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Moreover I am not one of top developers nor any of my apps have been promoted by Android Market. I am just an one among of thousands of Android developers with not to well known apps. And what may be really surprising all my apps are free as Google do not allow developers from my country (Poland) to sell apps via Android Market!

So keep in mind these facts: None of my apps has been ever promoted in Top of Android Market I am providing only free apps (mostly due of Android Market limitations) Even if I would be able to sell apps I would not use it as main income source… (I believe that you still can make more from ads…)

X-Ray Scanner (over 268 000 downloads) Cracked Screen (over 182 000 downloads) Virtual Drums (over 20 000 downloads) Daily Beauty Tips (over 11 000 downloads) Don’t push it (over 6 500 downloads) WP Stats (over 4 000 downloads)

Bump™ makes sharing photos, contacts, and apps with people as simple as bumping your phones together. Compatible with Android to iPhone too!

Bump for Android is an awesome app for quickly exchanging Contact info, Pictures and even Android apps! It’s such an easy way to share information on smartphones running the Bump app. It even works between Android and iPhones, so not just Android to Android or iPhone to iPhone bumps, but a mix of any phone running the app. Many users complain that you can’t Bump music transfers but understand there are legal issues involved there, something I’m sure Bump would not knowingly want to get involved with.

If you add multiple changes to the transaction (such as another add() or remove()) and call addToBackStack(), then all changes applied before you call commit() are added to the back stack as a single transaction and the BACK key will reverse them all together.

The most significant difference in lifecycle between an activity and a fragment is how one is stored in its respective back stack. An activity is placed into a back stack of activities that's managed by the system when it's stopped, by default (so that the user can navigate back to it with the BACK key, as discussed in Tasks and Back Stack). However, a fragment is placed into a back stack managed by the host activity only when you explicitly request that the instance be saved by calling addToBackStack() during a transaction that removes the fragment.

In some cases, you might need a fragment to share events with the activity. A good way to do that is to define a callback interface inside the fragment and require that the host activity implement it. When the activity receives a callback through the interface, it can share the information with other fragments in the layout as necessary.

它已经上市一个月了，但 Android 3.0 的生态环境却没有显示出应有的活力，至今只有约 50 款专用软件上架

还有另外一个原因导致开发者的热情不足，就是 Google 只把系统代码开放给了几个大厂商，例如摩托罗拉，三星，HTC 。大多数设备制造商和开发者根本接触不到 Android 3.0 的代码和技术细节，所以拖累了软件的开发进度

移动开发者 Justin Williams 在接受《连线》采访时说：“当年苹果的做法很明智，在 iPad 推出之前几个月就放出了开发工具。相比之下，Google 的开发者只是在 XOOM 发售之前几天才拿到开发工具。”所以在 iPad 发售时，商店里已经有了 1000 个专用软件。当 XOOM 发售时，这个数字是 15 。

An App Widget uses a special display control called RemoteViews. Unlike a regular View, a RemoteViews control is designed to display a collection of View controls in another process. Consequently, you can't simply add a button handler because that code would run in your application process, not in the process displaying the RemoteViews object (in this case, the Home Screen process).

In order to handle user interaction with an App Widget, the following tasks must be performed: Set a unique click handler for each App Widget control Have the click handler send a command to a registered receiver Process the command received and perform any action necessary Update the App Widget to reflect the changes

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

onReceive(): The default implementation of this method handles the BroadcastReceiver actions and makes the appropriate calls to the methods shown above. (Warning: A well-documented defect exists that requires the developer to handle certain cases explicitly. See the following note for more information.)

Creating a simple App Widget involves several steps: Create a RemoteView, which provides the user interface for the App Widget. Tie the RemoteView to an Activity that implements the AppWidgetProvider interface. Provide key App Widget configuration information in the Android manifest file.

An App Widget is basically just a BroadcastReceiver that handles specific actions.

Authentication with App Engine, regardless of where you're doing it, is a three-stage process: Obtain an authentication token. This can be done with ClientLogin for installed apps, for example, or with AuthSub for a webapp. When logging in directly to an application, this is the part of the login process where your user sees a Google signin screen. Take that authentication token, and use it to obtain an authentication cookie. Use that authentication cookie in all subsequent requests.

<uses-permission android:name="android.permission.GET_ACCOUNTS"></uses-permission> <uses-permission android:name="android.permission.USE_CREDENTIALS"></uses-permission> <uses-permission android:name="android.permission.INTERNET"></uses-permission>

<!-- Variation on the Light theme that turns off the title --><style name="Theme.IOSched" parent="android:style/Theme.Light">    <item name="android:windowNoTitle">true</item>    <item name="android:windowContentOverlay">@null</item></style>

The android:windowContentOverlay is your shadow, and setting it to @null in your theme will eliminate it. You can see this in action in the Google I|O 2010 conference app, which uses many of the same UI conventions as does the new Twitter app. However, right now, the Twitter app has not yet been open-sourced, which is why I point you to the I|O app. The code fragment above is from that app's styles.xml resource.

The Android system reuses Intents that match both action and scheme values—the "extras" values are not compared

In practice, this means the Intent for each App Widget identifier would actually be the same Intent. Fortunately, the solution is straightforward: define a scheme for your App Widget and use it to define unique Intent instances

// make this pending intent unique widgetUpdate.setData( Uri.withAppendedPath(Uri.parse( ImagesWidgetProvider.URI_SCHEME + "://widget/id/"), String.valueOf(appWidgetId)));

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.

Getting Started Welcome to Training for Android developers. Here you'll find sets of lessons within classes that describe how to accomplish a specific task with code samples you can re-use in your app. Classes are organized into several groups you can see at the top-level of the left navigation. This first group, Getting Started, teaches you the bare essentials for Android app development. If you're a new Android app developer, you should complete each of these classes in order:

An AppWidgetProvider is a BroadcastReceiver. That gives you two possibilities right off the bat: 1. Have it also handle whatever other Intents you were planning on setting up with a separate BroadcastReceiver, or 2. Send an Intent from whatever component you want to the AppWidgetProvider. In other words, don't worry about trying to talk directly to the app widget (which I suspect is impossible) -- just talk to your code that already talks to the app widget.

I update my widget from within my app, when I delete/add entries to a list. To do this, I have a method (updateWidget) and a static String (UPDATE_ACTION). My updateWidget() method sends a broadcast which is received by the widget class and then calls onUpdate() with the appropriate params: private void updateWidget() {                 Intent i = new Intent(this, TVWidget.class);                 i.setAction(TVWidget.UPDATE_ACTION);                 sendBroadcast(i);         } In TVWidget class: @Override         public void onReceive(Context context, Intent intent) {                 String action = intent.getAction();                 if (action != null && action.equals(UPDATE_ACTION)) {                         final AppWidgetManager manager = AppWidgetManager.getInstance (context);                         onUpdate(context, manager,                                         manager.getAppWidgetIds(new ComponentName(                                                         context, TVWidget.class)                                         )                         );                 }                 else {                         super.onReceive(context, intent);                 }         } This seems to work fine.

A facility for the application to tell the system about something it wants to be doing in the background

A facility for an application to expose some of its functionality to other applications.