Android PendingIntent实现原理和代码

对于Android的Intent相关内容，可能部分初级Android开发者不知道PendingIntent是干什么的? 对于Notification和SmsManager中的sendMessage以及AlarmManager中的set这些方法中均有 PendingIntent，到底PendingIntent和Intent有哪些不同呢?

　　一、Intent

　　通常Android中的Intent位于 android.content.Intent的实现比较简单，直接从Object类实现，内部主要是保存了一些String或Int、轻量级的数组，提供了一些方法主要是赋值或取值。

　　二、PendingIntent

　　这里和Intent的不同分在了android.app.PendingIntent这个包中，属于app层而不是数据存储封装的content层，从首段我们看到了PendingIntent是针对将要发生的事情，比如短信发送时，本对象用于跟踪未来短信的接收情况，主要是短信回执报告和发送成功或失败，因为GSM通讯到RIL再到移动基站的过程很漫长，通过开一个Thread等待对于我们的应用是比较麻烦和耗资源，而Android的框架层的TelephonyManager底层远程服务会跟踪，最终通过PendingIntent来跟踪，有关具体实现原理和代码如下:

Java代码：
public final class PendingIntent implements Parcelable {

//实现了Parcelable接口，可以方便的处理二进制数据和用于远程服务的数据交换



private final IIntentSender mTarget;

public static final int FLAG_ONE_SHOT = 1<<30;

public static final int FLAG_NO_CREATE = 1<<29;

public static final int FLAG_CANCEL_CURRENT = 1<<28;

public static final int FLAG_UPDATE_CURRENT = 1<<27;

public static class CanceledException extends AndroidException {





public CanceledException() {

}

public CanceledException(String name) {

super(name);

}

public CanceledException(Exception cause) {

super(cause);

}



}



public interface OnFinished {

void onSendFinished(PendingIntent pendingIntent, Intent intent,int resultCode, String resultData, Bundle resultExtras);



}



private static class FinishedDispatcher extends IIntentReceiver.Stub implements Runnable {



private final PendingIntent mPendingIntent;

private final OnFinished mWho;

private final Handler mHandler;

private Intent mIntent;

private int mResultCode;

private String mResultData;

private Bundle mResultExtras;



FinishedDispatcher(PendingIntent pi, OnFinished who, Handler handler) {

mPendingIntent = pi;

mHandler = handler;

}



public void performReceive(Intent intent, int resultCode,String data, Bundle extras, boolean serialized, boolean sticky) {



mIntent = intent;

mResultCode = resultCode;

mResultData = data;

mResultExtras = extras;

if (mHandler == null) {

run();

} else {

mHandler.post(this);

}



}



public void run() {

mWho.onSendFinished(mPendingIntent, mIntent, mResultCode,mResultData, mResultExtras);

}



}

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



String packageName = context.getPackageName();

String resolvedType = intent != null ? intent.resolveTypeIfNeeded(

context.getContentResolver()) : null;

try {

IIntentSender target =ActivityManagerNative.getDefault().getIntentSender(





IActivityManager.INTENT_SENDER_ACTIVITY, packageName,null, null, requestCode, intent, resolvedType, flags);

return target != null ? new PendingIntent(target) : null;

} catch (RemoteException e) {

}

return null;

}