使用Picasso Android Studio在GridView中显示图像

Question

我想在Android Studio中向GridView显示图像，但始终无法获取数据。你能告诉我为什么吗？

MainActivity.Java

 import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.util.ArrayList;
    import android.content.Intent;
    import android.os.AsyncTask;
    import android.os.Bundle;
    import android.support.v7.app.ActionBarActivity;
    import android.util.Log;
    import android.view.View;
    import android.widget.AdapterView;
    import android.widget.GridView;
    import android.widget.ProgressBar;
    import android.widget.Toast;

    import com.amobi.picassodemo.Model.GridItem;
    import com.amobi.picassodemo.adapter.GridViewAdapter;

    import org.apache.http.HttpResponse;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.impl.client.DefaultHttpClient;
    import org.json.JSONArray;
    import org.json.JSONException;
    import org.json.JSONObject;

public class MainActivity extends ActionBarActivity {
    private static final String TAG = MainActivity.class.getSimpleName();
    private GridView mGridView;
    private ProgressBar mProgressBar;
    private GridViewAdapter mGridAdapter;
    private ArrayList<GridItem> mGridData;
    private String URL="http://lomapod.azurewebsites.net/readBarang.php?id_penjual=1";
    private String FEED_URL = "http://lomapod.esy.es/assets/bronco_turkey.jpg";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mGridView = (GridView) findViewById(R.id.gridView);
        mProgressBar = (ProgressBar) findViewById(R.id.progressBar);

        //Initialize with empty data
        mGridData = new ArrayList<>();
        mGridAdapter = new GridViewAdapter(this, R.layout.grid_item_layout, mGridData);
        mGridView.setAdapter(mGridAdapter);

        //Start download
        new AsyncHttpTask().execute(URL);
        mProgressBar.setVisibility(View.VISIBLE);
    }

    public class AsyncHttpTask extends AsyncTask<String, Void, Integer> {

        @Override
        protected Integer doInBackground(String... params) {
            Integer result = 0;
            try {
                // Create Apache HttpClient
                HttpClient httpclient = new DefaultHttpClient();
                HttpResponse httpResponse = httpclient.execute(new HttpGet(params[0]));
                int statusCode = httpResponse.getStatusLine().getStatusCode();

                // 200 represents HTTP OK
                if (statusCode == 200) {
                    String response = streamToString(httpResponse.getEntity().getContent());
                    parseResult(response);
                    result = 1; // Successful
                } else {
                    result = 0; //"Failed
                }
            } catch (Exception e) {
                Log.d(TAG, e.getLocalizedMessage());
            }
            return result;
        }
        @Override
        protected void onPostExecute(Integer result) {
            // Download complete. Let us update UI
            if (result == 1) {
                mGridAdapter.setGridData(mGridData);
            } else {
                Toast.makeText(MainActivity.this, "Failed to fetch data!", Toast.LENGTH_SHORT).show();
            }
            mProgressBar.setVisibility(View.GONE);
        }
    }
    String streamToString(InputStream stream) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));
        String line;
        String result = "";
        while ((line = bufferedReader.readLine()) != null) {
            result += line;
        }

        // Close stream
        if (null != stream) {
            stream.close();
        }
        return result;
    }

    private void parseResult(String result) {
        try {
            JSONObject response = new JSONObject(result);
            JSONArray posts = response.optJSONArray("posts");
            GridItem item;
            for (int i = 0; i < posts.length(); i++) {
                JSONObject post = posts.optJSONObject(i);
                String title = post.optString("title");
                item = new GridItem();
                item.setBarang(title);
                JSONArray attachments = post.getJSONArray("attachments");
                if (null != attachments && attachments.length() > 0) {
                    JSONObject attachment = attachments.getJSONObject(0);
                    if (attachment != null)
                        item.setImage(attachment.getString(FEED_URL));
                }
                mGridData.add(item);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

GridItem.Java

public class GridItem {
    private String image;
    private String barang;

    public GridItem() {
        super();
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }
    public String getBarang() {

        return barang;
    }

    public void setBarang(String barang) {

        this.barang = barang;
    }
}

GridViewAdapter.Java

package com.amobi.picassodemo.adapter;

import android.app.Activity;
import android.content.Context;
import android.text.Html;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.amobi.picassodemo.Model.GridItem;
import com.amobi.picassodemo.R;
import com.squareup.picasso.Picasso;

import java.util.ArrayList;

/**
 * Created by Nicky-PC on 4/9/2016.
 */
public class GridViewAdapter extends ArrayAdapter<GridItem> {

    private Context mContext;
    private int layoutResourceId;
    private ArrayList<GridItem> mGridData = new ArrayList<GridItem>();

    public GridViewAdapter(Context mContext, int layoutResourceId, ArrayList<GridItem> mGridData) {
        super(mContext, layoutResourceId, mGridData);
        this.layoutResourceId = layoutResourceId;
        this.mContext = mContext;
        this.mGridData = mGridData;
    }


    /**
     * Updates grid data and refresh grid items.
     * @param mGridData
     */
    public void setGridData(ArrayList<GridItem> mGridData) {
        this.mGridData = mGridData;
        notifyDataSetChanged();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        ViewHolder holder;

        if (row == null) {
            LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
            row = inflater.inflate(layoutResourceId, parent, false);
            holder = new ViewHolder();
            holder.titleTextView = (TextView) row.findViewById(R.id.grid_item_title);
            holder.imageView = (ImageView) row.findViewById(R.id.grid_item_image);
            row.setTag(holder);
        } else {
            holder = (ViewHolder) row.getTag();
        }

        GridItem item = mGridData.get(position);
        holder.titleTextView.setText(Html.fromHtml(item.getBarang()));

        Picasso.with(mContext).load(item.getImage()).into(holder.imageView);
        return row;
    }

    static class ViewHolder {
        TextView titleTextView;
        ImageView imageView;
    }
}