PendingIntent详解

PendingIntent描述了一个Intent和目标action。这个类的实例是用getActivity(Context,int,Intent,int)方法和getBroadcast(Context,int,Intent,int)和getService(Context,int,Intent,int)方法创建的。创建出的pending
intent可以交给其它程序，于是它们可以在以后的某个时间以你的名义执行intent中所描述的动作。

通过给于一个PendingIntent，你可以使其它程序像你自己一样执行你所指定的操作（具有相同的权限和身份）。所以，你需要小心的创建PendingIntent：通常，你最基本的应该明确设置你的相关组件的名字，以保证将来intent是被发送给它而不是其它地方。

一个PendingIntent本是只是简单地引用一个由系统维护的一个令牌，这个令牌描述了用于取得PendingIntent的原始数据。这表示即使拥有这个PendingIntent的进程关闭了，但这个PendingIntent对于那些收到它的进程依然有效。如果创建这个PendingIntent的程序又重新运行并重新获取同一个类型的PendingIntent(相同的操作，action,数据，类型和组件以及相同的标志)，那么获取的还是这个PendingIntent，并且这个程序可以用cancel()来删除这个PendingIntent。

Intent和PendingIntent的区别?

intent英文意思是意图，pending表示即将发生或来临的事情。
PendingIntent这个类用于处理即将发生的事情。比如在通知Notification中用于跳转页面，但不是马上跳转。

Intent 是及时启动，intent 随所在的activity 消失而消失。
PendingIntent 可以看作是对intent的包装，通常通过getActivity,getBroadcast ,getService来得到pendingintent的实例，当前activity并不能马上启动它所包含的intent,而是在外部执行 pendingintent时，调用intent的。正由于pendingintent中
保存有当前App的Context，使它赋予外部App一种能力，使得外部App可以如同当前App一样的执行pendingintent里的 Intent，就算在执行时当前App已经不存在了，也能通过存在pendingintent里的Context照样执行Intent。另外还可以处理intent执行后的操作。常和alermanger 和notificationmanager一起使用。
Intent一般是用作Activity、Sercvice、BroadcastReceiver之间传递数据，而Pendingintent，一般用在 Notification上，可以理解为延迟执行的intent，PendingIntent是对Intent一个包装。

PendingIntent就是一个Intent的描述，我们可以把这个描述交给别的程序，别的程序根据这个描述在后面的别的时间做你安排做的事情（By giving a
PendingIntent to another application, you are granting it the right to perform the operation you have specified as if the other application was yourself，就相当于PendingIntent代表了Intent）。

本文翻译整理自：

http://developer.android.com/reference/android/app/PendingIntent.html

public final class

PendingIntent

extends Object

implements Parcelable

简介

PendingIntent用于描述Intent及其最终的行为.

你可以通过getActivity(Context context, int requestCode, Intent intent, int flags)系列方法从系统取得一个用于启动一个Activity的PendingIntent对象,

可以通过getService(Context context, int requestCode, Intent intent, int flags)方法从系统取得一个用于启动一个Service的PendingIntent对象

可以通过getBroadcast(Context context, int requestCode, Intent intent, int flags)方法从系统取得一个用于向BroadcastReceiver的Intent广播的PendingIntent对象

返回的PendingIntent可以递交给别的应用程序，然后继续处理。这里的话你可以稍后才处理PendingIntent中描述的Intent及其最终行为。

当你把PendingIntent递交给别的程序进行处理时,PendingIntent仍然拥有PendingIntent原程序所拥有的权限(with the same permissions and identity).当你从系统取得一个PendingIntent时，一定要非常小心才行。比如，通常，如果Intent目的地是你自己的component（Activity/Service/BroadcastReceiver）的话，你最好采用在Intent中显示指定目的component名字的方式，以确保Intent最终能发到目的，否则Intent最后可能不知道发到哪里了。一个PendingIntent就是Android系统中的一个token（节点，这个应该是Linux或C\C++用语）的一个对象引用，它描述了一些将用于retrieve的数据（这里，这些数据描述了Intent及其最终的行为）。

这就意味着即使PendingIntent原进程结束了的话, PendingIntent本身仍然还存在，可在其他进程（PendingIntent被递交到的其他程序）中继续使用.如果我在从系统中提取一个PendingIntent的，而系统中有一个和你描述的PendingIntent对等的PendingInent, 那么系统会直接返回和该PendingIntent其实是同一token的PendingIntent，而不是一个新的token和PendingIntent。然而你在从提取PendingIntent时，通过FLAG_CANCEL_CURRENT参数，让这个老PendingIntent的先cancel()掉，这样得到的pendingInten和其token的就是新的了。

通过FLAG_UPDATE_CURRENT参数的话，可以让新的Intent会更新之前PendingIntent中的Intent对象数据，例如更新Intent中的Extras。另外，我们也可以在PendingIntent的原进程中调用PendingIntent的cancel ()把其从系统中移除掉。

注意：两个PendingIntent对等是指它们的operation一样, 且其它们的Intent的action, data, categories, components和flags都一样。但是它们的Intent的Extra可以不一样。

主要常量

FLAG_CANCEL_CURRENT:如果当前系统中已经存在一个相同的PendingIntent对象，那么就将先将已有的PendingIntent取消，然后重新生成一个PendingIntent对象。

FLAG_NO_CREATE:如果当前系统中不存在相同的PendingIntent对象，系统将不会创建该PendingIntent对象而是直接返回null。

FLAG_ONE_SHOT:该PendingIntent只作用一次。在该PendingIntent对象通过send()方法触发过后，PendingIntent将自动调用cancel()进行销毁，那么如果你再调用send()方法的话，系统将会返回一个SendIntentException。

FLAG_UPDATE_CURRENT:如果系统中有一个和你描述的PendingIntent对等的PendingInent，那么系统将使用该PendingIntent对象，但是会使用新的Intent来更新之前PendingIntent中的Intent对象数据，例如更新Intent中的Extras。

主要成员函数

getActivities系列方法

该系列方法将从系统取得一个用于启动一个Activity的PendingIntent对象。

public static PendingIntent getActivity (Context context, int requestCode, Intent intent, int flags)

Since: API Level 1

Retrieve a PendingIntent that will start a new activity, like calling Context.startActivity(Intent). Note that the activity will be started outside of the context of an existing activity, so you must use the Intent.FLAG_ACTIVITY_NEW_TASK launch flag in the Intent.

因为对于Context的startActivity方法，如果不是在其子类（Activity）中调用，那么必须对Intent加上FLAG_ACTIVITY_NEW_TASK。

具体可以参照Context中对startActivity方法的说明或《Activity和Task的基本模型》

Parameters

context	The Context in which this PendingIntent should start the activity.
requestCode	Private request code for the sender (currently not used).
intent	Intent of the activity to be launched.
flags	May be `FLAG_ONE_SHOT`, `FLAG_NO_CREATE`, `FLAG_CANCEL_CURRENT`, `FLAG_UPDATE_CURRENT`, or any of the flags as supported by`Intent.fillIn()` to control which unspecified parts of the intent that can be supplied when the actual send happens. 当我们使用Intent.fillIn()方法时，表示其Intent的某个数据项可以被send方法的Inent参数进行覆盖重写。

Returns

Returns an existing or new PendingIntent matching the given parameters. May return null only if FLAG_NO_CREATE has been supplied.

public static PendingIntent getActivities (Context context, int requestCode, Intent[] intents, int flags)

Since: API Level 11

Like getActivity(Context, int, Intent, int), but allows an array of Intents to be supplied. The first Intent in the array is taken as the primary key for the PendingIntent, like the single Intent given to getActivity(Context, int, Intent, int). Upon sending the resulting PendingIntent, all of the Intents are started in the same way as they would be by passing them to startActivities(Intent[]).

The first intent in the array will be started outside of the context of an existing activity, so you must use the Intent.FLAG_ACTIVITY_NEW_TASK launch flag in the Intent. (Activities after the first in the array are started in the context of the previous activity in the array, so FLAG_ACTIVITY_NEW_TASK is not needed nor desired for them.)

The last intent in the array represents the key for the PendingIntent. In other words, it is the significant element for matching (as done with the single intent given togetActivity(Context, int, Intent, int), its content will be the subject of replacement by send(Context, int, Intent) andFLAG_UPDATE_CURRENT, etc. This is because it is the most specific of the supplied intents, and the UI the user actually sees when the intents are started.

Parameters

context	The Context in which this PendingIntent should start the activity.
requestCode	Private request code for the sender (currently not used).
intents	Array of Intents of the activities to be launched.
flags	May be `FLAG_ONE_SHOT`, `FLAG_NO_CREATE`, `FLAG_CANCEL_CURRENT`, `FLAG_UPDATE_CURRENT`, or any of the flags as supported by`Intent.fillIn()` to control which unspecified parts of the intent that can be supplied when the actual send happens. 当我们使用Inent.fillIn()所支持的flags时，表示其Intent的数据项可以被send方法的Intent参数覆盖重写。

Returns

Returns an existing or new PendingIntent matching the given parameters. May return null only if FLAG_NO_CREATE has been supplied.

getService方法

该方法将系统取得一个用于启动一个Service的PendingIntent对象.

public static PendingIntent getService (Context context, int requestCode, Intent intent, int flags)

Since: API Level 1

Retrieve a PendingIntent that will start a service, like calling Context.startService(). The start arguments given to the service will come from the extras of the Intent.

Parameters

context	The Context in which this PendingIntent should start the service.
requestCode	Private request code for the sender (currently not used).
intent	An Intent describing the service to be started.
flags	May be `FLAG_ONE_SHOT`, `FLAG_NO_CREATE`, `FLAG_CANCEL_CURRENT`, `FLAG_UPDATE_CURRENT`, or any of the flags as supported by`Intent.fillIn()` to control which unspecified parts of the intent that can be supplied when the actual send happens. 当我们使用Intent.fillIn()方法的flags时，它表示其Intent的数据项可以被send方法的Intent参数覆盖重写。

Returns

Returns an existing or new PendingIntent matching the given parameters. May return null only if FLAG_NO_CREATE has been supplied.

getBroadcast方法

该方法将从系统取得一个用于向BroadcastReceiver的Intent广播的PendingIntent对象

public static PendingIntent getBroadcast (Context context, int requestCode, Intent intent, int flags)

Since: API Level 1

Retrieve a PendingIntent that will perform a broadcast, like calling Context.sendBroadcast().

Parameters

context	The Context in which this PendingIntent should perform the broadcast.
requestCode	Private request code for the sender (currently not used).
intent	The Intent to be broadcast.
flags	May be `FLAG_ONE_SHOT`, `FLAG_NO_CREATE`, `FLAG_CANCEL_CURRENT`, `FLAG_UPDATE_CURRENT`, or any of the flags as supported by`Intent.fillIn()` to control which unspecified parts of the intent that can be supplied when the actual send happens. 当我们使用Intent.fillIn()方法的flags时，它表示其Intent的数据项可以被send方法的Intent参数覆盖重写。

Returns

Returns an existing or new PendingIntent matching the given parameters. May return null only if FLAG_NO_CREATE has been supplied.

send系列方法

该系列主要用于触发PendingIntent的Intent行为。用其Intent或启动一个Activity，或启动一个Service，或向BroadcastReceiver发送Intent广播。

public void send ()

Since: API Level 1

Perform the operation associated with this PendingIntent.

Throws

PendingIntent.CanceledException	Throws CanceledException if the PendingIntent is no longer allowing more intents to be sent through it.

public void send (Context context, int code, Intent intent)

Since: API Level 1

Perform the operation associated with this PendingIntent, allowing the caller to specify information about the Intent to use.

Parameters

context	The Context of the caller. 该参数是因为intent参数才需要提供的，所用如果你的intent参数不为null的话，该参数也不能为null.
code	Result code to supply back to the PendingIntent's target.
intent	Additional Intent data. See `Intent.fillIn()` for information on how this is applied to the original Intent.

Throws

PendingIntent.CanceledException	Throws CanceledException if the PendingIntent is no longer allowing more intents to be sent through it.

public void send (int code, PendingIntent.OnFinished onFinished, Handler handler)

Since: API Level 1

Perform the operation associated with this PendingIntent, allowing the caller to be notified when the send has completed.

Parameters

code	Result code to supply back to the PendingIntent's target.
onFinished	The object to call back on when the send has completed, or null for no callback. 通过该参数，我们可以设置在Intent发送成功后的回调函数。
handler	Handler identifying the thread on which the callback should happen. If null, the callback will happen from the thread pool of the process. 用于说明onFinished参数指定的回调函数，最终在哪个Handler中进行调用。

Throws

PendingIntent.CanceledException	Throws CanceledException if the PendingIntent is no longer allowing more intents to be sent through it.

public void send (Context context, int code, Intent intent, PendingIntent.OnFinished onFinished, Handler handler)

Since: API Level 1

Perform the operation associated with this PendingIntent, allowing the caller to specify information about the Intent to use and be notified when the send has completed.

For the intent parameter, a PendingIntent often has restrictions on which fields can be supplied here, based on how the PendingIntent was retrieved ingetActivity(Context, int, Intent, int), getBroadcast(Context, int, Intent, int), or getService(Context, int, Intent, int).

Parameters

context	The Context of the caller. This may be null if `intent` is also null. 该参数是因为intent参数才需要提供的，一般是当前的context，如果你的intent参数不为null的话，该函数也不能为null.
code	Result code to supply back to the PendingIntent's target.
intent	Additional Intent data. See `Intent.fillIn()` for information on how this is applied to the original Intent. Use null to not modify the original Intent.
onFinished	The object to call back on when the send has completed, or null for no callback. 通过该参数，我们可以指定Intent发送成功后的回调函数。
handler	Handler identifying the thread on which the callback should happen. If null, the callback will happen from the thread pool of the process. 该参数说明onFinished参数指定的回调函数将在哪个Handler中进行调用。

Throws

PendingIntent.CanceledException	Throws CanceledException if the PendingIntent is no longer allowing more intents to be sent through it.

cancel()函数

public void cancel ()

Since: API Level 1

Cancel a currently active PendingIntent. Only the original application owning an PendingIntent can cancel it.

只有PengdingIntent的原应用程序才能调用cancel()来把它从系统中移除掉。

getTargetPackage()函数

public String getTargetPackage ()

Since: API Level 1

Return the package name of the application that created this PendingIntent, that is the identity under which you will actually be sending the Intent. The returned string is supplied by the system, so that an application can not spoof its package.

Returns

The package name of the PendingIntent, or null if there is none associated with it.