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:
? 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?? //这里Android123友情提示如果你掌握了Android的RemoteService或Java RMI这里应该好理解
??????????? 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;
??????????? mWho = who;
??????????? 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;
??? }
??? public static PendingIntent getBroadcast(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_BROADCAST, packageName,
??????????????????? null, null, requestCode, intent, resolvedType, flags);
??????????? return target != null ? new PendingIntent(target) : null;
??????? } catch (RemoteException e) {
??????? }
??????? return null;
??? }
??? public static PendingIntent getService(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_SERVICE, packageName,
??????????????????? null, null, requestCode, intent, resolvedType, flags);
??????????? return target != null ? new PendingIntent(target) : null;
??????? } catch (RemoteException e) {
??????? }
??????? return null;
??? }
??? public IntentSender getIntentSender() {
??????? return new IntentSender(mTarget);
??? }
??? public void cancel() {
??????? try {
??????????? ActivityManagerNative.getDefault().cancelIntentSender(mTarget);
??????? } catch (RemoteException e) {
??????? }
??? }
??? public void send() throws CanceledException {
??????? send(null, 0, null, null, null);
??? }
??? public void send(int code) throws CanceledException {
??????? send(null, code, null, null, null);
??? }
??? public void send(Context context, int code, Intent intent)
??????????? throws CanceledException {
??????? send(context, code, intent, null, null);
??? }
??? public void send(int code, OnFinished onFinished, Handler handler)
??????????? throws CanceledException {
??????? send(null, code, null, onFinished, handler);
??? }
??? public void send(Context context, int code, Intent intent,
??????????? OnFinished onFinished, Handler handler) throws CanceledException {
??????? try {
??????????? String resolvedType = intent != null ?
??????????????????? intent.resolveTypeIfNeeded(context.getContentResolver())
??????????????????? : null;
??????????? int res = mTarget.send(code, intent, resolvedType,
??????????????????? onFinished != null
??????????????????? ? new FinishedDispatcher(this, onFinished, handler)
??????????????????? : null);
??????????? if (res < 0) {
??????????????? throw new CanceledException();
??????????? }
??????? } catch (RemoteException e) {
??????????? throw new CanceledException(e);
??????? }
??? }
??? public String getTargetPackage() {
??????? try {
??????????? return ActivityManagerNative.getDefault()
??????????????? .getPackageForIntentSender(mTarget);
??????? } catch (RemoteException e) {
??????????? // Should never happen.
??????????? return null;
??????? }
??? }
??? @Override
??? public boolean equals(Object otherObj) {
??????? if (otherObj instanceof PendingIntent) {
??????????? return mTarget.asBinder().equals(((PendingIntent)otherObj)
??????????????????? .mTarget.asBinder());
??????? }
??????? return false;
??? }
??? @Override
??? public int hashCode() {
??????? return mTarget.asBinder().hashCode();
??? }
??? @Override
??? public String toString() {
??????? StringBuilder sb = new StringBuilder(128);
??????? sb.append("PendingIntent{");
??????? sb.append(Integer.toHexString(System.identityHashCode(this)));
??????? sb.append(": ");
??????? sb.append(mTarget != null ? mTarget.asBinder() : null);
??????? sb.append('}');
??????? return sb.toString();
??? }
??? public int describeContents() {
??????? return 0;
??? }
??? public void writeToParcel(Parcel out, int flags) {
??????? out.writeStrongBinder(mTarget.asBinder());
??? }
??? public static final Parcelable.Creator<PendingIntent> CREATOR
??????????? = new Parcelable.Creator<PendingIntent>() {
??????? public PendingIntent createFromParcel(Parcel in) {
??????????? IBinder target = in.readStrongBinder();
??????????? return target != null ? new PendingIntent(target) : null;
??????? }
??????? public PendingIntent[] newArray(int size) {
??????????? return new PendingIntent[size];
??????? }
??? };
??? public static void writePendingIntentOrNullToParcel(PendingIntent sender,
??????????? Parcel out) {
??????? out.writeStrongBinder(sender != null ? sender.mTarget.asBinder()
??????????????? : null);
??? }
??? public static PendingIntent readPendingIntentOrNullFromParcel(Parcel in) {
??????? IBinder b = in.readStrongBinder();
??????? return b != null ? new PendingIntent(b) : null;
??? }
??? /*package*/ PendingIntent(IIntentSender target) {
??????? mTarget = target;
??? }
??? /*package*/ PendingIntent(IBinder target) {
??????? mTarget = IIntentSender.Stub.asInterface(target);
??? }
??? /** @hide */
??? public IIntentSender getTarget() {
??????? return mTarget;
??? }
}
? 整体来说PendingIntent的实现比较简单，主要和Android特定的的远程服务打交道（短信、通知、闹铃等），通常的应用无需使用。

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摘自：http://www.189works.com/article-16486-1.html