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
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
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 | currently not used). |
intent | Intent of the activity to be launched. |
flags | 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
FLAG_NO_CREATE
public static PendingIntent getActivities (Context context, int requestCode, Intent[] intents, int flags)
Since: API Level 11
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 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 | 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
FLAG_NO_CREATE
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
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 | 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
FLAG_NO_CREATE
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
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 | 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
FLAG_NO_CREATE
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
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 |
Throws
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
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.
getActivity(Context, int, Intent, int), getBroadcast(Context, int, Intent, int), or getService(Context, int, Intent, int).
Parameters
context | 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 | |
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
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.