发送http url请求

Question

我一直在尝试将Android开发人员页面中的HttpURLConnection代码段复制到我的项目中，只是为了查看是否可以建立Internet连接，并且每次运行该功能时，我的应用程序都会关闭。 我不知道为什么应用程序失败，任何帮助将不胜感激。 这段代码被放置在public class main extends Activity

main.java：

public void showHelp() throws IOException {
        URL url = new URL("http://www.android.com/");
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        try{
            InputStream in = new BufferedInputStream(urlConnection.getInputStream());
            //readStream(in);
        } finally{
            urlConnection.disconnect();
        }
    }

我评论了readStream，因为我认为转换可能是问题所在，但事实并非如此。 函数是：

private String readStream(InputStream is) {
        try {
          ByteArrayOutputStream bo = new ByteArrayOutputStream();
          int i = is.read();
          while(i != -1) {
            bo.write(i);
            i = is.read();
          }
          return bo.toString();
        } catch (IOException e) {
          return "";
        }
    }

如果发布日志猫结果有帮助，请告诉我。 我在android编程上还是一个新手，单击菜单选项时调用了第一个函数，但我认为这并不重要。 也

<uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

包含在android清单xml中

logcat错误：

02-04 21:27:14.468: W/dalvikvm(16978): threadid=1: thread exiting with uncaught exception (group=0x4208d2a0)
02-04 21:27:14.492: E/AndroidRuntime(16978): FATAL EXCEPTION: main
02-04 21:27:14.492: E/AndroidRuntime(16978): android.os.NetworkOnMainThreadException
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1118)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at java.net.InetAddress.getAllByName(InetAddress.java:214)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:315)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpEngine.connect(HttpEngine.java:310)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:289)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:239)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:273)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:168)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.MeadowEast.audiotest.MainActivity.showHelp(MainActivity.java:369)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.MeadowEast.audiotest.MainActivity.onOptionsItemSelected(MainActivity.java:97)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.app.Activity.onMenuItemSelected(Activity.java:2625)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1061)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.android.internal.view.menu.ListMenuPresenter.onItemClick(ListMenuPresenter.java:179)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.widget.AdapterView.performItemClick(AdapterView.java:298)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.widget.AbsListView.performItemClick(AbsListView.java:1280)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:3083)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.widget.AbsListView$1.run(AbsListView.java:3983)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.os.Handler.handleCallback(Handler.java:615)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.os.Looper.loop(Looper.java:137)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at android.app.ActivityThread.main(ActivityThread.java:4949)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at java.lang.reflect.Method.invokeNative(Native Method)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at java.lang.reflect.Method.invoke(Method.java:511)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1043)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:810)
02-04 21:27:14.492: E/AndroidRuntime(16978):    at dalvik.system.NativeStart.main(Native Method)

新的AsyncTask代码：

private abstract class myTask extends AsyncTask<String,Void,Void>{
        protected void doInBackground(String addressName) throws IOException {
            URL url = new URL(addressName);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            try{
                InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                //readStream(in);
            } finally{
                urlConnection.disconnect();
            }
         }

         protected void onProgressUpdate() {
             //do nothing
         }

         protected void onPostExecute() {
             //toast me
         }
    }

被称为：

 public void showHelp(){
        new myTask().execute("http://www.android.com/");
    }

我无法加载到android设备上，我遇到了问题：无法实例化类型main.mytask

Answer 1

我能想到的一个原因是您将网络通信置于主线程上。 您无权这样做。 您可以使用AsyncTask

http://developer.android.com/reference/android/os/AsyncTask.html 

为了进行测试，您可以在“主要活动”中添加以下内容，但这是不明智的做法。

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy); 

Answer 2

您应该在不同的线程中进行网络操作

Answer 3

看一下您的logcat，您的问题是NetworkOnMainThreadException，因此将您的urlconnection放入其他线程

new Thread(new Runnable() {

    @Override
    public void run() {
        // TODO Auto-generated method stub
        showHelp();
    }
}).start();