Java 使用回调异步加载listview中的图像
我正在我的应用程序中使用Parse,为了加载我的“配置文件”图像,我需要检索一个所谓的Parse文件。下载Parsefile时,它使用回调来通知何时完成。现在,这通常是一种很好的方法,但在使用Listview并使用异步任务下载图像时,我遇到了一个问题 问题如下: 在我的ListView适配器的Java 使用回调异步加载listview中的图像,java,android,android-listview,android-asynctask,parse-platform,Java,Android,Android Listview,Android Asynctask,Parse Platform,我正在我的应用程序中使用Parse,为了加载我的“配置文件”图像,我需要检索一个所谓的Parse文件。下载Parsefile时,它使用回调来通知何时完成。现在,这通常是一种很好的方法,但在使用Listview并使用异步任务下载图像时,我遇到了一个问题 问题如下: 在我的ListView适配器的getView方法中,我创建了一个异步任务并执行它,这个异步任务启动retrieveProfileImage(回调)函数。在回调中,我只是在UI线程上启动一个Runnable,用新的(检索到的图像)更新视图
getView
方法中,我创建了一个异步任务并执行它,这个异步任务启动retrieveProfileImage(回调)
函数。在回调中,我只是在UI线程上启动一个Runnable,用新的(检索到的图像)更新视图中的ImageView。然而,问题似乎是,一旦我开始AsyncTask,视图就会返回。因此,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说明我的问题
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);
}
}
我希望有人能帮我做这件事
问候,
蒂姆这个怎么样
在为listview设置适配器的MainActivity中使用AsyncTask,而不是在adapter类中使用AsyncTask。在回调或postExecute中的done方法中,更新对象并调用notifyDataSetChanged()
所以,本质上你可以在你的适配器类中有一个update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();
}
在getView()中,可以执行以下操作
profileImageBitmap = BitmapManager
.getBitmapFromByteArray(friends.get(pos).getImageData);
friendImage.setImageBitmap(profileImageBitmap);
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();
}
更新
最后一天,我发现了一个新的解决方案,您可以通过下面的代码获得和解析对象相关的用户数据,并在模型类中做了一些更改
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();
}
}
});
}
对像Universal Image Loader和毕加索这样的库使用延迟加载。使用UIL@Raghunandan问题是,我不能使用URL。我没有图像URL,检索图像(位图)的唯一方法是使用回调。解析库将我限制在那里。
ParseFile fileObject = (ParseFile) object.get("image_file");
User user = new User();
user = (User) ParseUser.getCurrentUser();
user.setProfile_pic_url(fileObject.getUrl().toString());
user.saveInBackground();
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();
}
}
});
}
@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);
}
}