基本使用

首先记得在build.gradle 和 配置文件分别加上依赖 和 网络权限

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implementation 'com.squareup.okhttp3:okhttp:4.8.1'
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<uses-permission android:name="android.permission.INTERNET"/>

OkHttp采用建造者模式设计，使用很方便

异步Get请求

  • 构造Request对象；
  • new OkHttpClient;
  • 通过前两步中的对象构建Call对象；
  • 通过Call#enqueue(Callback)方法来提交异步请求；
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String url = "http://wwww.baidu.com";
final Request request = new Request.Builder()
        .url(url)
        .get()//默认就是GET请求，可以不写
        .build();

//创建一个http客户端对象
OkHttpClient okHttpClient = new OkHttpClient();
Call call = okHttpClient.newCall(request);

call.enqueue(new Callback() {
    @Override
    public void onFailure(@NonNull Call call, @NonNull IOException e) {
        Log.d(TAG, "onFailure: ");
    }
    @Override
    public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

异步发起的请求会被加入到 Dispatcher 中的 runningAsyncCalls双端队列中通过线程池来执行。

同步Get请求

前面几个步骤和异步方式一样，只是最后一部是通过 Call#execute() 来提交请求，注意这种方式会阻塞调用线程，所以在Android中应放在子线程中执行，否则有可能引起ANR异常，Android3.0 以后已经不允许在主线程访问网络。

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String url = "http://wwww.baidu.com";
//创建一个http客户端对象
final Request request = new Request.Builder()
        .url(url)
        .get()//默认就是GET请求，可以不写
        .build();

//创建一个http客户端对象
OkHttpClient okHttpClient = new OkHttpClient();
Call call = okHttpClient.newCall(request);

//Android3.0 以后已经不允许在主线程访问网络。
new Thread(new Runnable() {
    @Override
    public void run() {
        try {
            Response response = call.execute();
            Log.d(TAG, "run:"+response.body().string());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}).start();

POST方式提交String

这种方式与前面的区别就是在构造Request对象时，需要多构造一个RequestBody对象，用它来携带我们要提交的数据。在构造 RequestBody 需要指定MediaType，用于描述请求/响应 body 的内容类型，关于 MediaType 的更多信息可以查看 RFC 2045.

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String url = "http://wwww.baidu.com";
MediaType mediaType = MediaType.parse("text/x-markdown; charset=utf-8");
String requestBody = "I am quanzi";
final Request request = new Request.Builder()
        .url(url)
        .post(RequestBody.Companion.create(requestBody,mediaType))
        .build();

//创建一个http客户端对象
OkHttpClient okHttpClient = new OkHttpClient();
Call call = okHttpClient.newCall(request);

call.enqueue(new Callback() {
    @Override
    public void onFailure(@NonNull Call call, @NonNull IOException e) {
        Log.d(TAG, "onFailure: ");
    }
    @Override
    public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST方式提交流

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RequestBody requestBody = new RequestBody() {
    @Nullable
    @Override
    public MediaType contentType() {
        return MediaType.parse("text/x-markdown; charset=utf-8");
    }

    @Override
    public void writeTo(@NonNull BufferedSink bufferedSink) throws IOException {
        bufferedSink.writeUtf8("I am quanzi.");
    }
};

Request request = new Request.Builder()
        .url("https://api.github.com/markdown/raw")
        .post(requestBody)
        .build();

//创建一个http客户端对象
OkHttpClient okHttpClient = new OkHttpClient();
Call call = okHttpClient.newCall(request);

call.enqueue(new Callback() {
    @Override
    public void onFailure(@NonNull Call call, @NonNull IOException e) {
        Log.d(TAG, "onFailure: ");
    }
    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, response.protocol() + " " +response.code() + " " + response.message());
        Headers headers = response.headers();
        for (int i = 0; i < headers.size(); i++) {
            Log.d(TAG, headers.name(i) + ":" + headers.value(i));
        }
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST方式提交文件

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MediaType mediaType = MediaType.parse("text/x-markdown; charset=utf-8");
File file = new File("test.md");
Request request = new Request.Builder()
        .url("https://api.github.com/markdown/raw")
        .post(RequestBody.Companion.create(file,mediaType))
        .build();

OkHttpClient okHttpClient = new OkHttpClient();
okHttpClient.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }
    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, response.protocol() + " " +response.code() + " " + response.message());
        Headers headers = response.headers();
        for (int i = 0; i < headers.size(); i++) {
            Log.d(TAG, headers.name(i) + ":" + headers.value(i));
        }
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST方式提交表单

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RequestBody requestBody = new FormBody.Builder()
        .add("search", "Jurassic Park")
        .build();
Request request = new Request.Builder()
        .url("https://en.wikipedia.org/w/index.php")
        .post(requestBody)
        .build();

OkHttpClient okHttpClient = new OkHttpClient();
okHttpClient.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        Log.d(TAG, response.protocol() + " " +response.code() + " " + response.message());
        Headers headers = response.headers();
        for (int i = 0; i < headers.size(); i++) {
            Log.d(TAG, headers.name(i) + ":" + headers.value(i));
        }
        Log.d(TAG, "onResponse: " + response.body().string());
    }
});

POST方式提交分块请求

MultipartBody 可以构建复杂的请求体，与HTML文件上传形式兼容。多块请求体中每块请求都是一个请求体，可以定义自己的请求头。这些请求头可以用来描述这块请求，例如它的 Content-Disposition 。如果 Content-Length 和 Content-Type 可用的话，他们会被自动添加到请求头中。

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String IMGUR_CLIENT_ID = "...";
MediaType MEDIA_TYPE_PNG = MediaType.parse("image/png");

// Use the imgur image upload API as documented at https://api.imgur.com/endpoints/image
MultipartBody body = new MultipartBody.Builder("AaB03x")
        .setType(MultipartBody.FORM)
        .addPart(
                Headers.of("Content-Disposition", "form-data; name=\"title\""),
                RequestBody.create(null, "Square Logo"))
        .addPart(
                Headers.of("Content-Disposition", "form-data; name=\"image\""),
                RequestBody.create(MEDIA_TYPE_PNG, new File("website/static/logo-square.png")))
        .build();

Request request = new Request.Builder()
        .header("Authorization", "Client-ID " + IMGUR_CLIENT_ID)
        .url("https://api.imgur.com/3/image")
        .post(body)
        .build();

OkHttpClient client = new OkHttpClient();
Call call = client.newCall(request);

call.enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
    }
    @Override
    public void onResponse(Call call, Response response) throws IOException {
        System.out.println(response.body().string());
    }
});

拦截器-interceptor

OkHttp的拦截器链可谓是其整个框架的精髓，用户可传入的 interceptor 分为两类：
①一类是全局的 interceptor，该类 interceptor 在整个拦截器链中最早被调用，通过 OkHttpClient.Builder#addInterceptor(Interceptor) 传入；
②另外一类是非网页请求的 interceptor ，这类拦截器只会在非网页请求中被调用，并且是在组装完请求之后，真正发起网络请求前被调用，所有的 interceptor 被保存在 List interceptors 集合中，按照添加顺序来逐个调用，具体可参考 RealCall#getResponseWithInterceptorChain() 方法。通过 OkHttpClient.Builder#addNetworkInterceptor(Interceptor) 传入；

这里举一个简单的例子，例如有这样一个需求，我要监控App通过 OkHttp 发出的所有原始请求，以及整个请求所耗费的时间，针对这样的需求就可以使用第一类全局的 interceptor 在拦截器链头去做。

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public class LoggingInterceptor implements Interceptor {

    private static final String TAG = "LoggingInterceptor";

    @NonNull
    @Override
    public Response intercept(@NonNull Chain chain) throws IOException {
        Request request = chain.request();

        long startTime = System.currentTimeMillis();
        Log.d(TAG, String.format("Sending request %s on %s%n%s", request.url(), chain.connection(), request.headers()));

        Response response = chain.proceed(request);

        long endTime = System.nanoTime();
        Log.d(TAG, String.format("Received response for %s in %.1fms%n%s", response.request().url(), (endTime - startTime) / 1e6d, response.headers()));

        return response;
    }

}
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OkHttpClient okHttpClient = new OkHttpClient.Builder()
        .addInterceptor(new LoggingInterceptor())
        .build();

Request request = new Request.Builder()
        .url("http://www.publicobject.com/helloworld.txt")
        .header("User-Agent", "OkHttp Example")
        .build();

okHttpClient.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(@NonNull Call call, @NonNull IOException e) {
        Log.d(TAG, "onFailure: " + e.getMessage());
    }
    @Override
    public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
        ResponseBody body = response.body();
        if (body != null) {
            Log.d(TAG, "onResponse: " + body.string());
            body.close();
        }
    }
});

其他

  1. 推荐让 OkHttpClient 保持单例，用同一个 OkHttpClient 实例来执行你的所有请求，因为每一个 OkHttpClient 实例都拥有自己的连接池和线程池，重用这些资源可以减少延时和节省资源，如果为每个请求创建一个 OkHttpClient 实例，显然就是一种资源的浪费。当然，也可以使用如下的方式来创建一个新的 OkHttpClient 实例，它们共享连接池、线程池和配置信息。
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    OkHttpClient eagerClient = client.newBuilder()
        .readTimeout(500, TimeUnit.MILLISECONDS)
        .build();
    Response response = eagerClient.newCall(request).execute();
  2. 每一个Call（其实现是RealCall）只能执行一次，否则会报异常，具体参见 RealCall#execute()