Android响应式编程开发RxAndroid（4）：flatMap

港控/mmm° 2023-10-17 11:19 65阅读 0赞

**Android响应式编程开发RxAndroid（4）：flatMap**

RxAndroid的map通过Function把一个对象转换为另外一个对象，作为结果输出。flatMap则可以通俗的理解为把一个集合元素对象拆分成单个元素对象，然后丢给Observer作为输入。例子：

package zhangphil.app;
    
    import android.app.Activity;
    import android.os.Bundle;
    import android.util.Log;
    
    import java.util.Arrays;
    import java.util.List;
    
    import io.reactivex.Observable;
    import io.reactivex.android.schedulers.AndroidSchedulers;
    import io.reactivex.functions.Function;
    import io.reactivex.observers.DisposableObserver;
    import io.reactivex.schedulers.Schedulers;
    
    public class MainActivity extends Activity {
    
        //假设一个数据源
        private String TAG = "zhangphil测试";
    
        private DisposableObserver<String> observer = new DisposableObserver<String>() {
    
            @Override
            public void onNext(String s) {
                Log.d(TAG, "onNext - Start");
                Log.d(TAG, String.valueOf(s));
                Log.d(TAG, "onNext - End");
            }
    
            @Override
            public void onComplete() {
                Log.d(TAG, "onComplete");
            }
    
            @Override
            public void onError(Throwable e) {
                Log.e(TAG, e.toString(), e);
            }
        };
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
    
            String[] source = {"zhang", "phil", "@", "csdn"};
            List<String> lists = Arrays.asList(source);
    
            Observable
                    .just(lists)
                    .subscribeOn(Schedulers.io())//执行任务的线程
                    .observeOn(AndroidSchedulers.mainThread())//回调发生的线程
                    .flatMap(function)
                    .subscribe(observer);
        }
    
        // 设置映射函数
        private Function<List<String>, Observable<String>> function = new Function<List<String>, Observable<String>>() {
            @Override
            public Observable<String> apply(List<String> lists) {
                String[] strs = new String[lists.size()];
                for (int i = 0; i < lists.size(); i++) {
                    strs[i] = lists.get(i).toUpperCase();
                }
                return Observable.fromArray(strs);
            }
        };
    }

代码运行结果输出：

03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - Start
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: ZHANG
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - End
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - Start
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: PHIL
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - End
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - Start
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: @
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - End
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - Start
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: CSDN
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onNext - End
    03-02 10:31:06.606 18037-18037/zhangphil.app D/zhangphil测试: onComplete

附录：  
1，《Android响应式编程RxAndroid（1）：简单例程》链接地址：[http://blog.csdn.net/zhangphil/article/details/58593782][http_blog.csdn.net_zhangphil_article_details_58593782]  
2，《Android响应式编程开发RxAndroid（2）：简单例程的Android改造 》链接地址：[http://blog.csdn.net/zhangphil/article/details/58597372][http_blog.csdn.net_zhangphil_article_details_58597372]  
3，《Android响应式编程开发RxAndroid（3）：map》链接地址：[http://blog.csdn.net/zhangphil/article/details/59130641][http_blog.csdn.net_zhangphil_article_details_59130641]

[http_blog.csdn.net_zhangphil_article_details_58593782]: http://blog.csdn.net/zhangphil/article/details/58593782
[http_blog.csdn.net_zhangphil_article_details_58597372]: http://blog.csdn.net/zhangphil/article/details/58597372
[http_blog.csdn.net_zhangphil_article_details_59130641]: http://blog.csdn.net/zhangphil/article/details/59130641