我在我的应用程序中使用Parse，为了加载我的'profile'图像，我需要检索一个所谓的Parsefile。当下载Parsefile时，它使用回调来通知它何时完成。现在这通常是一种很好的方法，但是当我使用Listview并使用Asynctask下载图像时遇到了这个问题。
问题如下：
在getView方法的ListView适配器中，我创建了一个AsyncTask并执行它，这个AsyncTask启动了retrieveProfileImage(callBack)函数。在我的回调中，我只是在UI线程上启动一个Runnable，用新的（检索到的图像）更新View中的ImageView。但是看起来问题是，只要我启动AsyncTask，就会返回View。所以我无法将其他图像设置为正确的行。我希望我的代码能更清楚地证明我的问题。
ListAdapter：
public class FriendListAdapter extends ArrayAdapter<Profile> {
private int resource;
private Context context;
private List<Profile> friends;
private Profile fProfile;
private Bitmap profileImageBitmap;
private ProgressBar friendImageProgressBar;
//ui
private ImageView friendImage;
public FriendListAdapter(Context context, int resource,
List<Profile> objects) {
super(context, resource, objects);
this.context = context;
this.resource = resource;
this.friends = objects;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
TextView friendName = null;
friendImage = null;
View rowView = convertView;
if (rowView == null) {
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
rowView = inflater.inflate(R.layout.friendslist_row, null);
friendName = (TextView) rowView.findViewById(R.id.fName);
friendImage = (ImageView) rowView
.findViewById(R.id.fImage);
friendImageProgressBar = (ProgressBar) rowView.findViewById(R.id.friendImageProgressBar);
} else {
friendName = (TextView) convertView.findViewById(R.id.fName);
friendImage = (ImageView) convertView.findViewById(R.id.fImage);
friendImageProgressBar = (ProgressBar) convertView.findViewById(R.id.friendImageProgressBar);
}
fProfile = friends.get(position);
DownloadProfileImage dImg = new DownloadProfileImage();
dImg.execute();
friendName.setText(fProfile.getName());
return rowView;
}
private class DownloadProfileImage extends AsyncTask<Void, Integer, String> {
@Override
protected String doInBackground(Void... arg0) {
Log.d("logpp", "Starting download image for " + fProfile.getName());
fProfile.retrieveProfileImage(new ProfileImageCallback());
return null;
}
}
private class ProfileImageCallback extends GetDataCallback {
@Override
public void done(byte[] bytearray, ParseException e) {
if (e == null) {
Log.d("logpp", "Done downloading image for " + fProfile.getName() + ". Setting bitmap to:" +
" " + friendImage.getId());
profileImageBitmap = BitmapManager
.getBitmapFromByteArray(bytearray);
((Activity) context).runOnUiThread(new UpdateUi());
}
}
}
private class UpdateUi implements Runnable {
@Override
public void run() {
friendImage.setImageBitmap(profileImageBitmap);
friendImage.setVisibility(View.VISIBLE);
friendImageProgressBar.setVisibility(View.INVISIBLE);
}
}
}
retrieveProfileImage方法：
public void retrieveProfileImage(GetDataCallback callBack) {
this.image.getDataInBackground(callBack);
}
我希望有人可以帮我这个。
此致
添
答案 0 :(得分：1)
我通过以下代码解决了这个问题
public View getView(int position, View convertView, ViewGroup parent) {
try {
if (inflater == null)
inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
if (convertView == null)
convertView = inflater.inflate(R.layout.answer_item, null);
TextView name = (TextView) convertView.findViewById(R.id.textView_ans_user_name);
TextView body = (TextView) convertView.findViewById(R.id.textView_ans_user_body);
TextView timestamp = (TextView) convertView.findViewById(R.id.textView_ans_user_timestamp);
final CircularImageView thumbnail = (CircularImageView) convertView.findViewById(R.id.imageView_ans_user);
Parse_answer_model ans = answers.get(position);
name.setText(ans.getAns_by());
body.setText(ans.getAns_body());
SimpleDateFormat sdfAmerica = new SimpleDateFormat("dd-M-yyyy hh:mm:ss a");
sdfAmerica.setTimeZone(TimeZone.getDefault());
String sDateInAmerica = sdfAmerica.format(ans.getCreatedAt());
timestamp.setText(sDateInAmerica);
ParseQuery<User> query = ParseQuery.getQuery("_User");
query.whereEqualTo("username", ans.getAns_by());
query.getFirstInBackground(new GetCallback<User>() {
public void done(User user, ParseException e) {
// TODO Auto-generated method stub
if (e == null) {
img.DisplayImage(user.getprofile_pic_url(), thumbnail, false);
} else {
}
}
});
} catch (Exception e) {
e.printStackTrace();
}
把你的imageview作为最终不要使它全局化你从geturl（）方法得到图像网址，它是由你在下面的例子中使用的解析所定义的
ParseFile fileObject = (ParseFile) object.get("image_file");
User user = new User();
user = (User) ParseUser.getCurrentUser();
user.setProfile_pic_url(fileObject.getUrl().toString());
user.saveInBackground();
<强>更新
去年我找到了新的解决方案，您可以通过以下代码获取与解析对象相关的用户数据，并在模型类中进行一些更改。
void getchats() {
pd.show();
ParseQuery<Parse_chat_dialogs> query = ParseQuery.getQuery("chat_dialogs");
query.addDescendingOrder("updatedAt");
query.whereContains("users", ParseUser.getCurrentUser().getUsername());
query.findInBackground(new FindCallback<Parse_chat_dialogs>() {
public void done(List<Parse_chat_dialogs> dilogs, ParseException e) {
if (e == null) {
pd.hide();
dialoglist = (ArrayList<Parse_chat_dialogs>) dilogs;
adp = new ChatDialogAdapter(Chat_list.this, dialoglist);
list.setAdapter(adp);
for (int i = 0; i < dialoglist.size(); i++) {
ParseQuery<User> query = ParseQuery.getQuery("_User");
query.whereEqualTo("username", dialoglist.get(i).getUsers().trim()
.replace(ParseUser.getCurrentUser().getUsername(), "").replace(",", ""));
User user = new User();
try {
user = query.getFirst();
dialoglist.get(i).setFirstname(user.getFirstname());
dialoglist.get(i).setLastname(user.getLastname());
dialoglist.get(i).setProfileurl(user.getprofile_pic_url());
adp.notifyDataSetChanged();
} catch (ParseException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
} else {
Toast.makeText(Chat_list.this, e.getMessage(), Toast.LENGTH_SHORT).show();
}
}
});
}
如上例所示，我在parseobejct模型类中添加了三个新参数，用于存储用户的firstname，lastname和profile url的值。 我也在分享模型类以获得更多想法
@ParseClassName("chat_dialogs")
public class Parse_chat_dialogs extends ParseObject {
private String firstname;
private String lastname;
private String profileurl;
public String getFirstname() {
return firstname;
}
public void setFirstname(String firstname) {
this.firstname = firstname;
}
public String getLastname() {
return lastname;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
public String getProfileurl() {
return profileurl;
}
public void setProfileurl(String profileurl) {
this.profileurl = profileurl;
}
/////////////////////////////////////////////////////////////////////////////
public String getLast_message() {
return getString("last_message");
}
public void setLast_message(String value) {
put("last_message", value);
}
public String getUsers() {
return getString("users");
}
public void setUsers(String value) {
put("users", value);
}
}
答案 1 :(得分：0)
这个怎么样！
不要在适配器类中使用AsyncTask，而是在MainActivity中使用它，您可以在其中为listview设置适配器。在Callback中的done方法或postExecute中更新对象/对象并调用notifyDataSetChanged（）。
所以，基本上你可以在你的适配器类中有一个更新方法，比如说，
public void updateObject(int pos, byte[] byteArray){
//Assuming your Profile Object has some member to store this image data
friends.get(pos).setImageData(byteArray); //friends is the list in adapter class and setImageData may be the setter in your Profile object class
notifyDataSetChanged();
}
并且在getView（）中，您可以执行类似这样的操作
profileImageBitmap = BitmapManager
.getBitmapFromByteArray(friends.get(pos).getImageData);
friendImage.setImageBitmap(profileImageBitmap);