Retrofit简单介绍及使用

1：Retrofit 2 是一个网络框架 底层是OKHTTP 一个公司出的 square

2：Retrofit 2可以跟 Rxjava交互

3：Rxjava是什么东西 相当于一个网络处理的调味品 基于java 完全异步，基于观察者模式

4：观察者模式
Observer（观察者） 和Observable（被观察者）

如何使用
1：导入各种依赖
2：写一个工具类用来初始化OKHTTP和Retrofit
3：声明一个接口能用注解去请求网络APIService  通过Retrofit里面一个create(xxxApi.class) 

这个是在项目的build.grade里面直接粘过去就OK

ext {
    // Sdk and tools
    minSdkVersion = 19
    targetSdkVersion = 26
    compileSdkVersion = 26
    buildToolsVersion = '26.0.2'
    //support版本
    supportVersion = '27.1.0'
    constraintLayout = '1.0.2'
    junit = '4.12'
    testRunner = '1.0.1'
    espressoCore = '3.0.1'

    interceptor = "3.11.0"
    retrofit = '2.3.0'
    converterGson = '2.3.0'
    rxandroid = '1.2.1'
    rxjava = '1.3.0'
    rxbus = '1.0.6'
    adapterRxjava = '2.0.2'
}

 implementation "com.squareup.okhttp3:logging-interceptor:$rootProject.interceptor"
    implementation "com.squareup.retrofit2:retrofit:$rootProject.retrofit"
    implementation "com.squareup.retrofit2:converter-gson:$rootProject.converterGson"
    implementation "io.reactivex:rxandroid:$rootProject.rxandroid"
    implementation "io.reactivex:rxjava:$rootProject.rxjava"
    implementation "com.hwangjr.rxbus:rxbus:$rootProject.rxbus"
    implementation "com.squareup.retrofit2:adapter-rxjava:$rootProject.adapterRxjava"
    implementation 'com.jakewharton:butterknife:8.8.1'
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

存放接口的类

//用来存放所有接口
public class Contacts {
    //总接口前缀
    public static final String BASE_URL = "http://www.zhaoapi.cn/";
    //登陆
    public static final String USER_LOGIN = "user/login";
    //用户信息
    public static final String USER_INFO = "user/getUserInfo";
    //上传图片
    public static final String UP_LOAD_IMAGE = "file/upload";

}

处理接口

/**
 * 他用来处理接口
 */
public interface MyApiService {
    //Retrofit + Rxjava
    @GET
    Observable get(@Url String url,@QueryMap Map map);
	//Observable 被观察者
    @POST
    Observable post(@Url String url, @QueryMap Map map);

    //这是Retrofit的使用
    @GET
    Call get();
}

接下来介绍工具类，注意包不要导错

import android.os.Environment;

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import okhttp3.MediaType;
import okhttp3.MultipartBody;
import okhttp3.OkHttpClient;
import okhttp3.RequestBody;
import okhttp3.ResponseBody;
import okhttp3.logging.HttpLoggingInterceptor;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava.RxJavaCallAdapterFactory;
import retrofit2.converter.gson.GsonConverterFactory;
import rx.Observer;
import rx.Scheduler;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;
import soexample.umeng.com.retrofitokhttpdemo.Contacts;

public class RetrofitUtils {

private MyApiService myApiService;

private RetrofitUtils() {
    HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
    loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
    OkHttpClient okHttpClient = new OkHttpClient.Builder()
            .readTimeout(20, TimeUnit.SECONDS)
            .connectTimeout(20, TimeUnit.SECONDS)
            .writeTimeout(20, TimeUnit.SECONDS)
            .addInterceptor(loggingInterceptor)
            //配置此客户端，以便在遇到连接问题时重试或不重试。默认情况下，
            //*该客户端从以下问题中悄悄恢复
            .retryOnConnectionFailure(true)
            .build();
    //初始化Retrofit 并结合各种操作
    Retrofit retrofit = new Retrofit.Builder()
            //结合Gson解析
            .addConverterFactory(GsonConverterFactory.create())
            //结合Rxjava
            .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
            .baseUrl(Contacts.BASE_URL)
            .client(okHttpClient)
            .build();
    //通过Retrofit创建完 这个ApiService 就可以调用方法了
    myApiService = retrofit.create(MyApiService.class);
}

public static RetrofitUtils getInstance() {
    return RetroHolder.retro;
}

private static class RetroHolder {
    private static final RetrofitUtils retro = new RetrofitUtils();
}
//封装Get方式  这里面采用构造者模式  就是调用这个方法有返回自己本身这个对象
public RetrofitUtils get(String url, Map map) {
    //这个订阅事件（处理网络请求）放生那个线程
    //Schedulers 线程调度器
    myApiService.get(url, map).subscribeOn(Schedulers.io())//io就是子线程
            //在主线程调用
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(observer);
    return RetrofitUtils.getInstance();
}


/**
 * 表单post请求
 */
public RetrofitUtils post(String url, Map map) {
    if (map == null) {
        map = new HashMap<>();
    }

    myApiService.post(url, map)
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(observer);
    return RetrofitUtils.getInstance();
}
//子类使用
private Subscriber subscriber = new Subscriber() {
    @Override
    public void onCompleted() {

    }

    @Override
    public void onError(Throwable e) {

    }

    @Override
    public void onNext(ResponseBody responseBody) {

    }
};
//重写一个观察者对象
private Observer observer = new Observer() {

    @Override
    public void onCompleted() {

    }
    //网络处理失败
    @Override
    public void onError(Throwable e) {
        if (httpListener != null) {
            httpListener.onError(e.getMessage());
        }
    }
    //网络处理成功
    @Override
    public void onNext(ResponseBody responseBody) {
        if (httpListener != null) {
            try {
                httpListener.onSuccess(responseBody.string());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
};

public interface HttpListener {
    void onSuccess(String jsonStr);

    void onError(String error);
}

private HttpListener httpListener;

public void setHttpListener(HttpListener listener) {
    this.httpListener = listener;
}

}

动态权限

private void checkPermission(int type) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this, Manifest.permission.INTERNET) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.INTERNET}, type);
            } else {
                startRequest(type);
            }
        } else {
            startRequest(type);
        }
    }

成功之后的调用

@Override
    public void onSuccess(Object data) {
        //因为是复用一个处理的  用java的一个关键字instanceof处理一下即可
        if (data instanceof LoginBean) {
            Toast.makeText(this, ((LoginBean) data).getMsg(), Toast.LENGTH_SHORT).show();
        } else if (data instanceof UserInfoBean) {
            UserInfoBean userIfo = (UserInfoBean) data;
            Toast.makeText(this, userIfo.getMsg(), Toast.LENGTH_SHORT).show();
        }
    }

5、让我们继续畅游在知识的海洋，一起去探究retrofit实现断点续传结合后台服务下载的魅力