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我能够在从解析 json 获得的列表视图中显示图像和数据。现在我有一个问题，如果 json 响应中没有图像，那么我想在列表视图中显示默认图像以及数据，但现在输出为空，即使数据显示没有图像。我该如何解决这个任何解决方案将不胜感激。以下是代码

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


    // Creating JSON Parser instance
            JSONParser jParser = new JSONParser();

            // getting JSON string from URL
            JSONObject json = jParser.getJSONFromUrl(URL);
            try {
        JSONArray posts = json.getJSONArray(KEY_POSTS);

    // looping through all song nodes <song>
            for(int i = 0; i < posts.length(); i++){
                JSONObject c = posts.getJSONObject(i);
                // Storing each json item in variable
                String id = c.getString(KEY_ID);
                String title = c.getString(KEY_TITLE);
                String date = c.getString(KEY_DATE);
                String content = c.getString(KEY_CONTENT);

                //authornumber is agin  JSON Object
                JSONObject author = c.getJSONObject(KEY_AUTHOR);
                String name = author.getString(KEY_NAME);

                JSONArray atta = c.getJSONArray("attachments");
                for(int j = 0; j < atta.length(); j++){

                    JSONObject d = atta.getJSONObject(j);

                    String slug = d.getString(KEY_SLUG);

                    JSONObject images = d.getJSONObject(KEY_IMAGES);

                    JSONObject thumbnail = images.getJSONObject(KEY_THUMB_URL);
                    String url = thumbnail.getString(KEY_URL);



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

        // adding each child node to HashMap key => value
        map.put(KEY_ID, id);
        map.put(KEY_TITLE, title);
        map.put(KEY_DATE, date);
        map.put(KEY_NAME, name);
        map.put(KEY_CONTENT, content);
        map.put(KEY_SLUG, slug);
        map.put(KEY_URL, url);


        // adding HashList to ArrayList
        songsList.add(map);
            }   }
            } catch (JSONException e) {
                e.printStackTrace();

                }


    list=(ListView)findViewById(R.id.list);

    // Getting adapter by passing json data ArrayList
    adapter=new LazyAdapter(this, songsList);        
    list.setAdapter(adapter);

LazyAdapter.java

public class LazyAdapter extends BaseAdapter {

private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader; 

public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
    activity = a;
    data=d;
    inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    imageLoader=new ImageLoader(activity.getApplicationContext());
}

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

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;
    if(convertView==null)
        vi = inflater.inflate(R.layout.list_row, null);

    TextView title = (TextView)vi.findViewById(R.id.title); // title
    TextView date = (TextView)vi.findViewById(R.id.artist); // artist name
    TextView content = (TextView)vi.findViewById(R.id.duration);  // duration
    TextView name = (TextView)vi.findViewById(R.id.name); 
    // duration
    ImageView thumb_image=(ImageView)vi.findViewById(R.id.list_image); // thumb image

    HashMap<String, String> song = new HashMap<String, String>();
    song = data.get(position);


    ListView list;
    // Setting all values in listview
   title.setText(song.get(CustomizedListView.KEY_TITLE));
    date.setText(song.get(CustomizedListView.KEY_DATE));
    content.setText(song.get(CustomizedListView.KEY_CONTENT));
    name.setText(song.get(CustomizedListView.KEY_NAME));

   imageLoader.DisplayImage(song.get(CustomizedListView.KEY_URL), thumb_image);
    return vi;
  }
 }

ImageLoader.java

public class ImageLoader {

MemoryCache memoryCache=new MemoryCache();
FileCache fileCache;
private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
ExecutorService executorService; 

public ImageLoader(Context context){
    fileCache=new FileCache(context);
    executorService=Executors.newFixedThreadPool(5);
}

final int stub_id = R.drawable.no_image;
public void DisplayImage(String url, ImageView imageView)
{
    imageViews.put(imageView, url);
    Bitmap bitmap=memoryCache.get(url);
    System.out.println("Image bitmap object from url*********$$$$$$$$"+bitmap);

    if(bitmap!=null)
        imageView.setImageBitmap(bitmap);
    else
    {
      System.out.println("In the else where there is null bitmap>>>>>>>>>");
        queuePhoto(url, imageView);
        imageView.setImageResource(stub_id);
    }
}

private void queuePhoto(String url, ImageView imageView)
{
    PhotoToLoad p=new PhotoToLoad(url, imageView);
    executorService.submit(new PhotosLoader(p));
}

private Bitmap getBitmap(String url)
{
    File f=fileCache.getFile(url);

    //from SD cache
    Bitmap b = decodeFile(f);
    if(b!=null)
        return b;

    //from web
    try {
        Bitmap bitmap=null;
        URL imageUrl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
        conn.setConnectTimeout(30000);
        conn.setReadTimeout(30000);
        conn.setInstanceFollowRedirects(true);
        InputStream is=conn.getInputStream();
        OutputStream os = new FileOutputStream(f);
        Utils.CopyStream(is, os);
        os.close();
        bitmap = decodeFile(f);
        return bitmap;
    } catch (Exception ex){
       ex.printStackTrace();
       return null;
    }
}

//decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f){
    try {
        //decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(new FileInputStream(f),null,o);

        //Find the correct scale value. It should be the power of 2.
        final int REQUIRED_SIZE=70;
        int width_tmp=o.outWidth, height_tmp=o.outHeight;
        int scale=1;
        while(true){
            if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                break;
            width_tmp/=2;
            height_tmp/=2;
            scale*=2;
        }

        //decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize=scale;
        return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
    } catch (FileNotFoundException e) {}
    return null;
}

//Task for the queue
private class PhotoToLoad
{
    public String url;
    public ImageView imageView;
    public PhotoToLoad(String u, ImageView i){
        url=u;
        imageView=i;
    }
}

class PhotosLoader implements Runnable {
    PhotoToLoad photoToLoad;
    PhotosLoader(PhotoToLoad photoToLoad){
        this.photoToLoad=photoToLoad;
    }

    @Override
    public void run() {
        if(imageViewReused(photoToLoad))
            return;
        Bitmap bmp=getBitmap(photoToLoad.url);
        memoryCache.put(photoToLoad.url, bmp);
        if(imageViewReused(photoToLoad))
            return;
        BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
        Activity a=(Activity)photoToLoad.imageView.getContext();
        a.runOnUiThread(bd);
    }
}

boolean imageViewReused(PhotoToLoad photoToLoad){
    String tag=imageViews.get(photoToLoad.imageView);
    if(tag==null || !tag.equals(photoToLoad.url))
        return true;
    return false;
}

//Used to display bitmap in the UI thread
class BitmapDisplayer implements Runnable
{
    Bitmap bitmap;
    PhotoToLoad photoToLoad;
    public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
    public void run()
    {
        if(imageViewReused(photoToLoad))
            return;
        if(bitmap!=null)
            photoToLoad.imageView.setImageBitmap(bitmap);
        else
            photoToLoad.imageView.setImageResource(stub_id);
    }
  }

  public void clearCache() {
     memoryCache.clear();
    fileCache.clear();
    }

  }
4

2 回答 2

0

使用此方法代替 LazyAdapter 的 getView() 来显示默认图像。

        public View getView(int position, View convertView, ViewGroup parent) {
            final ViewHolder holder;

            LayoutInflater vi = LayoutInflater.from(this.ctx);
            if (convertView == null) {
                try {
                    convertView = vi.inflate(
                            R.layout.siteselectionlistinflater, null);
                } catch (Exception e) {
                    // TODO: handle exception
                    e.printStackTrace();
                    e.getMessage();
                }
                holder = new ViewHolder();

holder.title = (TextView) convertView.findViewById(R.id.title); // title
    holder.date = (TextView) convertView.findViewById(R.id.artist); // artist name
   holder.content = (TextView) convertView.findViewById(R.id.duration);  // duration
    holder.name = (TextView) convertView.findViewById(R.id.name); 
    // duration
   holder.thumb_image=(ImageView) convertView.findViewById(R.id.list_image); 


                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }           
         HashMap<String, String> song = new HashMap<String, String>();
    song = data.get(position);


    ListView list;
    // Setting all values in listview
   title.setText(song.get(CustomizedListView.KEY_TITLE));
    date.setText(song.get(CustomizedListView.KEY_DATE));
    content.setText(song.get(CustomizedListView.KEY_CONTENT));
    name.setText(song.get(CustomizedListView.KEY_NAME));

  if(song.get(CustomizedListView.KEY_URL) != null && song.get(CustomizedListView.KEY_URL).compareTo("")!=0)
    {
         imageLoader.DisplayImage(song.get(CustomizedListView.KEY_URL), thumb_image);
    }
    else{

          thumb_image.setImageResource(R.drawable.DEFAULT_IMAGE);
    }

            return convertView;
        }

       class ViewHolder {
            TextView title;
            TextView date;
            TextView content;
                TextView name;
                 ImageView thumb_image;

        }
于 2013-01-04T06:45:56.743 回答
0

有两种方法可以解决这个问题.. 1.如果你使用的是lazyloader而不是那个文件，即ImageLoader.java，那里有这个方法..

final int stub_id=R.drawable.ic_launcher;
    public void DisplayImage(String url, ImageView imageView)
    {
        imageViews.put(imageView, url);
        Bitmap bitmap=memoryCache.get(url);
        if(bitmap!=null)
            imageView.setImageBitmap(bitmap);
        else
        {
            queuePhoto(url, imageView);
            imageView.setImageResource(stub_id);
        }
    }

在上面的代码中， stub_id 是您的默认图像，当 url 不正确或缓存中没有该 url 的图像时会设置该图像。因此，您可以通过更改可绘制对象中的 stub_id 来设置任何默认图像。

另一个解决方案是。2. 在解析 JSONNObject 时，您可以检查是否有任何可用的图像 url，如果没有，则在此处设置默认图像字符串。像这样的东西..

if(thumbnail.has("KEY_URL")){
    String url = thumbnail.getString(KEY_URL);
}else{
    String url = --- string path of your default image;
}

试试看。！它可能会帮助你。一切顺利。

于 2013-01-04T06:50:49.987 回答