android - 缓存图像并显示

Question

你好我面临一个特殊的问题，我需要下载图像并将它们显示到一个 ListView 对应于他们的特定 TextView's。我拥有的代码成功显示了我需要显示的 TextView's，但我不知道如何在 ListView 中的 TextView 旁边显示所有这些不同的图像。

在 SO 中经历了许多线程之后。最佳答案是通过以下方式解决此问题1. 懒人列表2. 通用图片加载器

我已经通过了这两种解决方案。我下载了惰性列表代码，其中 URL 是存储在数组中的硬编码字符串。我想做的是动态创建自己的字符串。将它们存储到缓存中并显示所有相应的图像。

这是我的代码:

public class Tools_ListItemActivity extends ListActivity 
{
    private Context context;
    String s;

    private static final String TAG_POSTS = "posts";
    private static final String TAG_MDNAME = "mdname";
    private static final String TAG_UTCOST = "utcost";
    private static final String TAG_IIMG= "iimg";
    JSONArray posts = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);
        s=getIntent().getExtras().getString("url");
        new ProgressTask(Tools_ListItemActivity.this).execute();
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        // TODO Auto-generated method stub
        super.onListItemClick(l, v, position, id);
    }

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

     ListView lv ;



      private class ProgressTask extends AsyncTask<String, Void, Boolean> {
      private ProgressDialog dialog;

       public ProgressTask(ListActivity activity) {

       Log.i("1", "Called");
       context = activity;
       dialog = new ProgressDialog(context);
      }

       /** progress dialog to show user that the backup is processing. */

       /** application context. */
      private Context context;

       protected void onPreExecute() {
       this.dialog.setMessage("Progress start");
       this.dialog.show();
      }

       @Override
      protected void onPostExecute(final Boolean success) {
       if (dialog.isShowing()) {
        dialog.dismiss();
       }
       ListAdapter adapter = new SimpleAdapter(context, jsonlist,
         R.layout.activity_toolsitem, new String[] { TAG_IIMG, TAG_MDNAME, TAG_UTCOST  }, new int[] {
           R.id.imageViewUrl, R.id.mdname, R.id.utcost });

        setListAdapter(adapter);

        // selecting single ListView item
        lv = getListView();

      }

       protected Boolean doInBackground(final String... args) {

        JSONParser jParser = new JSONParser();

        // getting JSON string from URL
        JSONObject json = jParser.getJSONFromUrl(s);


        try {
            posts = json.getJSONArray(TAG_POSTS);
        } catch (JSONException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        try
        {
        // looping through All Contacts
        for(int i = 0; i < posts.length(); i++){
            JSONObject c = posts.getJSONObject(i);

            // Storing each json item in variable
            String mdname = c.getString(TAG_MDNAME);
            String utcost= c.getString(TAG_UTCOST);
            String iimg=c.getString(TAG_IIMG);

            //Forming the Url of the image to be shown in the list view
            String imageUrl="My_App_URL"+iimg;

/*  try {

              String imageUrl="My_App_URL"+iimg;
              ImageView imageView = (ImageView)findViewById(R.id.imageViewUrl);
              Bitmap bitmap = BitmapFactory.decodeStream((InputStream)new URL(imageUrl).getContent());
              imageView.setImageBitmap(bitmap); 
            } catch (MalformedURLException e) {
              e.printStackTrace();
            } catch (IOException e) {
              e.printStackTrace();
            } */


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

            // adding each child node to HashMap key => value
            map.put(TAG_MDNAME, mdname);
            map.put(TAG_UTCOST, utcost);
            map.put(TAG_IIMG, iimg);



         jsonlist.add(map);
        } }catch (JSONException e) 
        {
         // TODO Auto-generated catch block
         e.printStackTrace();
        }


        return null;


       }

      }





}

在这里我已经调试并发现 imageUrl 正确形成。 Json 仅返回 jpg 的名称，因此我将其附加到 URL 并将其存储在 imageUrl 中。其他两个 TextView 正在正确解析和显示。如果有人也可以帮助我在 ImageView 中显示图像，那就太好了。谢谢。

更新:借助 Pankaj (https://github.com/AndroidBegin/Android-JSON-Parse-Images-and-Texts-Tutorial) 共享的链接和 Raghunandan 在下方共享的概念知识，我能够解决我的特定问题。请仔细阅读这些答案以获取详细说明以及延迟加载的实现。很抱歉，因为我离开了两天，所以无法用赏金来奖励答案。

Answer 1

使用 Universal Imageloader 进行延迟加载。将硬编码的 url 替换为图片的 url。

根据您的要求修改以下内容

What's LazyList? .详情请查看此链接。

MainActivity.java

public class MainActivity extends Activity {

  private String[] mStrings={
            "http://a3.twimg.com/profile_images/670625317/aam-logo-v3-twitter.png",
            "http://a3.twimg.com/profile_images/740897825/AndroidCast-350_normal.png",
            "http://a3.twimg.com/profile_images/121630227/Droid_normal.jpg",
            "http://a1.twimg.com/profile_images/957149154/twitterhalf_normal.jpg",
            "http://a1.twimg.com/profile_images/97470808/icon_normal.png",
            "http://a3.twimg.com/profile_images/511790713/AG.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar_normal.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man_normal.png",
            "http://a3.twimg.com/profile_images/72774055/AndroidHomme-LOGO_normal.jpg",
            "http://a1.twimg.com/profile_images/349012784/android_logo_small_normal.jpg",
            "http://a1.twimg.com/profile_images/841338368/ea-twitter-icon.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet_normal.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto_normal.jpg",
            "http://a1.twimg.com/profile_images/850960042/elandroidelibre-logo_300x300_normal.jpg",
            "http://a1.twimg.com/profile_images/655119538/andbook.png",
            "http://a3.twimg.com/profile_images/768060227/ap4u_normal.jpg",
            "http://a1.twimg.com/profile_images/74724754/android_logo_normal.png",
            "http://a3.twimg.com/profile_images/681537837/SmallAvatarx150_normal.png",
            "http://a1.twimg.com/profile_images/63737974/2008-11-06_1637_normal.png",
            "http://a3.twimg.com/profile_images/548410609/icon_8_73.png",
            "http://a1.twimg.com/profile_images/612232882/nexusoneavatar_normal.jpg",
            "http://a1.twimg.com/profile_images/213722080/Bugdroid-phone_normal.png",
            "http://a1.twimg.com/profile_images/645523828/OT_icon_090918_android_normal.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto_normal.jpg",
            "http://a1.twimg.com/profile_images/850960042/elandroidelibre-logo_300x300_normal.jpg",
            "http://a1.twimg.com/profile_images/655119538/andbook_normal.png",
            "http://a3.twimg.com/profile_images/511790713/AG_normal.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man_normal.png",
            "http://a3.twimg.com/profile_images/72774055/AndroidHomme-LOGO_normal.jpg",
            "http://a1.twimg.com/profile_images/349012784/android_logo_small_normal.jpg",
            "http://a1.twimg.com/profile_images/841338368/ea-twitter-icon_normal.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto_normal.jpg",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet_normal.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto_normal.jpg",
            "http://a1.twimg.com/profile_images/850960042/elandroidelibre-logo_300x300.jpg",
            "http://a1.twimg.com/profile_images/655119538/andbook_normal.png",
            "http://a3.twimg.com/profile_images/511790713/AG_normal.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar_normal.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man_normal.png",
            "http://a3.twimg.com/profile_images/121630227/Droid.jpg",
            "http://a1.twimg.com/profile_images/957149154/twitterhalf_normal.jpg",
            "http://a1.twimg.com/profile_images/97470808/icon_normal.png",
            "http://a3.twimg.com/profile_images/511790713/AG_normal.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar_normal.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man.png",
            "http://a3.twimg.com/profile_images/72774055/AndroidHomme-LOGO_normal.jpg",
            "http://a1.twimg.com/profile_images/349012784/android_logo_small_normal.jpg",
            "http://a1.twimg.com/profile_images/841338368/ea-twitter-icon_normal.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet.png",
            "http://a3.twimg.com/profile_images/670625317/aam-logo-v3-twitter_normal.png",
            "http://a3.twimg.com/profile_images/740897825/AndroidCast-350_normal.png",
            "http://a3.twimg.com/profile_images/121630227/Droid_normal.jpg",
            "http://a1.twimg.com/profile_images/957149154/twitterhalf_normal.jpg",
            "http://a1.twimg.com/profile_images/97470808/icon.png",
            "http://a3.twimg.com/profile_images/511790713/AG_normal.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar_normal.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man_normal.png",
            "http://a3.twimg.com/profile_images/72774055/AndroidHomme-LOGO_normal.jpg",
            "http://a1.twimg.com/profile_images/349012784/android_logo_small_normal.jpg",
            "http://a1.twimg.com/profile_images/841338368/ea-twitter-icon.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet_normal.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto_normal.jpg",
            "http://a1.twimg.com/profile_images/850960042/elandroidelibre-logo_300x300_normal.jpg",
            "http://a1.twimg.com/profile_images/655119538/andbook_normal.png",
            "http://a3.twimg.com/profile_images/768060227/ap4u_normal.jpg",
            "http://a1.twimg.com/profile_images/74724754/android_logo.png",
            "http://a3.twimg.com/profile_images/681537837/SmallAvatarx150_normal.png",
            "http://a1.twimg.com/profile_images/63737974/2008-11-06_1637_normal.png",
            "http://a3.twimg.com/profile_images/548410609/icon_8_73_normal.png",
            "http://a1.twimg.com/profile_images/612232882/nexusoneavatar_normal.jpg",
            "http://a1.twimg.com/profile_images/213722080/Bugdroid-phone_normal.png",
            "http://a1.twimg.com/profile_images/645523828/OT_icon_090918_android.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet_normal.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto_normal.jpg",
            "http://a1.twimg.com/profile_images/850960042/elandroidelibre-logo_300x300_normal.jpg",
            "http://a1.twimg.com/profile_images/655119538/andbook.png",
            "http://a3.twimg.com/profile_images/511790713/AG_normal.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar_normal.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man_normal.png",
            "http://a3.twimg.com/profile_images/72774055/AndroidHomme-LOGO_normal.jpg",
            "http://a1.twimg.com/profile_images/349012784/android_logo_small_normal.jpg",
            "http://a1.twimg.com/profile_images/841338368/ea-twitter-icon.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet_normal.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto_normal.jpg",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet_normal.png",
            "http://a1.twimg.com/profile_images/605536070/twitterProfilePhoto.jpg",
            "http://a1.twimg.com/profile_images/850960042/elandroidelibre-logo_300x300_normal.jpg",
            "http://a1.twimg.com/profile_images/655119538/andbook_normal.png",
            "http://a3.twimg.com/profile_images/511790713/AG_normal.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar_normal.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man_normal.png",
            "http://a3.twimg.com/profile_images/121630227/Droid_normal.jpg",
            "http://a1.twimg.com/profile_images/957149154/twitterhalf.jpg",
            "http://a1.twimg.com/profile_images/97470808/icon_normal.png",
            "http://a3.twimg.com/profile_images/511790713/AG_normal.png",
            "http://a3.twimg.com/profile_images/956404323/androinica-avatar_normal.png",
            "http://a1.twimg.com/profile_images/909231146/Android_Biz_Man_normal.png",
            "http://a3.twimg.com/profile_images/72774055/AndroidHomme-LOGO_normal.jpg",
            "http://a1.twimg.com/profile_images/349012784/android_logo_small.jpg",
            "http://a1.twimg.com/profile_images/841338368/ea-twitter-icon_normal.png",
            "http://a3.twimg.com/profile_images/64827025/android-wallpaper6_2560x160_normal.png",
            "http://a3.twimg.com/profile_images/77641093/AndroidPlanet_normal.png"
    };

    ListView lv;    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv= (ListView) findViewById(R.id.lv);
        lv.setAdapter(new LazyAdapter(this,mStrings));
    }
}

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/lv"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="#000000"
        android:focusableInTouchMode="false"
        android:listSelector="@android:color/transparent"
        android:layout_weight="2.0"
        android:divider="#000000"
        android:headerDividersEnabled="false"
        android:footerDividersEnabled="false"
        android:dividerHeight="8dp"
        android:drawSelectorOnTop="false"
        />
</RelativeLayout>

LazyAdapter.java

public class LazyAdapter extends BaseAdapter {
    private Activity activity;
    private String data[];
    private LayoutInflater inflater=null;
    public ImageLoader imageLoader; 
    DisplayImageOptions options;
    public LazyAdapter(Activity a, String[] d) {
        activity = a;
        data=d;
        inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        File cacheDir = StorageUtils.getOwnCacheDirectory(a, "MyFolderCache");

        // Get singletone instance of ImageLoader
        imageLoader = ImageLoader.getInstance();
        // Create configuration for ImageLoader (all options are optional)
        ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(a)
              // You can pass your own memory cache implementation
             .discCacheExtraOptions(1024, 1024, CompressFormat.PNG, 100)
             .discCache(new UnlimitedDiscCache(cacheDir)) // You can pass your own disc cache implementation
             .discCacheFileNameGenerator(new HashCodeFileNameGenerator())
             .enableLogging()
             .build();
        // Initialize ImageLoader with created configuration. Do it once.
        imageLoader.init(config);
        //imageLoader.init(ImageLoaderConfiguration.createDefault(a));
        // imageLoader=new ImageLoader(activity.getApplicationContext());
        options = new DisplayImageOptions.Builder()
             .showStubImage(R.drawable.ic_launcher)
             .cacheInMemory()
             .cacheOnDisc()
             .displayer(new RoundedBitmapDisplayer(20))
             .build();
    }

    public int getCount() {
        return data.length;
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        View vi=convertView;
        ViewHolder vh = new ViewHolder();;
        if(convertView==null)
        {

            vi = inflater.inflate(R.layout.row, null);   
            vh.iv=(ImageView)vi.findViewById(R.id.ivv); 
            vh.pb= (ProgressBar)vi.findViewById(R.id.pb); 
            vh.tv = (TextView) vi.findViewById(R.id.textView1);
            vh.tv1= (TextView) vi.findViewById(R.id.textView2);
        }
        vh.tv.setText("Image in postion =");
        vh.tv1.setText(""+position);
        display(vh.iv, data[position], vh.pb);
        //imageLoader.displayImage(data.get(position).toString(), image,options);
        return vi;
    }

    public void display(ImageView img, String url, final ProgressBar spinner)
    {
        imageLoader.displayImage(url, img, options, new ImageLoadingListener() {
            @Override
            public void onLoadingStarted(String imageUri, View view) {
                spinner.setVisibility(View.VISIBLE);
            }
            @Override
            public void onLoadingFailed(String imageUri, View view, FailReason failReason) {
                spinner.setVisibility(View.GONE);
            }
            @Override
            public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
            spinner.setVisibility(View.GONE);
            }
            @Override
            public void onLoadingCancelled(String imageUri, View view) {

            }
        });
    }

    public static class ViewHolder
    {
        ImageView iv;
        TextView tv,tv1;
        ProgressBar pb;
    }
}

row.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:src="@drawable/ic_launcher" />
    <ProgressBar 
        android:id="@+id/pb"
        android:layout_centerInParent="true"
        android:layout_gravity="center"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/textView2"
        android:layout_alignParentLeft="true"
        android:layout_marginBottom="21dp"
        android:layout_marginLeft="31dp"
        android:text="TextView" />
    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_alignParentBottom="true"
        android:text="TextView" />
</RelativeLayout>

在 list 中添加权限

 <uses-permission android:name="android.permission.INTERNET"/>