Android中Notification的PendingIntent无效问题解决

下面来一段代码，引出今天的梗

NotificationManager nm = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
Intent intent = new Intent();
intent.setClass(context, MainActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.putExtra("aa","bb");
PendingIntent mPendingIntent = PendingIntent.getActivity(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
Notification mNotification;
if (android.os.Build.VERSION.SDK_INT < 16) &#123;
   mNotification = new Notification();
   mNotification.icon = R.drawable.ic_launcher;// icon 的id
   mNotification.defaults = Notification.DEFAULT_ALL;
   mNotification.flags = Notification.FLAG_AUTO_CANCEL;
&#125; else &#123;
 	mNotification = new Notification.Builder(context)
  .setContentTitle(title).setContentText(message)
  .setSmallIcon(R.drawable.ic_launcher)
  .setDefaults(Notification.DEFAULT_ALL)
  .setAutoCancel(true).setContentIntent(mPendingIntent).build();
&#125;
nm.notify(0, mNotification);

上面的代码就是最基本的消息通知，然后启动相应的界面，现在世面上大多数也都是这么写的，但是最近却栽在这个坑上了，为啥这么说，因为当我们消息推送的时候在其他机型这样写都是OK的，唯独在华为上面，点击消息启动栏没有任何反应，也不闪退，也不给我们答案，就是通知状态没有了。纠结了一阵子，今天终于。。。。
我们先来看一下，作用于此事件的幕后黑手究竟是谁，上面的代码一目了然，PendingIntent.getActivity(Context context, int requestCode, Intent intent, int flags)，nm.notify(0, mNotification);就是这两个方法在搞怪，我们来看看里面的参数，PendingIntent.getActivity)官方的解释是这样的

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.

主要的意思就是使用PendingIntent来启动一个Activity，就像用Context.startActivity(Intent)来启动一个Activity一样，注意这里的activity将是上下文之外现有的activity，所以你必须使用Intent.FLAG_ACTIVITY_NEW_TASK标记位来启动一个intent。

这里面的第一个，第三个参数这里不打算细说了。

* @param context The Context in which this PendingIntent should start
* the activity.
* @param requestCode Private request code for the sender
* @param intent Intent of the activity to be launched.
* @param flags May be {@link #FLAG_ONE_SHOT}, {@link #FLAG_NO_CREATE},
* {@link #FLAG_CANCEL_CURRENT}, {@link #FLAG_UPDATE_CURRENT},
* or any of the flags as supported by
* {@link Intent#fillIn Intent.fillIn()} to control which unspecified parts
* of the intent that can be supplied when the actual send happens.

摘自源码，当我们点进去getActivity方法时是这样的

public static PendingIntent getActivity(Context context, int requestCode,
            Intent intent, @Flags int flags) {
        return getActivity(context, requestCode, intent, flags, null);
    }
public static PendingIntent getActivity(Context context, int requestCode,
            @NonNull Intent intent, @Flags int flags, @Nullable Bundle options) {
        String packageName = context.getPackageName();
        String resolvedType = intent != null ? intent.resolveTypeIfNeeded(
                context.getContentResolver()) : null;
        try {
            intent.migrateExtraStreamToClipData();
            intent.prepareToLeaveProcess();
            IIntentSender target =
                ActivityManagerNative.getDefault().getIntentSender(
                    ActivityManager.INTENT_SENDER_ACTIVITY, packageName,
                    null, null, requestCode, new Intent[] { intent },
                    resolvedType != null ? new String[] { resolvedType } : null,
                    flags, options, UserHandle.myUserId());
            return target != null ? new PendingIntent(target) : null;
        } catch (RemoteException e) {
        }
        return null;
    }

第四个参数Flag我挨个换了一遍还是不行，排除法，最后剩下requestCode了，可是网上都是这么写的啊，不然，就是他的原因。我们可以从源码中可以看出来，我们把requestCode传进去之后，重新传给了IIntentSender对象，看源码涉及到IPC机制，贴出getIntentSender()源码

public IIntentSender getIntentSender(int type,
           String packageName, IBinder token, String resultWho,
           int requestCode, Intent[] intents, String[] resolvedTypes, int flags,
           Bundle options, int userId) throws RemoteException {
       Parcel data = Parcel.obtain();
       Parcel reply = Parcel.obtain();
       data.writeInterfaceToken(IActivityManager.descriptor);
       data.writeInt(type);
       data.writeString(packageName);
       data.writeStrongBinder(token);
       data.writeString(resultWho);
       data.writeInt(requestCode);
       if (intents != null) {
           data.writeInt(1);
           data.writeTypedArray(intents, 0);
           data.writeStringArray(resolvedTypes);
       } else {
           data.writeInt(0);
       }
       data.writeInt(flags);
       if (options != null) {
           data.writeInt(1);
           options.writeToParcel(data, 0);
       } else {
           data.writeInt(0);
       }
       data.writeInt(userId);
       mRemote.transact(GET_INTENT_SENDER_TRANSACTION, data, reply, 0);
       reply.readException();
       IIntentSender res = IIntentSender.Stub.asInterface(
               reply.readStrongBinder());
       data.recycle();
       reply.recycle();
       return res;
   }

这里首先获取Parcel对象，Parcel.obtain(),然后将我们传递过来的参数打包到Parcel对象中，parcel.write(),最后将我们打包好的数据发送出去 mRemote.transact(),最后回收parcel对象，data.recycle();reply.recycle();
猜测应该是sender用requestCode来区分不同的PendingIntent对象，然后对应。因为之前我们传递的都是0，所以这里我们将requestCode的值改为每条消息都不一样就好了。这里也要记住，getActivity中requestCode和notiy中的id要保持一致，我将这里改成了

PendingIntent mPendingIntent = PendingIntent.getActivity(context, (int)System.currentTimeMillis()/1000, intent, PendingIntent.FLAG_UPDATE_CURRENT);
nm.notify((int) (System.currentTimeMillis()/1000), mNotification);

这样就解决问题了。

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