我一直在尝试更新我的图片GridView
仅当我再次设置适配器时,图像才会更新。再次设置适配器使我的活动滚动到顶部,我尽量避免这种情况。
以下是一些代码:
private class LoadImagesTask extends AsyncTask<Object,Void, Object> {
private ImageAdapter imageAdapter;
private ArrayList<Integer> idsArray;
@Override
protected void onPreExecute() {
imageAdapter = new ImageAdapter(getApplicationContext());
Bitmap bmap = BitmapFactory.decodeResource(getResources(),
R.drawable.locked_image);
idsArray = dbHelper.getPicturesIdsByAlbumId(1);
for(int i = 0;i<idsArray.size();i++){
imageAdapter.bitmaps.add(bmap);
}
gridView.setAdapter(imageAdapter);
}
@Override
protected Void doInBackground(Object... arg) {
for(int i = 0;i<idsArray.size();i++){
byte[] data = dbHelper.getPictureById(idsArray.get(i)).littlePicBytes;
imageAdapter.bitmaps.set(i, BitmapFactory.decodeByteArray(data, 0, data.length));
publishProgress(); //********** This line calls onProgressUpdate() *********
}
return null;
}
}
现在,此代码适用于更新视图:
@Override
protected void onProgressUpdate(Void... params) {
gridView.setAdapter(imageAdapter);
}
但这并不是:
@Override
protected void onProgressUpdate(Void... params) {
imageAdapter.notifyDataSetChanged();
gridView.invalidateViews();
}
不更新我的观点可能是什么原因?谢谢!
编辑: ImageAdapter代码:
public class ImageAdapter extends BaseAdapter {
private Context mContext;
public ArrayList<Bitmap> bitmaps = new ArrayList<Bitmap>();
public ImageAdapter(Context c) {
mContext = c;
}
public int getCount() {
return bitmaps.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) mContext
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View gridView;
if (convertView == null) {
gridView = new View(mContext);
// get layout from mobile.xml
gridView = inflater.inflate(R.layout.image_adapter, null);
// set image based on selected text
ImageView imageView = (ImageView) gridView
.findViewById(R.id.imageView);
imageView.setImageBitmap(bitmaps.get(position));
}
else{
gridView = (View) convertView;
}
return gridView;
}
}
答案 0 :(得分:1)
您的代码中存在两个主要问题:
更改了适配器的数据,这不是线程安全的操作,因为适配器可能会在您更改时从数据中读取。我正在谈论这一行:
imageAdapter.bitmaps.set(i, BitmapFactory.decodeByteArray(data, 0, data.length));
相反,您应该仅在UI线程上更新其数据,例如在onProgressUpdate内部。
,您已经错误地实现了它。当convertView不为null时,您永远不会更新imageView的内容。应该是什么样的:
public View getView(int position, View convertView, ViewGroup parent) { View rootView=convertView; ViewHolder holder; if (rootView != null) holder=(ViewHolder) rootView.getTag(); else { rootView = inflater.inflate(R.layout.image_adapter, null,false); holder = new ViewHolder(); holder.imageView = (ImageView) rootView.findViewById(R.id.imageView); rootView.setTag(holder); } holder.imageView.setImageBitmap(getItem(position)); return rootView; } private Bitmap getItem(final int position) { return bitmaps.get(position); } private static class ViewHolder { ImageView imageView; }