您好stackoverflow我正在尝试为Gallery的特定目录开发类似SD Card的应用程序。例如，我已经使用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，每件事情都很好，但问题是图片在one shot全部加载，因此滚动速度非常慢，有时OutOfMemoryException decoded文件会出现BitMapFactory任何人都可以帮我解决这个难题。
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;
}
感谢。
答案 0 :(得分：3)
您应该使用延迟加载
访问本教程以了解延迟加载here非常简单。 如果您有任何问题，请告诉我。
Edit
public class MainActivity extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String path = Environment.getExternalStorageDirectory()+"/WhatsApp/Media/WhatsApp Images";
final List<Model> list = new ArrayList<Model>();
final File file = new File(path);
final ProgressDialog dialog = ProgressDialog.show(MainActivity.this, "",
"Please Wait...", true);
new Thread(new Runnable() {
public void run() {
dismissDialog(dialog);
for(File fileChild : file.listFiles()){
list.add(get(fileChild.getName(), fileChild.getAbsolutePath()));
}
}
}).start();
ArrayAdapter<Model> adapter = new MyCustomArrayAdapter(this, list);
setListAdapter(adapter);
}
public void dismissDialog(final ProgressDialog dialog) {
runOnUiThread(new Runnable() {
public void run() {
dialog.dismiss();
}
});
}
private Model get(String s, String url) {
return new Model(s, url);
}
}
答案 1 :(得分：0)
这可能会有所帮助：UniversalImageLoader
这就是我所做的：
/**
* UniversalImageLoader載入遠端圖片，僅使用RAM做圖片快取 (Load pic & use RAM as cache)
* @param android.content.Context
* @author https://github.com/nostra13/Android-Universal-Image-Loader
* @param android.widget.ImageView - 顯示圖片的元件 (your image container)
* @param int - 載入失敗的預設圖片Resource ID (default pic if load fail, I put default pic in resources folder)
* @param java.lang.String - 檔案URL (pic URL or path)
*/
public static void imageLoaderMemoryCache(Context context, final ImageView img, final int failImgID, String url)
{
ImageLoader imageLoader=ImageLoader.getInstance();
ImageLoaderConfiguration config=new ImageLoaderConfiguration.Builder(context)
.memoryCacheExtraOptions(100, 100) // max width, max height
.threadPoolSize(5)
.threadPriority(Thread.NORM_PRIORITY+1)
.denyCacheImageMultipleSizesInMemory()
.tasksProcessingOrder(QueueProcessingType.FIFO)
.defaultDisplayImageOptions(DisplayImageOptions.createSimple())
.enableLogging()
.build();
imageLoader.init(config);
DisplayImageOptions options = new DisplayImageOptions.Builder()
.showImageForEmptyUri(R.drawable.cover_sample)
.cacheInMemory(true)
.imageScaleType(ImageScaleType.IN_SAMPLE_INT)
.bitmapConfig(Bitmap.Config.RGB_565)
.delayBeforeLoading(1)
.displayer(new FadeInBitmapDisplayer(500))
.build();
imageLoader.displayImage(url, img, options, new ImageLoadingListener()
{
@Override
public void onLoadingStarted(String url, View view)
{img.setImageResource(failImgID);} //一開始先顯示預設圖 (display default pic at first)
@Override
public void onLoadingFailed(String url, View view, FailReason failReason)
{img.setImageResource(failImgID);}
@Override
public void onLoadingComplete(String url, View view, Bitmap loadedImage)
{}
@Override
public void onLoadingCancelled(String url, View view)
{}
});
}
用法（ListView）
public View getView(...)
{
vh.imgCover=(ImageView)convertView.findViewById(R.id.imgCover);
//...
// some stuff
//...
Util.imageLoaderDiskCache(getActivity(), vh.imgCover, R.drawable.cover_sample, "(pic file path)");
}
希望有所帮助〜