阅读笔记2

1。Note: In order to receive implicit intents, you must include the CATEGORY_DEFAULT category in the intent filter. The methods startActivity() and startActivityForResult() treat all intents as if they declared the CATEGORY_DEFAULT category. If you do not declare this category in your intent filter, no implicit intents will resolve to your activity.

注意：为了能接收到隐式意图，你必须在intent filter里包含category 为CATEGORY_DEFAULT。startActivity和startActivityForResult将所有的intents看成他们所声明的CATEGORY_DEFAULT category。如果你不声明该属性，没有隐式意图将会解析你的activity

2.Caution: To avoid inadvertently running a different app'sService, always use an explicit intent to start your own service and do not declare intent filters for your service.  为了避免无意中打开不同APP的Service，确保用显示意图来开启自己的service，并且在service中不要声明intent filters

3.Major use cases for a pending intent include:

• Declare an intent to be executed when the user performs an action with your Notification (the Android system's NotificationManager executes the Intent).
• Declare an intent to be executed when the user performs an action with your App Widget (the Home screen app executes the Intent).
• Declare an intent to be executed at a specified time in the future (the Android system's AlarmManagerexecutes the Intent).
• pendingintent 主要的使用情况宝包括以下:
• 1。当用户点击了你的通知的时候，声明一个即将要执行的intent。安卓系统的NotificationManager执行intent。
• 2.当用户操作你的应有程序的窗口小组件的时候，声明一个即将要执行的intent。主屏幕的app执行intent。
• 3.声明一个在未来某个指定的时间执行的intent。比如闹钟

4. You must instead declare the intended component type when you create thePendingIntent by calling the respective creator method:

• PendingIntent.getActivity() for an Intent that starts an Activity.
• PendingIntent.getService() for an Intent that starts a Service.
• PendingIntent.getBroadcast() for a Intent that starts an BroadcastReceiver.
• Unless your app is receiving pending intents from other apps, the above methods to create a PendingIntentare the only PendingIntent methods you'll probably ever need.
  
• 你必须用个自己的创建方法来代替声明的intent，除非你的app接收到了来自其他app的pending intents，否则上述的方法你将不需要

5.When the system receives an implicit intent to start an activity, it searches for the best activity for the intent by comparing the intent to intent filters based on three aspects:

• The intent action
• The intent data (both URI and data type)
• The intent category

The following sections describe how intents are matched to the appropriate component(s) in terms of how the intent filter is declared in an app's manifest file.

当你的系统受到隐式意图来打开一个activity时，系统将会通过比较intent filters的三个方面来选出最适合的activity。intent action，intent data，intent category。intents怎么来匹配最合适的组件是根据app 的manifest file中intent的定义来实现的。

To get through this filter, the action specified in the Intent must match one of the actions listed in the filter.

If the filter does not list any actions, there is nothing for an intent to match, so all intents fail the test. However, if an Intent does not specify an action, it will pass the test (as long as the filter contains at least one action).

如果声明了action，就一定要有匹配的action，否则没有intent会相应。如果intent没有指定，则通过匹配(filter至少要有一个action)

For an intent to pass the category test, every category in the Intent must match a category in the filter. The reverse is not necessary—the intent filter may declare more categories than are specified in the Intent and theIntent will still pass. Therefore, an intent with no categories should always pass this test, regardless of what categories are declared in the filter.

categories ,如果一个intent设置了一个或者多个category，必须全部与intent filter里德category匹配才能通过匹配。intent filter的category可以多于intent里设置的，但是intent里设置了的就必须要有匹配。intent没有设置，通过匹配，不管filter里怎么声明的。

Note: Android automatically applies the the CATEGORY_DEFAULT category to all implicit intents passed tostartActivity() and startActivityForResult(). So if you want your activity to receive implicit intents, it must include a category for "android.intent.category.DEFAULT" in its intent filters (as shown in the previous <intent-filter> example.

所有的隐式意图在调用startActivity或者forReslut时，会默认加上category为default。如果你想你的activity来匹配该隐式意图，你必须在你的intent filter声明中加入default的category声明。

6.Each <data> element can specify a URI structure and a data type (MIME media type). There are separate attributes — scheme, host, port, and path — for each part of the URI:

<scheme>://<host>:<port>/<path>

For example:

content://com.example.project:200/folder/subfolder/etc

data的组成。

Each of these attributes is optional in a <data> element, but there are linear dependencies:

• If a scheme is not specified, the host is ignored.
• If a host is not specified, the port is ignored.
• If both the scheme and host are not specified, the path is ignored.

三个属性是可选的，如果scheme没有指定，host将被忽略，下面的类似。

When the URI in an intent is compared to a URI specification in a filter, it's compared only to the parts of the URI included in the filter. For example:

• If a filter specifies only a scheme, all URIs with that scheme match the filter.
• If a filter specifies a scheme and an authority but no path, all URIs with the same scheme and authority pass the filter, regardless of their paths.
• If a filter specifies a scheme, an authority, and a path, only URIs with the same scheme, authority, and path pass the filter.

匹配规则：如果filter至指定了，scheme，只要scheme匹配就都匹配

如果制定了scheme和acthority，但是并没有指定path，只要两者匹配即可。

如果都指定了，全部匹配才行

The rules are as follows:

1. An intent that contains neither a URI nor a MIME type passes the test only if the filter does not specify any URIs or MIME types.
2. An intent that contains a URI but no MIME type (neither explicit nor inferable from the URI) passes the test only if its URI matches the filter's URI format and the filter likewise does not specify a MIME type.
3. An intent that contains a MIME type but not a URI passes the test only if the filter lists the same MIME type and does not specify a URI format.
4. An intent that contains both a URI and a MIME type (either explicit or inferable from the URI) passes the MIME type part of the test only if that type matches a type listed in the filter. It passes the URI part of the test either if its URI matches a URI in the filter or if it has a content: or file: URI and the filter does not specify a URI. In other words, a component is presumed to support content: and file: data if its filter lists only a MIME type.

Your application can use intent matching in a similar way. The PackageManager has a set of query...()methods that return all components that can accept a particular intent, and a similar series of resolve...()methods that determine the best component to respond to an intent. For example,queryIntentActivities() returns a list of all activities that can perform the intent passed as an argument, and queryIntentServices() returns a similar list of services. Neither method activates the components; they just list the ones that can respond. There's a similar method, queryBroadcastReceivers(), for broadcast receivers.intent并没有指定URI和MIME type，通过的唯一可能是filter也没指定任何URI和MIME

intent制定了URI没有指定MIME，通过的唯一情况是URI匹配，并且filter并没有指定MIME

intent 指定了MIME没有指定URI，通过的唯一情况是MIME类型匹配，并且fileter没有指定URI

intent指定了URI和MIME，通过MIME type部分必须匹配filter列出的MIME的类型。它通过URI的部分要么filter的UR与intent的URI相匹配，要么intent含有content：或者file：而filter并没有指定URI。换句话说，一个组件假定支持contnet：和file：data类型，当filter仅仅列出mime type的时候。

queryIntentActivities() returns a list of all activities that can perform the intent passed as an argument, and queryIntentServices() returns a similar list of services. Neither method activates the components; they just list the ones that can respond. There's a similar method, queryBroadcastReceivers(), for broadcast receivers.

三个方法~