這是幾小時我搜索的東西,但它似乎並沒有幫助.. Android Studio不會啓動任何錯誤,但屏幕保持空白。爲什麼?Android之後notifyDataSetChanged ListView保持空白
package org.newapp;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import org.xml.sax.SAXException;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import saxrssreader.*;
public class MainActivity extends Activity {
private ArrayAdapter<RssItem> rssItemsArrayAdapter;
ListView codeLearnLessons;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RssItem[] rssItems = new RssItem[]{};
rssItemsArrayAdapter = new ArrayAdapter<RssItem>(this, android.R.layout.simple_list_item_1, rssItems);
new WebCall().execute(rssItems);
codeLearnLessons = (ListView)findViewById(R.id.listView1);
codeLearnLessons.setAdapter(rssItemsArrayAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
private class WebCall extends AsyncTask<RssItem, Void, Void> {
@Override
protected Void doInBackground(RssItem... items) {
URL url = null;
try {
url = new URL("http://www.somewpsite.com/feed");
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
ArrayList<RssItem> listItems = RssReader.read(url).getRssItems();
items = listItems.toArray(new RssItem[listItems.size()]);
final int l = items.length;
runOnUiThread(new Runnable() {
@Override
public void run() {
codeLearnLessons.invalidateViews();
rssItemsArrayAdapter.notifyDataSetChanged();
Log.i("rec", "rec" + l);
}
});
} catch (SAXException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPreExecute() {
/*ProgressDialog mDialog = new ProgressDialog(MainActivity.this);
mDialog.setMessage("Please wait...");
mDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
mDialog.setIndeterminate(true);
mDialog.setCancelable(false);
mDialog.show();*/
}
}
}
RssItems可能爲空,所以適配器沒有要顯示的數據。檢查webCall.execute()方法後rssItems的長度。 –
它在這裏簽入:Log.i(「rec」,「rec」+ l); l是15 – LowFieldTheory
再次檢查rssItems _After_ webCall.execute()方法的長度。它將爲0,正如其他人在下面所述,因爲您正在創建一個新數組而不是更新rssItems數組。 –