Android Dev

To find your minimum width and height in density-independent pixels (dp), use this formula: (number of cells * 74) - 2

how often the App Widget framework should request an update from the AppWidgetProvider by calling the onUpdate() method

exactly on time

stay around

whose lifecycle is separate from the current context

If used from an Activity context, the receiver is being registered within that activity.

XLP Energy Harvesting Development Board The XLP 16-bit Energy Harvesting Development Kit is a true development platform for realizing energy harvesting applications. The Microchip nanoWatt XLP PIC MCUs are ideal for these low power applications with sleep currents down to 20nA, active mode currents down to 50uA/MHz, code execution efficiency, and multiple wake-up sources. Powered only by light, the XLP kit enables rapid prototyping of low power applications such as RF sensors, temperature/environmental sensors, utility meters, remote controls, and security sensors to name just a few. For software development and programming, the kit includes the PICkit 3 programmer/debugger for use with the Microchip’s free MPLAB™ Integrated Development Environment.

UART to USB bridge for use in prototyping and PC communication

Solar Energy Harvester with EnerChip storage devices providing backup power

does not

request to Android Market

launches the pending intent

checkout flow finishes

An open source project to provide push notification support for Android -- a xmpp based notification server and a client tool kit. This project is currently being hosted at http://sourceforge.net/projects/androidpn/.

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.

如果你呼叫 startService() 多次，每一次的呼叫都會被轉成一個 message，並放在 mServiceLooper 的 message queue 中，等待被服務。一個 message 所對應的工作被完成後，才會繼續服務下一個工作。所以，這些等待被服務的工作，並不是一起並行 (Concurrent) 的，而是循序執行。

從研究這個 IntentService 的原始碼，我們可以學到如何運用簡單的 pattern (Service + Handler + HandlerThread)，幫我們更簡易與有系統地，完成我們所想要做的事

最後我們先前說過，在 IntentServcie 中等待被服務的工作，並不會被一起並行，而是循序執行。如果你今天想要這些等待被服務的工作，能夠一起被並行，在研讀完這個 IntentService 的原始碼後，你自己知不知道如何寫個可支援並行工作的 IntentService？ 提示：可以用 Service + AsyncTask 的組合

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

So the basic idea is: launch an AsyncTask making your service call, show a nifty progress dialog while the task thread is running, and have the task’s result be posted back to your activity once it completes. Cool, but what if the user decides to rotate the screen while your task is running? Or a phone call comes in, interrupting your app, and Android decides to kill it? Both these actions will effectively terminateyour activity, and recreate it when resuming (yes, a screen rotation kills your activity, very clever, isn’t it?). Unfortunately, any AsyncTask that was still running now holds a stale reference to your activity, because the restarted activity will be an entirely different object in memory (and it will go through onCreate(), as if the activity had started for the first time). I’m not entirely sure whether AsyncTask will actually post back the data to the old activity object (if it was a weak reference, it may already have been garbage collected), but in any case, your “new” activity will never see it, because it’s a different instance.

Consumers want immediate access to what’s relevant and QR codes are being used to make that possible.

Bar codes are linear one-dimensional codes and can only hold up to 20 numerical digits, whereas QR codes are two-dimensional (2D) matrix barcodes that can hold thousands of alphanumeric characters of information. Their ability to hold more information and their ease of use makes them practical for small businesses.

When you scan or read a QR code with your iPhone, Android or other camera-enabled Smartphone, you can link to digital content on the web; activate a number of phone functions including email, IM and SMS; and connect the mobile device to a web browser.

For completeness we really should handle the possibility of the task getting cancelled. This can happen when the user navigates away from the app and the task is killed before its completed. This will cause the onPostExecute() method to not be called and so the onRefreshComplete() method won’t be called. Depending on how the user navigates through the app, they could return to this activity without going through the complete onCreate() lifecycle, and you’ll end up with the screen still showing the “loading” progress message in the header. This is common when using tabs between multiple ListViews. Also, the documented best practices for implementing an AsyncTask says that in long running background work you should periodically check if the task has been cancelled and try to gracefully quit your work and exit. So let’s get all of that in there.