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I’ve run into the following generalized question a lot recently: I have an event that occurs in the background. I want to update my activity, if the activity is on the screen. Otherwise, I want to raise a Notification.

Hence, the recipe for the activity-or-Notification pattern is: Define an action string you will use when the event occurs that you want to go to the activity or notification (e.g., com.commonsware.java.packages.are.fun.EVENT). Dynamically register a BroadcastReceiever in your activity, with an IntentFilter set up for the aforementioned action string and with a positive priority (the default priority for a filter is 0). This receiver should then have the activity do whatever it needs to do to update the UI based on this event. The receiver should also call abortBroadcast() to prevent others from getting it. Be sure to register the receiver in onStart() or onResume() and unregister the receiver in the corresponding onStop or onPause() method. Register in your manifest a BroadcastReceiver, with an <intent-filter> set up for the aforementioned action string. This receiver should raise the Notification. In your service (e.g., an IntentService), when the event occurs, call sendOrderedBroadcast(). And that’s it. If the activity is on-screen, its receiver will be registered, so it will get the event, process it, and cancel the broadcast. If the activity is not on-screen, its receiver will not be registered, so the event will go to the default handler, in the form of your manifest-registered BroadcastReceiver, which will raise the Notification.

It allows third-party application servers to send lightweight messages to their Android applications. The messaging service is not designed for sending a lot of user content via the messages. Rather, it should be used to tell the application that there is new data on the server, so that the application can fetch it. C2DM makes no guarantees about delivery or the order of messages. So, for example, while you might use this feature to tell an instant messaging application that the user has new messages, you probably would not use it to pass the actual messages. An application on an Android device doesn’t need to be running to receive messages. The system will wake up the application via Intent broadcast when the the message arrives, as long as the application is set up with the proper broadcast receiver and permissions.

It uses an existing connection for Google services. This requires users to set up their Google account on their mobile devices.

C2DM imposes the following limitations: The message size limit is 1024 bytes. Google limits the number of messages a sender sends in aggregate, and the number of messages a sender sends to a specific device

GreenDroid is a development library for the Android platform. It is intented to make UI developments easier and consistent through your applications

Path for me should have been file:///sdcard/DumbDumpers/DumbDumper.jpg

So in my example you need: emailIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("file://"+ sPhotoFileName));

AsyncTask要点 1、必须从主线程调用，或者线程中有Handler或Looper。 2、不要在一个可能会被另外一个AsyncTask调用的库里面使用AsyncTask（AsyncTask是不可重入的） 3、如果从一个activity中调用，activity进程可能会在AsyncTask结束前退出，例如： 用户退出了activity 系统内存不足 系统暂存了activity的状态留待后用 系统干掉了你的线程 如果AsyncTask中的工作很重要，应该使用……

IntentService 的好处 Acitivity的进程，当处理Intent的时候，会产生一个对应的Service Android的进程处理器现在会尽可能的不kill掉你 非常容易使用

总结 离开主线程！ 磁盘和网络操作不是马上就能完的 了解sqlite在干嘛 进度展示很好

Droid-Fu offers both support classes meant to be used alongside existing Android code, as well as self-contained, ready-to-be-used components like new adapters and widgets. The areas tackled by Droid-Fu include: application life-cycle helpers support classes for handling Intents and diagnostics better support for background tasks super-easy and robust HTTP messaging powerful caching of Objects, HTTP responses, and remote images custom adapters and views I suggest you read this introductory article, and anything that follows.