使用 Arraylist 时 Gridview 上的空白屏幕

Question

尝试通过自定义适配器解析 json 时出现空白屏幕。

我几乎可以肯定这是由于名为 oslist 的数组列表存在问题

我正在从一个示例开始工作，您每次都传递一个索引/变量（但这是针对列表视图，我现在正在尝试网格视图），但是我为网格视图遵循的教程将整个数组传递到适配器。

我希望收到来自 json 文件的路径列表

这些路径是图片的链接

这些图像需要在我的应用程序中显示在网格视图中

我正在使用毕加索来处理图像（不是说它应该有所作为

主活动

package com.example.alex.jsonparsegridview;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.AdapterView;
import android.widget.GridView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.view.View;
import android.widget.AdapterView.OnItemClickListener;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.HashMap;

public class MainActivity extends Activity {

    GridView gridView;

    static final String[] MOBILE_OS = new String[]{
            "Android", "iOS", "Windows", "Blackberry"};

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        new JSONParse().execute();

    }


    private class JSONParse extends AsyncTask<String, String, JSONArray> {
        private ProgressDialog pDialog;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            pDialog = new ProgressDialog(MainActivity.this);
            pDialog.setMessage("Getting Data ...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();

        }

        @Override
        protected JSONArray doInBackground(String... args) {

            JSONParser jParser = new JSONParser();

            // Getting JSON from URL

            String url = "http://www.500kgiveaway.co.uk/getimagesmob.php";
            JSONArray json = jParser.getJSONFromUrl(url);
            return json;
        }

        @Override
        protected void onPostExecute(JSONArray json) {
            pDialog.dismiss();
            try {
                // Getting JSON Array from URL

                JSONArray android = json;
                String TAG_PATH = "path";
                ArrayList<HashMap<String, String>> oslist = new ArrayList<HashMap<String, String>>();

                for (int i = 0; i < android.length(); i++) {

                    JSONObject c = android.getJSONObject(i);

                    // Storing  JSON item in a Variable
                    String path = c.getString(TAG_PATH);

                    // Adding value HashMap key => value

                    HashMap<String, String> map = new HashMap<String, String>();

                    map.put(TAG_PATH, path);

                    oslist.add(map);


                }
                 //copied from onCreate
                    gridView = (GridView) findViewById(R.id.gridView1);

                    gridView.setAdapter(new ImageAdapter(MainActivity.this, oslist));

                    gridView.setOnItemClickListener(new OnItemClickListener() {
                        public void onItemClick(AdapterView<?> parent, View v,
                                                int position, long id) {
                            Toast.makeText(
                                    getApplicationContext(),
                                    ((TextView) v.findViewById(R.id.grid_item_label))
                                            .getText(), Toast.LENGTH_SHORT).show();

                        }
                    });

                 //End Copy



            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }
}

图像适配器

package com.example.alex.jsonparsegridview;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.squareup.picasso.Picasso;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class ImageAdapter extends BaseAdapter {
    private Context context;


    public ImageAdapter(Context context,  List<? extends Map<String, ?>> data) {
        this.context = context;

    }

    public View getView(int position, View convertView, ViewGroup parent) {

        LayoutInflater inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View gridView;

        if (convertView == null) {

            gridView = new View(context);

            // get layout from mobile.xml
            gridView = inflater.inflate(R.layout.mobile, null);

            // set value into textview
            TextView textView = (TextView) gridView
                    .findViewById(R.id.grid_item_label);
            textView.setText(((Map)getItem(position)).get("path").toString());

            // set image based on selected text
            ImageView imageView = (ImageView) gridView
                    .findViewById(R.id.grid_item_image);


            Picasso.with(context).load("http://www.500kgiveaway.co.uk/" + ((Map) getItem(position)).get("path").toString()).into(imageView);

        } else {
            gridView = (View) convertView;
        }

        return gridView;
    }

    @Override
    public int getCount() {
        return 0;
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

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

}

Answer 1

getCount 应该返回数据集的大小，而不是 0。否则不会调用 getView。 getItem 应该返回数据集位置的项目，而不是 null。