Question

有人可以告诉我为什么我在Cannot resolve symbol和on create方法on start时遇到mRssFeed错误？顺便说一句，这只是我的RSS Feed片段类。谢谢。

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class FeedFragmentPortrait extends android.support.v4.app.Fragment {

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    return inflater.inflate(R.layout.feed_fragment_portrait, container, false);

    View rootView = inflater.inflate(R.layout.feed_fragment_portrait, container, false);
    mRssFeed = (TextView) rootView.findViewById(R.id.rss_feed);
    return rootView;
}

@Override
public void onStart() {
    super.onStart();
    InputStream in = null;
    try {
        URL url = new URL("http://www.google.com/feed/main.xml");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        in = conn.getInputStream();
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        for (int count; (count = in.read(buffer)) != -1; ) {
            out.write(buffer, 0, count);
        }
        byte[] response = out.toByteArray();
        String rssFeed = new String(response, "UTF-8");
        mRssFeed.setText(rssFeed);
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (in != null) {
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

}

Answer 1

从oncreateView中删除此行 return inflater.inflate(R.layout.feed_fragment_portrait, container, false);

您在初始化mRssFeed之前返回

这就是为什么系统无法知道mRssFeed是什么

修改

此外，您应该在后台任务中执行所有api调用

@Override
public void onStart(Intent intent, int startId) {
    super.onStart(intent, startId);

        new DownloadInfo().execute("http://example.com/xxx.php");
}

和Asynctask就是这样的

class DownloadInfo extends AsyncTask<String, String, String> {
    @Override
    protected String doInBackground(String... url) {
        // constants 
    InputStream in = null;
    try {

    HttpURLConnection conn = ((HttpURLConnection) new URL(url[0]).openConnection();
    in = conn.getInputStream();
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    for (int count; (count = in.read(buffer)) != -1; ) {
        out.write(buffer, 0, count);
    }
    byte[] response = out.toByteArray();
    return new String(response, "UTF-8");

} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (in != null) {
        try {
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
        return null;
    }

    @Override
    protected void onPostExecute(String result) {

            if (result != null) {
               mRssFeed.setText(rssFeed);
            }
    }

无法解析文本和rss视图中的符号

1 个答案: