如何在RxJava中处理可观察对象的map()中的异常 [英] How do I handle exceptions in map() in an Observable in RxJava

问题描述

我要这样做：

Observable.just(bitmap)
            .map(new Func1<Bitmap, File>() {
                @Override
                public File call(Bitmap photoBitmap) {

                    //File creation throws IOException, 
                    //I just want it to hit the onError() inside subscribe()

                    File photoFile = new File(App.getAppContext().getCacheDir(), "userprofilepic_temp.jpg");
                    if(photoFile.isFile()) {//delete the file first if it exists otherwise the new file won't be created
                        photoFile.delete();
                    }
                    photoFile.createNewFile(); //saves the file in the cache dir

                    FileOutputStream fos = new FileOutputStream(photoFile);
                    photoBitmap.compress(Bitmap.CompressFormat.JPEG, 90, fos);//jpeg format
                    fos.close();

                    return photoFile;

                }
            })
            .subscribe(//continue implementation...);

基本上在call()方法中，它可以抛出异常。如何让观察者在onError()中处理它。或者这不是思考这件事的正确方式吗？

推荐答案

rx始终会捕获错误，即使这是运行异常。 因此您可以在Catch挡路中抛出某种运行时异常。这就是它的实际工作方式。

 Observable.just(bitmap)
                .map(b -> {
                    try {
                        // do some work which throws IOException
                        throw new IOException("something went wrong");
                    } catch (IOException e) {
                        throw new RXIOException(e);
                        // Or you can use 
                        throw Exceptions.propagate(e);
                        // This helper method will wrap your exception with runtime one
                    }
                }).subscribe(o -> {
                    // do something here
                }, exception -> exception.printStackTrace());

public static class RXIOException extends RuntimeException {
        public RXIOException(IOException throwable) {
            super(throwable);
        }
}

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