Android Volley：结合JsonObjectRequest和ImageLoader，NullPointerException

Question

I encounter a situation that first the image's url should be get from weibo's API, and then, I wanna show the image based on the URL:

The Volley Lib is used here, and Here is my code:

JsonObjectRequest jsObjRequest = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    Log.i("Result", response.toString());
                    try {
                        String weiboNickName = response.getString("name");
                        weiboNameMain.setText(weiboNickName);

                        weiboUrl = response.getString("avatar_hd");

                        weiboUrl = weiboUrl.replace("\\", "");

                        Toast.makeText(MainPage.this, "url: " + weiboUrl, Toast.LENGTH_SHORT).show();                                                       imageLoader = new ImageLoader(queue, new BitmapLruCache(BitmapLruCache.getDefaultLruCacheSize()));

                    } catch (JSONException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                }
            });
            queue.add(jsObjRequest);
            imageLoader.get(weiboUrl,ImageLoader.getImageListener(weiboAvatarMain,R.drawable.user, R.drawable.user));

However, I will get a NullPointerException when use a weiboUrl for the last sentense:

     imageLoader.get(weiboUrl,ImageLoader.getImageListener(weiboAvatarMain,R.drawable.user, R.drawable.user));

I know this is because that Volley will create another Thread, so I should not use the reference in the main thread before Thread in Request ended.

Is there some ideas that could use to overcome this problem?

Thanks in advance.

Best

---Updated

The Problem is that I put

imageLoader.get(weiboUrl,ImageLoader.getImageListener(weiboAvatarMain,R.drawable.user, R.drawable.user));

in a wrong position. If I put it within the jsObject's onResponse() method, the problem will be gone. Then the image cache could be used. ( ImageRequest does not own cache mechanism itself)

Answer 1

JsonObjectRequest jsObjRequest = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    Log.i("Result", response.toString());
                    try {
                        String weiboNickName = response.getString("name");
                        weiboNameMain.setText(weiboNickName);

                        weiboUrl = response.getString("avatar_hd");

                        weiboUrl = weiboUrl.replace("\\", "");


                        Response.Listener<Bitmap> listener = new Response.Listener<Bitmap>() {
                            @Override
                            public void onResponse(Bitmap bitmap) {
                                String weiboAvatar = ImageHandler.storeImage(bitmap, getRoot(), getWeiboAvatarName());

                                Log.i("store info", weiboAvatar);
                                Editor edit = preference.edit();
                                edit.putString("weiboAvatar", weiboAvatar);
                                edit.apply(); 

                                weiboAvatarMain.setImageBitmap(bitmap);
                            }
                        };

                        ImageRequest imgRequest = new ImageRequest(weiboUrl, listener, 0, 0, null, null);
                        queue.add(imgRequest);
                    } catch (JSONException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                }
            });
            queue.add(jsObjRequest);

I use the ImageRequest instead of ImageLoader to overcome this, it works. The scenario here is the image will not change overtime, so I then save it into the local file.

However, as ImageLoader support cache for image reading, I really need the solutions for cache reading.

Thanks.