我犯了一点错误,我不知道怎么出去。
最初,代码是这样的,它可以工作:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // getting XML
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
// looping through all item nodes <item>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_NAME, parser.getValue(e, KEY_NAME));
map.put(KEY_COST, parser.getValue(e, KEY_COST));
// adding HashList to ArrayList
menuItems.add(map);
}
// Adding menuItems to ListView
ListAdapter adapter = new SimpleAdapter(this, menuItems,
R.layout.list_item,
new String[] { KEY_NAME, KEY_COST }, new int[] {
R.id.name, R.id.cost });
setListAdapter(adapter);
}
既然我做了另一项活动,我就错了。
我稍微研究了一下,发现你需要异步执行任务,但不知道如何结束。
这是密码:
public class TaskAsincrono extends AsyncTask<ArrayList<String>, Void, ArrayList<String>> {
@Override
protected void onPreExecute(){
}
@Override
protected void onProgressUpdate(Void[] values) {
};
@Override
protected ArrayList<String> doInBackground(ArrayList<String>... params) {
ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // getting XML
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
// looping through all item nodes <item>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_NAME, parser.getValue(e, KEY_NAME));
map.put(KEY_COST, parser.getValue(e, KEY_COST));
// adding HashList to ArrayList
menuItems.add(map);
}
return menuItems;
}
@Override
protected void onPostExecute(ArrayList<String> success) {
//se l'alert è visibile viene rimosso
if(dialog.isShowing()) dialog.dismiss();
ListAdapter adapter = new SimpleAdapter(this, menuItems,
R.layout.list_item,
new String[] { KEY_NAME, KEY_COST }, new int[] {
R.id.name, R.id.cost });
setListAdapter(adapter);
}
@Override
protected void onCancelled() {
mAuthTask = null;
}
}
我该怎么办?
非常感谢
最佳答案
就按照拉古南丹的建议去做。
如果返回类型是arraylist则返回arraylist的原因。
更改为:
public class TaskAsincrono extends AsyncTask<ArrayList<String>, Void, ArrayList<String>>
到
public class TaskAsincrono extends AsyncTask<String, Void, ArrayList<HashMap<String,String>>>
还有:
@Override
protected ArrayList<String> doInBackground(ArrayList<String>... params)
到
@Override
protected ArrayList<HashMap<String,String>> doInBackground(String... params)
我认为程序中的doinbackground()需要url作为参数,因此可以将其从arraylist更改为simple string[]。
异步任务框架类似于:
public class TaskAsincrono extends AsyncTask<String, Void, ArrayList<HashMap<String, String>>> {
@Override,
protected void onPreExecute(){
//what you want to do before AsyncTask execution(runs on UI thread)
......................
}
@Override
protected void onProgressUpdate(Void[] values) {
//About updates..........
};
@Override
protected ArrayList<HashMap<String, String>> doInBackground(String... params) {
ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();
for (String extraUrl : params) {
//do all stuffs here
//like parse xml stuffs
//put them to hashmap then add the hashmap to arraylist(menuitems)....
}
return menuItems;
}
}
现在您可以从AsyncTask外部(比如button onclick或oncreate())获取ArrayList,如下所示。
TaskAsincrono task = new TaskAsincrono ();
try {
ArrayList<HashMap<String, String>> arr = new ArrayList<HashMap<String, String>>();
arr = task.execute(URL).get();
也可以按照Developer Link For AsyncTask了解更多信息。
万事如意