RxJava源码阅读,map操作符(二)

悠悠 2022-01-19 04:25 167阅读 0赞

## 1.基本写法 ##

Observable.just("https://user-gold-cdn.xitu.io/2019/5/17/16ac4f7f486ca77a?imageView2/1/w/180/h/180/q/85/interlace/1")
                       .map(new Function<String, Bitmap>() {
                           @Override
                           public Bitmap apply(String urlPath) throws Exception {
                               URL url = new URL(urlPath);
                               HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
                               InputStream inputStream = urlConnection.getInputStream();
                               Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                               return bitmap;
                           }
                       }).subscribe(new Consumer<Bitmap>() {
                           @Override
                           public void onNext(final Bitmap bitmap) {
                               runOnUiThread(new Runnable() {
                                   @Override
                                   public void run() {
                                       mImage.setImageBitmap(bitmap);
                                   }
                               });
                           }
                       });
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## 2.map做了什么 ##

跟[RxJava源码阅读(一)][RxJava] 一样Observable.just()创建了一个`ObservableJust`,通过map操作符后生成了一个`ObservableMap`

public ObservableMap(ObservableSource<T> source, Function<? super T, ? extends U> function) {
            super(source);
            this.function = function;
    }
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`ObservableMap`构造方法中第一个参数持有了`ObservableJust`引用,相当于是`ObservableJust`的动态代理。同样,最终执行的是`ObservableMap`的`subscribeActual`方法

@Override
    public void subscribeActual(Observer<? super U> t) {
        source.subscribe(new MapObserver<T, U>(t, function));
    }
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其中`source`就是传入的`ObservableJust`,只是在调用`subscribe`方法时又包裹了下，将传入的Observer包装成MapObserver

## 3.总结 ##

Observable.just("")
            .map(new Function<String, String>() {
                @Override
                public String apply(String urlPath) {
                    return urlPath;
                }
            })
            .map(new Function<String, String>() {
                @Override
                public String apply(String urlPath) {
                    return urlPath;
                }
            }).subscribe(new Consumer<String>() {
            @Override
                public void onNext(final String bitmap) {
                }
            });
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转载于:https://juejin.im/post/5ce5138cf265da1bc07e0fcf

[RxJava]: https://juejin.im/post/5cde514551882525ef3f99bb