从 volley onResponse 返回值

Question

I am trying to make a more object oriented program with Volley. Currently I have the problem of not being able to extract data from inside the onResponse method of volley.

 private void getMember(String memberid){
    Response.Listener<String> responseListener = new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            try {
                JSONObject jsonResponse = new JSONObject(response);
                boolean success = jsonResponse.getBoolean("success"); //key["success"]
                String userid = jsonResponse.getString("userid");
                if(success){
                    byte[] decoded_img = Base64.decode(jsonResponse.getString("userpic"), Base64.DEFAULT);
                    Bitmap member_pic = BitmapFactory.decodeByteArray(decoded_img, 0, decoded_img.length);
                    FamMember member = new FamMember(jsonResponse.getString("username")); // creating new object

////// where I need to capture the image/ any data that I get in the Json response///
                    AlertDialog.Builder builder = new AlertDialog.Builder(LandingActivity.this);
                    builder.setMessage(member.username)
                            .setNegativeButton("Retry",null)
                            .create()
                            .show(); //properly displays newly created object 'username'
                } else {
                    AlertDialog.Builder builder = new AlertDialog.Builder(LandingActivity.this);
                    builder.setMessage("Unable to Login")
                            .setNegativeButton("Retry",null)
                            .create()
                            .show();
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    };
    //HAPPENS AFTER RESPONSE HAS BEEN GIVEN FROM SERVER////////
    MemberRequest memberRequest = new MemberRequest(type,memberid,responseListener);
    RequestQueue queue  = Volley.newRequestQueue(LandingActivity.this);
    queue.add(memberRequest); //puts actual request into the queue for processing
}

I have to be able to get the response and use them as variables to pass into my activity. How do I go about doing this when I am given the error that I cannot have any returns on the methods above?

Answer 1

Create a new interface like this :

  public interface VolleyCallback {
            void onSuccess(String result);
            void onError(String result);
        }

Where you use callback interfaces :

 public void getString(final VolleyCallback callback) {
      StringRequest strReq = new StringRequest(Request.Method.GET, url,
           new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                    callback.onSuccess(response);
            }
           }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError volleyError) {
               callback.onError(volleyError + "");
            }
        });
        Volley.newRequestQueue(MyApplication.getAppContext()).add(strReq);
      }

Use interface on your activity class like:

 FunctionName(new VolleyCallback(){
         @Override
         public void onSuccess(String result){
             ... //do stuff here
         }
         @Override
         public void onError(String result) {
             ... //show error here         
         }
    });

Answer 2

Create Global variable outside of the Volley block

    public String response_var="";

    public void getMember()
    {
    @Override
    public void onResponse(String response) {
    {
 response_var=response;
    }

    }

Answer 3

Volley and other asynchronous HTTP libraries are well asynchronous . Your activity cannot directly get hold of the http response. You need to process the data with in the onResponse method and then communicate with the activity. One way is to send a local broadcast.

Answer 4

You can create a method that takes the response (or part of the response you want) as argument. For example:

private void processResponse(String encodedUserPic, String userName) {

    // Use the response as you need
    byte[] decodedImg = Base64.decode(encodedUserPic), Base64.DEFAULT);
    Bitmap memberPic = BitmapFactory.decodeByteArray(decodedImg, 0, decodedImg.length);
    FamMember member = new FamMember(userName); 
}

Then, you can pass the response to this method from inside the onResponse method:

private void getMember(String memberid){
    Response.Listener<String> responseListener = new Response.Listener<String>() {
    @Override
    public void onResponse(String response) {
        try {
            JSONObject jsonResponse = new JSONObject(response);
            boolean success = jsonResponse.getBoolean("success"); //key["success"]
            String userid = jsonResponse.getString("userid");

            if(success){
                String encodedUserPic = jsonResponse.getString("userpic");
                String userName = jsonResponse.getString("username");
                // Callback:
                processResponse(encodedUserPic, userName);
                ...
            }
            ...

Margin note: in Java, lower camelcase notation is the convention, instead of underscored.

Hope you find this useful!