Android学习--使用Http协议访问网络

手动发送HTTP请求

1、使用HttpsURLConnection

1)布局文件activity_main.xml

2)主MainActivity

package com.example.networktest;

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

import javax.net.ssl.HttpsURLConnection;

public class MainActivity extends AppCompatActivity {

    TextView responseText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final Button sendRequest = (Button) findViewById(R.id.send_request);
        responseText = (TextView) findViewById(R.id.response_text);
        sendRequest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                sendRequestWithHttpURLConnection();
            }
        });
    }

    private void sendRequestWithHttpURLConnection(){
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpsURLConnection connection = null;
                BufferedReader reader = null;
                try {
                    URL url = new URL("https://www.baidu.com");
                    connection = (HttpsURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(8000);
                    connection.setReadTimeout(8000);
                    InputStream in = connection.getInputStream();
                    //对获取到的地输入流进行读取
                    reader = new BufferedReader(new InputStreamReader(in));
                    StringBuilder responses = new StringBuilder();
                    String line;
                    while ((line = reader.readLine())!= null){
                        responses.append(line);
                    }
                    showResponse(responses.toString());
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    if ( reader != null){
                        try {
                            reader.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                    if (connection != null){
                        connection.disconnect();
                    }
                }
            }
        }).start();
    }

    private void showResponse(final String response){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                responseText.setText(response);
            }
        });
    }

}

3)AndroidManifest.xml添加网络权限

......

运行效果图（点击button）

若使用HttpURLConnection发送POST请求

//发送POST请求
connection.setRequestMethod("GET");
DataOutputStream out = new DataOutputStream(connection.getOutputStream());
out.writeBytes("username=admin&password=123456");

2、使用OkHttp

1)在build.gradle中添加包依赖

dependencies {
    ......
    compile 'com.squareup.okhttp3:okhttp:3.4.1'
}

2)修改MainActivity代码

package com.example.networktest;

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.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;

import javax.net.ssl.HttpsURLConnection;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity {

    TextView responseText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final Button sendRequest = (Button) findViewById(R.id.send_request);
        responseText = (TextView) findViewById(R.id.response_text);
        sendRequest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                sendRequestWithOkHttp();
            }
        });
    }

    private void showResponse(final String response){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                responseText.setText(response);
            }
        });
    }
    
    private void sendRequestWithOkHttp(){
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    OkHttpClient client = new OkHttpClient();
                    Request request = new Request.Builder()
                            .url("http://www.baidu.com")
                            .build();
                    Response response = client.newCall(request).execute();
                    String responseData = response.body().toString();
                    showResponse(responseData);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
}

发送POST请求

//发送POST请求
RequestBody requestBody = new FormBody.Builder()
        .add("username", "admin")
        .add("password", "123456")
        .build();
Request request = new Request.Builder()
        .url("http://www.baidu.com")
        .post(requestBody)
        .build();