Intent学习

简介：

intent 可以启动一个activity,broadcast或者service,实现一种运行时的绑定。

intent 结构

最重要的两个信息是

• 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

其他信息：

• category -- Gives additional information about the action to execute. For example, CATEGORY_LAUNCHER means it should appear in the Launcher as a top-level application, while CATEGORY_ALTERNATIVE means it should be included in a list of alternative actions the user can perform on a piece of data.

• type -- 指定传递的数据类型(使用 MIME type) 

• component -- 显式的指定了处理intent的组件

• extras -- This is a Bundle of any additional information. This can be used to provide extended information to the component. For example, if we have a action to send an e-mail message, we could also include extra pieces of data here to supply a subject, body, etc.

• 总而言之, the set of actions, data types, categories, and extra data defines a language for the system allowing for the expression of phrases such as “call john smith's cell

Intent有两种形式：

显式：指定要处理Intent的组件，通过 setComponent(ComponentName) 或者setClass(Context, Class)，常用于启动同一个应用内的活动。

隐式：Intent定义好信息后，由系统的Intent resolution来进行匹配， which maps an Intent to an Activity, BroadcastReceiver, or Service (or sometimes two or more activities/receivers) that can handle it.

Intent resolution 将Intent与安装好的应用包中的意图过滤器进行比对从而确定谁来响应。

只比对三个信息：action, type, and category