有用的Android系统资源

Question

Android comes with lots of system resources ( android.R ) that can be used to save you time and make your application lighter.

For example, I recently discovered that Android provides localized strings for Yes ( android.R.string.yes ), No ( android.R.string.no ), Cancel ( android.R.string.cancel ) and Ok ( android.R.string.ok ), among other strings.

What other system resources do you recommend using? Or is there a reason to avoid using system resources?

Edit: As noted by Tomas, some of this resources might not produce the results you would expect (particularly, android.R.string.yes/no returns OK/Cancel instead of Yes/No , as reported here ). For greater control, you can copy system resources from the Android source code.

Answer 1

You can find a full listing of all system resources in the android package .

Every time I want to do something on Android I check to see if there's a system resource that covers what I want to do. It is helpful to import the Android source code (in particular, their /res/ folder ) when searching for already-implemented resources that you might want, so you can see their specific implementation.

Personally, I find myself most often using:

• Built-in Android layouts for standard tasks, such as spinner dropdowns.
• Android ids ( android.R.id ), because you are often required to use these if you want to use some of Android's widgets (for example, TabHost/TabWidget requires you to use " android:id/tabhost ", " android:id/tabs " and " android:id/tabcontent " if you want to implement an XML layout).
• Built-in colors, especially android.R.color.transparent .
• Android's built-in fade-in and fade-out animations in android.R.anim .

Answer 2

您可以通过使用android包名称限定来自xml的系统资源 ，即"@android:string/ok"

Answer 3

As CommonsWare mentioned, you don't have to download the Android source repository to inspect the resources; just go to <android-sdk-dir>/platforms/android-XX/data/res/ . However, if you start using these you will quickly become disappointed to find that most of them are not available through the android.R class. Most of the time I have to import them into my Eclipse workspace anyway. :-(

My favorite resources are the drawables that show differently based on a control's focused/pressed/disabled states (like android.R.drawable.btn_default). I use those or tweak them to create custom buttons for my apps. As you can see if you look at /data/res/drawable/btn_default.xml , they are defined as a <selector> XML element, which gets inflated into a StateListDrawable at runtime. You could also create your own StateListDrawables and they're super useful, both as View backgrounds and as a button's "compound drawable" (see TextView.setCompoundDrawables() ).

Answer 4

Please note that the translations are really bad.

For example the German "no" in android-25 is "Abbrechen" which actually means "cancel". "Yes" is translated as "OK"...

I'm not sure how good the other languages are, so I would use an own translation.