Android的活动没有得到来自当地的服务广播 [英] Android activity not getting broadcast from local service

问题描述

从这个例子看起来简单。也许你能告诉我我做错了什么。我不能让一个活动接收来自本地服务发送一个广播。

我有活性1启动服务1：

  startService（新意图（Activity1.this，Service1.class））;
 

活动1然后启动活性2：

  startActivity（新意图（Activity1.this，Activity2.class））;
 

服务1，本地服务，监听下载：

 保护最后的BroadcastReceiver service2DownloadBroadcastReceiver =新的BroadcastReceiver（）
{
    公共无效的onReceive（最终上下文的背景下，最终的意图意图）
    {
        ...
        broadcastDownloadFinished（Uri.fromFile（downloadedFile））;
 

服务1的广播接收器，然后广播自己的消息：

 保护意图broadcastDownloadFinished（最终乌里URI）
{
    最终意向意图=新的意图（ACTION_DOWNLOAD_FINISHED）.setData（checkNotNull（URI））;
    sendBroadcast（意向）;
 

使用其自己的广播接收机

活性2，这是在前景的时候，侦听ACTION_DOWNLOAD_FINISHED意图：

 私人最终的BroadcastReceiver activity2DownloadBroadcastReceiver =新的BroadcastReceiver（）
{
    公共无效的onReceive（最终上下文的背景下，最终的意图意图）
    {
        Log.i（Activity2.class.getSimpleName（），接收到的下载活动：+ intent.getAction（）++ intent.getData（））;
 

当然，活性2寄存器接收器：

 保护无效onResume（）
{
    super.onResume（）;
    最后的IntentFilter downloadIntentFilter =新的IntentFilter（）;
    downloadIntentFilter.addAction（ACTION_DOWNLOAD_FINISHED）;
    registerReceiver（activity2DownloadBroadcastReceiver，downloadIntentFilter）;
 

在情况下它的事项， ACTION_DOWNLOAD_FINISHED 是像com.example.intent.action.DOWNLOAD_FINISHED。

服务1接收下载管理器事件的接收器，显然广播自己的自定义事件，但活性2似乎永远不会接受它。我做了什么错？是一个问题，在广播处理另一个之一的中间的意图是什么？ （我不这么认为---这是异步的，对吧？）

更新：的只是为了确保没有问题，在接收广播的中间发送广播，我改变了我的广播code到实际执行广播三秒钟后在主主题：

  Log.i（的getClass（）getSimpleName（），...准备播出的。）;
    最终意向意图=新的意图（ACTION_DOWNLOAD_FINISHED）.setData（checkNotNull（URI））;
    mainThreadHandler.postDelayed（新的Runnable（）
    {
        公共无效的run（）
        {
            Log.i（的getClass（）getSimpleName（），...广播。）;
            sendBroadcast（意向）;
            Log.i（的getClass（）getSimpleName（），...广播。）;
        }
    }，3000）;
    Log.i（的getClass（）getSimpleName（），...预定广播。）;
 

正如预期的那样，该日志称：

  ...准备播出
...预定播出
...广播
...播放
 

然而没有被接收在活动。请大家帮帮忙。

解决方案

尤里卡！我找到了！的问题是，我在广播意图提供的数据的URI。 Android的意图匹配规则变得有些复杂。如果提供的数据URI，那么你的意图过滤器必须指定一个匹配的MIME类型。

不幸的是，尽管Android的文件说，该数据类型可以从数据URI来推断，显然是Android不知道，文件：//.../example.jpg 是一个图像。所以，这不工作：

  intentFilter.addDataType（图像/ *）;
 

不过，而不是指定的类型，我可以指定一个计划，我接受：

  intentFilter.addDataScheme（文件）;
 

这作品！这是一个有点粗糙---和一点点人为的限制我的节目，以文件：的URI，但因为这是所有我使用的那一刻，它的工作原理

请注意，显然我可以手动指定MIME类型的意图，当我播放它，但是这太麻烦了，因为我从Picasa下载图片，所以我已经知道他们是图像（并且不关心具体的MIME类型）。如果它变得太麻烦了，我可以完全抛弃整个使用setData（）的事情，并设置一个额外的 - 但当然，我想要做的事情的正确方法。

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.

解决方案

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.

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