Android系統提供了兩種HTTP通信類，HttpURLConnection和HttpClient。
盡管Google在大部分安卓版本中推薦使用HttpURLConnection，但是這個類相比HttpClient實在是太難用，太弱爆了。
OkHttp是一個相對成熟的解決方案，據說Android4.4的源碼中可以看到HttpURLConnection已經替換成OkHttp實現了。所以我們更有理由相信OkHttp的強大。
使用范圍
OkHttp支持Android 2.3及其以上版本。
對于Java, JDK1.7以上。
基本使用
HTTP GET
OkHttpClient client = new OkHttpClient();String run(String url) throws IOException { Request request = new Request.Builder().url(url).build(); Response response = client.newCall(request).execute(); if (response.isSuccessful()) { return response.body().string(); } else { throw new IOException("Unexpected code " + response); }}Request是OkHttp中訪問的請求，Builder是輔助類。Response即OkHttp中的響應。
Response類：
public boolean isSuccessful()Returns true if the code is in [200..300), which means the request was successfully received, understood, and accepted.
response.body()返回ResponseBody類
可以方便的獲取string
public final String string() throws IOExceptionReturns the response as a string decoded with the charset of the Content-Type header. If that header is either absent or lacks a charset, this will attempt to decode the response body as UTF-8.Throws:IOException
當然也能獲取到流的形式：
public final InputStream byteStream()
HTTP POST
POST提交Json數據
public static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");OkHttpClient client = new OkHttpClient();String post(String url, String json) throws IOException { RequestBody body = RequestBody.create(JSON, json); Request request = new Request.Builder() .url(url) .post(body) .build(); Response response = client.newCall(request).execute(); f (response.isSuccessful()) { return response.body().string(); } else { throw new IOException("Unexpected code " + response); }} 使用Request的post方法來提交請求體RequestBody
POST提交鍵值對
很多時候我們會需要通過POST方式把鍵值對數據傳送到服務器。 OkHttp提供了很方便的方式來做這件事情。
OkHttpClient client = new OkHttpClient();String post(String url, String json) throws IOException { RequestBody formBody = new FormEncodingBuilder() .add("platform", "android") .add("name", "bug") .add("subject", "XXXXXXXXXXXXXXX") .build(); Request request = new Request.Builder() .url(url) .post(body) .build(); Response response = client.newCall(request).execute(); if (response.isSuccessful()) { return response.body().string(); } else { throw new IOException("Unexpected code " + response); }}注意：
import java.io.IOException;import java.util.List;import java.util.concurrent.TimeUnit;import org.apache.http.client.utils.URLEncodedUtils;import org.apache.http.message.BasicNameValuePair;import cn.wiz.sdk.constant.WizConstant;import com.squareup.okhttp.Callback;import com.squareup.okhttp.OkHttpClient;import com.squareup.okhttp.Request;import com.squareup.okhttp.Response; public class OkHttpUtil { private static final OkHttpClient mOkHttpClient = new OkHttpClient(); static{ mOkHttpClient.setConnectTimeout(30, TimeUnit.SECONDS); } /** * 該不會開啟異步線程。 * @param request * @return * @throws IOException */ public static Response execute(Request request) throws IOException{ return mOkHttpClient.newCall(request).execute(); } /** * 開啟異步線程訪問網絡 * @param request * @param responseCallback */ public static void enqueue(Request request, Callback responseCallback){ mOkHttpClient.newCall(request).enqueue(responseCallback); } /** * 開啟異步線程訪問網絡, 且不在意返回結果（實現空callback） * @param request */ public static void enqueue(Request request){ mOkHttpClient.newCall(request).enqueue(new Callback() { @Override public void onResponse(Response arg0) throws IOException { } @Override public void onFailure(Request arg0, IOException arg1) { } }); } public static String getStringFromServer(String url) throws IOException{ Request request = new Request.Builder().url(url).build(); Response response = execute(request); if (response.isSuccessful()) { String responseUrl = response.body().string(); return responseUrl; } else { throw new IOException("Unexpected code " + response); } } private static final String CHARSET_NAME = "UTF-8"; /** * 這里使用了HttpClinet的API。只是為了方便 * @param params * @return */ public static String formatParams(List<BasicNameValuePair> params){ return URLEncodedUtils.format(params, CHARSET_NAME); } /** * 為HttpGet 的 url 方便的添加多個name value 參數。 * @param url * @param params * @return */ public static String attachHttpGetParams(String url, List<BasicNameValuePair> params){ return url + "?" + formatParams(params); } /** * 為HttpGet 的 url 方便的添加1個name value 參數。 * @param url * @param name * @param value * @return */ public static String attachHttpGetParam(String url, String name, String value){ return url + "?" + name + "=" + value; }}總結
通過上面的例子我們可以發現，OkHttp在很多時候使用都是很方便的，而且很多代碼也有重復，因此特地整理了下面的工具類。
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