半天学会RxJava的简单使用

参考文章：https://www.jianshu.com/p/031745744bfa

1. 准备

安装依赖

    compile 'io.reactivex.rxjava2:rxjava:2.0.2'
    compile 'io.reactivex.rxjava2:rxandroid:2.0.2'

2. 使用

创建一个按钮点击被观察者，且规定发射出来的sourse的类型为String

    Observable.create(new ObservableOnSubscribe<String>() {}）

实现订阅方法，给mainButton2按钮绑定点击事件，然后将mainEdit1输入框的文字发射出去，并且在emitter取消的时候将mainButton2的监听移除，防止内存泄露

    public void subscribe(final ObservableEmitter<String> emitter) throws Exception {
       mainButton2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                emitter.onNext(mainEdit1.getText().toString());
            }
        });
        emitter.setCancellable(new Cancellable() {
            @Override
            public void cancel() throws Exception {
                mainButton2.setOnClickListener(null);
            }
        });
    }

创建观察者，且订阅按钮点击被观察者

    searchTextObservable
      .subscribe(new Consumer<String>() {
        @Override
        public void accept(String result) throws Exception {
          showResult(result);
        }
      });
    }

模拟耗时任务，睡眠2s，返回只包含输入框文字的数组

    private static class SearchEngine {
        ArrayList<String> strings;
        private List<String> search(String txt) {
            strings = new ArrayList<>();
            strings.add(txt);
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return strings;
        }
    }

运用filter操作符实现Predicate接口进行条件判定过滤，运用debounce操作符设定发射间隔

    buttonClickObservable
        .filter(new Predicate<String>() {
            @Override
            public boolean test(@NonNull String s) throws Exception {
                return s.length() > 1;
            }
        })
        .debounce(2, TimeUnit.SECONDS);

再创建一个输入文字改变被观察者

    private Observable<String> createTextChangeObservable() {
        Observable<String> textChangeObservable = Observable.create(new ObservableOnSubscribe<String>() {
            @Override
            public void subscribe(final ObservableEmitter<String> emitter) throws Exception {
                final TextWatcher watcher = new TextWatcher() {
                    @Override
                    public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

                    @Override
                    public void afterTextChanged(Editable s) {}

                    @Override
                    public void onTextChanged(CharSequence s, int start, int before, int count) {
                        emitter.onNext(s.toString());
                    }
                };

                mainEdit1.addTextChangedListener(watcher);

                emitter.setCancellable(new Cancellable() {
                    @Override
                    public void cancel() throws Exception {
                        mainEdit1.removeTextChangedListener(watcher);
                    }
                });
            }
        });

        return textChangeObservable
                .filter(new Predicate<String>() {
                    @Override
                    public boolean test(@NonNull String s) throws Exception {
                        return s.length() > 1;
                    }
                })
                .debounce(2, TimeUnit.SECONDS);
    }

运用merge操作符将以上两个被观察者联合起来

    Observable<String> searchTextObservable = createButtonClickObservable();
    Observable<String> textChangeObservable = createTextChangeObservable();
    Observable<String> observable = Observable.merge(searchTextObservable,textChangeObservable);

切换线程
先切换到主线程，将进度条显示出来
再切换到子线程，进行耗时的搜索工作
再切换到主线程，隐藏进度条且将搜索结果显示出来

    mDisposable = observable
                .observeOn(AndroidSchedulers.mainThread())
                .doOnNext(new Consumer<String>() {
                    @Override
                    public void accept(String s) throws Exception {
                        showProgress();
                    }
                })
                .observeOn(Schedulers.io())
                .map(new Function<String, List<String>>() {
                    @Override
                    public List<String> apply(@NonNull String query) throws Exception {
                        return mSearchEngine.search(query);
                    }
                })
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<List<String>>() {
                    @Override
                    public void accept(List<String> result) throws Exception {
                        hideProgress();
                        showResult(result);
                    }
                });

在onStop中解除订阅

    @Override
    protected void onStop() {
        super.onStop();
        if (!mDisposable.isDisposed()) {
            mDisposable.dispose();
        }
    }

写于2018-4-4