[英] 使用 Android 注解来改善开发代码
If you haven’t heard of the Android Support Annotations library yet, you’re missing out on a neat new package that will help you catch bugs in your apps. Included in the library is a number of Java annotations, that will help Android Studio check your code for possible errors and report them to you. There are quite a few of them, so I only plan to go over a few of them here, but you should definitely check out the docs for more info about the rest.
@NonNull / @Nullable
@NonNull and @Nullable are probably the most basic of the support annotations, but also some of the most helpful! Annotate a parameter or method with either of these to denote if the parameter or method’s return value can be null or not, and voila, now Android Studio can give us a nice warning that we’re doing something unsafe.
Turn this:
![[英] 使用 Android 注解来改善开发代码](http://www.liuhaihua.cn/wp-content/uploads/2015/07/iuAVvi7.png "Method with no annotations")
into this:
![[英] 使用 Android 注解来改善开发代码](http://www.liuhaihua.cn/wp-content/uploads/2015/07/bqeMzua.png "with @NonNull")
Bonus points: We can even take this example one step further with the @CheckResult annotation, to tell us know that the return type of this method is something that we are expected to use, rather than the method having a side effect.
![[英] 使用 Android 注解来改善开发代码](http://www.liuhaihua.cn/wp-content/uploads/2015/07/bABFfyn.png "Check that return type!")
@StringRes / @DrawableRes / etc.
Have you ever attempted to call setText on a TextView, and gotten a somewhat mysterious android.content.res.Resources$NotFoundException: String resource ID #0x3039 exception? If you pass an integer to setText, TextView assumes it’s a String resource id, and will look it up in order to set the text. If only there were a way to denote that integers are not valid ids for this method… @StringRes to the rescue!
public void setText(@StringRes int id) { // Do something like getString(id), etc. }Now if you try to pass a non-String resource id to this method, you get something like this:
![[英] 使用 Android 注解来改善开发代码](http://www.liuhaihua.cn/wp-content/uploads/2015/07/6BNJZv.png "Method takes a @StringRes id, not an int")
(There are resouce annotations for all resoruce types, @DrawableRes , @ColorRes , @InterpolatorRes , etc.)
@Keep
Today I discovered a new support annotation @Keep . According to the support annotation docs, this annotation hasn’t been hooked up to the Gradle plugin yet 1 , but it will let you annotate methods and classes that should be retained when minimizing the app.
If you’ve ever messed around with the cryptic -keep class com.foo.bar { public static <methods> } incantations that you need to use to summon the Proguard Gods, you’ll know how painful it is to rip your hair out, while trying to exclude a particular method or class from being optimized away. This handy annotation will tell Proguard to leave the method or class alone – like so:
public class Example { @Keep public void doSomething() { // hopefully this method does something } ... } The best part is – if you’re using appcompat-v7 , you’re already including support-annotations , so just start using them already!
正文到此结束
热门推荐
相关文章
近期评论
-
文章和留言都翻到11页了 没有OOM
-
-
朋友，翻页到11页，及以后，会出现OOM，无法访问
-
-
搞个gitee的项目
-
-
版本号是多少，你可以下载哪个代码仓库，jdk选1.8 直接跑就行
-
-
-
Loading...
![[HBLOG]公众号](https://www.liuhaihua.cn/img/qrcode_gzh.jpg)
