如何使用 RxAndroid 将流正确拆分为 4 个操作？答案

【问题标题】：How to split a stream correctly into 4 Actions using RxAndroid?如何使用 RxAndroid 将流正确拆分为 4 个操作？
【发布时间】：2018-08-10 05:58:46
【问题描述】：

我第一次尝试接触反应式编程。我正在使用适用于 Android 的 ReactiveLocation 库，并且我有 4 个文本视图需要在收到新位置时填充位置数据。

所以这是在每次位置更新时为我提供位置的代码：

    locationProvider = new ReactiveLocationProvider(getApplicationContext());
    lastKnownLocationObservable = locationProvider.getLastKnownLocation();

    final LocationRequest locationRequest = LocationRequest.create()
            .setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
            .setNumUpdates(150)
            .setInterval(100);
    locationUpdatesObservable = locationProvider
            .checkLocationSettings(
                    new LocationSettingsRequest.Builder()
                            .addLocationRequest(locationRequest)
                            .setAlwaysShow(true)  //Refrence: http://stackoverflow.com/questions/29824408/google-play-services-locationservices-api-new-option-never
                            .build()
            )
            .doOnNext(new Action1<LocationSettingsResult>() {
                @Override
                public void call(LocationSettingsResult locationSettingsResult) {
                    Status status = locationSettingsResult.getStatus();
                    if (status.getStatusCode() == LocationSettingsStatusCodes.RESOLUTION_REQUIRED) {
                        try {
                            status.startResolutionForResult(MainActivity.this, REQUEST_CHECK_SETTINGS);
                        } catch (IntentSender.SendIntentException th) {
                            Log.e("MainActivity", "Error opening settings activity.", th);
                        }
                    }
                }
            })
            .flatMap(new Func1<LocationSettingsResult, Observable<Location>>() {
                @Override
                public Observable<Location> call(LocationSettingsResult locationSettingsResult) {
                    return locationProvider.getUpdatedLocation(locationRequest);
                }
            });

我也有这个函数，它将位置拆分为一个由 4 个字符串组成的数组：

public class LocationToStringsArrayListFunc implements Func1<Location, ArrayList<String>> {
    @Override
    public ArrayList<String> call(Location location) {
        ArrayList<String> locationDetails = null;
        if (location != null) {
            locationDetails = new ArrayList<>();
            locationDetails.add(String.valueOf(location.getLatitude()));
            locationDetails.add(String.valueOf(location.getLongitude()));
            locationDetails.add(String.valueOf(location.getTime()));
            locationDetails.add(String.valueOf(location.getSpeed()));
        }
        return locationDetails;
    }
}

最后我有这个动作来用文本填充 TextView：

public class DisplayTextOnViewAction implements Action1<String> {
   private final TextView target;

    public DisplayTextOnViewAction(TextView target) {
        this.target = target;
    }

    @Override
    public void call(String s) {
        target.setText(s);
    }
}

我现在想要的是每次将此流拆分为 4 个视图，我知道对于其中一个，我将执行以下操作：

 mUpdatableLocationSubscription = locationUpdatesObservable 
            .map(new LocationToStringsArrayListFunc())
            .map(new Func1<ArrayList<String>, String>() {

                @Override
                public String call(ArrayList<String> stringArrayList) {
                    return stringArrayList.get(0);
                }
            })
            .subscribe(new DisplayTextOnViewAction(tvLatitudeValue), new ErrorHandler());

如何使用同一流填充其他 3 个 TextView：LongitudeValue、tvLastUpdateValue、tvSpeedValue？

【问题讨论】：

标签： android rx-java rx-android android-reactivelocation

【解决方案1】：

.share() 运算符是您应该查看的。

有了这个“助手”类：

public class ListItemFunc extends Func1<ArrayList<String>, String>{

    private final int index;

    public ListItemFunc(int index) {
        this.index = index;
    }

    @Override
    public String call(ArrayList<String> strings) {
        return strings.get(index);
    }
}

您的代码可能如下所示：

Observable<ArrayList<String>> sharedObservable =
        locationUpdatesObservable.map(new LocationToStringsArrayListFunc()).share();

latitudeSubscription = sharedObservable
        .map(new ListItemFunc(0))
        .subscribe(new DisplayTextOnViewAction(tvLatitudeValue), new ErrorHandler());

longitudeSubscription = sharedObservable
        .map(new ListItemFunc(1))
        .subscribe(new DisplayTextOnViewAction(tvLongitudeValue), new ErrorHandler());

lastUpdateSubscription = sharedObservable
        .map(new ListItemFunc(2))
        .subscribe(new DisplayTextOnViewAction(tvLastUpdateValue), new ErrorHandler());

speedSubscription = sharedObservable
        .map(new ListItemFunc(3))
        .subscribe(new DisplayTextOnViewAction(tvSpeedValue), new ErrorHandler());

【讨论】：