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Android封装网络请求

在现代Android开发中，网络请求是不可或缺的一部分，为了提高代码的可维护性和复用性，封装一个高效的网络请求框架显得尤为重要，本文将详细介绍如何在Android项目中封装网络请求，主要使用OkHttp和Retrofit这两个流行的网络请求库。

二、选择合适的网络请求库

1、Volley：由Google开发，适用于简单的网络请求，易于使用且性能卓越。

2、OkHttp：高性能HTTP客户端，支持同步和异步请求，具备连接池和缓存策略。

3、Retrofit：基于OkHttp的网络请求库，通过注解定义接口，简化了HTTP请求的编写。

4、其他库：如Android-Async-Http等，也具备特定场景下的优势。

三、封装OkHttp实例

我们需要创建一个单例模式的OkHttpClientUtil类，以便在整个应用程序中复用同一个OkHttp实例。

public class OkHttpClientUtil {
    private static volatile OkHttpClientUtil okHttpUtil;
    private boolean mIsIntercept = true;
    private long mReadTimeOut = 20000;
    private long mConnectTimeOut = 20000;
    private long mWriteTimeOut = 20000;
    private OkHttpClientUtil() {
    }
    public static OkHttpClientUtil getInstance() {
        if (okHttpUtil == null) {
            synchronized (OkHttpClientUtil.class) {
                if (okHttpUtil == null) {
                    okHttpUtil = new OkHttpClientUtil();
                }
            }
        }
        return okHttpUtil;
    }
    public OkHttpClient build() {
        return new OkHttpClient.Builder()
                .readTimeout(mReadTimeOut, TimeUnit.MILLISECONDS)
                .connectTimeout(mConnectTimeOut, TimeUnit.MILLISECONDS)
                .writeTimeout(mWriteTimeOut, TimeUnit.MILLISECONDS)
                .build();
    }
    // Getter and Setter methods...
}

四、封装OkHttp拦截器

为了方便调试和监控网络请求，我们可以添加一个拦截器来打印请求和响应信息。

public class HttpRequestInterceptor implements Interceptor {
    @NotNull
    @Override
    public Response intercept(@NotNull Chain chain) throws IOException {
        Request request = chain.request();
        long startTime = System.currentTimeMillis();
        okhttp3.Response response = chain.proceed(request);
        long endTime = System.currentTimeMillis();
        long duration = endTime startTime;
        okhttp3.MediaType mediaType = response.body().contentType();
        String content = response.body().string();
        Log.d("request", "请求地址：| " + request.toString());
        if (request.body() != null) {
            printParams(request.body());
        }
        Log.d("request", "请求体返回：| Response:" + content);
        Log.d("request", "--请求耗时：" + duration + "毫秒");
        return response;
    }
}

五、封装Retrofit实例

Retrofit通过注解方式定义网络请求接口，极大地简化了代码编写，我们可以通过创建一个单例模式的RetrofitClient类来管理Retrofit实例。

public class RetrofitClient {
    private static RetrofitClient instance;
    private Retrofit retrofit;
    private RetrofitClient() {
        retrofit = new Retrofit.Builder()
                .client(getOkHttpClient())
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl("http://你的服务器地址")
                .build();
    }
    public static RetrofitClient getInstance() {
        if (instance == null) {
            synchronized (RetrofitClient.class) {
                if (instance == null) {
                    instance = new RetrofitClient();
                }
            }
        }
        return instance;
    }
    private OkHttpClient getOkHttpClient() {
        return new OkHttpClient.Builder()
                .connectTimeout(120, TimeUnit.SECONDS)
                .readTimeout(120, TimeUnit.SECONDS)
                .writeTimeout(120, TimeUnit.SECONDS)
                .connectionPool(new ConnectionPool(8, 15, TimeUnit.SECONDS))
                .addInterceptor(new HttpRequestInterceptor())
                .build();
    }
}

六、封装Retrofit注解通用类

为了简化接口定义，我们可以封装一些常用的注解通用类。

public interface BaseApiService {
    @GET("api/helloworld")
    Call<String> getHelloWorld();
    
    @POST("api/login")
    @FormUrlEncoded
    Call<User> login(@Field("username") String username, @Field("password") String password);
}

七、增加请求失败重试功能

为了增强网络请求的健壮性，我们可以实现请求失败后的重试机制。

public class RetryInterceptor implements Interceptor {
    private int maxRetries;
    private long retryInterval; // in milliseconds
    private TimeUnit timeUnit;
    public RetryInterceptor(int maxRetries, long retryInterval, TimeUnit timeUnit) {
        this.maxRetries = maxRetries;
        this.retryInterval = retryInterval;
        this.timeUnit = timeUnit;
    }
    @NotNull
    @Override
    public Response intercept(@NotNull Chain chain) throws IOException {
        Request request = chain.request();
        int tryCount = 0;
        while (true) {
            try {
                return chain.proceed(request);
            } catch (IOException e) {
                tryCount++;
                if (tryCount > maxRetries) {
                    throw e;
                } else {
                    Thread.sleep(retryInterval);
                }
            }
        }
    }
}

八、封装返回结果处理

为了更好地处理网络请求的返回结果，我们可以封装一个通用的结果处理类。

public class Result<T> {
    private T data;
    private String message;
    private int code;
    public T getData() {
        return data;
    }
    public void setData(T data) {
        this.data = data;
    }
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
    public int getCode() {
        return code;
    }
    public void setCode(int code) {
        this.code = code;
    }
}

九、组装完整的网络请求框架

我们将上述各个部分组装起来，形成一个完整的网络请求框架。

public class NetworkManager {
    private static NetworkManager instance;
    private Retrofit retrofit;
    private OkHttpClient okHttpClient;
    private ProgressDialog progressDialog;
    private Context context;
    private NetworkManager(Context context) {
        this.context = context;
        this.okHttpClient = OkHttpClientUtil.getInstance().build();
        this.retrofit = RetrofitClient.getInstance().getRetrofit();
        this.progressDialog = new ProgressDialog(context);
    }
    public static NetworkManager getInstance(Context context) {
        if (instance == null) {
            synchronized (NetworkManager.class) {
                if (instance == null) {
                    instance = new NetworkManager(context);
                }
            }
        }
        return instance;
    }
    
    public <T> doGet(String url, Map<String, String> params, Class<T> clazz, Callback<T> callback) {
        // Implementation of GET request using OkHttp or Retrofit...
    }
    
    public <T> doPost(String url, Map<String, String> params, Class<T> clazz, Callback<T> callback) {
        // Implementation of POST request using OkHttp or Retrofit...
    }
    // Other HTTP methods...
}

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