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This page is offered as a service of Bristle Software, Inc. New tips are sent to an associated mailing list when they are posted here. Please send comments, corrections, any tips you'd like to contribute, or requests to be added to the mailing list, to tips bristle. The primary place to find info about Android programming is the official site: See the Android Development row of my links page: Use the wizard to create a sample Android app.
Wire up the behavior in familiar Java code. Run or debug the app in Eclipse, and it connects to your Android device via USB or fires up an emulator so you can test it, step through it, etc. Once you get something simple working, you'll want to learn more about the Android architecture see free android robot icon packs download apk tip and begin exploring Android's extensive Java class libraries.
Android apps use a message-driven architecture with various type of components: Intent A message string of text typically specifying an action to be performed or an event that has occurred. Activity A UI free android robot icon packs download apk to be displayed to the user.
Typically launched at app startup or displayed by sending it an Intent. Fills the entire screen -- the user cannot see 2 Activities at the same time. Fragment A reusable portion of an Activity -- a region of a UI screen. Added in Android version 3. View A single UI "control", like a checkbox, edit field, etc. Resides in an Activity or a Fragment. Service A behind-the-scenes block of code with no UI. Typically invoked by sending it an Intent. Broadcast Receiver Listens for Intents that are broadcast by the system or by the enclosing app or any other app.
Typically does little work other than to dispatch the Intent to an Activity or a Service. There are very complete and detailed instructions on how to publish an app to "Google Play" the new name of the "Android Market" at:. However, it glosses over some issues that I think are important and some gotcha's that were not obvious to me, while giving more detail than I needed for other parts.
Beware factoring versionCode out of the manifest file and into a free android robot icon packs download apk file. Works fine, but Google Play refuses to publish the app. Android allows and the tools encourage you to factor displayable strings out of your Java source files into "resource files" like strings.
This is very useful for internationalization and for any situation where you want to separate the display strings from the code. You can factor them out of your Java source files, and also out of other resource files and even the manifest file. I decided to do the same for the versionName string, which is ordinarily specified directly in the AndroidManifest. This allowed me to easily refer to the string free android robot icon packs download apk my Java classes and in my other resource files, which made it easy to display to the user.
I added it to strings. This would be especially handy if I want to automate the process of updating these values as part of my build process.
At first, I tried to do exactly the same thing, adding it to strings. I was able free android robot icon packs download apk build and run the app in the emulator and on my physical Android phone, but when I tried to upload the APK to Google Play, I got the error: The file is invalid: The easiest way to show a popup message in Android is via the Toast class, which shows a message for a couple seconds, then clear itself.
Beware using too many Toast messages because they can get queued up and be annoying. For example, while debugging some keystroke-handling code, I chose to show a Toast message in response to each keystroke, but when I typed faster than the Toast delay, I piled up lots of Toast messages.
Toast only shows one message at a time, and it shows each message for its full duration, so it took a long time for them all to get displayed and cleared. Worse, I made the mistake of holding down an auto-repeating key for a couple seconds, and queued up enough Toast messages to display for several minutes.
Even when I switched to a different app, each Toast message remained on the screen for its full duration, and the queued messages continued to pop up.
If you are just debugging, it is usually better to use the built-in Android Log class instead, as: For more info on Toast and Log, see the Android Javadocs: If you want to respond to every keystroke a user types during data entry, it is free android robot icon packs download apk to respond to events like key down, key up, etc.
However, beware that such events may be generated only for hardware keys, not by the on-screen keyboard. I found it worked for these cases But not for these cases I used a TextChangedListener instead, which is a better idea anyhow because For more info see: Want to switch the Android emulator from portrait to landscape layout? When running the emulator, use the following keypresses: A message string of text typically specifying an action to free android robot icon packs download apk performed or an event that has occurred.
A UI screen to be displayed to free android robot icon packs download apk user. A reusable portion of an Activity -- a region of a UI screen. A single UI "control", like a checkbox, edit field, etc. A behind-the-scenes block of code with no UI.
Listens for Intents that are broadcast by the system or by the enclosing app or any other app. Provides access to local or remote data files, databases, Internet resources, etc. Typically called directly actually via a ContentResolvernot via an Intent. Also lists permissions needed by the app, hardware features used by the app, etc.