1.It, in effect, filters in intents of a desired type, while filtering out unwanted intents — but only unwanted implicit intents (those that don‘t namea target class). An explicit intent is always delivered to its target, no matter what it contains;
the filter is not consulted. But an implicit intent is delivered to a component only if it can pass through one of the component‘s filters.(即filter只对没有指名目标的Intent进行过滤，广播？)
2.一个妙用就是，一个应用程序可以启动另一个应用程序的某个功能模块
3.Android system must know about the capabilities of a component before it can launch that component
4.A filter has fields that parallel the action, data, and category fields of an Intent object. An implicit intent is tested against the filter in all three areas.If it fails even one of them, the Android system won‘t deliver it to the component
5.However, since a component can have multiple intent filters, an intent that does not pass through one of a component‘s filters might make it through on another.
6.an Intent object that doesn‘t specify an action automatically passes the test — as long as the filter contains at least one action.
7.An Intent object is a bundle of information. It contains
information of interest to the component that receives the intent (such as the action to be taken and the data to act on) plus information of interest to the Android system (such as the category of component that should handle the intent and instructions on
how to launch a target activity).