使用HTTP协议访问网络 原网址https://www.2cto.com/kf/201701/552932.html

1 获取HttpURLConnection的实例：

URL url = new URL（“https://www.baidu.com”）；
HttpURLConnection connection = （HttpURLConnection）url.openConnection;
2 设置请求的方法：GET POST 获取/提交
connection.setRequsestMethod(“get”);
3 自由设置
connection.setConnectionTimeout(8000);
connection.setReadTimeout(8000);
4 获取服务器返回的输入流
InputStream in = connection.getInputStream（）；
5 最后调用connection.disconnect();

实例：get

"match_parent" android:layout_width= "match_parent" android:orientation= "vertical" xmlns:android= "https://schemas.android.com/apk/res/android" xmlns:tools= "https://schemas.android.com/tools" > "@+id/send_request" android:layout_height= "wrap_content" android:layout_width= "match_parent" android:text= "Send Request" >

    "match_parent" android:layout_width= "match_parent" >
        "@+id/response_text" android:layout_height= "wrap_content" android:layout_width= "match_parent" >

package com.example.networktest;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    public static  final  int SHOW_RESPONSE = 0 ;
    private Button sendRquest;
    private TextView responseText;
    private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
           switch (msg.what) {
               case SHOW_RESPONSE:
                   String response = (String) msg.obj;
                   //进行UI操作
                   responseText.setText(response);
           }

        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        sendRquest = (Button) findViewById(R.id.send_request);
        responseText = (TextView) findViewById(R.id.response_text);
        sendRquest.setOnClickListener( this );
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.send_request){
            sendRequestWithHttpURLConnection();
        }
    }

    private  void sendRequestWithHttpURLConnection(){
        //开启线程
        new Thread( new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null ;
                try {
                    URL url = new URL( "https://www.baidu.com" );
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod( "GET" );
                    connection.setConnectTimeout( 8000 );
                    connection.setReadTimeout( 8000 );
                    InputStream in = connection.getInputStream();
                    BufferedReader reader = new BufferedReader(( new InputStreamReader(in)));
                    StringBuilder response = new StringBuilder();
                    String line ;
                    while ((line = reader.readLine())!= null ){
                        response.append(line);
                    }

                    Message message = new Message() ;
                    message.what = SHOW_RESPONSE ;
                    message.obj = response.toString();
                    handler.sendMessage(message);

                } catch (Exception e){
                    e.printStackTrace();
                } finally {
                    if (connection!= null ){
                        connection.disconnect();
                    }
                }
            }
        }).start();
    }
}

"android.permission.INTERNET" >

post

public static String loginOfPost(String username, String password) {
                HttpURLConnection conn = null ;
                try {
                        // 创建一个URL对象
                        URL mURL = new URL( "https://192.168.0.100:8080/android/servlet/LoginServlet" );
                        // 调用URL的openConnection()方法,获取HttpURLConnection对象
                        conn = (HttpURLConnection) mURL.openConnection();

                        conn.setRequestMethod( "POST" ); // 设置请求方法为post
                        conn.setReadTimeout( 5000 ); // 设置读取超时为5秒
                        conn.setConnectTimeout( 10000 ); // 设置连接网络超时为10秒
                        conn.setDoOutput( true ); // 设置此方法,允许向服务器输出内容

                        // post请求的参数
                        String data = "username=" + username + "&password=" + password;
                        // 获得一个输出流,向服务器写数据,默认情况下,系统不允许向服务器输出内容
                        OutputStream out = conn.getOutputStream(); // 获得一个输出流,向服务器写数据
                        out.write(data.getBytes());
                        out.flush(); // 刷新对象输出流，将任何字节都写入潜在的流中
                        out.close();

                        int responseCode = conn.getResponseCode(); // 调用此方法就不必再使用conn.connect()方法
                        if (responseCode == 200 ) {

                                InputStream is = conn.getInputStream();
                                String state = getStringFromInputStream(is);
                                return state;
                        } else {
                                Log.i(TAG, "访问失败" + responseCode);
                        }

                } catch (Exception e) {
                        e.printStackTrace();
                } finally {
                        if (conn != null ) {
                                conn.disconnect(); // 关闭连接
                        }
                }

                return null ;
        }

2 使用HttpClient （在Android 6.0（API 23） 中，Google已经移除了Apache HttpClient 想关类，推荐使用HttpUrlConnection，如果要继续使用，在Android studio对应的module下的build.gradle文件中加入：
android {
useLibrary ‘org.apache.http.legacy’
}）

package com.example.networktest;

import android.net.Uri;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;

import org.apache.http.HttpEntity;
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 org.apache.http.util.EntityUtils;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    public static final int SHOW_RESPONSE = 0 ;
    private Button sendRquest;
    private TextView responseText;
    private Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case SHOW_RESPONSE:
                    String response = (String) msg.obj;
                    //进行UI操作
                    responseText.setText(response);
            }

        }
    };
    /**
     * ATTENTION: This was auto-generated to implement the App Indexing API.
     * See https://g.co/AppIndexing/AndroidStudio for more information.
     */
    private GoogleApiClient client;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super .onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        sendRquest = (Button) findViewById(R.id.send_request);
        responseText = (TextView) findViewById(R.id.response_text);
        sendRquest.setOnClickListener( this );
        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client = new GoogleApiClient.Builder( this ).addApi(AppIndex.API).build();
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.send_request) {
            // sendRequestWithHttpURLConnection();
            sendRequestWithHttpClient();
        }
    }

    private void sendRequestWithHttpURLConnection() {
        //开启线程
        new Thread( new Runnable() {
            @Override
            public void run() {

                HttpURLConnection connection = null ;
                try {

                    URL url = new URL( "https://www.baidu.com" );
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod( "GET" );
                    connection.setConnectTimeout( 8000 );
                    connection.setReadTimeout( 8000 );
                    InputStream in = connection.getInputStream();
                    BufferedReader reader = new BufferedReader(( new InputStreamReader(in)));
                    StringBuilder response = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null ) {
                        response.append(line);
                    }

                    Message message = new Message();
                    message.what = SHOW_RESPONSE;
                    message.obj = response.toString();
                    handler.sendMessage(message);

                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (connection != null ) {
                        connection.disconnect();
                    }
                }
            }
        }).start();
    }

    private void sendRequestWithHttpClient() {
        new Thread( new Runnable() {
            @Override
            public void run() {
                try {
                    HttpClient httpClient = new DefaultHttpClient();
                    HttpGet httpGet = new HttpGet( "https://www.baidu.com" );
                    HttpResponse httpResponse = httpClient.execute(httpGet);
                    if (httpResponse.getStatusLine().getStatusCode() == 200 ){
                        HttpEntity entity =httpResponse.getEntity();
                        String response = EntityUtils.toString(entity, "utf-8" );
                        Message message = new Message();
                        message.what = SHOW_RESPONSE ;
                        message.obj = response.toString();
                        handler.sendMessage(message);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    @Override
    public void onStart() {
        super .onStart();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client.connect();
        Action viewAction = Action.newAction(
                Action.TYPE_VIEW, // TODO: choose an action type.
                "Main Page" , // TODO: Define a title for the content shown.
                // TODO: If you have web page content that matches this app activity's content,
                // make sure this auto-generated web page URL is correct.
                // Otherwise, set the URL to null.
                Uri.parse( "https://host/path" ),
                // TODO: Make sure this auto-generated app URL is correct.
                Uri.parse( "android-app://com.example.networktest/http/host/path" )
        );
        AppIndex.AppIndexApi.start(client, viewAction);
    }

    @Override
    public void onStop() {
        super .onStop();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        Action viewAction = Action.newAction(
                Action.TYPE_VIEW, // TODO: choose an action type.
                "Main Page" , // TODO: Define a title for the content shown.
                // TODO: If you have web page content that matches this app activity's content,
                // make sure this auto-generated web page URL is correct.
                // Otherwise, set the URL to null.
                Uri.parse( "https://host/path" ),
                // TODO: Make sure this auto-generated app URL is correct.
                Uri.parse( "android-app://com.example.networktest/http/host/path" )
        );
        AppIndex.AppIndexApi.end(client, viewAction);
        client.disconnect();
    }
}