您好stackoverflow，我正在尝试开发一个应用程序，例如Gallery针对SD Card. 例如我拿了WhatsApp Images目录，这是我的代码
public class WhatsAppInboxImagesActivity extends Activity {
private ImageAdapter imageAdapter;
private ProgressDialog pd;
ArrayList<String> f = null;
File[] listFile;
Button btnDelete;
HashSet<String> selectedFile = null;
GridView imagegrid;
AlertDialog alertDialog = null;
static
{
File noFile = new File(Environment.getExternalStorageDirectory().getPath(), "/WhatsApp/Media/WhatsApp Images/Sent/.nomedia");
if(noFile.exists())
{
noFile.delete();
}
}//End of static block
private void initialize()
{
imagegrid = (GridView) findViewById(R.id.PhoneImageGrid);
btnDelete = (Button) findViewById(R.id.btnDeleteImg);
selectedFile = new HashSet<String>();// list of file paths boolean checked
f = new ArrayList<String>();// list of file paths
}//End of initialize method
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_whats_app_images_inbox);
this.initialize();
getFromSdcard();
imageAdapter = new ImageAdapter();
/*
* Performing time consuming actions
*/
new AsyncTask<Void, Void, Void>()
{
@Override
protected void onPreExecute()
{
pd = ProgressDialog.show(WhatsAppInboxImagesActivity.this,
"Loading..", "Please Wait", true, false);
}// End of onPreExecute method
@Override
protected Void doInBackground(Void... params)
{
return null;
}// End of doInBackground method
@Override
protected void onPostExecute(Void result)
{
imagegrid.setAdapter(imageAdapter);
imageAdapter.notifyDataSetChanged();
pd.dismiss();
}
}.execute((Void[]) null);
btnDelete.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
new AsyncTask<Void, Void, Void>()
{
@Override
protected void onPreExecute()
{
pd = ProgressDialog.show(WhatsAppInboxImagesActivity.this,
"Loading..", "Please Wait", true, false);
}// End of onPreExecute method
@Override
protected Void doInBackground(Void... params)
{
@SuppressWarnings("rawtypes")
Iterator iterator = selectedFile.iterator();
while (iterator.hasNext())
{
new File(iterator.next().toString()).delete();
}//End of while loop
return null;
}// End of doInBackground method
@Override
protected void onPostExecute(Void result)
{
pd.dismiss();
}//End of onPostExecute method
}.execute((Void[]) null);
finish();
startActivity(getIntent());
}//End of onClick method
});//End of btnDelete anonymous class
}//End of onCreate method
public void getFromSdcard()
{
File file = new File( Environment.getExternalStorageDirectory().getPath(), "/WhatsApp/Media/WhatsApp Images");
if (file.isDirectory())
{
listFile = file.listFiles();
for (int i = 0; i < listFile.length; i++)
{
if(listFile[i].isDirectory())
{
continue;
}
f.add(listFile[i].getAbsolutePath());
}//End of for loop
}//End of if condition
}//End of getFromSdcard method
public class ImageAdapter extends BaseAdapter
{
private LayoutInflater mInflater;
public ImageAdapter()
{
mInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}//End of ImageAdapter constructor
public int getCount()
{
return f.size();
}//End of getCount method
public Object getItem(int position)
{
return position;
}//End of getItem method
public long getItemId(int position)
{
return position;
}//End of getItemId method
public View getView(int position, View convertView, ViewGroup parent)
{
ViewHolder holder;
if (convertView == null)
{
holder = new ViewHolder();
convertView = mInflater.inflate(R.layout.galleryitem, null);
holder.imageview = (ImageView) convertView.findViewById(R.id.thumbImage);
holder.checkbox = (CheckBox) convertView.findViewById(R.id.itemCheckBox);
convertView.setTag(holder);
}//End of if condition
else
{
holder = (ViewHolder) convertView.getTag();
}//End of else
BitmapFactory.Options options = new BitmapFactory.Options();
// will results in a much smaller image than the original
options.inSampleSize = 4;
// don't ever use a path to /sdcard like this, but I'm sure you have a sane way to do that
// in this case nebulae.jpg is a 19MB 8000x3874px image
final Bitmap b = BitmapFactory.decodeFile(f.get(position), options);
holder.imageview.setImageBitmap(b);
return convertView;
}//End of getView method
}//End of ImageAdapter instance inner class
class ViewHolder
{
ImageView imageview;
CheckBox checkbox;
int id;
}//End of ViewHolder instance inner class
}//End of WhatsAppImagesActivity
到目前为止，一切都很好，但问题是图像全部加载one shot，所以滚动非常慢，有时OutOfMemoryException会出现decoded文件BitMapFactory，请任何人帮助我解决这个难题。
编辑：
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = null;
if (convertView == null) {
LayoutInflater inflator = context.getLayoutInflater();
view = inflator.inflate(R.layout.list_layout, null);
final ViewHolder viewHolder = new ViewHolder();
viewHolder.text = (TextView) view.findViewById(R.id.label);
viewHolder.text.setTextColor(Color.BLACK);
viewHolder.image = (ImageView) view.findViewById(R.id.image);
viewHolder.image.setVisibility(View.GONE);
viewHolder.cb = (CheckBox) view.findViewById(R.id.item_check_box);
viewHolder.pb = (ProgressBar) view.findViewById(R.id.progressBar);
view.setTag(viewHolder);
} else {
view = convertView;
}
final int pos = position;
ViewHolder holder = (ViewHolder) view.getTag();
holder.text.setText(list.get(position).getName());
holder.image.setTag(list.get(position).getURL());
holder.image.setId(position);
PbAndImage pb_and_image = new PbAndImage();
pb_and_image.setImg(holder.image);
pb_and_image.setPb(holder.pb);
new DownloadImageTask().execute(pb_and_image);
return view;
}
谢谢。