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我是 android 应用程序的新手，我正在尝试在列表视图中添加图像和文本，并且来自服务器的响应是 JSON 响应。现在我在列表视图中添加了相应的文本，我需要为每个文本添加图像，其中图像不固定。我正在使用以下代码，但我的模拟器中没有显示任何内容。谁能纠正我我哪里错了？

public class CustomizedListView extends Activity {
JSONArray posts = null;

// All static variables
static final String URL = "http://website/?json=get_recent_posts";



static final String KEY_POSTS = "posts";
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_DATE = "date";
static final String KEY_CONTENT = "content";
static final String KEY_AUTHOR = "author";
static final String KEY_NAME = "name";
static final String KEY_THUMB_URL = "thumbnail";
static final String KEY_IMAGES = "images";

ListView list;
LazyAdapter adapter;

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


    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 {
            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);

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

                JSONObject images = c.getJSONObject(KEY_IMAGES);
                String thumbnail = images.getString(KEY_THUMB_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_THUMB_URL,thumbnail);
        // 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);


    // Click event for single list row
    list.setOnItemClickListener(new OnItemClickListener() {

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


        }
    });     
}   
 }

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_THUMB_URL), thumb_image);
    return vi;
}

}

图像加载器.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);
    if(bitmap!=null)
        imageView.setImageBitmap(bitmap);
    else
    {
        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

1 回答 1

0

使用惰性列表适配器

例如：

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

LazyAdapter adapter=new LazyAdapter(con, ar);
        list.setAdapter(adapter);

public class LazyAdapter extends BaseAdapter {

    private Context activity;
    private ArrayList<HashMap<String, String>> data;
    private LayoutInflater inflater=null;
    //public ImageLoader imageLoader; 
    private URL url;
    private Bitmap bmp;

    public LazyAdapter(Context 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.lis, null);   
        TextView title = (TextView)vi.findViewById(R.id.textView11); // title
        TextView artist = (TextView)vi.findViewById(R.id.textView21); // artist nameduration
        ImageView im=(ImageView)vi.findViewById(R.id.imageView1);

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

        // Setting all values in listview
        title.setText(song.get("name"));
        artist.setText(song.get("adr"));
        try {
            url = new URL(song.get("icon"));
             bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
               im.setImageBitmap(bmp);
        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


        return vi;
    }
}
于 2012-12-04T07:00:30.893 回答