Question

我试图创建一个应用程序来连接Internet和Return Html。但它不起作用我不知道原因！请帮我解决我的问题：tnQ

错误： java.lang.NullPointerException：println需要一条消息

我的代码：

package net.learn2develop.http3; 
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import android.util.Log;
import android.widget.TextView;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {




        Log.d("location", " 0 as start");

        InputStream in=null;
        int response=-1;
        String urlString="http://www.tabnak.ir";
        try
        {
        URL url=new URL(urlString);
        URLConnection conn=url.openConnection();
        if(!(conn instanceof  HttpURLConnection))
        throw new IOException("Not ann 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();}
            else{ 
                Log.d("location", " 1");
                }
            TextView intxt=(TextView)findViewById(R.id.mytxt); 
            intxt.setText(in.toString());

        }
        catch(Exception ex0)
        {
            Log.d("e:",ex0.getLocalizedMessage());
        }

        }
        catch(Exception ex)
        {
            Log.d("location 2 Exception : ", ex.toString());
        }




        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);




    }

Answer 1

我建议使用此库http://loopj.com/android-async-http/

有了这个，你只需要放入这段代码，并在onSuccess方法中满足你的需求。

AsyncHttpClient client = new AsyncHttpClient();
client.get("http://www.tabnak.ir", new AsyncHttpResponseHandler() {

@Override
public void onStart() {
    // called before request is started
}

@Override
public void onSuccess(int statusCode, Header[] headers, byte[] response) {
    // called when response HTTP status is "200 OK"
}

@Override
public void onFailure(int statusCode, Header[] headers, byte[] errorResponse, Throwable e) {
    // called when response HTTP status is "4XX" (eg. 401, 403, 404)
}

@Override
public void onRetry(int retryNo) {
    // called when request is retried
}

}）;

为什么我的代码（http连接android）不起作用

1 个答案: