Is android.intent.action.DOWNLOAD_COMPLETE an explicit broadcast?

问题

My app (targetSdk=25) has a broadcast receiver defined in the manifest as follows:

<receiver android:name="my.package.DownloadManagerReceiver"
     android:exported="true">
     <intent-filter>
          <action android:name="android.intent.action.DOWNLOAD_COMPLETE" />
     </intent-filter>
</receiver>

My DownloadManagerReceiver is notified whenever Android's DownloadManager finishes downloading a file, so I can do some processing on the file that was downloaded.

I'm working on migrating my app's targetSdk to 27 (Oreo). According to https://developer.android.com/about/versions/oreo/background#broadcasts, implicit broadcast receivers registered through the manifest are not supposed to work in Android O (except for those whitelisted exceptions).

However, when I run my app using an emulator running Android 8.0 and targetSdk=27 my broadcast receiver defined in the manifest is still notified by the DownloadManager after a download completes.

I tried to find the source code where the DownloadManager sends its broadcast to understand how it sends its broadcasts but I couldn't find it.

Does anybody know whether android.intent.action.DOWNLOAD_COMPLETE is an explicit broadcast rather than an implicit one? Any ideas why my receiver is still receiving that broadcast?

回答1:

Here's what I found after digging further into the platform's source code:

1) When we instantiate the DownloadManager, it keeps a reference to the context of the app and extracts the app's package name from that context

2) That package name is inserted into the downloads database into column Downloads.Impl.COLUMN_NOTIFICATION_PACKAGE when the download is requested

3) When the download completes, the DownloadInfo.sendIntentIfRequested() method will call Intent.setPackage() passing the package name. According to the description of method Intent.setPackage():

(Usually optional) Set an explicit application package name that limits the components this Intent will resolve to. If left to the default value of null, all components in all applications will considered. If non-null, the Intent can only match the components in the given application package.

Based on that description, my understanding is that the broadcast intent will be targeted at my app, thus working as an explicit intent.

来源：https://stackoverflow.com/questions/51674327/is-android-intent-action-download-complete-an-explicit-broadcast