Sending hashmao from java to react native

问题

I have a hashmap that contains Map<String, List<Custom_object> = new ConcurrentHashMap<>();

The data gets filed in this map, and I need to send the updated map data to react native JS bridge. How can I achieve the same?

Thanks in advance, Siva

回答1:

I usually convert my Custom Object to json String then I parse it to writableMap and return it like below.

@ReactMethod
    public void yourBridgeMethod(final ReadableMap argument, final Promise promise) {

    
try {
                    Object x = getMapCustom;
                    final Gson gson = new Gson();
                    final String response = gson.toJson(x);
                    WritableMap returnMap = this.util.convertJsonToMap(new JSONObject(response));
                    promise.resolve(returnMap);
                } catch (JSONException e) {
                    promise.reject("401", e.getLocalizedMessage());
                }

}

You could create a util class with this methods to handle your conversions

    public WritableMap convertJsonToMap(JSONObject jsonObject) throws JSONException {
        WritableMap map = new WritableNativeMap();

        Iterator<String> iterator = jsonObject.keys();
        while (iterator.hasNext()) {
            String key = iterator.next();
            Object value = jsonObject.get(key);
            if (value instanceof JSONObject) {
                map.putMap(key, convertJsonToMap((JSONObject) value));
            } else if (value instanceof JSONArray) {
                map.putArray(key, convertJsonToArray((JSONArray) value));
                if (("option_values").equals(key)) {
                    map.putArray("options", convertJsonToArray((JSONArray) value));
                }
            } else if (value instanceof Boolean) {
                map.putBoolean(key, (Boolean) value);
            } else if (value instanceof Integer) {
                map.putInt(key, (Integer) value);
            } else if (value instanceof Double) {
                map.putDouble(key, (Double) value);
            } else if (value instanceof String) {
                map.putString(key, (String) value);
            } else {
                map.putString(key, value.toString());
            }
        }
        return map;
    }

    public WritableArray convertJsonToArray(JSONArray jsonArray) throws JSONException {
        WritableArray array = new WritableNativeArray();

        for (int i = 0; i < jsonArray.length(); i++) {
            Object value = jsonArray.get(i);
            if (value instanceof JSONObject) {
                array.pushMap(this.convertJsonToMap((JSONObject) value));
            } else if (value instanceof JSONArray) {
                array.pushArray(convertJsonToArray((JSONArray) value));
            } else if (value instanceof Boolean) {
                array.pushBoolean((Boolean) value);
            } else if (value instanceof Integer) {
                array.pushInt((Integer) value);
            } else if (value instanceof Double) {
                array.pushDouble((Double) value);
            } else if (value instanceof String) {
                array.pushString((String) value);
            } else {
                array.pushString(value.toString());
            }
        }
        return array;
    }

    public JSONObject convertMapToJson(ReadableMap readableMap) throws JSONException {
        JSONObject object = new JSONObject();
        ReadableMapKeySetIterator iterator = readableMap.keySetIterator();
        while (iterator.hasNextKey()) {
            String key = iterator.nextKey();
            switch (readableMap.getType(key)) {
                case Null:
                    object.put(key, JSONObject.NULL);
                    break;
                case Boolean:
                    object.put(key, readableMap.getBoolean(key));
                    break;
                case Number:
                    object.put(key, readableMap.getDouble(key));
                    break;
                case String:
                    object.put(key, readableMap.getString(key));
                    break;
                case Map:
                    object.put(key, convertMapToJson(readableMap.getMap(key)));
                    break;
                case Array:
                    object.put(key, convertArrayToJson(readableMap.getArray(key)));
                    break;
            }
        }
        return object;
    }

    public JSONArray convertArrayToJson(ReadableArray readableArray) throws JSONException {

        JSONArray array = new JSONArray();

        for (int i = 0; i < readableArray.size(); i++) {
            switch (readableArray.getType(i)) {
                case Null:
                    break;
                case Boolean:
                    array.put(readableArray.getBoolean(i));
                    break;
                case Number:
                    array.put(readableArray.getDouble(i));
                    break;
                case String:
                    array.put(readableArray.getString(i));
                    break;
                case Map:
                    array.put(convertMapToJson(readableArray.getMap(i)));
                    break;
                case Array:
                    array.put(convertArrayToJson(readableArray.getArray(i)));
                    break;
            }
        }
        return array;
    }

回答2:

I'm having a hard time understanding the need of parsing the json to a ReadableMap in JavaScript and then back to json in Java, vice versa. Instead I just pas the json as a string. Is this a bad practice?

JavaScript code:

static methodOne(paramOne: ParamOne) {
    let paramObjectAsJson = JSON.stringify(paramOne);
    return Bridge.methodOne(paramObjectAsJson) as Promise<string>;
}

Java code:

@ReactMethod
public void methodOne(final String paramObjectAsJson, final Promise promise) {
    try {
        ParamOneJavaClass request = fromVariantJson(paramObjectAsJson);
        ...
        promise.resolve(null);
    catch(Exception e) {
        promise.reject(e.getMessage());
    }
}

private ParamOneJavaClass fromVariantJson(String json) {
    return createDefaultGson().fromJson(json, ParamOneJavaClass.class);
}

private static Gson createDefaultGson() {
    GsonBuilder builder = new GsonBuilder();
    return builder.create();
}

来源：https://stackoverflow.com/questions/63900706/sending-hashmao-from-java-to-react-native