【zZ】RxJava使用心得（一）

使用RxJava结合Retrofit进行网络数据的请求

网络请求：

/**
* e.g.
* https://api.github.com/user/1 *
* @param id id号
* @return
*/
@GET ("/user/{id}")
Observable<UserEntity> getUser(@Path ("id") long id);

返回的数据可能的是成功查询到id=1的用户，或者返回没有查询到。

成功：

{"login":"50","id":12736272,"avatar_url":"https://avatars.githubusercontent.com/u/12736272?v=3","gravatar_id":"","url":"https://api.github.com/users/50","html_url":"https://github.com/50","followers_url":"https://api.github.com/users/50/followers","following_url":"https://api.github.com/users/50/following{/other_user}","gists_url":"https://api.github.com/users/50/gists{/gist_id}","starred_url":"https://api.github.com/users/50/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/50/subscriptions","organizations_url":"https://api.github.com/users/50/orgs","repos_url":"https://api.github.com/users/50/repos","events_url":"https://api.github.com/users/50/events{/privacy}","received_events_url":"https://api.github.com/users/50/received_events","type":"User","site_admin":false,"name":null,"company":null,"blog":null,"location":null,"email":null,"hireable":null,"bio":null,"public_repos":0,"public_gists":0,"followers":0,"following":0,"created_at":"2015-06-03T18:53:22Z","updated_at":"2015-06-03T19:17:43Z"}

失败：

{"message":"Not Found","documentation_url":"https://developer.github.com/v3"}

问题来了 ， 因为Retrofit可以自动填充POJO对象，但是对于没有返回正确数据的时候就会回调failure方法

像这样儿

ApiAction.getApiService().getUser(id, new Callback<UserEntity>() {
@Override
public void success(UserEntity userEntity, Response response) {
Uri uri = Uri.parse(userEntity.getAvatar_url());
mSDVImageView = (SimpleDraweeView) findViewById(R.id.sdv_image_view);
mSDVImageView.setImageURI(uri);
Timber.d("success  id ---->  " + id);
}

@Override
public void failure(RetrofitError error) {
id++;
Timber.d("failure  id ---->  " + id);
}
});

但是如果使用Rxjava出现这种情况呢？doOnError?

NO，因为这个是在Retrofit的层次出的错，所以doOnError方法将不会起效，我们需要使用其他的操作符

onErrorResumeNext( ) — instructs an Observable to emit a sequence of items if it encounters an error

onErrorReturn( ) — instructs an Observable to emit a particular item when it encounters an error

onExceptionResumeNext( ) — instructs an Observable to continue emitting items after it encounters an exception (but not another variety of throwable)

retry( ) — if a source Observable emits an error, resubscribe to it in the hopes that it will complete without error

retryWhen( ) — if a source Observable emits an error, pass that error to another Observable to determine whether to resubscribe to the source

我英文不好，做不到流畅的翻译就将就看吧。