为什么这不适用于 ICS [重复]答案

【问题标题】：Why this doesn't work for ICS [duplicate]为什么这不适用于 ICS [重复]
【发布时间】：2012-06-23 09:20:33
【问题描述】：

可能重复：
Strange NetworkOnMainThreadException in Android app?
Trying To Upload To Dropbox: NetworkOnMainThreadException?

我使用下面的代码从 url 读取 HTML 内容。这适用于 2.3.3，但是当我尝试运行相同的代码时，它不适用于 ICS。

我正在尝试将这些 html 内容附加到 edittext。但是当我在 ICS 上运行代码时，它总是为空。可能是什么问题？

public class Quiz1Activity extends Activity {
    private static BufferedReader reader = null;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

EditText ed = (EditText) findViewById(R.id.editText1);

        try {
            ed.append(getStringFromUrl("http://www.google.com"));
            //getInputStreamFromUrl("").close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public static InputStream getInputStreamFromUrl(String url){
           InputStream contentStream = null;

           try{
             HttpClient httpclient = new DefaultHttpClient();
             HttpResponse response = httpclient.execute(new HttpGet(url));
             contentStream = response.getEntity().getContent();
           } catch(Exception e){
              e.printStackTrace();
           }
           System.out.println("Content stream is " + contentStream);
           return contentStream;
        }

    public static String getStringFromUrl(String url) throws IOException{
        reader = new BufferedReader(new InputStreamReader(getInputStreamFromUrl(url)));

        StringBuilder sb = new StringBuilder();
        try{
        String line = null;
        while((line = reader.readLine()) != null)
        {
            sb.append(line);
        }    
        }catch (IOException e){
         e.printStackTrace();
        }
       getInputStreamFromUrl(url).close();
        return sb.toString();
    }
}

【问题讨论】：

在这里阅读我的答案stackoverflow.com/a/10892925/1321873
+1 拉杰什。在 ICS 中，如果您没有实现 AsyncTask 或 AsyncTaskLoader，则会出现 NetworkOnMainThreadException 异常。
您最好尝试查看 Logcat 输出。

标签： java android html android-4.0-ice-cream-sandwich

【解决方案1】：

但当我在 ICS 上运行代码时，它总是为空。可能是什么问题？

问题是 ICS 不允许您在主线程上执行异步任务，因此请将您的异步移动到新线程中。

您应该在单独的线程中移动以下代码。

public static InputStream getInputStreamFromUrl(String url){
           InputStream contentStream = null;

           try{
             HttpClient httpclient = new DefaultHttpClient();
             HttpResponse response = httpclient.execute(new HttpGet(url));
             contentStream = response.getEntity().getContent();
           } catch(Exception e){
              e.printStackTrace();
           }
           System.out.println("Content stream is " + contentStream);
           return contentStream;
        }

【讨论】：

【解决方案2】：

就像@Vipul Shah 所说，你必须将 getInputStreamFromUrl() 移动到另一个线程中使用异步任务，这是在 ICS 上工作的：

package com.home.anas;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.EditText;

public class WebPageContentActivity extends Activity {
    private EditText ed;


/** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ed = (EditText) findViewById(R.id.editText1);
        readWebpage();
    }

    private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            String response = "";
            for (String url : urls) {
                DefaultHttpClient client = new DefaultHttpClient();
                HttpGet httpGet = new HttpGet(url);
                try {
                    HttpResponse execute = client.execute(httpGet);
                    InputStream content = execute.getEntity().getContent();

                    BufferedReader buffer = new BufferedReader(new InputStreamReader(content));
                    String s = "";
                    while ((s = buffer.readLine()) != null) {
                        response += s;
                    }

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            return response;
        }

        @Override
        protected void onPostExecute(String result) {
            ed.setText(result);
        }
    }

    public void readWebpage() {
        DownloadWebPageTask task = new DownloadWebPageTask();
        task.execute(new String[] { "http://www.google.com" });

    }
}

【讨论】：