如何为 android6(API23) 配置 retrolambda

Question

我想为我的项目添加 Java8 支持。我找到的唯一合适的解决方案是 retrolambda gradle 插件项目。这是我的 build.gradle 个项目和模块的相对文件。

注意：请不要建议迁移到 Android Studio 3，因为我想了解为什么它不起作用。

项目build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'
        classpath 'me.tatarka:gradle-retrolambda:3.7.0'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

模块build.gradle

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

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"
    defaultConfig {
        applicationId "com.test.test"
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

retrolambda {
    javaVersion JavaVersion.VERSION_1_7
    defaultMethods true
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:26+'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
}

该应用程序本身非常简单。它只有一个默认的 activity，带有 Java8 代码，像这样：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        List<String> strings = new ArrayList<>();
        strings.add("Hello");
        strings.add("World");
        strings.stream().forEach(System.out::println);
    }
}

启动应用程序时出现以下错误：

FATAL EXCEPTION: main Process: com.slesh.mtbbank, PID: 25338 java.lang.NoSuchMethodError: No interface method stream()Ljava/util/stream/Stream; in class Ljava/util/List; or its super classes (declaration of 'java.util.List' appears in /system/framework/core-libart.jar) at com.slesh.mtbbank.MainActivity.onCreate(MainActivity.java:19) at android.app.Activity.performCreate(Activity.java:6303) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2402) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2509) at android.app.ActivityThread.access00(ActivityThread.java:153) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1373) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:5529) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629)

错过了什么？知道为什么它不起作用吗？

提前致谢！

Answer 1

strings.stream().forEach(System.out::println)

Retrolambda 的功能正如它的名字所暗示的那样：它允许您使用 lambda。它不支持流。有向后移植流 API 的库，但 retrolambda 没有。

如何为 android6(API23) 配置 retrolambda

How to configure retrolambda for android6(API23)

android

retrolambda