Android:通过 SimpleAdapter 在 imageview 中显示图像

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【中文标题】Android:通过 SimpleAdapter 在 imageview 中显示图像【英文标题】:Android: Display image in imageview by SimpleAdapter 【发布时间】:2014-07-22 01:18:36 【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】:

SimpleAdapter.setViewImage 适用于系统资源,而不适用于网络资源。您需要下载网络图像并将位图显式设置为 ImageView。你可以试试这个answer。 感谢您的评论。你能帮我如何在我的代码中应用 setViewImage 吗? 你好@VuthySok 你在吗? 【参考方案1】:

好的。所以我在这里假设你坚持使用SimpleAdapter。没有问题,问题解决了,按照以下步骤操作:

首先让我们为我们的ListView 创建我们的自定义row.xml,它将只包含一个ImageView。(您可以稍后添加任何您喜欢的内容,但现在我假设你只想加载ImageView)

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

    <ImageView
        android:id="@+id/imageView1"
        android:layout_
        android:layout_
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="5dp"
        android:layout_marginTop="5dp"
        android:src="@drawable/ic_launcher" />


</RelativeLayout>

其次让我们创建我们的自定义 SimpleAdapter

package com.example.helpstack;

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

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

public class MySimpleAdapter extends SimpleAdapter 
    private Context mContext;
    public LayoutInflater inflater = null;

    public MySimpleAdapter(Context context,
            List<? extends Map<String, ?>> data, int resource, String[] from,
            int[] to) 
        super(context, data, resource, from, to);
        mContext = context;
        inflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    

    @Override
    public View getView(int position, View convertView, ViewGroup parent) 
        View vi = convertView;
        if (convertView == null)
            vi = inflater.inflate(R.layout.row, null);

        HashMap<String, Object> data = (HashMap<String, Object>) getItem(position);

        new DownloadTask((ImageView) vi.findViewById(R.id.imageView1))
                .execute((String) data.get("uri"));

        return vi;
    


第三个让我们创建我们的DownloadTask,这个类将下载图像:

package com.example.helpstack;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.widget.ImageView;

public class DownloadTask extends AsyncTask<String, Void, Boolean> 
    ImageView v;
    String url;
    Bitmap bm;

    public DownloadTask(ImageView v) 
        this.v = v;
    

    @Override
    protected Boolean doInBackground(String... params) 
        url = params[0];
        bm = loadBitmap(url);
        return true;
    

    @Override
    protected void onPostExecute(Boolean result) 
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        v.setImageBitmap(bm);
    

    public static Bitmap loadBitmap(String url) 
        try 
            URL newurl = new URL(url);
            Bitmap b = BitmapFactory.decodeStream(newurl.openConnection()
                    .getInputStream());
            return b;
         catch (MalformedURLException e) 
            // TODO Auto-generated catch block
            e.printStackTrace();
         catch (IOException e) 
            // TODO Auto-generated catch block
            e.printStackTrace();
        
        return null;
    

现在 DownloadTask 正在 SimpleAdapter 的 getView() 内部使用

第四,让我们从 MainActivity.java

运行我们惊人的小项目
package com.example.helpstack;

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

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

public class MainActivity extends Activity 
    ListView lv;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) findViewById(R.id.listView1);
        List<Map<String, Object>> data = new ArrayList<Map<String, Object>>();
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("uri",
                "http://upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Wiktionary_small.svg/350px-Wiktionary_small.svg.png");
        //here u can add as many uri as u want
        data.add(map);
        MySimpleAdapter adapter = new MySimpleAdapter(MainActivity.this, data,
                R.layout.row, new String[] , new int[] );
        lv.setAdapter(adapter);
    

【讨论】:

我确实遵循了您的代码,但运行时总是关闭应用程序 您是否在清单文件中添加了互联网权限?它不应该关闭。尝试添加权限,如果它不起作用,我会把我的样品寄给你。但我建议你告诉我们 logcat 中发生的错误是什么 是的,我确实添加了权限 。我不确定问题,但我打开应用程序总是显示消息“不幸的是,我的 SimpleAdapter 已停止”。 这是共享的项目:docs.google.com/…【参考方案2】:

您可以使用任何图像缓存库。例如,Picasa、通用图像加载器..

您可以缓存来自 URL 的图片,然后您可以在您的应用中使用这些图片。

您可以在以下链接中找到这些库

http://square.github.io/picasso/ 和 https://github.com/nostra13/Android-Universal-Image-Loader

【讨论】:

【参考方案3】:

您可以使用多线程下载和解码位图。请关注本网站并尝试了解android开发人员如何使用线程池执行器在线程中执行不同的图像。 http://developer.android.com/training/multiple-threads/create-threadpool.html

【讨论】:

【参考方案4】:

1) 要将图像 Uri 设置为 ImageView,您可以使用 ViewBinder 你必须实现抽象类并覆盖setViewValue

2) 您可以使用Picasso 在后台线程中加载图像并缓存它们。 setViewValue 方法如下所示:

boolean setViewValue (View view, Object data, String textRepresentation) 
  if(view.getId() == R.id.imageView1) 
    Picasso.with(view.getContext()).load(textRepresentation).into((ImageView) view);
    return true;
  
  return false;

如果您想处理绑定,请返回 true。您返回 false 作为默认行为。

3) 通过调用adapter.setViewBinder(ViewBinder);adapter 设置为使用ViewBinder

【讨论】:

【参考方案5】:

现在,我给你的建议是: 1.从url下载图片 2.将其保存为可绘制在存储中 3.将此drawable设置为imageview的图片src (我没有看到你从你的代码中完成这部分工作......)

【讨论】:

【参考方案6】:

本教程是使用 json 解析来解析图像并将其显示在列表视图中的最佳示例:http://www.androidbegin.com/tutorial/android-json-parse-images-and-texts-tutorial/

其他一些:

http://imagelistviewdynamic.blogspot.in/2012/12/image-parsed-from-json-using-async-into.html

http://www.java2s.com/Open-Source/Android_Free_Code/JSON/Download_Free_code_Android_JSON_Parse_Images_and_Texts_Tutorial.htm

【讨论】:

【参考方案7】:

我建议你使用Universal Image Loader,它使用异步图像下载、缓存和显示,你可以找到如何实现它的示例。完成后,您不必担心图像的数量或大小。

如果您下载该项目,您会发现这个示例可以完成您想要的所有工作:

/**
 * @author Sergey Tarasevich (nostra13[at]gmail[dot]com)
 */
public class ImageListActivity extends AbsListViewBaseActivity 

    DisplayImageOptions options;

    String[] imageUrls;

    @Override
    public void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ac_image_list);

            // here you get a String array with images URL
        Bundle bundle = getIntent().getExtras();
        imageUrls = bundle.getStringArray(Extra.IMAGES);

        options = new DisplayImageOptions.Builder()
            .showImageOnLoading(R.drawable.ic_stub)
            .showImageForEmptyUri(R.drawable.ic_empty)
            .showImageOnFail(R.drawable.ic_error)
            .cacheInMemory(true)
            .cacheOnDisc(true)
            .considerExifParams(true)
            .displayer(new RoundedBitmapDisplayer(20))
            .build();

        listView = (ListView) findViewById(android.R.id.list);
        ((ListView) listView).setAdapter(new ItemAdapter());
        listView.setOnItemClickListener(new OnItemClickListener() 
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) 
                startImagePagerActivity(position);
            
        );
    

    @Override
    public void onBackPressed() 
        AnimateFirstDisplayListener.displayedImages.clear();
        super.onBackPressed();
    
    // it gets the position of listView and opens that image in a new Activity
    private void startImagePagerActivity(int position) 
        Intent intent = new Intent(this, ImagePagerActivity.class);
        intent.putExtra(Extra.IMAGES, imageUrls);
        intent.putExtra(Extra.IMAGE_POSITION, position);
        startActivity(intent);
    

    class ItemAdapter extends BaseAdapter 

        private ImageLoadingListener animateFirstListener = new AnimateFirstDisplayListener();

        private class ViewHolder 
            public TextView text;
            public ImageView image;
        

        @Override
        public int getCount() 
            return imageUrls.length;
        

        @Override
        public Object getItem(int position) 
            return position;
        

        @Override
        public long getItemId(int position) 
            return position;
        

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) 
            View view = convertView;
            final ViewHolder holder;
            if (convertView == null) 
                view = getLayoutInflater().inflate(R.layout.item_list_image, parent, false);
                holder = new ViewHolder();
                holder.text = (TextView) view.findViewById(R.id.text);
                holder.image = (ImageView) view.findViewById(R.id.image);
                view.setTag(holder);
             else 
                holder = (ViewHolder) view.getTag();
            

            holder.text.setText("Item " + (position + 1));
                    // here is the place where is loaded the image using Universal ImageLoader , imageUrls[position] is a list of images URL
            imageLoader.displayImage(imageUrls[position], holder.image, options, animateFirstListener);

            return view;
        
    

    private static class AnimateFirstDisplayListener extends SimpleImageLoadingListener 

        static final List<String> displayedImages = Collections.synchronizedList(new LinkedList<String>());

        @Override
        public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) 
            if (loadedImage != null) 
                ImageView imageView = (ImageView) view;
                boolean firstDisplay = !displayedImages.contains(imageUri);
                if (firstDisplay) 
                    FadeInBitmapDisplayer.animate(imageView, 500);
                    displayedImages.add(imageUri);
                
            
        
    

【讨论】:

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