通过 SimpleAdapter 在 imageview 中显示图像

Posted 2023-05-07

【中文标题】通过 SimpleAdapter 在 imageview 中显示图像

【英文标题】：Display image in imageview by SimpleAdapter

【发布时间】：2014-07-18 16:54:51

【问题描述】：

我是新的 android 现在我想显示来自 url 的图像。我在列表视图中使用图像视图。我想将图像列表添加到列表项的每一行中。我使用了 SimpleAdapter，但 imageview 显示为空白。

这是主要活动：

package com.example.mysqltest;

    import java.util.ArrayList;
    import java.util.HashMap;
    import org.json.JSONArray;
    import org.json.JSONException;
    import org.json.JSONObject;
    import android.app.ListActivity;
    import android.app.ProgressDialog;
    import android.content.Intent;
    import android.os.AsyncTask;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.AdapterView;
    import android.widget.AdapterView.OnItemClickListener;
    import android.widget.ListAdapter;
    import android.widget.ListView;
    import android.widget.SimpleAdapter;

    public class ReadComments extends ListActivity 

        // Progress Dialog
        private ProgressDialog pDialog;

        // testing on Emulator:
        private static final String READ_COMMENTS_URL = "http://192.168.30.198/test/webservice/comments.php";


        // JSON IDS:
        private static final String TAG_SUCCESS = "success";
        private static final String TAG_TITLE = "title";
        private static final String TAG_POSTS = "posts";
        private static final String TAG_POST_ID = "post_id";
        private static final String TAG_USERNAME = "username";
        private static final String TAG_MESSAGE = "message";
        private static final String TAG_IMAGE = "image";


        // An array of all of our comments
        private JSONArray mComments = null;
        // manages all of our comments in a list.
        private ArrayList<HashMap<String, String>> mCommentList;

        @Override
        protected void onCreate(Bundle savedInstanceState) 
            super.onCreate(savedInstanceState);
            // note that use read_comments.xml instead of our single_post.xml
            setContentView(R.layout.read_comments);
        

        @Override
        protected void onResume() 
            // TODO Auto-generated method stub
            super.onResume();
            // loading the comments via AsyncTask
            new LoadComments().execute();
        

        public void addComment(View v) 
            Intent i = new Intent(ReadComments.this, AddComment.class);
            startActivity(i);
        

        /**
         * Retrieves recent post data from the server.
         */
        public void updateJSONdata() 
            mCommentList = new ArrayList<HashMap<String, String>>();

            JSONParser jParser = new JSONParser();      
            JSONObject json = jParser.getJSONFromUrl(READ_COMMENTS_URL);

            try 
                mComments = json.getJSONArray(TAG_POSTS);

                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 image = c.getString(TAG_IMAGE);

                    // 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_IMAGE, image);

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

             catch (JSONException e) 
                e.printStackTrace();
            
        

        /**
         * Inserts the parsed data into the listview.
         */
        private void updateList()  
            ListAdapter adapter = new SimpleAdapter(this, mCommentList,
                    R.layout.single_post, new String[]  TAG_TITLE, TAG_MESSAGE,
                            TAG_USERNAME,TAG_IMAGE , new int[]  R.id.title, R.id.message,
                            R.id.username, R.id.imageView1 );

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

            ListView lv = getListView();    
            lv.setOnItemClickListener(new OnItemClickListener() 

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

        public class LoadComments extends AsyncTask<Void, Void, Boolean> 

            @Override
            protected void onPreExecute() 
                super.onPreExecute();
                pDialog = new ProgressDialog(ReadComments.this);
                pDialog.setMessage("Loading Comments...");
                pDialog.setIndeterminate(false);
                pDialog.setCancelable(true);
                pDialog.show();
            

            @Override
            protected Boolean doInBackground(Void... arg0) 
                updateJSONdata();
                return null;

            

            @Override
            protected void onPostExecute(Boolean result) 
                super.onPostExecute(result);
                pDialog.dismiss();
                updateList();
            
        
    

【问题讨论】：

您在map.put(TAG_IMAGE, image); 中保存了什么？

单独使用SimpleAdapter 是不可能的。您需要创建一个自定义适配器扩展 SimpleAdapter 或任何其他适配器（BaseAdapter、ArrayAdapter 等）来实现这一点..

你有创建自定义 SimpleAdapter 的例子吗？

【参考方案1】：

在您的 MainActivity

上的 setContentView(R.layout.read_comments); 之后添加此代码

 if (android.os.Build.VERSION.SDK_INT > 9) 
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);
    

IDE 会自动要求您导入 android.os.StrictMode 库。

并考虑使用基本适配器