我现在可以在 Android 开发中“使用”Java 8 吗？

Can I "use" Java 8 with Android Development now?

提问by wayway

I currently have Java 7 JDK installed. It's been like that for awhile. However, recently, my professor is instructing the class to uninstall Java JDK 7 and install Java JDK 8 instead to be able to work on homework and such.

我目前安装了 Java 7 JDK。已经有一段时间了。但是，最近，我的教授指示全班卸载 Java JDK 7 并安装 Java JDK 8，以便能够完成家庭作业等。

I've been using Java JDK 7 to write and deploy Android apps without any problems so I'm wondering if it's safe to make the upgrade now the JDK 8? I'm assuming that I won't be needing any Java 8 specific methods or functions in my Android development. So if I stay away from that, will my Android development be at all affected?

我一直在使用 Java JDK 7 编写和部署 Android 应用程序，没有任何问题，所以我想知道现在升级 JDK 8 是否安全？我假设在我的 Android 开发中不需要任何 Java 8 特定的方法或函数。那么如果我远离它，我的Android开发会受到影响吗？

On a side note, I haven't been able to find any official documentation that states whether or not Java JDK 8 is safe or not or how to make it safe. Either way, I'm going to have to upgrade to Java 8 soon...

附带说明一下，我找不到任何说明 Java JDK 8 是否安全或如何使其安全的官方文档。无论哪种方式，我都将不得不很快升级到 Java 8...

采纳答案by ChiefTwoPencils

If you've been using Java 7 to deploy Android apps then it's certain, up to this point, you haven't used any Java 8 features so I don't see how it would matter.

如果您一直在使用 Java 7 来部署 Android 应用程序，那么可以肯定，到目前为止，您还没有使用任何 Java 8 功能，所以我看不出这有什么关系。

Follow your instructor's directions and when you do an assignment for school simply select either the JDK or Language Level in the Project Structure.

按照老师的指示，当你为学校做作业时，只需在项目结构中选择 JDK 或语言级别。

CTRL+ ALT+ S, select Project

CTRL+ ALT+ S，选择Project

You can default to the Java 8 SDK but limit it to Java 7's features for your Android apps. Or you can simply set your homework projects to the Java 8 SDK.

您可以默认使用 Java 8 SDK，但将其限制为 Java 7 的 Android 应用程序功能。或者，您可以简单地将作业项目设置为 Java 8 SDK。

Going out on a limb here assuming Android Studio includes the core settings of Intellij.

假设 Android Studio 包含 Intellij 的核心设置，这里就有点冒险了。

回答by Zeyad Assem

In Google I/O 2016, they announced that Android now supports some features of Java 8, but not all the features.

在 Google I/O 2016 上，他们宣布 Android 现在支持 Java 8 的一些功能，但不是所有功能。

Features like

功能如

• 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)

• 默认和静态接口方法
• Lambda 表达式（也可用于 API 级别 23 及更低级别）
• 可重复的注释
• 方法参考（也可用于 API 级别 23 及更低级别）
• 类型注释（也可用于 API 级别 23 及更低级别）

Additionally, the following Java 8 language APIs are also available:

此外，还提供以下 Java 8 语言 API：

• 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

• 反射和语言相关的 API
  • java.lang.FunctionalInterface
  • java.lang.annotation.Repeatable
  • java.lang.reflect.Method.isDefault()
  • 和与可重复注释关联的反射 API，例如 AnnotatedElement.getAnnotationsByType(Class)
• 实用程序 API
  • java.util.function
  • java.util.stream

All what you should do is to use the new Hyman compiler, to do this you have just to add this to your gradle file build.gradle (Module: app):

您应该做的就是使用新的 Hyman 编译器，为此您只需将其添加到您的 gradle 文件中build.gradle (Module: app)：

android {
  ...
  defaultConfig {
    ...
    HymanOptions {
      enabled true
    }
  }
  compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
  }
}

References:

参考：

• https://developer.android.com/guide/platform/j8-Hyman.html
• https://www.youtube.com/watch?v=B08iLAtS3AQ&feature=youtu.be&t=28m14s

• https://developer.android.com/guide/platform/j8-Hyman.html
• https://www.youtube.com/watch?v=B08iLAtS3AQ&feature=youtu.be&t=28m14s

回答by Angel Koh

It's safe if you don't use the java 8 features.

如果您不使用 java 8 功能，那是安全的。

although you may be keen on java 8 with retroLambda and collectionsQuery. https://github.com/evant/gradle-retrolambdaand https://bitbucket.org/mart_bogdan/collectionsquery/src

尽管您可能对带有 retroLambda 和 collectionsQuery 的 Java 8 感兴趣。 https://github.com/evant/gradle-retrolambda和 https://bitbucket.org/mart_bogdan/collectionsquery/src

This will allow you to write your code to something like the following: -

这将允许您将代码编写为如下所示：-

mButton.setOnClickListener( v-> doClickEvent()); 

mView.postDelayed( () -> someMethodToRun() , 1000);

Queryable.from(listOfObject).forEachR(r -> doProcess(r));

as opposed to the clunky

相对于笨重

mButton.setOnClickListener( new View.OnClickListener(){
     @Override
      public void onClick(View v) {
         doClickEvent();
      }
});

to use java 8 with retrolambda just add in the gradle file.

要将 java 8 与 retrolambda 结合使用，只需在 gradle 文件中添加即可。

apply plugin: 'com.android.application'
apply plugin: 'me.tatarka.retrolambda'

android {

    // :
    // Snips the rest of configuration.
    // :
    compileOptions {
        encoding "UTF-8"
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {

    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'  

    compile 'com.android.support:appcompat-v7:23.1.1' 

    compile 'com.innahema:collections-query:0.2.9'
}

and at the project gradle.build file add the following...

并在项目 gradle.build 文件中添加以下内容...

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.5.0'

        classpath 'me.tatarka:gradle-retrolambda:3.2.3'
        classpath 'me.tatarka.retrolambda.projectlombok:lombok.ast:0.2.3.a2' //fix lint issue

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

回答by Robert McHardy

I guess you should just give it a try. On a side note: You can easily run JDK 7 and JDK 8 side by side. I don't know about Android Studio, but in Eclipse you can configure the build path.

我想你应该试一试。附带说明：您可以轻松地同时运行 JDK 7 和 JDK 8。我不了解 Android Studio，但在 Eclipse 中您可以配置构建路径。

Despite that: Are you using Java 8 specific features for your homework? If you don't use lambdas or JavaFX 8, I don't think you will needJDK 8. Sounds more like your professor just wants to use the latest version of Java (judging from your first sentence).

尽管如此：您是否在作业中使用 Java 8 特定功能？如果您不使用 lambdas 或 JavaFX 8，我认为您不需要JDK 8。听起来更像是您的教授只想使用最新版本的 Java（从您的第一句话判断）。