我是 android/java 的初学者。基本上我想将 XML 数据显示到 ListView 中，但是当我运行应用程序时，ListView 根本不显示。我猜想我一定对 ListView 做错了什么，但我就是不知道是什么。这是我的源代码
我知道我的代码有点困惑。我正在研究这个。
content_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.example.azrie.dummyvoice.MainActivity"
tools:showIn="@layout/app_bar_main">
<ListView
android:id="@+id/list_item"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</ListView>
</RelativeLayout>
activity_listview.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:weightSum="1">
<TextView
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/title_text"
android:layout_weight="0.09" />
<TextView
android:layout_width="80dp"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="Small Text"
android:id="@+id/date_text"
android:layout_gravity="right"
android:layout_weight="0.05" />
</LinearLayout>
MainActivity.java(onCreate)
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
listView = (ListView) findViewById(R.id.list_item);
//new ReadRSS(this,"http://www.thestar.com.my/rss/editors-choice/main/").execute();
//new ReadRSS(this,"http://www.sciencemag.org/rss/news_current.xml").execute();
//new ReadRSS(this,"https://www.androidpit.com/feed/main.xml").execute();
new ReadRSS(this, listView, "http://malaysiakini.com/en/news.rss").execute();
}
读取RSS.java
public class ReadRSS extends AsyncTask<Void, Void, Void> {
//Initialize progress dialog
Context context;
String address;
ProgressDialog progressDialog;
XmlPullParserFactory xmlPullParserFactory;
volatile boolean parsingComplete = true;
ArrayList<FeedItem> feedItems = new ArrayList<>();
ListView listView;
public ReadRSS(Context context, ListView listView, String retrieveAddress) {
//Create a new progress dialog
this.listView = listView;
this.address = retrieveAddress;
this.context = context;
progressDialog = new ProgressDialog(context);
progressDialog.setMessage("Loading....");
}
// Runs in UI before background thread is called
@Override
protected void onPreExecute() {
//Display progress dialog
progressDialog.show();
super.onPreExecute();
}
// This is run in a background thread
@Override
protected Void doInBackground(Void... voids) {
fetchXML();
return null;
}
// This is called from background thread but runs in UI
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
// This runs in UI when background thread finishes
@Override
protected void onPostExecute(Void aVoid) {
//Dismiss progress dialog
super.onPostExecute(aVoid);
progressDialog.dismiss(); if(listView!=null) {
MyAdapter adapter = new MyAdapter(context,feedItems);
listView.setAdapter(adapter);
}
}
public void parseXMLAndStoreIt(XmlPullParser myParser) {
int event;
String text=null;
try {
event = myParser.getEventType();
FeedItem item = new FeedItem();
while (event != XmlPullParser.END_DOCUMENT) {
String tagName = myParser.getName();
switch (event){
case XmlPullParser.START_TAG:
if(tagName.equalsIgnoreCase("item")){
int eventChild = myParser.next();
while(eventChild != XmlPullParser.END_DOCUMENT){
String tagNameChild = myParser.getName();
switch (eventChild){
case XmlPullParser.START_TAG:
break;
case XmlPullParser.TEXT:
text = myParser.getText();
break;
case XmlPullParser.END_TAG:
if(tagNameChild.equalsIgnoreCase("title")){
item.setTitle(text);
}
else if(tagNameChild.equalsIgnoreCase("link")){
item.setLink(text);
}
else if(tagNameChild.equalsIgnoreCase("description")){
String plain = Html.fromHtml(text).toString();
//stripHtml(text);
item.setDescription(plain);item.getDescription());
}
else if(tagNameChild.equalsIgnoreCase("pubDate")){
item.setPubDate(text); //Log.d("pudDate",text);
}
else if(tagNameChild.equalsIgnoreCase("media:thumbnail") || tagNameChild.equalsIgnoreCase("media:content") || tagName.equalsIgnoreCase("enclosure")){
if(myParser.getAttributeValue(null,"url") != null) {
item.setThumbnailUrl(text);item.getThumbnailUrl());
//Log.d("ItemThumbnailUrl",myParser.getAttributeValue(null,"url"));
}
}
else if(tagNameChild.equalsIgnoreCase("item")){
}
break;
}
}
}
break;
case XmlPullParser.TEXT:
break;
case XmlPullParser.END_TAG:
break;
}
event = myParser.next();
}
parsingComplete = false;
}
catch (Exception e) {
e.printStackTrace();
}
}
public void fetchXML(){
Thread thread = new Thread(new Runnable(){
@Override
public void run() {
try {
URL url = new URL(address);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(10000 );
conn.setConnectTimeout(15000 );
conn.setRequestMethod("GET");
conn.setDoInput(true);
// Starts the query
conn.connect();
InputStream stream = conn.getInputStream();
xmlPullParserFactory = XmlPullParserFactory.newInstance();
XmlPullParser myparser = xmlPullParserFactory.newPullParser();
myparser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
myparser.setInput(stream, null);
parseXMLAndStoreIt(myparser);
stream.close();
}
catch (Exception e) {
}
}
});
thread.start();
}
}
MyAdapter.java
public class MyAdapter extends BaseAdapter {
Context context;
ArrayList<FeedItem> feedItems;
LayoutInflater inflater = null;
public MyAdapter(Context context, ArrayList<FeedItem> feedItems){
this.context = context;
this.feedItems = feedItems;
inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
return feedItems.size();
}
@Override
public Object getItem(int i) {
return i;
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int i, View view, ViewGroup viewGroup) {
ViewHolder viewHolder;
if (view == null) {
viewHolder = new ViewHolder();
view = inflater.inflate(R.layout.activity_listview, viewGroup, false);
viewHolder.text_title = (TextView) view.findViewById(R.id.title_text);
viewHolder.text_date = (TextView) view.findViewById(R.id.date_text);
view.setTag(viewHolder);
}
else{
viewHolder = (ViewHolder) view.getTag();
}
FeedItem objFeed = feedItems.get(i);
viewHolder.text_title.setText(objFeed.getTitle());
viewHolder.text_date.setText(objFeed.getPubDate());
return view;
}
static class ViewHolder{
TextView text_title;
TextView text_date;
}
}
最佳答案
您可以尝试一下下面的代码吗？
@Override
protected void onPostExecute(Void aVoid) {
//Dismiss progress dialog
super.onPostExecute(aVoid);
progressDialog.dismiss();
// ADD LINES BELOW
if(listView != null) {
MyAdapter adapter = new MyAdapter(context,android.R.layout.simple_list_item_1,feedItems);
listView.setAdapter(adapter);
}
}
您的 ListView View 未显示，因为您没有为其设置任何适配器。这样，ListView就没有要显示的项目了。
关于java - ListView 不会显示 - 空白屏幕，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38554045/