Question

我正在尝试构建一个RSS阅读器并将rss feed fetch作为ansyctask，返回列表视图中的提要，或返回“无网络连接”的文本视图但应用程序仍然崩溃，我不知道什么是错的，你能帮忙吗。

这是代码：

package rss;

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
import android.widget.TextView;

import com.enporan.polytechoran.R;

public class RSSActivity extends ActionBarActivity {
    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_news);


           rssfeedget alpha = new rssfeedget();
          alpha.execute();



    }

    private class rssfeedget extends AsyncTask<String, Void, FeedSource> {


        protected void onPreExecute() {

        }

        @Override
        protected FeedSource doInBackground(String... params) {
            FeedSource f = new HttpFeedSource();
            if(f!=null)
                return f;
            else {
               return null;
            }
        }

        @Override
        protected void onPostExecute(FeedSource result){
            ListView rssItemList = (ListView) findViewById(R.id.rssListview);
            rssItemList.setVerticalFadingEdgeEnabled(true);
            if(doInBackground()==null){
                TextView tv= (TextView) findViewById(R.id.textView2);
                tv.setText("No internet Connection...");

            }
            else{

                RSSItemAdapter adapter = new RSSItemAdapter(getApplicationContext(), R.layout.rssitem, doInBackground().getFeed());
                rssItemList.setAdapter(adapter);
            }

        }
    }




    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_news, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

}

Answer 1

正如@coelho指出的那样，FeedSource.getFeed()不应该在UI线程中执行。您现在必须在UI线程内执行onPreExecute和onPostExecute方法，而doInBackground方法不是。

您可以执行以下操作：在AsyncTask类中，添加一个私有成员：private List<RSSItem> result;（在此处用getFeed返回的集合类型替换RSSItem。）

然后，更新doInBackground：

FeedSource f = new HttpFeedSource();
if (f != null)
    return f;
else {
    this.result = f.getFeed(); // Execute getFeed in doInBackground
    return null;
}

然后，在onPostExecute方法中，您将能够使用此私有成员：

RSSItemAdapter adapter = new RSSItemAdapter(getApplicationContext(), R.layout.rssitem, this.result);

Answer 2

以下是代码：

private class rssfeedget extends AsyncTask<String, Void, List<RSSItem>> {
    private List<RSSItem> result;

    protected void onPreExecute() {

    }

    @Override
    protected List<RSSItem> doInBackground(String... params) {
        FeedSource f = new HttpFeedSource();
        if(f.getFeed()==null)
            return null;
        else {
            this.result = f.getFeed(); // Execute getFeed in doInBackground
            return result;
        }
    }

    @Override
    protected void onPostExecute(List<RSSItem> result){


        if(doInBackground()==null){
            TextView tv= (TextView) findViewById(R.id.textView2);
            tv.setText("No internet Connection...");

        }
        else{
            ListView rssItemList = (ListView) findViewById(R.id.rssListview);
            rssItemList.setVerticalFadingEdgeEnabled(true);
            RSSItemAdapter adapter = new RSSItemAdapter(getApplicationContext(), R.layout.rssitem, this.result);
            rssItemList.setAdapter(adapter);
        }

    }
}

Android AsyncTask活动崩溃RSS阅读器

2 个答案: