这个简单的应用程序从用户获取一个标签,并在ListView中显示与标签匹配的前10个闪烁图像。我使用了this简单教程,我只修改了它,因此可以使用闪烁搜索,而不是硬编码链接。它工作但不知何故它在一些视图中一个接一个地加载图像。因此用户可以看到视图中的图像会发生一段时间的变化。如果用户滚动,它会再次重新加载它们。如果它是一个指针问题,我无法解决它。我将静态ViewHolder更改为非静态类,但没有任何更改。为什么会发生这种情况?如何解决?
主要课程:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" id="files" multiple>
<ol></ol>
适配器类:
public class FlickerSearchMain extends AppCompatActivity implements AdapterView.OnItemClickListener, View.OnClickListener{
private EditText tag;
private Button send;
private ListView listView;
ArrayList<ListItem> listData;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_flicker_search_main);
send = (Button) findViewById(R.id.send_button);
send.setOnClickListener(this);
tag = (EditText) findViewById(R.id.tag_input);
//ArrayList<ListItem> listData = getListData();
listView = (ListView) findViewById(R.id.list);
listView.setOnItemClickListener(this);
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
int itemPosition = position;
Toast.makeText(getApplicationContext(),
"Position :"+ itemPosition, Toast.LENGTH_SHORT)
.show();
}
@Override
public void onClick(View v) {
if(v == send){
String input = tag.getText().toString();
new FlickerRequest(this).execute(input);
}
}
private class FlickerRequest extends AsyncTask<String, Void, ArrayList<ListItem>>{
ArrayList<ListItem> elements_list;
Context context;
public FlickerRequest(Context context){
this.context = context;
this.elements_list = new ArrayList<ListItem>();
}
@Override
protected ArrayList<ListItem> doInBackground(String... params) {
String tag = params[0];
int SIZE = 10;
URL flicker;
URLConnection urlcon;
BufferedReader in = null;
try {
flicker = new URL("https://api.flickr.com/services/feeds/photos_public.gne?tags="
+ tag + "&format=json");
urlcon = flicker.openConnection();
in = new BufferedReader(new InputStreamReader(urlcon.getInputStream()));
String inputLine;
StringBuilder strbuilder = new StringBuilder();
in.skip(15);
while ((inputLine = in.readLine()) != null)
strbuilder.append(inputLine);
in.close();
JSONObject job = new JSONObject(strbuilder.toString());
JSONArray items = job.getJSONArray("items");
for(int i=0; i<SIZE; i++) {
JSONObject item = items.getJSONObject(i);
ListItem newdata = new ListItem();
newdata.setHeadline(item.getString("title"));
newdata.setAuthor(item.getString("author"));
newdata.setDate(item.getString("date_taken"));
newdata.setUrl(item.getJSONObject("media").getString("m"));
elements_list.add(newdata);
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return elements_list;
}
protected void onPostExecute(ArrayList<ListItem> result) {
if(listData == null) {
listData = result;
listView.setAdapter(new FlickerAdapter(context, listData));
}
else{
listData = result;
((BaseAdapter) listView.getAdapter()).notifyDataSetChanged();
}
}
}
}
AsynTask ImageLoader类
public class FlickerAdapter extends BaseAdapter {
private ArrayList<ListItem> listData;
private LayoutInflater layoutInflater;
public FlickerAdapter(Context context, ArrayList<ListItem> listData) {
this.listData = listData;
layoutInflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return listData.size();
}
@Override
public Object getItem(int position) {
return listData.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (convertView == null) {
convertView = layoutInflater.inflate(R.layout.list_row_layout, null);
holder = new ViewHolder();
holder.headlineView = (TextView) convertView.findViewById(R.id.title);
holder.authorView = (TextView) convertView.findViewById(R.id.author);
holder.dateView = (TextView) convertView.findViewById(R.id.date);
holder.imageView = (ImageView) convertView.findViewById(R.id.image);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
ListItem newsItem = listData.get(position);
holder.headlineView.setText(newsItem.getHeadline());
holder.authorView.setText("By, " + newsItem.getAuthor());
holder.dateView.setText(newsItem.getDate());
if (holder.imageView != null) {
new ImageDownloaderTask(holder.imageView).execute(newsItem.getUrl());
}
return convertView;
}
static class ViewHolder {
TextView headlineView;
TextView authorView;
TextView dateView;
ImageView imageView;
}
}
答案 0 :(得分:0)
您必须确保填充ImageView
的任务是ImageView
的最新任务,因为在ImageView
被回收之后,任务可能无法完成
这就是我的所作所为:
if (holder.imageView != null) {
Drawable placeholder = holder.imageView.getContext().getResources().getDrawable(R.drawable.penguin);
holder.imageView.setImageDrawable(placeholder);
ImageDownloaderTask task = new ImageDownloaderTask(holder.imageView);
holder.imageView.setTag(R.id.tag_key, task);
task.execute(newsItem.getUrl());
}
...
@Override
protected void onPostExecute(Bitmap bitmap) {
if (isCancelled()) {
bitmap = null;
}
if (bitmap != null && imageViewReference != null) {
ImageView imageView = imageViewReference.get();
if (imageView != null && imageView.getTag(R.id.tag_key) == this) {
imageView.setImageBitmap(bitmap);
imageView.setTag(R.id.tag_key, null);
}
}
}
在您的资源中:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<item name="tag_key" type="id" />
</resources>