/**
     * OkHttp 客户端
     * 注意 : 该类型对象较大, 尽量在应用中创建较少的该类型对象
     * 推荐使用单例
     */
    OkHttpClient mOkHttpClient;
    // 初始化操作 
    mOkHttpClient = new OkHttpClient();

// Request 中封装了请求相关信息
        Request request = new Request.Builder()
                .url("https://www.baidu.com")   // 设置请求地址
                .get()                          // 使用 Get 方法
                .build();

// 同步 Get 请求
new Thread(new Runnable() {
    @Override
    public void run() {
        Response response = null;
        try {
            response = mOkHttpClient.newCall(request).execute();
        } catch (IOException e) {
            e.printStackTrace();
        }
        String result = null;
        try {
            result = response.body().string();
        } catch (IOException e) {
            e.printStackTrace();
        }
        Log.i(TAG, "result : " + result);
    }
}).start();

package com.example.okhttp;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import com.example.okhttp.databinding.ActivityMainBinding;
import java.io.IOException;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    /**
     * ViewBinding 类
     * activity_main 布局映射出来的类
     * 该类主要作用是封装组件的获取
     */
    ActivityMainBinding binding;
    /**
     * OkHttp 客户端
     * 注意 : 该类型对象较大, 尽量在应用中创建较少的该类型对象
     * 推荐使用单例
     */
    OkHttpClient mOkHttpClient;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());
        mOkHttpClient = new OkHttpClient();
        binding.button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                httpGet();
            }
        });
    }
    /**
     * OkHttp Get 请求
     */
    private void httpGet() {
        // Request 中封装了请求相关信息
        Request request = new Request.Builder()
                .url("https://www.baidu.com")   // 设置请求地址
                .get()                          // 使用 Get 方法
                .build();
        // 同步 Get 请求
        new Thread(new Runnable() {
            @Override
            public void run() {
                Response response = null;
                try {
                    response = mOkHttpClient.newCall(request).execute();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                String result = null;
                try {
                    result = response.body().string();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                Log.i(TAG, "result : " + result);
            }
        }).start();
    }
}

plugins {
    id 'com.android.application'
}
android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"
    defaultConfig {
        applicationId "com.example.okhttp"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    android.buildFeatures.viewBinding = true
}
dependencies {
    implementation 'androidx.appcompat:appcompat:1.3.0'
    implementation 'com.google.android.material:material:1.3.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    implementation 'com.squareup.okhttp3:okhttp:3.14.+'
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.okhttp">
    <uses-permission android:name="android.permission.INTERNET" />
    <application
        android:networkSecurityConfig="@xml/network_security_config"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.OkHttp">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

HTTP 兼容配置文件 : src/main/res/xml 目录下 ;
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <!-- Android 9.0 之后不允许使用 HTTP, 只能使用 HTTPS,
         如果要使用 HTTP , 必须在 application 节点的 android:networkSecurityConfig 属性中
         配置本文件 -->
    <base-config cleartextTrafficPermitted="true" />
</network-security-config>