Android activity not getting broadcast from local service

问题

From the examples this looked straightforward. Maybe you can show me what I did wrong. I can't get an activity to receive a broadcast sent from a local service.

I have Activity1 that start Service1:

startService(new Intent(Activity1.this, Service1.class));

Activity1 then starts Activity2:

startActivity(new Intent(Activity1.this, Activity2.class));

Service1, a local service, listens for downloads:

protected final BroadcastReceiver service2DownloadBroadcastReceiver = new BroadcastReceiver()
{
    public void onReceive(final Context context, final Intent intent)
    {
        ...
        broadcastDownloadFinished(Uri.fromFile(downloadedFile));

The broadcast receiver of Service1 then broadcasts its own message:

protected Intent broadcastDownloadFinished(final Uri uri)
{
    final Intent intent = new Intent(ACTION_DOWNLOAD_FINISHED).setData(checkNotNull(uri));
    sendBroadcast(intent);

Activity2, which is in the foreground at the time, listens for the ACTION_DOWNLOAD_FINISHED intent using its own broadcast receiver:

private final BroadcastReceiver activity2DownloadBroadcastReceiver = new BroadcastReceiver()
{
    public void onReceive(final Context context, final Intent intent)
    {
        Log.i(Activity2.class.getSimpleName(), "Received download event: " + intent.getAction() + " " + intent.getData());

Activity2 of course registers the receiver:

protected void onResume()
{
    super.onResume();
    final IntentFilter downloadIntentFilter = new IntentFilter();
    downloadIntentFilter.addAction(ACTION_DOWNLOAD_FINISHED);
    registerReceiver(activity2DownloadBroadcastReceiver, downloadIntentFilter);

In case it matters, ACTION_DOWNLOAD_FINISHED is something like "com.example.intent.action.DOWNLOAD_FINISHED".

Service1 receives the download manager event in its receiver and apparently broadcasts its own custom event, but Activity2 never seems to receive it. What did I do wrong? Is it a problem to broadcast an intent in the middle of processing another one? (I wouldn't think so---this is asynchronous, right?)

Update: Just to make sure there is no problem sending a broadcast in the middle of receiving a broadcast, I changed my broadcast code to actually perform the broadcast three seconds later on the main thread:

    Log.i(getClass().getSimpleName(), "...ready to broadcast");     
    final Intent intent = new Intent(ACTION_DOWNLOAD_FINISHED).setData(checkNotNull(uri));
    mainThreadHandler.postDelayed(new Runnable()
    {
        public void run()
        {
            Log.i(getClass().getSimpleName(), "...broadcasting");
            sendBroadcast(intent);
            Log.i(getClass().getSimpleName(), "...broadcasted");                
        }
    }, 3000);
    Log.i(getClass().getSimpleName(), "...scheduled to broadcast");

As expected, the log says:

...ready to broadcast
...scheduled to broadcast
...broadcasting
...broadcasted

Yet nothing is received in the activity. Please help.

回答1:

Eureka! I found it! The problem is that I supplied a data URI in my broadcast intent. The Android intent matching rules get a little complicated. If you supply a data URI, then your intent filter must specify a matching MIME type.

Unfortunately, although the Android documentation says that the data type can be inferred from the data URI, apparently Android doesn't know that a file://.../example.jpg is an image. So this doesn't work:

intentFilter.addDataType("image/*");

However, instead of specifying a type, I can specify a scheme that I accept:

intentFilter.addDataScheme("file");

That works! It's a little rough---and a little artificial to restrict my broadcasts to file: URIs, but as that's all I'm using for the moment, it works.

Note that apparently I could manually specify the MIME type in the intent when I broadcast it, but that's too much trouble for now, as I'm downloading images from Picasa so I already know that they are images (and don't care the specific MIME type). And if it gets too much trouble, I could ditch the whole setData() thing altogether and set an extra---but of course I want to do things the Right Way.

回答2:

have you included your receiver in your activity's manifest?

<receiver
  android:name=".YourReceiver">
  <intent-filter>
    <action
      android:name="intent_name"></action>
  </intent-filter>
</receiver>

来源：https://stackoverflow.com/questions/8112164/android-activity-not-getting-broadcast-from-local-service