3
我想用自定义的适配器（带图片和文本）显示ListView。ANDROID：在列表中加载异步图片
图像从远端服务器加载，所以我决定使用AsyncTask。
事实上，图片显示良好，但如果我迅速向下滚动，在1/2 secondes显示了错误的图片（加载后，会显示正确的图片）
这里是我的适配器代码：
public class GiAdapter extends BaseAdapter {
private Context mContext;
private List<SiteStaff> mListAppInfo;
private HashMap<Integer, ImageView> views;
private HashMap<String,Bitmap> oldPicts = new HashMap<String,Bitmap>();
private LayoutInflater mInflater;
private boolean auto;
private final String BUNDLE_URL = "url";
private final String BUNDLE_BM = "bm";
private final String BUNDLE_POS = "pos";
private final String BUNDLE_ID = "id";
public GiAdapter(Context context, List<SiteStaff> list) {
mContext = context;
mListAppInfo = list;
views = new HashMap<Integer, ImageView>();
mInflater = LayoutInflater.from(mContext);
}
@Override
public int getCount() {
return mListAppInfo.size();
}
@Override
public Object getItem(int position) {
return mListAppInfo.get(position).getId();
}
@Override
public long getItemId(int position) {
return mListAppInfo.get(position).getId();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LinearLayout layoutItem;
// reuse of convertView
if (convertView == null) {
layoutItem = (LinearLayout) mInflater.inflate(R.layout.auto_gi, parent, false);
} else {
layoutItem = (LinearLayout) convertView;
}
// infos for the current element
SiteStaff entry = mListAppInfo.get(position);
//set some text fields
TextView name = (TextView) layoutItem.findViewById(R.id.name);
TextView size = (TextView) layoutItem.findViewById(R.id.size);
name.setText(entry.getName());
size.setText(entry.getSize());
// get the imageView for the current object
ImageView v = (ImageView) layoutItem.findViewById(R.id.gi_image);
// put infos in bundle and send to the LoadImage class
Bundle b = new Bundle();
//url of the pict
b.putString(BUNDLE_URL, entry.getUrl());
//position in the listView
b.putInt(BUNDLE_POS, position);
//id of the current object
b.putInt(BUNDLE_ID, entry.getId());
//put info in the map in order to display in the onPostExecute
views.put(position, v);
// thread
new LoadImage().execute(b);
return layoutItem;
}
//asyncTackClass for loadingpictures
private class LoadImage extends AsyncTask<Bundle, Void, Bundle> {
@Override
protected Bundle doInBackground(Bundle... b) {
Bitmap bm =null;
//cache: for better performance, check if url alredy exists
if(oldPicts.get(b[0].getString(BUNDLE_URL))==null){
bm = Utils.getBitMapFromUrl(b[0].getString(BUNDLE_URL));
oldPicts.put(b[0].getString(BUNDLE_URL),bm);
}else{
bm = oldPicts.get(b[0].getString(BUNDLE_URL));
}
// get info from bundle
Bundle bundle = new Bundle();
bundle.putParcelable(BUNDLE_BM, bm);
bundle.putInt(BUNDLE_POS, b[0].getInt(BUNDLE_POS));
return bundle;
}
@Override
protected void onPostExecute(Bundle result) {
super.onPostExecute(result);
//get picture saved in the map + set
ImageView view = views.get(result.getInt(BUNDLE_POS));
Bitmap bm = (Bitmap) result.getParcelable(BUNDLE_BM);
if (bm != null){ //if bitmap exists...
view.setImageBitmap(bm);
}else{ //if not picture, display the default ressource
view.setImageResource(R.drawable.unknow);
}
}
}
}
谢谢！
谢谢〜我试着用你的代码和图片完美的显示！ – johann 2012-03-23 02:08:39
请注意，通过第一种方法，您基本上为列表视图的每一行膨胀视图（一个非常昂贵的操作），这意味着您的ListView不会顺利滚动。 – Christian 2012-04-18 20:42:55