一.使用HttpURLConnection

①首先獲取HttpURLConnection的例項

URL url = new URL("https://www.baidu.com");
connection = (HttpURLConnection)url.openConnection();

②在得到HttpURLConnection的例項後，可以設定HTTP請求所使用的方法。常用的方法主要有兩個：GET和POST。GET表示從伺服器那裡獲取資料，POST則是將資料提交給伺服器。

connection.setRequestMethod("GET");

③自由定製

// 設定是否使用快取
connection.setUseCaches(true);
// 設定此 HttpURLConnection 例項是否應該自動執行 HTTP 重定向
connection.setInstanceFollowRedirects(true);
// 設定超時時間
connection.setConnectTimeout(3000);
 

④利用getInputStream()方法獲取輸入流，然後讀取

InputStream in =connection.getInputStream();

⑤關閉HTTP連線

if(connection != null){
    connection.disconnect();
}

⑥完整Activity程式碼

package com.example.administrator.myapplication;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
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.HttpURLConnection;
import java.net.URL;

public class HttpActivity extends AppCompatActivity implements View.OnClickListener {
    TextView mtx;
    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.http);
        Button btn = findViewById(R.id.button2);
        mtx = findViewById(R.id.textView);
        btn.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        if(v.getId() == R.id.button2){
            sendRequstHttp();
        }
    }

    private void sendRequstHttp() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                BufferedReader reader = null;
                try{
                    URL url = new URL("https://www.baidu.com");
                    connection = (HttpURLConnection)url.openConnection();
/*                    connection.setRequestMethod("POST");
                    DataOutputStream out = new DataOutputStream(connection.getOutputStream());
                    out.writeBytes("username=admin&password=123456");向伺服器傳值*/
                    //請求方式
                    connection.setRequestMethod("GET");
                    //連線超出時間
                    connection.setConnectTimeout(8000);
                    //獲取內容超時
                    connection.setReadTimeout(8000);
                    InputStream in =connection.getInputStream();
                    reader = new BufferedReader((new InputStreamReader(in)));
                    StringBuilder response = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null){
                        response.append(line);
                    }
                    showResponse(response.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() {
                mtx.setText(response);
            }
        });
    }
}

 

完整xml檔案

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Button" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/textView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </ScrollView>


</LinearLayout>
 

需要在AndroidManifest.xml中新增許可權

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

二.使用OkHttp

①首先在app/build.gradle檔案中的dependencies閉包新增如下內容

implementation 'com.squareup.okhttp3:okhttp:3.11.0'

②然後建立一個OkHttpClient的例項

OkHttpClient client = new OkHttpClient();

③建立一個Request物件

Request request = new Request.Builder().url("https://www.baidu.com").build();

④呼叫OkHttpClient的newCall方法來建立一個Call物件，並呼叫它的execute()方法來發生請求並獲取伺服器返回的資料

 Response response = client.newCall(request).execute();

⑤用如下方法獲取具體內容

String responseData = response.body().string();

使用POST請求

如果發起一條POST請求，首先構建一個RequestBody物件來存放代提交的引數

RequestBody requestBody = new FormBody.Builder().add("1","1").build();

然後在Request.Builder中呼叫post()方法，並將RequestBody物件傳入

Request request = new Request.Builder().url("https://www.baidu.com").post(requestBody).build();

具體程式碼如下

package com.example.administrator.myapplication;

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

import okhttp3.FormBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;
import okhttp3.ResponseBody;

public class OkHttpActivity extends AppCompatActivity implements View.OnClickListener {
    TextView mtx;
    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.http);
        Button btn = findViewById(R.id.button2);
        mtx = findViewById(R.id.textView);
        btn.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        if(v.getId() == R.id.button2){
            sendRequestOkHttp();
        }
    }

    private void sendRequestOkHttp() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    OkHttpClient client = new OkHttpClient();
/*                    RequestBody requestBody = new FormBody.Builder().add("1","1").build();
                    Request request = new Request.Builder().url("https://www.baidu.com").post(requestBody).build();*/
                    Request request = new Request.Builder().url("https://www.baidu.com").build();
                    Response response = client.newCall(request).execute();
                    String responseData = response.body().string();
                    showResponse(responseData);
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
        }).start();
    }
    private void showResponse(final String response) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                mtx.setText(response);
            }
        });
    }
}