如何在Android中的列表视图中添加imageview

Question

我想从列表视图中的json url显示图像。
这是我的代码：

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <ListView
        android:id="@+id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/getdata" />

    <Button
        android:id="@+id/getdata"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="23dp"
        android:text="Get Data" />

</RelativeLayout><br>

list_v.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/feed"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/tags"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <ImageView
        android:id="@+id/img"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout><br>

MainActivity.java

package learn2crack.listview;

import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

import learn2crack.listview.library.JSONParser;

public class MainActivity extends Activity {
    ListView list;
    TextView feed_id;
    TextView tags;
    ImageView thumbnail;
    Button Btngetdata;
    ArrayList<HashMap<String, String>> snowlist = new ArrayList<HashMap<String, String>>();
    // URL to get JSON Array
    private static String url = "http://instaapi.social-fair.com.208-91-199-15.md-plesk-web1.webhostbox.net/api.php?type=tag&tag=snow";

    // JSON Node Names
    private static final String TAG_main = "main";
    private static final String TAG_feed = "feed_id";
    private static final String TAG_tags = "tags";
    private static final String TAG_thumb = "thumbnail";

    JSONArray android = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);
        snowlist = new ArrayList<HashMap<String, String>>();

        Btngetdata = (Button) findViewById(R.id.getdata);
        Btngetdata.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                new JSONParse().execute();
            }
        });
    }

    private class JSONParse extends AsyncTask<String, String, JSONObject> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            feed_id = (TextView) findViewById(R.id.feed);
            tags = (TextView) findViewById(R.id.tags);
            thumbnail = (ImageView) findViewById(R.id.img);
        }

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

            JSONParser jParser = new JSONParser();

            // Getting JSON from URL
            JSONObject json = jParser.getJSONFromUrl(url);
            return json;
        }

        @Override
        protected void onPostExecute(JSONObject json) {

            try {
                // Getting JSON Array from URL
                android = json.getJSONArray(TAG_main);
                for (int i = 0; i < android.length(); i++) {
                    JSONObject c = android.getJSONObject(i);

                    // Storing JSON item in a Variable
                    String feed = c.getString(TAG_feed);
                    String tags = c.getString(TAG_tags);
                    String thumb = c.getString(TAG_thumb);

                    // Adding value HashMap key => value
                    HashMap<String, String> map = new HashMap<String, String>();

                    map.put(TAG_feed, feed);
                    map.put(TAG_tags, tags);
                    map.put(TAG_thumb, thumb);

                    snowlist.add(map);
                    list = (ListView) findViewById(R.id.list);

                    ListAdapter adapter = new SimpleAdapter(MainActivity.this,
                            snowlist, R.layout.list_v, new String[] { TAG_feed,
                                    TAG_tags, TAG_thumb }, new int[] {
                                    R.id.feed, R.id.tags, R.id.img });
                    list.setAdapter(adapter);
                    list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

                        @Override
                        public void onItemClick(AdapterView<?> parent,
                                View view, int position, long id) {
                            Toast.makeText(
                                    MainActivity.this,
                                    "You Clicked at "
                                            + snowlist.get(+position).get(
                                                    "tags"), Toast.LENGTH_SHORT)
                                    .show();

                        }
                    });

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

        }
    }

}

JSonParser.java

package learn2crack.listview.library;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();           

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

它显示来自json url的文本，但不显示图像
请帮我如何在列表视图中显示图像？
谢谢...

Answer 1

正在使用包含URL的字符串设置ImageView。 您必须从Internet获得该图像，可以使用Google提供的此类类ImageDownloadTask

您可以在设置图像时在适配器上调用它，如下所示：

new ImageDownloaderTask(imgLocal,position,this).execute(objectPlace.objectInfo.image);