如何在java方法中返回字符串？

Question

I have a problem where i am unable to return a string from this method. I was unsuccessful when I tried creating a new variable outside the Response.Listener. This is probably very simple but how do I go about returning a string from this method. The string I want to return is the 'featured_img_url' string.

public String secondServiceCall(String featuredmedia){

    JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
            "http://www.gadgetsinnepal.com/wp-json/wp/v2/media/"+featuredmedia, null, new Response.Listener<JSONObject>() {

        @Override
        public void onResponse(JSONObject nested_response) {

            try {
                JSONObject guilld = nested_response.getJSONObject("guid");
                String featured_img_url = guilld.getString("rendered");
                Toast.makeText(getApplicationContext(),"IMAGE :" + featured_img_url,Toast.LENGTH_LONG).show();

            } catch (JSONException e) {
                e.printStackTrace();
                Toast.makeText(getApplicationContext(),
                        "Error: " + e.getMessage(),
                        Toast.LENGTH_LONG).show();
            }
        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            Toast.makeText(getApplicationContext(),
                    "ERROR "+error.getMessage(), Toast.LENGTH_LONG).show();

        }
    });
    MySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsonObjReq);

    return featured_img_url;
}

Answer 1

update your code to:

String featured_img_url = null;    
public String secondServiceCall(String featuredmedia){
JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
        "http://www.gadgetsinnepal.com/wp-json/wp/v2/media/"+featuredmedia, null, new Response.Listener<JSONObject>() {

    @Override
    public void onResponse(JSONObject nested_response) {

        try {
            JSONObject guilld = nested_response.getJSONObject("guid");
            featured_img_url = guilld.getString("rendered");
            Toast.makeText(getApplicationContext(),"IMAGE :" + featured_img_url,Toast.LENGTH_LONG).show();

        } catch (JSONException e) {
            e.printStackTrace();
            Toast.makeText(getApplicationContext(),
                    "Error: " + e.getMessage(),
                    Toast.LENGTH_LONG).show();
        }
    }
}, new Response.ErrorListener() {

    @Override
    public void onErrorResponse(VolleyError error) {
        Toast.makeText(getApplicationContext(),
                "ERROR "+error.getMessage(), Toast.LENGTH_LONG).show();

    }
});
MySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsonObjReq);

return featured_img_url;
}

Answer 2

Here, you should simply pass the instance that call this methods to execute the methods from the response.

So change the methods to :

public void secondServiceCall(String featuredmedia, final MyClass caller){

Note that this will return nothing. And the caller instance need to be final to be used in the inner class JsonObjectRequest .

and in the response, you need to pass the value to the instance of MyClass . So add a method in MyClass

public void setFeatureImgUrl(String featuredImgUrl){ ... }

and you just need to call this in the response.

public void onResponse(JSONObject nested_response) {
    ...
    caller.setFeatureImgUrl(feature_img_url);
    ...
}

Note : This could be done with an Observer pattern but I know that some people doesn't like it. I could add an example of it if needed.