目前Android中的網路請求最主要的就是UrlConnection和OkHttp了。而UrlConnection聽說在安卓4.4以後也在內部實現了OkHttp。網路上OkHttp的封裝框架也挺多比如鴻羊大神的okhttputils。框架雖有很多，基礎我們更是需要了解的 ，看他們都是封裝的啥內容。首先先從其最基本的用法開始

OkHttp的用法步驟：
引入最新的gradle依賴

    compile 'com.squareup.okhttp3:okhttp:3.5.0'
    compile 'com.squareup.okio:okio:1.11.0'

Get:

1. 建立okHttpClient的物件。我們可直接new出來 也可以通過OkHttpClient.Builder()構建。
2. 建立Request物件。
3. 封裝成一個請求的任務Call
4. 執行任務 call.execute();是同步請求直接返回Response但需要在子執行緒中執行。call.enqueue()時非同步請求。內部一個執行的回撥。

Post:

1. 建立okHttpClient的物件。我們可直接new出來 也可以通過OkHttpClient.Builder()構建。
2. 建立RequestBody
3. 建立Request物件。
4. 封裝成一個請求的任務Call
5. 執行任務 call.execute();是同步請求直接返回Response但需要在子執行緒中執行。call.enqueue()時非同步請求。內部一個執行的回撥。

示例程式碼：（官方文件）

package com.chs.okhttpdemo;

import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.TimeUnit;

import
 
 okhttp3.Call;
import okhttp3.Callback;
import okhttp3.FormBody;
import okhttp3.MediaType;
import okhttp3.MultipartBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;
import okio.BufferedSink;

public class MainActivity extends AppCompatActivity {
    public static final MediaType MEDIA_TYPE_MARKDOWN
            = MediaType.parse("text/x-markdown; charset=utf-8");
    private static final MediaType MEDIA_TYPE_JPG = MediaType.parse("application/octet-stream");

    OkHttpClient okHttpClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //1.拿到OkHttpClient物件
        okHttpClient = new OkHttpClient.Builder().
                connectTimeout(10, TimeUnit.SECONDS)
                .writeTimeout(10, TimeUnit.SECONDS)
                .readTimeout(30, TimeUnit.SECONDS)
                .build();
    }

    public void doGet(View view) {
        //建立request物件
        Request.Builder builder = new Request.Builder();
        Request request = builder.get().url("http://192.168.1.63:8080/album/login?name=chs&password=123").build();
        execute(request);
    }

    //post提交（表單）鍵值對
    public void doPost(View view) {
        //拿到body的構建器
        FormBody.Builder builder = new FormBody.Builder();
        //新增引數
        builder.add("name", "chs")
                .add("password", "123");
        //拿到requestBody
        RequestBody requestBody = builder.build();
        //建立request物件
        Request request = new Request.Builder()
                .url("http://192.168.1.63:8080/album/login")
                .post(requestBody)
                .build();
        execute(request);
    }

    //post提交String   這個API最好不要傳送大於1M的字串
    public void doPostString(View view) {
        String postBody = "{name:chs,pwd:123}";
        //建立requestBody
        RequestBody requestBody = RequestBody.create(MEDIA_TYPE_MARKDOWN, postBody);
        //建立request
        Request request = new Request.Builder()
                .url("http://192.168.1.63:8080/album/login")
                .post(requestBody)
                .build();
        execute(request);
    }
    //post提交流
    public void doPostStream(View view) {
        RequestBody requestBody = new RequestBody() {
            @Override
            public MediaType contentType() {
                return MEDIA_TYPE_MARKDOWN;
            }

            @Override
            public void writeTo(BufferedSink sink) throws IOException {
                sink.writeUtf8("doPostStream\n");
                sink.writeUtf8("{name:doPostStream,title:doPostStream}");
            }
        };

        Request request = new Request.Builder()
                .url("http://192.168.1.63:8080/album/login")
                .post(requestBody)
                .build();
        execute(request);
    }


    //post提交File
    public void doPostFile(View view) {
        //圖片在手機上的路徑
        String path = Environment.getExternalStorageDirectory().getPath()+"/BXT_SetPic/20170118/1484724630838.jpg";
        LogUtil.i("path:"+path);
        File file = new File(path);
        //建立requestBody
        RequestBody requestBody = RequestBody.create(MEDIA_TYPE_MARKDOWN, file);
        Request request = new Request.Builder()
                .url("http://192.168.1.63:8080/album/login")
                .post(requestBody)
                .build();
        execute(request);
    }
    //post提交Multipart   鍵值對和file一起提交
    public void doPostMultipart(View view) {
        //圖片在手機上的路徑
        String path = Environment.getExternalStorageDirectory().getPath()+"/BXT_SetPic/20170118/1484724630838.jpg";
        LogUtil.i("pth:"+path);
        File file = new File(path);
        RequestBody requestBody = new MultipartBody.Builder()
                .setType(MultipartBody.FORM)
                .addFormDataPart("name", "Square")
                .addFormDataPart("password", "1111")
                .addFormDataPart("image", "1484724630838.jpg", RequestBody.create(MEDIA_TYPE_JPG, file))
                .build();
        //封裝一層來獲取上傳的進度
        CountingRequestBody countRequestBody = new CountingRequestBody(requestBody, new CountingRequestBody.OnProgressListener() {
            @Override
            public void OnProgress(long byteWrite, long contentLength) {
                LogUtil.i(byteWrite+"/"+contentLength);
            }
        });
        Request request = new Request.Builder()
                .url("http://192.168.1.63:8080/album/login")
                .post(countRequestBody)
                .build();
        execute(request);
    }
    //下載
    public void doDownLoad(View view) {
        //建立request物件
        Request.Builder builder = new Request.Builder();
        Request request = builder.get().url("http://192.168.1.63:8080/album//files/album.jpg").build();
        //封裝成一個請求的任務
        Call call = okHttpClient.newCall(request);
        //同步的請求 Response response = call.execute();
        //  執行請求(非同步的請求)
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                LogUtil.i("請求失敗:" + e.toString());
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                LogUtil.i("請求成功:");
                //總的長度
                long totalLength = response.body().contentLength();
                //下載的進度
                long sum = 0;
                InputStream is = response.body().byteStream();
                int len = 0;
                byte [] buff = new byte[1024];
                File file = new File(Environment.getExternalStorageDirectory(),"album.jpg");
                FileOutputStream os = new FileOutputStream(file);
                while ((len=is.read(buff))!=-1){
                    os.write(buff,0,len);
                    sum+=len;
                    LogUtil.i(sum+"/"+totalLength);
                }
                os.flush();;
                os.close();
                is.close();
                LogUtil.i("success");
            }
        });
    }



    private void execute(Request request) {
        //封裝成一個請求的任務
        Call call = okHttpClient.newCall(request);
        //同步的請求 Response response = call.execute();
        //  執行請求(非同步的請求)
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                LogUtil.i("請求失敗:" + e.toString());
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                LogUtil.i("請求成功:" + response.body().string());
            }
        });
    }
}

因為RequestBody沒有提供上傳的進度，所以在上傳的時候包裝RequestBody用來計算上傳的進度

package com.chs.okhttpdemo;

import java.io.IOException;

import okhttp3.MediaType;
import okhttp3.RequestBody;
import okio.Buffer;
import okio.BufferedSink;
import okio.ForwardingSink;
import okio.Okio;
import okio.Sink;

/**
 * 作者：chs on 2017/1/19 16:05
 * 郵箱：[email protected]
 * 包裝RequestBody用來計算上傳的進度
 */

public class ProgressRequestBody extends RequestBody {
    //真正的mRequestBody
    private RequestBody mRequestBody;
    //上傳回調介面
    private OnProgressListener mProgressListener;

    public ProgressRequestBody(RequestBody requestBody, OnProgressListener progressListener) {
        mRequestBody = requestBody;
        mProgressListener = progressListener;
    }

    public interface OnProgressListener {
        void OnProgress(long byteWrite,long contentLength);
    }
    @Override
    public MediaType contentType() {
        return mRequestBody.contentType();
    }

    @Override
    public long contentLength() {
        try {
            return mRequestBody.contentLength();
        } catch (IOException e) {
            return -1;
        }
    }

    @Override
    public void writeTo(BufferedSink sink) throws IOException {
        CountingSink countingSink = new CountingSink(sink);
        BufferedSink bufferedSink = Okio.buffer(countingSink);
        mRequestBody.writeTo(bufferedSink);
        bufferedSink.flush();
    }

    protected final class CountingSink extends ForwardingSink{
        private long byteWrite;
        public CountingSink(Sink delegate) {
            super(delegate);
        }

        @Override
        public void write(Buffer source, long byteCount) throws IOException {
            super.write(source, byteCount);
            byteWrite+=byteCount;
            mProgressListener.OnProgress(byteWrite,contentLength());
        }
    }
}