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Lambda表达式和Rx非常契合, 可以省略大量的内部类, 如Func和Action. 我们把上个示例, 用Lambda再写一次, 功能相同.

如果编译器出现”Method references are not supported at this language level” 请按下alt+enter 然后选择 “Set language level to 8 - Lambdas, type annotations, etc.”

添加Gradle配置 在app下的build.gradle如下:

apply plugin: 'me.tatarka.retrolambda'

android {
  ...
}

在根目录下的build.gradle如下：

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.1.0'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
        classpath 'me.tatarka:gradle-retrolambda:3.2.5'
    }
}

源码如下：

public class LambdaActivity extends Activity {

    @Bind(R.id.simple_tv_text) TextView mTvText;

    final String[] mManyWords = {"Hello", "I", "am", "your", "friend", "Spike"};
    final List<String> mManyWordList = Arrays.asList(mManyWords);

    @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_simple);
        ButterKnife.bind(this);

        // 添加字符串, 省略Action的其他方法, 只使用一个onNext.
        Observable<String> obShow = Observable.just(sayMyName());

        // 先映射, 再设置TextView
        obShow.observeOn(AndroidSchedulers.mainThread())
                .map(String::toUpperCase).subscribe(mTvText::setText);

        // 单独显示数组中的每个元素
        Observable<String> obMap = Observable.from(mManyWords);

        // 映射之后分发
        obMap.observeOn(AndroidSchedulers.mainThread())
                .map(String::toUpperCase)
                .subscribe(this::showToast);

        // 优化过的代码, 直接获取数组, 再分发, 再合并, 再显示toast, Toast顺次执行.
        Observable.just(mManyWordList)
                .observeOn(AndroidSchedulers.mainThread())
                .flatMap(Observable::from)
                .reduce(this::mergeString)
                .subscribe(this::showToast);
    }

    // 创建字符串
    private String sayMyName() {
        return "Hello, I am your friend, Spike!";
    }

    // 显示Toast
    private void showToast(String s) {
        Toast.makeText(LambdaActivity.this, s, Toast.LENGTH_SHORT).show();
    }

    // 合并字符串
    private String mergeString(String s1, String s2) {
        return String.format("%s %s", s1, s2);
    }
}