Android在listview中显示来自url的图像 [英] Android display images from url in listview

问题描述

我想在我的应用程序中显示图像，我从mysql数据库中获取这些图像的URL。目前它只显示图像的网址为文本

I want to display images in my app, I get the urls of this images from a mysql databse. Currently it only displays the urls of the images as text

如何下​​载图像并在列表视图中显示？

How can I download the images and display them in the listview?

 /**
 * Retrieves recent post data from the server.
 */
public void updateJSONdata() {

    // Instantiate the arraylist to contain all the JSON data.
    // we are going to use a bunch of key-value pairs, referring
    // to the json element name, and the content, for example,
    // message it the tag, and "I'm awesome" as the content..

    mCommentList = new ArrayList<HashMap<String, String>>();

    // Bro, it's time to power up the J parser
    JSONParser jParser = new JSONParser();
    // Feed the beast our comments url, and it spits us
    //back a JSON object.  Boo-yeah Jerome.
    JSONObject json = jParser.getJSONFromUrl(READ_COMMENTS_URL);

    //when parsing JSON stuff, we should probably
    //try to catch any exceptions:
    try {

        //I know I said we would check if "Posts were Avail." (success==1)
        //before we tried to read the individual posts, but I lied...
        //mComments will tell us how many "posts" or comments are
        //available
        mComments = json.getJSONArray(TAG_POSTS);

        // looping through all posts according to the json object returned
        for (int i = 0; i < mComments.length(); i++) {
            JSONObject c = mComments.getJSONObject(i);

            //gets the content of each tag
            String title = c.getString(TAG_TITLE);
            String content = c.getString(TAG_MESSAGE);
            String username = c.getString(TAG_USERNAME);
            String url = c.getString(TAG_URL);




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

            map.put(TAG_TITLE, title);
            map.put(TAG_MESSAGE, content);
            map.put(TAG_USERNAME, username);
            map.put(TAG_URL, url);

            // adding HashList to ArrayList
            mCommentList.add(map);

            //annndddd, our JSON data is up to date same with our array list
        }

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



/**
 * Inserts the parsed data into the listview.
 */
private void updateList() {
    // For a ListActivity we need to set the List Adapter, and in order to do
    //that, we need to create a ListAdapter.  This SimpleAdapter,
    //will utilize our updated Hashmapped ArrayList,
    //use our single_post xml template for each item in our list,
    //and place the appropriate info from the list to the
    //correct GUI id.  Order is important here.
    ListAdapter adapter = new SimpleAdapter(this, mCommentList,
            R.layout.single_post, new String[] { TAG_TITLE, TAG_MESSAGE,
            TAG_USERNAME, TAG_URL }, new int[] { R.id.title, R.id.message,
            R.id.username, R.id.url });

    // I shouldn't have to comment on this one:
    setListAdapter(adapter);

    // Optional: when the user clicks a list item we
    //could do something.  However, we will choose
    //to do nothing...
    ListView lv = getListView();
    lv.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {

            // This method is triggered if an item is click within our
            // list. For our example we won't be using this, but
            // it is useful to know in real life applications.

        }
    });

编辑：JSONParser.java

 package com.test.mysqltest;

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

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
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(final String url) {

        // Making HTTP request
        try {
            // Construct the client and the HTTP request.
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            // Execute the POST request and store the response locally.
            HttpResponse httpResponse = httpClient.execute(httpPost);
            // Extract data from the response.
            HttpEntity httpEntity = httpResponse.getEntity();
            // Open an inputStream with the data content.
            is = httpEntity.getContent();

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

        try {
            // Create a BufferedReader to parse through the inputStream.
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            // Declare a string builder to help with the parsing.
            StringBuilder sb = new StringBuilder();
            // Declare a string to store the JSON object data in string form.
            String line = null;

            // Build the string until null.
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }

            // Close the input stream.
            is.close();
            // Convert the string builder data to an actual string.
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // Try to 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 the JSON Object.
        return jObj;

    }


    // function get json from url
    // by making HTTP POST or GET mehtod
    public JSONObject makeHttpRequest(String url, String method,
                                      List<NameValuePair> params) {

        // Making HTTP request
        try {

            // check for request method
            if(method == "POST"){
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));

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

            }else if(method == "GET"){
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);

                HttpResponse httpResponse = httpClient.execute(httpGet);
                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;

    }
}

推荐答案

看看这篇文章 http://www.androidhive.info/2014/07/android-custom-listview-with-image-and-text-using-volley/

这是使用Volley库获取和显示图像的示例。

The is an example of fetching and displaying of images using Volley library.

问题出在ListAdapter中。 SimpleAdapter只是将字段显示为字符串。

Well the problem is in your ListAdapter. SimpleAdapter just show fields as strings.

使用自定义视图实现自己的适配器。

Implement your own Adapter with custom view.

这篇关于Android在listview中显示来自url的图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！