无法在所需的布局中获取json输出？

Question

I am trying to fetch country flags into my GridView , but it's not showing anything and I am not getting any error in logcat either. when I try debugging its showing response but not showing that in GridView .

here is my code:

    private GridView gridView;

    //ArrayList for Storing image urls and titles
    private ArrayList<String> images;
    private ArrayList<String> count;
    private ArrayList<String> Id;
    private ArrayList<String> country;
    ArrayList<CountryDetails> al = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pmfanciers);


        getSupportActionBar().hide();


        mtoolbar = (ImageButton) findViewById(R.id.toolbar_new);
        mtoolbar.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Intent intent = new Intent(PMFanciersActivity.this, PMDashboardActivity.class);
                intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);
                finish(); //
                return false;
            }
        });
        gridView = (GridView) findViewById(R.id.gridView);

        images = new ArrayList<>();
        count = new ArrayList<>();
        Id = new ArrayList<>();
        country = new ArrayList<>();


        getData();


    }

    private void getData() {
        //Showing a progress dialog while our app fetches the data from url
        final ProgressDialog loading = ProgressDialog.show(this, "Please wait...", "Fetching data...", false, false);

        StringRequest stringRequest = new StringRequest(Request.Method.POST, DATA_URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        //Toast.makeText(PMPigeonListingActivity.this,response,Toast.LENGTH_LONG).show();
                        loading.dismiss();
                        try {


                            JSONObject jObj = new JSONObject(response);
                          JSONArray arr = jObj.getJSONArray("country_details");

                            /*JSONArray json = new JSONArray(response);*/

                            for (int i = 0; i < arr.length(); i++) {
                                //Creating a json object of the current index
                                JSONObject obj = null;
                                CountryDetails cd=new CountryDetails();
                                try {
                                    //getting json object from current index
                                    obj = arr.getJSONObject(i);
                                    Id.add(String.valueOf(obj.getInt("country_code")));
                                    count.add(obj.getString(TAG_COUNT));
                                    images.add(obj.getString("country_flag"));
                                    country.add(obj.getString("country_name"));
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                }
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }

                        //Creating GridViewAdapter Object
                      final   PMFanciersAdapter pmFanciersAdapter = new PMFanciersAdapter(getApplicationContext(), images, count, Id, country);

                        //Adding adapter to gridview


                        runOnUiThread(new Runnable(){
                            @Override
                            public void run(){
                                // change UI elements here
                                gridView.setAdapter(pmFanciersAdapter);
                                pmFanciersAdapter.notifyDataSetChanged();
                            }
                        });


                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        //Toast.makeText(PMPigeonListingActivity.this, error.toString(), Toast.LENGTH_LONG).show();
                    }
                }) {

        };

        RequestQueue requestQueue = Volley.newRequestQueue(this);
        requestQueue.add(stringRequest);


    }

}

json output:

{
  "status_code": 200,
  "status": "OK",
  "status_message": "Success",
  "country_details": [
    {
      "country_code": "AF",
      "country_name": "America",
      "country_iso": "AFG",
      "country_flag": "http://........./128x128/af.png",
      "calling_code": "93",
      "fancier_count": 3
    },
    {
      "country_code": "AL",
      "country_name": "Africa",
      "country_iso": "ALB",
      "country_flag": "http://.......128x128/al.png",
      "calling_code": "355",
      "fancier_count": 0
    },

here is my gridview adapter..

public class PMFanciersAdapter extends BaseAdapter {

    //Imageloader to load images
    private ImageLoader imageLoader;

    //Context
    private Context context;

    //Array List that would contain the urls and the titles for the images
    private ArrayList<String> images;
    private ArrayList<String> count;
    private ArrayList<String> Id;
    private ArrayList<String> country;

    public PMFanciersAdapter(Context context, ArrayList CountryDetails){
        //Getting all the values
        this.context = context;

        this.images = images;
        this.count = count;
        this.Id = Id;
        this.country = country;
    }

    static class ViewHolder {
        ImageView imageView;
        TextView textView;
        LinearLayout grid_id;
    }

    @Override
    public int getCount() {
        return images.size();
    }

    @Override
    public Object getItem(int position) {
        return images.get(position);
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        //Creating a linear layout
        View view = convertView;
        final ViewHolder gridViewImageHolder;
//             check to see if we have a view
        if (view == null) {
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            view = inflater.inflate(R.layout.fanciers_grid_item, parent, false);
            gridViewImageHolder = new ViewHolder();
            gridViewImageHolder.imageView = (ImageView) view.findViewById(R.id.imageView1);
            gridViewImageHolder.textView = (TextView) view.findViewById(R.id.text1);
            gridViewImageHolder.grid_id = (LinearLayout) view.findViewById(R.id.grid_id);

            view.setTag(gridViewImageHolder);
        } else {
            gridViewImageHolder = (ViewHolder) view.getTag();
        }


        NetworkImageView networkImageView = new NetworkImageView(context);

        imageLoader = PMCustomVolleyRequest.getInstance(context).getImageLoader();
        imageLoader.get(images.get(position), ImageLoader.getImageListener(networkImageView, R.drawable.loader, android.R.drawable.ic_dialog_alert));

        networkImageView = (NetworkImageView) gridViewImageHolder.imageView;
        networkImageView.setDefaultImageResId(R.color.white);
        networkImageView.setAdjustViewBounds(true);
        networkImageView.setImageUrl(images.get(position), imageLoader);


        gridViewImageHolder.textView.setText(count.get(position));
        gridViewImageHolder.grid_id.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(context, PMMemberListingActivity.class);
                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                intent.putExtra("CountryID", Id.get(position));
                intent.putExtra("countryName",country.get(position));
                context.startActivity(intent);
            }
        });

        return view;
    }
}

CountryDetails class:

public class CountryDetails {

    @SerializedName("country_code")
    @Expose
    private String countryCode;
    @SerializedName("country_name")
    @Expose
    private String countryName;
    @SerializedName("country_iso")
    @Expose
    private String countryIso;
    @SerializedName("country_flag")
    @Expose
    private String countryFlag;
    @SerializedName("calling_code")
    @Expose
    private String callingCode;
    @SerializedName("fancier_count")
    @Expose
    private Integer fancierCount;

    public String getCountryCode() {
        return countryCode;
    }

    public void setCountryCode(String countryCode) {
        this.countryCode = countryCode;
    }

    public String getCountryName() {
        return countryName;
    }

    public void setCountryName(String countryName) {
        this.countryName = countryName;
    }

    public String getCountryIso() {
        return countryIso;
    }

    public void setCountryIso(String countryIso) {
        this.countryIso = countryIso;
    }

    public String getCountryFlag() {
        return countryFlag;
    }

    public void setCountryFlag(String countryFlag) {
        this.countryFlag = countryFlag;
    }

    public String getCallingCode() {
        return callingCode;
    }

    public void setCallingCode(String callingCode) {
        this.callingCode = callingCode;
    }

    public Integer getFancierCount() {
        return fancierCount;
    }

    public void setFancierCount(Integer fancierCount) {
        this.fancierCount = fancierCount;
    }

}

Answer 1

You cannot change UI elements from a non-UI thread. Try using runOnUiThread.

 runOnUiThread(new Runnable(){
        @Override
        public void run(){
            // change UI elements here
                         gridView.setAdapter(pmFanciersAdapter);
                        pmFanciersAdapter.notifyDataSetChanged();
        }
    });

you adapter code

private void getData() {
        //Showing a progress dialog while our app fetches the data from url
        final ProgressDialog loading = ProgressDialog.show(this, "Please wait...", "Fetching data...", false, false);

        StringRequest stringRequest = new StringRequest(Request.Method.POST, DATA_URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        //Toast.makeText(PMPigeonListingActivity.this,response,Toast.LENGTH_LONG).show();
                        loading.dismiss();
                        try {


                            JSONObject jObj = new JSONObject(response);
                            JSONArray arr = jObj.getJSONArray("country_details");

                            /*JSONArray json = new JSONArray(response);*/
                            for (int i = 0; i < arr.length(); i++) {
                                //Creating a json object of the current index
                                JSONObject obj = null;
                                try {
                                    //getting json object from current index
                                    obj = arr.getJSONObject(i);
                                    Id.add(String.valueOf(obj.getInt("country_code")));
                                    count.add(obj.getString(TAG_COUNT));
                                    images.add(obj.getString("country_flag"));
                                    country.add(obj.getString("country_name"));
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                }
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }

                        //Creating GridViewAdapter Object
                        PMFanciersAdapter pmFanciersAdapter = new PMFanciersAdapter(getApplicationContext(), images, count, Id, country);

                        //Adding adapter to gridview


                      runOnUiThread(new Runnable(){
                    @Override
                          public void run(){
                             // change UI elements here
                               gridView.setAdapter(pmFanciersAdapter);
                                pmFanciersAdapter.notifyDataSetChanged();
                           }
                        });


                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        //Toast.makeText(PMPigeonListingActivity.this, error.toString(), Toast.LENGTH_LONG).show();
                    }
                }) {

        };

        RequestQueue requestQueue = Volley.newRequestQueue(this);
        requestQueue.add(stringRequest);


    }

}

Answer 2

To achieve this you should not send Id, country, flags separately. If you do so, You can't map which id is for which country and for which flag. So you should make one Pojo class (say CountryDetails ). Add code, name, flag, id as fields.

Then Create ArrayList of type Pojo in Activity:
ArrayList<CountryDetails> al = new ArrayList<>();

Then in your for loop create object of CountryDetails and add all values to it. Later add al to your Adapter. Change constructor of PMFanciersAdapter having only Context and ArrayList<CountryDetails> as parameters.

First correct this because even if you are able to display with your code, in some cases images and country names will mismatch. I hope you can do further work after fixing this.