Android HttpURLConnection 仅在硬件设备上连接错误（不在模拟器中）

Question

我是 android 开发的新手，我正在寻找一种将图片和文本从互联网下载到我的应用程序的方法。我找到了一些教程并将代码包含在我的项目中。当我在模拟器上运行应用程序时，一切正常。如果我在我的设备（三星 Galaxy S4）上运行该应用程序，我会收到“连接错误”（在 HttpDownload.java 中），我不知道为什么，因为在其他应用程序中互联网正在运行。

感谢您的帮助。

代码如下：

HttpDownload.java：

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;

public class HttpDownload extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    private InputStream OpenHttpConnection(String urlString)
            throws IOException
    {
        InputStream in = null;
        int response = -1;

        URL url = new URL(urlString);
        URLConnection conn = url.openConnection();

        if (!(conn instanceof HttpURLConnection))
            throw new IOException("Not an HTTP connection");

        try{
            HttpURLConnection httpConn = (HttpURLConnection) conn;
            httpConn.setAllowUserInteraction(false);
            httpConn.setInstanceFollowRedirects(true);
            httpConn.setRequestMethod("GET");
            httpConn.connect();

            response = httpConn.getResponseCode();
            if (response == HttpURLConnection.HTTP_OK) {
                in = httpConn.getInputStream();
            }
        }
        catch (Exception ex)
        {
            throw new IOException("Error connecting");
        }
        return in;
    }

    public Bitmap DownloadImage(String URL)
    {
        Bitmap bitmap = null;
        InputStream in = null;
        try {
            in = OpenHttpConnection(URL);
            bitmap = BitmapFactory.decodeStream(in);
            in.close();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        return bitmap;
    }

    public String DownloadText(String URL)
    {
        int BUFFER_SIZE = 2000;
        InputStream in = null;
        try {
            in = OpenHttpConnection(URL);
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
            return "";
        }

        InputStreamReader isr = new InputStreamReader(in);
        int charRead;
        String str = "";
        char[] inputBuffer = new char[BUFFER_SIZE];
        try {
            while ((charRead = isr.read(inputBuffer))>0)
            {
                //---convert the chars to a String---
                String readString =
                        String.copyValueOf(inputBuffer, 0, charRead);
                str += readString;
                inputBuffer = new char[BUFFER_SIZE];
            }
            in.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "";
        }
        return str;
    }

}

main_activity：

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;


public class MainActivity extends ActionBarActivity {

    TextView meinText;
    ImageView meinBild;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        meinBild = (ImageView)findViewById(R.id.meinBild);
        meinText = (TextView)findViewById(R.id.meinText);
    }

    public void laden (View view) {
        HttpDownload download = new HttpDownload();
        meinBild.setImageBitmap(download.DownloadImage("http://www.queness.com/resources/images/png/apple_ex.png"));
    }

}

Logcat：

    Local Branch:
    Remote Branch:
    Local Patches:
    Reconstruct Branch:
04-29 16:36:28.757  32038-32038/com.example.itsme.internetdaten D/OpenGLRenderer﹕ Enabling debug mode 0
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ java.io.IOException: Error connecting
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at com.example.itsme.internetdaten.HttpDownload.OpenHttpConnection(HttpDownload.java:50)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at com.example.itsme.internetdaten.HttpDownload.DownloadImage(HttpDownload.java:60)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at com.example.itsme.internetdaten.MainActivity.laden(MainActivity.java:29)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at java.lang.reflect.Method.invokeNative(Native Method)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:515)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at android.view.View$1.onClick(View.java:3964)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at android.view.View.performClick(View.java:4633)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at android.view.View$PerformClick.run(View.java:19330)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at android.os.Handler.handleCallback(Handler.java:733)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:95)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at android.os.Looper.loop(Looper.java:157)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5356)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at java.lang.reflect.Method.invokeNative(Native Method)
04-29 16:36:53.862  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:515)
04-29 16:36:53.882  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
04-29 16:36:53.882  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
04-29 16:36:53.882  32038-32038/com.example.itsme.internetdaten W/System.err﹕ at dalvik.system.NativeStart.main(Native Method)
04-29 16:36:53.882  32038-32038/com.example.itsme.internetdaten I/Choreographer﹕ Skipped 61 frames!  The application may be doing too much work on its main thread.

清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.itsme.internetdaten" >

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

改变：

  catch (Exception ex)
        { 
            throw new IOException("Error connecting");
        } 

到

catch (Exception ex)
        { 
           Log.d("error", ex.toString());
        } 

并分享发生的确切异常

还可以从互联网下载图像，您可以简单地使用：

 URL url = new URL(address);
 Object content = url.getContent();

第三，可能是您没有活动的互联网连接而引发异常。

Answer 2

  HttpDownload download = new HttpDownload();

由于 HttpDownload 是一个 Activity，你不能以这种方式实例化它。您必须使用 Intent 来启动 Activity。

Answer 3

所以问题是网络调用在 Main_Activity（一个 UI 活动）中。就像凯已经说过的那样，这不再起作用了。为什么它在我的模拟器中工作很简单：他使用的是 Android 2.3，这是可能的。

更多信息：

http://www.androiddesignpatterns.com/2012/06/app-force-close-honeycomb-ics.html

How to fix android.os.NetworkOnMainThreadException?

我更改了我的代码，一切正常：

下载.java

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.ExecutionException;

public class Download {

    public Bitmap downloadBild (String URL) {
        Bitmap bild;
        try {
            bild = new DownloadBildTask().execute(URL).get();
        } catch (InterruptedException e) {
            bild = null;
        } catch (ExecutionException e) {
            bild = null;
        }
        return bild;
    }

    public String downloadText (String URL) {
        String ergebnis;
        try {
            ergebnis = new DownloadTextTask().execute(URL).get();
        } catch (InterruptedException e) {
            ergebnis = "Keine Daten";
        } catch (ExecutionException e) {
            ergebnis = "Keine Daten";
        }
        return ergebnis;
    }

    private class DownloadTextTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            try {
                InputStream inputStream = downloadInhalt(urls[0]);
                String Text = InputStreamToString(inputStream);
                inputStream.close();
                return Text;

            } catch (IOException e) {
                return "Unable to retrieve web page. URL may be invalid.";
            }
        }
    }

    private class DownloadBildTask extends AsyncTask<String, Void, Bitmap> {
        @Override
        protected Bitmap doInBackground(String... urls) {
            try {
                InputStream inputStream = downloadInhalt(urls[0]);
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                inputStream.close();
                return bitmap;

            } catch (IOException e) {
                return null;
            }
        }
    }

    private InputStream downloadInhalt(String myurl) throws IOException {
        InputStream is;

        try {
            URL url = new URL(myurl);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(10000 /* milliseconds */);
            conn.setConnectTimeout(15000 /* milliseconds */);
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            conn.connect();
            is = conn.getInputStream();
            return is;
        } catch (Exception e) {
            return null;
        }
    }

    private String InputStreamToString(InputStream stream) throws IOException {
        BufferedReader r = new BufferedReader(new InputStreamReader(stream));
        StringBuilder total = new StringBuilder();
        String line;
        while ((line = r.readLine()) != null) {
            total.append(line);
        }
        return total.toString();
    }

}

Main_Activity

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;


public class MainActivity extends ActionBarActivity {

    TextView meinText;
    ImageView meinBild;
    Download download = new Download();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        meinBild = (ImageView)findViewById(R.id.meinBild);
        meinText = (TextView)findViewById(R.id.meinText);
    }

    public void textLaden(View view) {
        String stringUrl = "http://www.openligadb.de/api/getmatchdata/bl1/2014/15";
        meinBild.setImageBitmap(null);
        meinText.setText(download.downloadText(stringUrl));
    }

    public void bildLaden(View view) {
        String stringUrl = "http://www.queness.com/resources/images/png/apple_ex.png";
        meinText.setText("");
        meinBild.setImageBitmap(download.downloadBild(stringUrl));
    }

}

在清单中：

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

感谢您的帮助