Question

我在Android应用中使用RxJava和Retrofit从服务器获取数据。我有这段代码的测试活动。

    String text;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        viewMenu = (LinearLayout) findViewById(R.id.view_menu);
        tabMenu.initTabBar(viewMenu, this);
        CapabilitiesHolder.createIfNotExist().getCapabilities().subscribe(this::handleResponse, RestErrorHandler::handle);
        Toast.makeText(this, text, Toast.LENGTH_SHORT).show();
    }



    private void handleResponse(CapabilitiesResponse capabilitiesResponse) {
        if (capabilitiesResponse.isSuccess()) {
            text = capabilitiesResponse.getSupportedCurrencies().get(0).getDescription();
        } else {
            RestErrorHandler.handle(null, capabilitiesResponse);
        }
    }

还有一个Singleton类，用于在应用程序的整个生命周期内包含来自服务器的数据。

public class CapabilitiesHolder {


    private static CapabilitiesHolder mInstance = null;

    private CapabilitiesResponse capabilities;


    public static CapabilitiesHolder createIfNotExist() {
        if (mInstance == null) {
            mInstance = new CapabilitiesHolder();
        }
        return mInstance;
    }

    private CapabilitiesHolder() {
        requestCapabilities();
    }

    public Observable<CapabilitiesResponse> getCapabilities() {
        return Observable.fromCallable(() -> capabilities);
    }

    private CompositeSubscription compositeSubscription = new CompositeSubscription();

    private void requestCapabilities() {
        Observable<CapabilitiesResponse> o = RestServiceFactory.get().getServerCapabilities();
        compositeSubscription.add(o.subscribe(this::handleResponse, RestErrorHandler::handle));
    }

    private void handleResponse(CapabilitiesResponse capabilitiesResponse) {
        if (capabilitiesResponse.isSuccess()) {
            capabilities = capabilitiesResponse;
        } else {
            RestErrorHandler.handle(null, capabilitiesResponse);
        }
    }

    public void update() {
        mInstance = null;
        mInstance = new CapabilitiesHolder();
    }
}

因此，当我的测试Activity第一次创建，并立即调用CapabilitiesHolder.createIfNotExist().getCapabilities()时，tost为空，因为响应中的数据需要一些时间来加载。当onCreate稍后调用时，一切都还可以。

问题是，我可以在调用之前使用（使用RxJava？）getCapabilities()方法等待来自服务器的响应。

提前致谢！

Answer 1

简短回答 - 不要阻止UI线程并等待任何事情。

将Toast移动到处理响应的方法

 private void handleResponse(CapabilitiesResponse capabilitiesResponse) {
    if (capabilitiesResponse.isSuccess()) {
        text = capabilitiesResponse.getSupportedCurrencies().get(0).getDescription();
        // Toast here 
    } else {
        RestErrorHandler.handle(null, capabilitiesResponse);
    }

Answer 2

我建议您重建课程CapabilitiesHolder。如果你想使用那样的持有者，你不应该在构造函数中请求任何数据。阻止UI线程的还有不良做法。

private CapabilitiesHolder() {
    //empty
}

public Observable<CapabilitiesResponse> getCapabilities() {
    if(capabilities!=null){
        return Observable.fromCallable(() -> capabilities);
    } else {
        return RestServiceFactory.get()
                .getServerCapabilities()
                .doOnNext(capabilitiesResponse -> capabilities = capabilitiesResponse);
    }
}

Rx Android - 等待服务器响应

2 个答案: