我有一个由ListView组成的ImageView元素。我使用AsyncTask获取了新图片，并且在onPostExecute(Object result)方法中，我使用setImageUri(Uri uri)设置了图片，但它没有更新。
如果我更改活动或在应用之间，图像会完美显示，但我想立即显示图像。
我尝试使用invalidate()，扩展ImageView，父BaseAdapter的所有组合来调用ListView，但没有任何效果。我尝试过许多其他技巧，例如调用setImageResource(0)，setImageUri(null)，但没有结果......
编辑：
这里是部分代码：
public class ThingItemAdapter extends BaseAdapter {
protected List<Thing> things;
LayoutInflater inflater;
public ThingItemAdapter(Context context, List<Thing> things) {
this.things = things;
this.inflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return things.size();
}
@Override
public Thing getItem(int position) {
return things.get(position);
}
@Override
public long getItemId(int position) {
return things.get(position).getId();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
final int pos = position;
final ViewHolder holder;
if (convertView == null) {
holder = new ViewHolder();
convertView = this.inflater.inflate(R.layout.thing_list_item, parent, false);
holder.thingImageView = (ImageView) convertView.findViewById(R.id.thing_preview);
holder.button = (ImageButton) convertView.findViewById(R.id.apply_button);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
final Thing thing = things.get(position);
final long thingId = thing.getId();
final Uri thingUri = thing.getPicture();
holder.thingImageView.setImageURI(thingUri);
holder.button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// generate new file
final TypedFile typedFile = new TypedFile("multipart/form-data", new File(thingUri.getPath()));
new ReadAndStorePictureTask()
.execute(new Object[] { typedFile, holder.thingImageView, thing });
}
});
// item detailed view listener
holder.thingImageView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent((ThingApplication) ThingApplication.getContext(), ThingActivity.class);
intent.putExtra(ThingActivity.EXTRA_THING_ID, thingId);
context.startActivity(intent);
}
});
return convertView;
}
private class ViewHolder {
ImageView thingImageView;
ImageButton button;
}
private class ReadAndStorePictureTask extends AsyncTask<Object, Void, Void> {
ImageView imageView;
Thing thing;
ViewGroup parent;
protected Void doInBackground(Object... params) {
final TypedFile typedFile = (TypedFile) params[0];
imageView = (ImageView) params[1];
thing = (Thing) params[2];
((ThingApplication) ThingApplication.getContext()).getClient().apply(typedFile,
new Callback<Response>() {
@Override
public void failure(RetrofitError error) {
...
}
@Override
public void success(Response nothing, Response response) {
try {
byte[] bytes = ThingApplication.getBytesFromStream(response.getBody().in());
Uri newImageURI = Uri.parse("uri://valid_uri"); // whatever, it exists in real code
thing.setPicture(newImageURI);
File file = ((ThingApplication) ThingApplication.getContext())
.getFileFromURI(newImageURI); // this method works
ThingApplication.saveBytesToFile(bytes, file.getAbsolutePath());
thingService.storeThing(thing);
} catch (Exception e) {
...
}
}
});
return null;
}
@Override
protected void onPostExecute(Void result) {
imageView.setImageURI(thing.getPicture());
// force redraw. FIXME not working
/*
* ANSWER HERE, PLEASE
*/
}
}
}
如何在onPostExecute(Object result)方法中立即显示更新的URI？
答案 0 :(得分：0)
onPostExecute您更新它链接到ListView适配器的图像列表，然后通过调用通知适配器您更改了列表中的项目：
adapter.notifyDataSetChanged();
答案 1 :(得分：0)
您可以这样做：
- 在asynctask调用中更改第三个参数。
new ReadAndStorePictureTask().execute(
new Object[] { typedFile, holder.thingImageView, pos });
- 然后，修改asynctask里面的列表项并刷新。
private class ReadAndStorePictureTask extends AsyncTask<Object, Void, Void> {
ImageView imageView;
int position;
ViewGroup parent;
protected Void doInBackground(Object... params) {
final TypedFile typedFile = (TypedFile) params[0];
imageView = (ImageView) params[1];
position = (Integer) params[2];
((ThingApplication) ThingApplication.getContext()).getClient().apply(typedFile,
new Callback<Response>() {
@Override
public void failure(RetrofitError error) {
...
}
@Override
public void success(Response nothing, Response response) {
try {
byte[] bytes = ThingApplication.getBytesFromStream(response.getBody().in());
Uri newImageURI = Uri.parse("uri://valid_uri"); // whatever, it exists in real code
things.get(position).setPicture(newImageURI);
File file = ((ThingApplication) ThingApplication.getContext())
.getFileFromURI(newImageURI); // this method works
ThingApplication.saveBytesToFile(bytes, file.getAbsolutePath());
thingService.storeThing(things.get(position));
} catch (Exception e) {
...
}
}
});
return null;
}
@Override
protected void onPostExecute(Void result) {
notifyDataSetChanged();
}
}