CODEWITHSUNDEEP
rx-java
Luca Looz
Luca Looz

Reputation: 281

Single operation with multiple callbacks in RxJava

How a single operation with multiple callbacks (e.g. START with some params, PROGRESS called multiple times with other params and END with other params) should be exposed in RxJava?

I'm thinking to use a wrapper object that contains an observable for each kind of callback and that a subscription on any of those observable triggers the start of the operation with the other binded on the same underlying operation

EDIT: An example callback interface for a download operation 

interface Callback {
    void onDownloadStarted(long contentLength, String mimeType, String nameHint);
    void onDownloadProgress(long downloadedBytes);
    void onDownloadCompleted(File file);
}

Upvotes: 1

Views: 523

Answers (1)

Dave Moten
Dave Moten

Reputation: 12097

You could think of your operation as an Observable<Status> where

public static class Info {
    public final long contentLength;
    public final String mimeType;
    public final String nameHint;
    public Info(long contentLength, String mimeType, String nameHint) {
        this.contentLength = contentLength;
        this.mimeType = mimeType;
        this.nameHint = nameHint;
    }
}
public static class Status {
    public final Info info;
    public final long downloadProgress; //in bytes
    public final Optional<File> file;
    public Status(Info info, long downloadProgress, Optional<File> file) {
        this.info = info;
        this.downloadProgress = downloadProgress;
        this.file = file;
    }
}

Then you could model your download operation as:

Observable<Status> download();

You get no emissions till the download has started and the final emission has the File result.

You could use it like this:

download()
   .doOnNext(status -> System.out.println(
        "downloaded " 
        + status.downloadProgress 
        + " bytes of " + status.contentLength))
   .last()
   .doOnNext(status -> System.out.println(
        "downloaded " + status.file.get())
   .doOnError(e -> logError(e))
   .subscribe();

Upvotes: 1

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