so you do not need to specify the type attribute.

Once the action and data attributes are specified for intent, android can start a specific application based on the specified data type and perform corresponding operations on the specified data. The following describes the combination of several actions and data attributes:

Action_view content: // com. Android. Contacts/contacts/1: displays the contact information marked as 1.

Action_edit content: // com. Android. Contacts/contacts/1: edit the contact information marked as 1

Action_dial content: // com. Android. Contacts/contacts/1: display the interface for dialing contacts marked as 1

Action_view Tel: 123: display the interface for dialing to the specified number 123

Action_dial Tel: 123: display the interface for dialing to the specified number 123

Action_view content: // contacts/people/: displays information about all contacts. This combination allows you to conveniently view system contacts.

4. Extra attributes

The extra attribute of intent is usually used for data exchange among multiple actions. The extra attribute value of intent should be a bundle object, and the bundle object is like a map object, it can store multiple key-value pairs, so that you can exchange data between different activities through intent.