通过 android 连接到 web 服务时遇到问题

Question

我目前在 Android 上连接到我的网络服务时遇到问题。我正在使用 Jetty Web 服务并使用 ANT 构建它。在我的笔记本电脑上，它运行良好并显示我数据库中的项目。但它似乎无法连接到我的 Android 应用程序。附件是代码和LOGCAT报告。

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import android.app.Activity;
import android.os.Bundle;
import android.widget.EditText;
import android.widget.TextView;
public class Android2Servlet extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.dbtest);
TextView txtresp = (TextView)findViewById(R.id.servlet_response);

String url = "http://(MY LAPTOPS IP):8085/DB";
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet(url);
try{
System.out.println("About to execute");
HttpResponse response = client.execute(request);
String helpedResp=HttpUnpack.request(response); 
System.out.println(helpedResp); 
txtresp.setText(helpedResp);
System.out.println(response);
}catch(Exception ex){
txtresp.setText("Failed!");
ex.printStackTrace();
}
} }

HTTP Unpack 文件

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpResponse;
public class HttpUnpack {
public static String request(HttpResponse response){
String result = "";
try{ InputStream in = response.getEntity().getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
StringBuilder str = new StringBuilder();
String line = null;
while((line = reader.readLine()) != null){
str.append(line + "\n");
}
in.close();
result = str.toString();
}catch(Exception ex){
result = "Error retrieving response";
}
return result;
}
}

HTTP Unpack 和 Android2Servlet 不会导致任何错误，但文本框仅返回“失败！”。

LOGCAT 文件

W/System.err(1282): android.os.NetworkOnMainThreadException
W/System.err(1282):     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099)
W/System.err(1282):     at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
W/System.err(1282):     at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
W/System.err(1282):     at libcore.io.IoBridge.connect(IoBridge.java:112)
W/System.err(1282):     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
W/System.err(1282):     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
W/System.err(1282):     at java.net.Socket.connect(Socket.java:842)
W/System.err(1282):     at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
W/System.err(1282):     at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
W/System.err(1282):     at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
W/System.err(1282):     at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
W/System.err(1282):     at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
W/System.err(1282):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
W/System.err(1282):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
W/System.err(1282):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
W/System.err(1282):     at myFood.myFood.Android2Servlet.onCreate(Android2Servlet.java:24)
W/System.err(1282):     at android.app.Activity.performCreate(Activity.java:4465)
W/System.err(1282):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
W/System.err(1282):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
W/System.err(1282):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
W/System.err(1282):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
W/System.err(1282):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
W/System.err(1282):     at android.os.Handler.dispatchMessage(Handler.java:99)
W/System.err(1282):     at android.os.Looper.loop(Looper.java:137)
W/System.err(1282):     at android.app.ActivityThread.main(ActivityThread.java:4424)
W/System.err(1282):     at java.lang.reflect.Method.invokeNative(Native Method)
W/System.err(1282):     at java.lang.reflect.Method.invoke(Method.java:511)
W/System.err(1282):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
W/System.err(1282):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
W/System.err(1282):     at dalvik.system.NativeStart.main(Native Method)

任何回应都会非常有帮助。

问候。

编辑：

我现在已经删除了网络访问并将其放入另一个 Java 类中。并称其为另一个类。它仍然返回相同的错误。还有其他建议吗？

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
public class androidconnectors {

    public static final String main(String args[]) throws Exception {


String txtresp = "";
try{
    String url = "http://(LAPTOPS IP):8085/Hello";
    HttpClient client = new DefaultHttpClient();
    HttpGet request = new HttpGet(url);
System.out.println("About to execute");
HttpResponse response = client.execute(request);
String helpedResp=HttpUnpack.request(response); // Http Unpack is not part of
System.out.println(helpedResp); // of HttpClient library
txtresp =(helpedResp);
System.out.println(response);
}catch(Exception ex){
    ex.printStackTrace();
}
return txtresp;
}
}

还有android类。

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class Settings extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dbtest);
        Button mybutton = (Button) findViewById(R.id.buttonpress);
        mybutton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                TextView txtresp = (TextView)findViewById(R.id.servlet_response);
            String[] args = null;
            try {
                String x = androidconnectors.main(args);
                txtresp.setText(x);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                txtresp.setText("Failed");
            }

            }
        });
}
}

Answer 1

看起来，基于 快速谷歌搜索，自从 Honeycomb 你不应该在应用程序的主线程上执行网络访问（以提高响应能力）。

按照此处的建议创建另一个用于网络访问的线程。

Answer 2

您无法在 UI 线程上更好地使用 AsyncTask/Service/IntentService

NetworkOnMainThreadException

进行网络操作

当应用程序尝试执行某个操作时抛出的异常
在其主线程上进行网络操作。（自 API 11 起）

Answer 3

要解决 StrictMode 问题，您需要在活动中使用以下代码 -

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