在网上搜索,还不清楚Android开发是否支持Java 8。
在我下载/安装Java 8之前,能不能有人给我指出任何“官方”文档,说Java 8是或不支持Android开发。
在网上搜索,还不清楚Android开发是否支持Java 8。
在我下载/安装Java 8之前,能不能有人给我指出任何“官方”文档,说Java 8是或不支持Android开发。
当前回答
在2019年最新的Android Studio 3.4+上,上述所有解决方案似乎都不起作用。
我想出了一个完美的和最新的解决方案,将您的Android项目迁移或升级到Java 8。
解决方案: 点击文件->项目结构->模块->属性选项卡。 将源兼容性和目标兼容性更改为1.8 (Java 8)
其他回答
当我在大约2年前问这个问题时,答案确实是“官方的”否定的,但是正如ekcr1的答案所指出的那样,如果您使用retrolamba,您可以获得最受期待的特性之一(lambdas)。当时我仍在使用eclipse,因为Android Studio处于“预览”模式,所以我从未走上这条道路。
今天,我认为“官方”的答案仍然是否定的,虽然retrolamba看起来仍然是一个不错的选择,但对于那些愿意走一条有点“非官方”路线的人来说,还有另一个选择,那就是Kotlin。
今天Kotlin达到了1.0.0。对于那些不熟悉Kotlin的人,更多的信息可以在他们的网站上找到:
https://kotlinlang.org
或者观看Jake Wharton的演讲视频
https://www.youtube.com/watch?v=A2LukgT2mKc
添加这个配置版本。Gradle和同步Gradle:
android {
...
defaultConfig {
...
jackOptions {
enabled true
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
// or
//sourceCompatibility 1.8
//targetCompatibility 1.8
}
}
更新2019/10/28
Android Studio 4.0解决了这个问题。
D8编译器在编译时将Java 8原生api的反向端口补丁到APK中,你的应用程序将在运行时使用该代码,而不是原生api。这个过程被称为脱糖。
Android在Android N正式支持Java 8。
特性公告如下,Java 8语言公告如下:
Improved Java 8 language support - We’re excited to bring Java 8 language features to Android. With Android's Jack compiler, you can now use many popular Java 8 language features, including lambdas and more, on Android versions as far back as Gingerbread. The new features help reduce boilerplate code. For example, lambdas can replace anonymous inner classes when providing event listeners. Some Java 8 language features --like default and static methods, streams, and functional interfaces -- are also now available on N and above. With Jack, we’re looking forward to tracking the Java language more closely while maintaining backward compatibility.
我想我应该发布一个更新的答案给那些寻找一些更当前的东西的人。
目前Android和Android Studio支持Java 8特性的一个子集。根据他们网站上的Android文档,谷歌说:
Support for Java 8 language features requires a new compiler called Jack. Jack is supported only on Android Studio 2.1 and higher. So if you want to use Java 8 language features, you need to use Android Studio 2.1 to build your app. If you already have Android Studio installed, make sure you update to the latest version by clicking Help > Check for Update (on Mac, Android Studio > Check for Updates). If you don't already have the IDE installed on your workstation, download Android Studio here. Supported Java 8 Language Features and APIs Android does not support all Java 8 language features. However, the following features are available when developing apps targeting Android 7.0 (API level 24): Default and static interface methods Lambda expressions (also available on API level 23 and lower) Repeatable annotations Method References (also available on API level 23 and lower) Type Annotations (also available on API level 23 and lower)
此外,以下Java 8语言api也可用:
Reflection and language-related APIs: java.lang.FunctionalInterface java.lang.annotation.Repeatable java.lang.reflect.Method.isDefault() and Reflection APIs associated with repeatable annotations, such as AnnotatedElement.getAnnotationsByType(Class) Utility APIs: java.util.function java.util.stream In order to use the new Java 8 language features, you need to also use the Jack toolchain. This new Android toolchain compiles Java language sources into Android-readable DEX bytecode, has its own .jack library format, and provides most toolchain features as part of a single tool: repackaging, shrinking, obfuscation and multidex. Here is a comparison of the two toolchains used to build Android DEX files: Legacy javac toolchain: javac (.java → .class) → dx (.class → .dex) New Jack toolchain: Jack (.java → .jack → .dex)