我没有从代码中获得所需的输出。
我使用XML DOM解析从链接中获取标题，pubdate，描述和图像：http://autosportsindia.com/feed
通过编写的代码，没有获得输出。即使Logcat显示正从链接中提取数据。
请告诉我代码中的错误是什么。建议使用代码或链接进行XML解析的任何其他方法。
public class MainActivity extends AppCompatActivity implements ResultsCallBack {
PlaceholderFragment taskFragment;
ListView articlesListView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
taskFragment = new PlaceholderFragment();
getSupportFragmentManager().beginTransaction().add(taskFragment, "MyFragment").commit();
} else {
taskFragment = (PlaceholderFragment) getSupportFragmentManager().findFragmentByTag("MyFragment");
}
taskFragment.startTask();
articlesListView = (ListView) findViewById(R.id.articlesListView);
}
@Override
public void onPreExecute() {
}
@Override
public void onPostExecute(ArrayList<HashMap<String, String>> results) {
articlesListView.setAdapter(new MyAdapter(this, results));
}
public static class PlaceholderFragment extends Fragment {
AutoSportsIndia downloadTask;
ResultsCallBack callBack;
public PlaceholderFragment() {
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
callBack = (ResultsCallBack) activity;
if(downloadTask!=null)
{
downloadTask.onAttach(callBack);
}
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setRetainInstance(true);
}
public void startTask() {
if (downloadTask != null) {
downloadTask.cancel(true);
} else {
downloadTask = new AutoSportsIndia(callBack);
downloadTask.execute();
}
}
@Override
public void onDetach() {
super.onDetach();
callBack = null;
if(downloadTask!=null) {
downloadTask.onDetach();
}
}
}
public static class AutoSportsIndia extends AsyncTask<Void, Void, ArrayList<HashMap<String, String>>> {
ResultsCallBack callBack =null;
public AutoSportsIndia(ResultsCallBack callBack) {
this.callBack = callBack;
}
public void onAttach(ResultsCallBack callBack) {
this.callBack = callBack;
}
public void onDetach() {
callBack = null;
}
protected void onPreExecute() {
if(callBack!=null)
{
callBack.onPreExecute();
}
}
@Override
protected ArrayList<HashMap<String, String>> doInBackground(Void... params) {
String downloadURL = "http://autosportsindia.com/feed";
ArrayList<HashMap<String, String>> results = new ArrayList<>();
try {
URL url = new URL(downloadURL);
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("GET");
InputStream inputStream = connection.getInputStream();
processXML(inputStream);
} catch (Exception e) {
L.m(e + "");
}
return results;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
if(callBack!=null)
{
callBack.onPostExecute(result);
}
}
public ArrayList<HashMap<String, String>> processXML(InputStream inputStream) throws Exception {
DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
Document xmlDocument = documentBuilder.parse(inputStream);
Element rootElement = xmlDocument.getDocumentElement();
L.m("" + rootElement.getTagName());
NodeList itemsList = rootElement.getElementsByTagName("item");
NodeList itemChildren = null;
Node currentItem = null;
Node currentChild = null;
int count = 0;
ArrayList<HashMap<String, String>> results = new ArrayList<>();
HashMap<String, String> currentMap = null;
for (int i = 0; i < itemsList.getLength(); i++) {
currentItem = itemsList.item(i);
itemChildren = currentItem.getChildNodes();
currentMap = new HashMap<>();
for (int j = 0; j < itemChildren.getLength(); j++) {
currentChild = itemChildren.item(j);
if (currentChild.getNodeName().equalsIgnoreCase("title")) {
currentMap.put("title", currentChild.getTextContent());
String temp="title: "+currentChild.getTextContent();
L.m(temp);
}
if (currentChild.getNodeName().equalsIgnoreCase("pubDate")) {
String temp1="pubDate: "+currentChild.getTextContent();
currentMap.put("pubDate", currentChild.getTextContent());
L.m(temp1);
}
if (currentChild.getNodeName().equalsIgnoreCase("description")) {
currentMap.put("description", currentChild.getTextContent());
String temp="description: "+currentChild.getTextContent();
L.m(temp);
}
if (currentChild.getNodeName().equalsIgnoreCase("media:thumbnail")) {
count++;
if (count == 2) {
L.m(currentChild.getAttributes().item(0).getTextContent());
currentMap.put("imageURL", currentChild.getAttributes().item(0).getTextContent());
}
}
if (currentMap != null && !currentMap.isEmpty()) {
results.add(currentMap);
}
}
count = 0;
}
return results;
}
}
}
interface ResultsCallBack {
public void onPreExecute();
public void onPostExecute(ArrayList<HashMap<String, String>> results);
}
class MyAdapter extends BaseAdapter {
ArrayList<HashMap<String, String>> dataSource = new ArrayList<>();
Context context;
LayoutInflater layoutInflater;
public MyAdapter(Context context, ArrayList<HashMap<String, String>> dataSource) {
this.context = context;
this.dataSource = dataSource;
layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
return dataSource.size();
}
@Override
public Object getItem(int position) {
return dataSource.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
MyHolder holder = null;
if(row == null)
{
row = layoutInflater.inflate(R.layout.custom_view, parent, false);
holder = new MyHolder(row);
row.setTag(holder);
}
else
{
holder = (MyHolder)row.getTag();
}
HashMap<String, String> currentItem = dataSource.get(position);
holder.articleTitleText.setText(currentItem.get("title"));
holder.articlePublishedDateText.setText(currentItem.get("pubDate"));
// holder.articleImage.setImageURI(Uri.parse(currentItem.get("imageURL")));
holder.articleDescriptionText.setText(currentItem.get("description"));
return row;
}
}
class MyHolder {
TextView articleTitleText;
TextView articlePublishedDateText;
ImageView articleImage;
TextView articleDescriptionText;
public MyHolder(View view) {
articleTitleText = (TextView)
view.findViewById(R.id.articleTitleText);
articlePublishedDateText = (TextView) view.findViewById(R.id.articlePublishedDate);
articleImage = (ImageView) view.findViewById(R.id.articleImage);
articleDescriptionText = (TextView) view.findViewById(R.id.articleDescriptionText);
}
}
XML页面： -
activity_main.xml中
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/articlesListView"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
custom_view.xml
<TextView
android:id="@+id/articleTitleText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:padding="12dp"
android:text="Title"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#444"/>
<TextView
android:id="@+id/articlePublishedDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_below="@+id/articleTitleText"
android:paddingBottom="4dp"
android:paddingLeft="12dp"
android:paddingRight="12dp"
android:paddingTop="4dp"
android:text="Date"
android:textAppearance="?android:attr/textAppearanceSmall"
android:textColor="#444"/>
<View
android:id="@+id/separator1"
android:layout_width="match_parent"
android:layout_height="2dp"
android:layout_below="@+id/articlePublishedDate"
android:layout_marginLeft="12dp"
android:layout_marginRight="12dp"
android:background="#e67e22"/>
<ImageView
android:id="@+id/articleImage"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/separator1"
android:scaleType="fitCenter"
android:src="@drawable/ic_launcher"/>
<TextView
android:id="@+id/articleDescriptionText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/articleImage"
android:padding="12dp"
android:text="Description"
android:textColor="#444"/>
答案 0 :(得分：0)
processXML方法构建并返回ArrayList<HashMap<String, String>>。
在doInBackground方法中调用它，但返回值被丢弃。 doInBackground然后返回一个本地results对象，这是一个空列表。
如果您已经通过processXML和doInBackground方法进行了调试，那么您会看到这一点。当我在评论中询问“您是否尝试调试代码，单步执行并查看正在处理的值”时，您显然没有。